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UNDER THE SPELL OF LANDAU When Theoretical Physics was Shaping Destinies Copyright © 2013 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher.

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CONTENTS

From the Editor xiii M. Shifman

PART I

Chapter 1: Lev Landau ... 2 Lev Davidovich Landau 5 Boris Ioﬀe Landau as I Knew Him 30 S. S. Gershtein Chapter 2: Arkady Migdal ... 52 Arkady Benediktovich Migdal 55 N. O. Agasyan, S. T. Belyayev, L. B. Okun, and E. E. Sapershtein Remembering AB 67 S. T. Belyayev A. B. Migdal in My Life 74 Anatoly Larkin Memories of A. B. Migdal 88 V. A. Khodel Memories of AB 101 V. G. Vaks Grand Master 114 Alexander Polyakov

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vi Contents

Chapter 3: Yakov Zeldovich ... 120

On the Path Towards Universal Weak Interaction 123 S. S. Gershtein A Simple Love Story 154 Anna Shiryaeva

Chapter 4: Yakov Smorodinsky ... 160

Yakov Abramovich Smorodinsky 163 Noemi Smorodinskaya Yakov Abramovich Smorodinsky at Leningrad State University 171 I. V. Komarov About Hydrotechnical Laboratory, Professor Smorodinsky, and Nucleon–Nucleon Scattering 174 R. M. Ryndin Remembering Yakov Abramovich Smorodinsky 178 F. Calogero Remembering Yakov Abramovich 181 A. Frenkel Yakov Abramovich Smorodinsky and His Inﬂuence on My Life 183 P. Winternitz Yakov Abramovich as I Remember Him 189 Julia Ny´ıri About Yakov Abramovich 194 P´al Ny´ıri

Chapter 5: Karen Ter-Martirosyan ... 196

Karen Avetovich Ter-Martirosyan 199 Karen Avetovich 203 M. Shifman May 13, 2013 14:28 WSPC/Trim Size: 9in x 6in for Proceedings 1a˙Contents

Contents vii

K. A. Ter-Martirosyan as I Remember Him 207 A. V. Smilga Memories of Karen Avetovich 212 Roman Nevzorov A Few Lines about Karen 219 Noemi Smorodinskaya Chapter 6: David Kirzhnits ... 220 David Abramovich Kirzhnits 223 B. M. Bolotovsky, Yu. M. Bruk, V. L. Ginzburg, V. I. Ritus, and G. V. Shpatakovskaya Memoirs 226 David Kirzhnits Memories of David Kirzhnits 243 B. M. Bolotovsky David Abramovich 266 A. D. Linde Chapter 7: Vladimir Gribov ... 274 Vladimir Naumovich Gribov: Introduction 277 Vladimir Naumovich Gribov 284 A. Frenkel V. N. Gribov: 1930–1997 287 Yuri Dokshitzer On V. N. Gribov 296 B. L. Ioﬀe In Memory of a Friend 302 S. S. Gershtein Chapter 8: Anatoly Larkin ... 310 Anatoly Ivanovich Larkin 313 My Brother Tolya 318 Alexander I. Larkin May 13, 2013 14:28 WSPC/Trim Size: 9in x 6in for Proceedings 1a˙Contents

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Glimpses of Tolya Larkin 328 V. G. Vaks A Student’s Memories 332 Yuri Ovchinnikov He Lived Among Us 336 V. L. Pokrovsky Remembering Larkin 344 Andrei Varlamov Tolya Larkin at the Institute 347 M. Shifman Chapter 9: Alexei Anselm ... 352 Alexei Andreevich Anselm 355 D. I. Diakonov Alyosha and I were Close Friends 362 A. M. Polyakov Memoirs 367 Ludmila Anselm Chapter 10: Time and Destinies ... 378 Snapshots from the 1950s 381 Yuri F. Orlov Bruno Pontecorvo: Recollections and Reﬂections 399 S. S. Gershtein ITEP Theory Department: Glimpses 428 M. Shifman Living in Truth: V. N. Gribov and the Post-War Generation of Soviet Physics 437 P´al Ny´ıri and Joana Breidenbach May 13, 2013 14:28 WSPC/Trim Size: 9in x 6in for Proceedings 1a˙Contents

Contents ix

PART I I

Chapter 11: Some Details for Experts ... 448 Great Universalist of the 20th Century 451 S. S. Gershtein Landau and Modern Physics 465 V. L. Pokrovsky Strong Interactions at High Energies in the Reggeon Approach 488 K. G. Boreskov, A. B. Kaidalov, and O. V. Kancheli Anselm’s Discovery of the Gross–Neveu Model in 1958 524 M. Shifman A Model of Field Theory with Nonvanishing Renormalized Charge 526 A. A. Anselm

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INTRODCTION May 13, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 1b_Intro-divider May 13, 2013 15:48 WSPC/Trim Size: 9in x 6in for Proceedings 13˙Index

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FROM THE EDITOR∗

M. SHIFMAN William I. Fine Theoretical Physics Institute University of Minnesota Minneapolis, MN 55455, USA [email protected]

The year 2008 marked the centenary of Landau’s birth. Lev Lan- dau created the Soviet school of theoretical physics, renowned for its seminal achievements. His life and work are legend. Although I never saw Landau with my own eyes, his students and followers taught me. His course in theoretical physics guided my path in physics. For generations of young theoreticians, his texts were a primary source of knowledge, and even today, a half century after Landau’s course appeared in print, for many topics it remains definitive.a Landau could be thought fortunate to have lived and worked shortly after the dawn of quantum physics. He became a trailblazer in the quantum world. Among the most influential physicists of the twentieth century, Lev Davidovich Landau was a great universalist who made fundamental contributions in many different fields: quantum mechanics, the theory of magnetism, the theory of phase transitions, nuclear physics and the physics of elementary particles, quantum electrodynamics, the physics of low temperatures, hydrodynamics, the theory of atomic collisions, the theory of chemical reactions... and much more. From my vantage point as a contem-

∗Parts of this article were translated from Russian by Forrest Rhoads, Milla Grin, and James Manteith. aFor a detailed discussion and historical perspective see Karl Hall, “Think less about foundations: A Short Course on the Course of Theoretical Physics of Landau and Lif- shitz”, in Pedagogy and the Practice of Science: Historical and Contemporary Perspec- tives, Ed. David Kaiser, (MIT Press, 2005), p. 253.

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xiv M. Shifman

porary physicist, I would venture to call Landau theoretical physics’ last great universalist. The breadth of Landau’s scientific interests was astonishing, as was the depth of his insights in various physics disciplines. An incomplete list of his eponymous achievements might include: Landau diamagnetism, Landau levels in magnetic fields, the ferromagnetic domain structure, the Ginsburg-Landau theory of superconductivity, superfluid helium, the theory of the Fermi liquid, Landau damping, the Landau zero charge in quantum electrodynamics, the two- component neutrino theory, Landau’s equations for S matrix singularities... Soon after the tragic automobile accident which cut short his scientific life, he was awarded the Nobel Prize “for his pioneering theories of condensed matter, especially liquid helium” (1962). Much has been written about Landau; his life and achievements have been examined from all sides. My idea was to compile a collection of essays and memoirs not just about Landau, but rather about the Landau School. At first I wanted to entitle this collection “The Last Wave” and even began a bit of a collaboration with Gennady Gorelik, the well-known historian of science and Landau specialist. But for several reasons this project didn’t work. I returned to it in a somewhat different form after four years or so. Why “The Last Wave”? Landau’s school was a unique, endemic event in the recent history of physics, never to be repeated. The School was born and developed in very particular conditions: a revolutionary breakthrough in physics, dramatic social changes in Russia and the accompanying great expectations, a large group of young science enthusiasts gathering in Moscow, a strong leader with unquestionable authority and readiness to assume the mission of a founding father, complete isolation from the rest of the world starting in the mid-1930s, the high prestige of physics associated with the atomic project – it’s hardly conceivable that such factors will combine again in the future. Landau was always surrounded by students. He himself hardly ever read the scientific literature. His students read and told him about it. As a rule Landau was only interested in a work’s concept and in its result, which he would later reproduce himself. Shared May 13, 2013 16:8 WSPC/Trim Size: 9in x 6in for Proceedings 1c˙MShif˙intro

From the Editor xv

day-to-day activities bonded together a group of like-minded people around Landau – people who considered physics more important than anything else and generously gave it all their heart and talent. Landau was unquestionably the leader, and his school, a world- class school, was one of the very few real achievements of the Soviet Union. Thanks to his supreme authority among his colleagues and students, for many years he shaped his school’s growth and determined the main paths for theoretical research. It takes more than being a great physicist to establish a school. In addition to demanding great scientific talent, creating a school implies willingness to surround oneself with young people, inspire them, and constantly and constructively interact with them. Then they will enthusiastically follow. This is a special skill which Landau enjoyed. The School didn’t die with Landau’s automobile accident in 1962, despite the death of its founder’s scientific activity. The School stayed alive in Landau’s students. When I came to ITEPb in 1969 or ’70 and decided to become a theoretical physicist, I had to pass a number of examinations, the famous Landau theoretical minimum. My examiners were V.B. Berestetsky and K.A. Ter-Martirosyan. This was as important as keeping alive Landau’s attitude to physics, his insightful informal approach to physical problems, which he so cherished. Theoretical physics, like the Olympic torch, passes from hand to hand. The understanding that theoretical physics is about developing a deep intuition in the phenomenon that you study, day after day, to the extent that you see it in dreams at night, and then, all of a sudden, the answer you look for miraculously surfaces in your mind, in the beginning quite vaguely, in an approximate form, before the actual calculation is done – this understanding is passed from hand to hand. Landau ignited the Olympic flame, and his pupils carried it on. The situation in theoretical physics changed after the collapse of the Soviet Union. The Landau School is gradually fading. Some

bThe Institute of Theoretical and Experimental Physics, in Moscow. May 13, 2013 16:8 WSPC/Trim Size: 9in x 6in for Proceedings 1c˙MShif˙intro

xvi M. Shifman

physicists left for the West, and some have passed away. Physics doesn’t hold the same attraction for the new generations coming to replace the old. To some degree this is connected with the fact that in the past physics offered an escape from the insane, inside-out world of Soviet life. Bright young people flocked to physics, as to music, wanting to have nothing at all to do with ugly official ideology or anything associated with it. This motivation fell away. “The time is out of joint,”c and who can pass the torch from hand to hand now? To whom? Will the spirit of Landau continue to drive theoretical physics in the future? My initial goal, as I saw it before I started, was to acquaint the reader with Landau’s best students, the ones who had Landau as their thesis adviser and who later carried on his glorious legacy. Shortly after I began work on this collection, it became apparent that the Landau School is an enormous topic, a prodigious undertaking beyond my grasp for many reasons. First, some of his students, fortunately, are still with us, and in this case it makes sense for them to write their autobiographies. A couple of memoir books of this type have been published and are rather well-known. Probably the best example is the excellent book by I.M. Khalatnikov.d My interference in these cases would be totally inappropriate. Second, I can’t write about people I didn’t know personally. For a comprehensive book about Landau’s disciples, a professional historian of science would be needed. (If any are listening, I offer them this topic as a generous gift.) Accordingly, I decided to narrow my task in some ways and expand it in others. This book will focus on just a few people from Landau’s “cohort” whom I knew personally and who – alas – departed this world in the years after the demise of the Soviet Union... I’ve put cohort in quotes because I use this term in a broad sense. This collection is not only about those who actually passed the theoretical minimum and whom Landau officially agreed to take on as his students.e To my mind, the meaning of the Landau School is

cWilliam Shakespeare, Hamlet. dI.M. Khalatnikov, Dau, Kentavr I Drugie (Top Nonsecret), (Fizmatlit, Moscow, 2007). eThose who didn’t pass Landau’s theoretical minimum exam formally were not consid- May 13, 2013 16:8 WSPC/Trim Size: 9in x 6in for Proceedings 1c˙MShif˙intro

From the Editor xvii

broader. It includes people from Landau’s circle, participants in his seminar, students of his students, and so forth – all those whose scientific vision was shaped by Landau’s ideas and attitude about physics. It simplifies my task immensely that the narrative below concerns people whom I knew personally. Eight chapters, eight human beings and outstanding theoretical physicists... Migdal, Zel- dovich, Smorodinsky, Ter-Martirosyan, Kirzhnits, Gribov, Larkin, Anselm. Their lives intertwined in a remarkable way. For example, Ter-Martirosyan taught Anselm. Larkin was a student of Migdal, who in turn played a very special role in Landau’s circle. Larkin’s excellent essay on Migdal is included here. They were all inhabitants of the small, magical world reflected in this book’s pages, and they all knew each other. Their names can be found here in various combinations and episodes, scientific and non-scientific. Besides the presence of the physicists named above, an immaterial substance permeates each of this book’s chapters: the atmosphere of the age these people lived in. I wanted to convey a sense of everyday

ered by Landau to be “his” theorists. Here’s how David Kirzhnits described his situation at a seminar in honor of Landau at the Institute of Theoretical and Experimental Physics in 1988: “... I want to tell the story about how I didn’t become Landau’s student. It was around 1948. I was working on my undergraduate thesis in quantum electrodynamics. This was a hot topic then, with Lamb shift experiments recently ﬁnished. The ﬁrst publications by Weisskopf and French, by Hans Bethe, were appearing in journals, and I was right in the middle of this uproar. I had only passed half of Landau’s theoretical minimum exam. To put it succinctly, I had fallen behind in my studies, because I couldn’t tear myself away from my current work... The moment came when I needed serious advice. I consulted a few times with Galanin, Berestetsky and Pomeranchuk, but still this wasn’t enough, and after having consulted with Kompaneyets, I decided to go to Landau, although I understood that I was in a hopeless situation, since I hadn’t been preparing for his exam for a year or more. I must say that this encounter didn’t end well, although it left the impression of the utmost fairness. I told Landau about the results of my work and he gave me a scolding, criticizing some parts while praising some other parts, and the parts that he praised are still viable today, and even applicable, albeit in other areas. At the end Landau said, ‘I have an unbreakable rule. A person who doesn’t complete my theoretical minimum exams and starts independent research is a person I want nothing to do with.’ ... Of course later, when I returned from industry to the academic world, I had other meetings with Landau, but they didn’t always leave a taste of perfect fairness, as in this earlier encounter, which stood as a high point in my memory.” See D. Kirzhnits, “Memories of L.D. Landau,” in D.A. Kirzhnits, Trudy po Teoreticheskoy Fizike i Vospominaniya, (Fizmatlit, Moscow, 2001), Vol. 1, p. 347. May 13, 2013 16:8 WSPC/Trim Size: 9in x 6in for Proceedings 1c˙MShif˙intro

xviii M. Shifman

life in Soviet society and to provide a snapshot of the conditions which Landau and his students worked under, because without such an understanding the reader cannot fully comprehend the memories each contributor shares. A special chapter of the book entitled “Time and Destinies” will hopefully prove valuable for this purpose. In my opinion, the physicists’ memoirs in this chapter vividly depict the complexities of their time – an era gone forever. These pages could be seen as a kind of impressionistic portrait of Atlantis... This collection bears little resemblance to a glossy magazine with fairy tales of celebrities. Stalin’s system, under which Landau lived, was built on absolute authority and the strictest hierarchy, with sig- nals flowing only in one direction, from the top of the pyramid down- ward. This pyramid structure partly penetrated the Landau School as well. The School functioned to a significant degree like a medieval guild with Grand Masters and knights, with Landau the grandest of all. But instead of the brute force that reined among Stalin’s satraps, it was Landau’s scientific prowess that gave him superior authority. He had the power to “execute and pardon.” If he thought one of his pupils had erred either in physics or in life, he could “excommuni- cate” the offender from his seminar forever or for a season. Landau once excommunicated Pomeranchuk from the seminar over Pomer- anchuk publishing a paper with Ivanenko, whom Landau considered a bad person (probably with good reason). Ioffe’s Landau memoirf recounts an episode involving Landau’s discovery of combined parity conservation. The young theorists Ioffe, Rudik and Okun, at their own peril, had begun to research the very hot topic of parity nonconservation in field theory. Ioffe and Rudik discovered that if P is broken, so is C, and vice versa. Landau frowned on this. He didn’t believe P could be broken in any way. Pomeranchuk convinced him, with difficulty, to listen to the young people. Landau listened. Lan- dau’s manuscript on CP conservation appeared the next morning. At first Ioffe and Rudik were not even mentioned in this article, but communal pressure forced Landau to mention them in acknowledgments, albeit not in alphabetical order.

f See this collection, p. 5. May 13, 2013 16:8 WSPC/Trim Size: 9in x 6in for Proceedings 1c˙MShif˙intro

From the Editor xix

As Ioffe maintains, “If Landau thought he understood a subject more deeply than others, even if they initiated the study of this very subject, he considered himself the true originator of the discovery.”g A similar situation transpired between Landau and A.B. Migdal. As I.I. Goldman recounts,h “I remember the Sunday of February 11, 1990, in Washington ... Migdal started talking about Landau. It seemed to me that his attitude toward Dau had changed, and Migdal confirmed the change. Migdal recalled the years when he was working on his doctorate, and showed his calculations on liquid helium to Landau (Landau’s work on superfluids contained a footnote acknowledging Migdal’s calculations). Migdal said bitterly that he had told Landau more than just these calculations. To my question about why he didn’t publish his research himself, Migdal responded that Landau had let him know that this was unacceptable, and that the work was Landau’s.” That this was no careless, offhand remark is confirmed by Miron Amusia’s recollection:i “At the Gatchina school around 1981, I heard AB’s talk in which Landau was criticized, seemingly for the first time ever. AB spoke of Landau’s categorical judgments and a sort of ‘personality cult’ around him which, being based on Landau’s enormous contributions in physics, on the one hand propelled Soviet physics to outstanding heights, but on the other hand was not always harmless. It is in this context that I first heard AB speaking publicly about the benefits of freedom in science. He remarked that one could publish not only papers in which one was certain that everything from A to Z was correct. That there should be a place for conjectures. AB said that Puritanism and extreme demands of a complete theoretical rigor to some extent hindered rather than helped the development of physics as a unified science. At that time I considered AB’s re-

gIn this connection, an episode with A. Dykhne described by V. Pokrovsky in his article in the chapter “Some Details for Experts” adds an extra touch to the overall picture, see footnote in Pokrovsky’s article, p. 480 of this collection. hI.I. Goldman, “Arkady Benediktovich, Nastavnik, Drug,” in Vospominaniya ob Aka- demike Migdale, (Moscow, Fizmatlit, 2003), p. 163. iUFN Tribune, March 2011, and private communications. May 13, 2013 16:8 WSPC/Trim Size: 9in x 6in for Proceedings 1c˙MShif˙intro

xx M. Shifman

versal as something reflecting the ‘corrupting’ influence of the West, communications with which, including science, were becoming more intense.” When the zero charge was discovered, Landau pronounced field theory dead. After this, no one doing research in field theory could remain in Landau’s circle. The Landau School’s negative attitude toward field theory continued for a long time, even after Landau’s death, until nearly 1972. The Yang-Mills theory by which our world functions was not considered a subject for serious research. I clearly remember the negative attitude toward field theory at ITEP at that time. One additional topic I would like to touch upon in passing in my introductory note concerns Landau and women. When I was a student at MIPTj in the late 1960s, many legends on this subject circulated among the students. All this was still very fresh in people’s “operational” memories. In his circle, Landau never tried to hide that he appreciated only one attribute in women: their sexual attractiveness. This detail suddenly acquired a scandalous connotation in 1999 when a memoir by Landau’s wife, Kora Drobantseva-Landau, was published.k Her memoir painted a rather unpleasant picture. In 2008, a notorious Russian TV series based on this book appeared, which – I hasten to add – was heavily criticized by some of Landau’s students. Who knows the extent of the truth of this book and movie? I don’t think we’ll ever find the answer to this question. Landau had a multifaceted and sometimes contradictory personality. The aspects which his students saw had no meaning for his wife, and vice versa. Is this important? Not for a legend. Landau lived in a cruel and tragic time. He was a product of the environment that created him, and if he’d acted differently, who knows if there would have been a Landau School? We value him for what he did for physics. One cannot (and should not) project

jMoscow Institute for Physics and Technology in Dolgoprudny, 12 miles north of Moscow. kKora Drobantseva-Landau, Akademik Landau. Kak My Zhili, (Zakharov Publishers, Moscow, 1999). May 13, 2013 16:8 WSPC/Trim Size: 9in x 6in for Proceedings 1c˙MShif˙intro

From the Editor xxi

today’s moral standards on an earlier time. To do so is categorically incorrect. As time goes by, living witnesses pass away, memories fade, and the realities of the world surrounding us change. The changes are so drastic that when I tell various stories about Landau and his disciples and colleagues to my graduate students (including Russian graduate students), they don’t believe me. They think these are all my fantasies. Sometimes I don’t even believe myself, and find myself asking, “Could that really have happened?” Preserving the precious memories of this glorious and unique page of theoretical physics in the 20th century and making them available to Western readers seems to be more than timely. All the articles in this volume were written relatively recently and are virtually unknown in the West. Don’t ask why I chose these particular articles and not others. I picked the ones I liked, which held interest for me and which, in my judgment, Western readers would find instructive. There was no rigorous and scientific selection system. This volume is intended for a broad audience. At least the first (and largest) part requires minimal knowledge of physics, if at all. More technical reviews of scientific issues are collected in the final chapter, “Some Details for Experts.” The first chapter, devoted to Landau himself, plays a special role. The memoir literature on Landau is enormous. Here I could mention two books: Academician Landau by A.A. Abrikosov and Memories of L.D. Landau, edited by I.M. Khalatnikov. I made no attempt at a representative selection. Instead, to set the stage necessary for understanding the subsequent articles, I present in this chapter two recent essays, by B.L. Ioffe and S.S. Gershtein, respectively, which have never been previously translated into English. If not stated to the contrary, the footnotes in this book belong to me.

Acknowledgments First and foremost, I want to say thank you to all of this book’s contributors, especially to those who wrote articles expressly for this collection: L. Anselm, Alexander Larkin, Roman Nevzorov, Yu. N. May 13, 2013 16:8 WSPC/Trim Size: 9in x 6in for Proceedings 1c˙MShif˙intro

xxii M. Shifman

Ovchinnikov, Valery Pokrovsky, Andrei Smilga, Noemi Smorodin- skaya, V.G. Vaks, Andrei Varlamov, and P. Winternitz. I am indebted to Miron Amusia, M. Feigelman, Semyon Ger- shtein,G.Gorelik,BorisIoffe,D.Khmelnitsky,RomanKris,James Manteith, Vadim Matyushin, and Boris Shklovskii for valuable advice, assistance, and many communications. I am very grateful to A. Cherman, Denise Gabuzda, Milla Grin, A. Isaakyan, Petr Kravchuk, Vadim Matyushin, Julia Ny´ıri, Forrest Rhoads, Noemi Smorodinskaya, Thomas Whitney, and, especially, to James Manteith, who carried the main burden of translation from Russian. My deep gratitude goes to A. Cherman, Stephen Gasiorowicz, Ju- lia Ny´ıri, Jenny Ouchveridze, Noemi Smorodinskaya, and, especially, to Jennifer Cafarella, for proofreading parts of the manuscript and providing expert advice on English grammar. I am grateful to Alexei Kobrinsky, who was responsible for type- setting a part of this volume in LATEX. I am thankful to Marie Rahne and Ursula Becker, who handled all the financial aspects of this project. I owe much gratitude to the World Scientific Senior Editor Lakshmi Narayanan for her patience and continued encouragement. Special thanks go to Polina Tylevich, who worked hard to make this book visually appealing. The graphic design of the cover and throughout the book belongs to her. Previously published articles are reprinted with kind permission of the publishers: Phasis (Moscow), Fizmatlit (Moscow), Chapman & Hall/CRC (Boca Raton), Nauka (Moscow), Springer Verlag, Berkovich-Zametki po Evreyskoy Istorii, Turpion-IOP (Moscow), and URSS Publishers (Moscow).

February 2013

Disclaimer: The opinions expressed by the writers herein are not necessarily those of the Editor. May 15, 2013 10:58 WSPC/Trim Size: 9in x 6in for Proceedings 2a_PartI+Chap1-divider

PART I May 15, 2013 10:58 WSPC/Trim Size: 9in x 6in for Proceedings 2a_PartI+Chap1-divider

CHAPTER 1 May 15, 2013 10:58 WSPC/Trim Size: 9in x 6in for Proceedings 2a_PartI+Chap1-divider May 13, 2013 17:29 WSPC/Trim Size: 9in x 6in for Proceedings 2b˙Page4

Lev Landau (left) and Pyotr Kapitsa. For technical reviews see pp. 451 and 465. April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

LEV DAVIDOVICH LANDAU∗

BORIS IOFFE Institute of Theoretical and Experimental Physics B. Cheremushkinskaya 25, Moscow 117259, Russia ioﬀ[email protected]

Landau’s Theoretical Minimum I’ll start with how I became a student of Landau. In my third year at the physics department of Moscow State University I realized I wanted to be a theorist, but doubted whether I was suﬃciently talented. It seemed to me that David Kirzhnits, who studied in the same group as me, had more talent than me and could be one, but whether I could was unknown. Still, after some thought I signed up and was enrolled in the theory group. But the department of theoretical physics was weak (I knew this even then, in 1947): all the high-level theorists – Landau, Tamm, Leontovich – had been pushed out of it. Yet along the lines of Marxist-Leninist philosophy great experts remained, hostile to quantum mechanics and relativity. As my classmate Gertsen Kopylov said in his poem “Eugene Stromykin”: I was there when Lednev,a Gathering the professors’ qahal Kicked with an intrepid toe At Einstein, the lion gone senile.

And so, in the summer of 1947, I summoned all my courage and

∗Published in Russian in B.L. Ioﬀe, Bez Retushi, (Phasis, Moscow, 2004). Translated from Russian by James Manteith. aN. A. Lednev was a professor of mathematical physics at the Physics Department.

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6 B. Ioﬀe

took a decisive step: I phoned Landaub and asked if I could start taking his theoretical minimum exam. He told me to come by in the next few days. I passed the entrance exam in mathematics rather easily, and Landau gave me a typewritten program of the seven other exams (in fact there was also an eighth, mathematics II: complex variables, special functions, integral transforms, etc.). At that time the only books out yet in the Landau course were Landau-Pyatigorsky’s Mechanics, Landau-Lifshitz’s Field Theory, Mechanics of Continu- ous Media and the first (classic) part of Statistical Physics. All the other courses required study of various books and original articles, in many cases. The articles were in English and German; for instance, in the course on quantum mechanics there were two large articles – 100 pages apiece – by Bethe, from Annalen der Physik. That is, it went without saying that the exam-taker knew both languages. The exam took place as follows. A student would call Landau and say he wanted to take a test for a certain course (the order of testing for courses was more or less arbitrary). “Fine, come at this or that time.” The visitor had to leave any books, notes, etc. in the hallway. Then Landau invited him into a small second-floor room containing a round table with several sheets of blank paper, a chair and nothing else. Landau formulated the problem and left, but every 15 to 20 minutes he came and looked over the exam-taker’s shoulders to see what was done. If he kept silent, that was a good sign, but sometimes he said “Hmm” – and that was a bad sign. I have no personal experience of what happened in those cases when a student failed an exam. (I only know that re-testing was permitted.) I approached the dangerous line only once, while taking the statistical physics exam. I started solving a problem differently than Landau expected. Landau came up, peered over my shoulder, said “Hmm” and left. After 20 minutes he came back, took another peek and said “Hmm” in a still more displeased tone. Then Lifshitz dropped by on some business. He also had a look at my notes and yelled, “Dau, don’t waste time, get him out of here!” But Dau disagreed: “Let’s give him another 20 minutes.” During this time I got an answer, and

bHis friends and colleagues used to call him Dau. May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

Lev Davidovich Landau 7

the answer was correct! Dau saw the answer, took another look at my calculations and acknowledged I was right. He and Lifshitz asked me a few simple questions, and the exam was passed. The problems Landau assigned could be quite complex, and the student had to solve each of them in about an hour. (Typically the exam included one or two complex problems and a single easier one.) So exam preparation required a lot of practice in solving problems. To get this practice, I tried to find problems wherever I could. (After all, there were no problem books or collections of the problems now available in Landau’s Course in question form.) I asked Abrikosov, who had passed the theoretical minimum ahead of me, what problems he’d gotten – but not their solutions! – and I solved them. After several exams I discovered that Landau had a fairly limited supply of problems – sometimes he gave me the same problems he’d given Abrikosov. I think Landau realized that the exam-takers were telling each other which problems he assigned, but this didn’t bother him: to assess a student’s capabilities and knowledge, it was enough for him to see how a problem was solved. Here’s an example: a question on macroscopic electrodynamics. A dielectric ball with electric and magnetic susceptibilities ε1 and μ1 rotates with angular frequency ω in a medium characterized by ε2 and μ2 in a constant electric field E . The angle between the axis of rotation and vector E is equal to α. Find the electric and magnetic field inside the ball and in the medium. Now here’s an episode to characterize the level of teaching at the university compared to Landau’s minimum. In spring 1948 it was time to take the exam on quantum mechanics at the physics department. The course was lectured by Blokhintsev, but I didn’t attend his lectures. I studied quantum mechanics based on the minimum’s program and figured my level still wasn’t good enough to take the exam with Landau: I still had a lot of work to do. Once in the university courtyard I met Dmitry Shirkov, who was a student at the theory department. “I’m going to take the early quantum mechanics exam with Blokhintsev. Do you want to join in?” “Let’s go,” I said after a moment’s reflection. April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

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We passed the exam; I got a five, Shirkov a four.c But I could only pass the exam with Landau in September, after another three months of preparation. Passing the minimum took me almost two years. (During the same two years I did two scientific works advised by Pomeranchuk (Chuk).) In June 1949, after I passed the last exam, Landau included me in the list of his students. Not long – about two or three weeks – before the tragic car accident on January 7, 1962, that ended his creative life, Landau made a list of everyone who had passed the theoretical minimum. For the first twenty years, Landau held all the exams himself. However, since the number of people who wanted to take the minimum exam picked up sharply in the 1950s, sometime in 1954 or 1955, Landau decided to start holding only the first entrance exam in mathematics himself and have the rest held by his team from the Institute of Physical Problems (IPP) – Lifshitz, Khalatnikov, Abrikosov, Gorkov and others. Now, after many years, looking at this list, it is possible to say with certainty who among those who passed the theoretical minimum really achieved significance as a theoretical physicist and who stayed at an average level. And it so happens that a rather sharp boundary shows up around 1954-1955: there are significantly more well-known theorists on the left half of the sheet than on the right. A thought comes to my mind that the important thing was not only the content of the theoretical minimum and the selection of exam problems: there was importance in the role of the examiner. Probably during the exam Landau could see who was really talented and who wasn’t. His students apparently had a harder time in this. Well ... a great person is beyond replication. But Landau too sometimes permitted loopholes. Absent from the list of who passed the theoretical minimum exam is V. Khozyainov, who passed it in 1950 (or 1951). And this wasn’t forgetfulness on Landau’s part. Khozyainov studied at the physics department in the same class as me, but was older. During allocation among departments he didn’t go into theory, but applied to some other department

cFive corresponds to A, four to B. May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

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and was enrolled there. But when several students (myself included) transferred from the theory department to the “Structure of Matter” department (more on this below), the physics department administration decided the theory department needed reinforcement. “Re- inforce” always also meant “reinforce politically.” Khozyainov and another student were transferred to the theory department by special order. Khozyainov was a [Communist] Party member, perhaps even a member of the physics department’s Party Committee. That’s how he became a theorist. That he later passed Landau’s minimum surprised me greatly. I found out about this from Landau himself. Landau added that he planned to accept Khozyainov in the graduate program. I tried to talk him out of this, telling him how Khozyainov had gotten into theory and that I thought Khozyainov was weak as a physicist and personally rather shady. But this had no eﬀect on Landau, and he gave one answer to all my arguments: “He passed the minimum!” After some time (probably a year and a half to two years later), Landau gave me Khozyainov’s dissertation and asked for my opinion. The dissertation was on particle physics, but formal (I don’t recall its contents), and I assessed it rather sourly. Landau asked, “Is there any nonsense in it? It doesn’t contradict anything?” “No,” I answered, “but there’s not much content.” “Never mind, – said Landau. – Then it can be defended.” Khozyainov ﬁnished his defense, then commenced his zealous activities. Within a short time he became secretary of the Party Com- mittee of the Institute of Physical Problems. Remember, this was 1952 – the height of anti-cosmopolitanism,d that is, simply the height of the anti-Semitic campaign. In the IPP theory department headed by Landau the percent of Jews exceeded all permissible norms. In fact, in the department (besides Khozyainov) there was only one Rus- sian (based on his passport): Alexey Abrikosov, who actually was half-Jewish. To rectify this situation, the IPP authorities created a second theory department headed by V. A. Fock.e Fock greatly

dSee the last footnote, p. 34. eVladimir Aleksandrovich Fock was a Soviet physicist who did foundational work on quantum mechanics and quantum electrodynamics. April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

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disliked this role, but apparently couldn’t refuse. Khozyainov, as the Party committee secretary, took energetic action to replace Landau with Fock as the head of the entire theory department. (Conceivably, though, it wasn’t his initiative and he was only charged with carrying it out.) But his time for success ran out: Stalin died. A short time later, Khozyainov was ﬁred from IPP. Landau never mentioned him again.

Landau’s Seminar Being Landau’s student was a title that came with no privileges, just duties, since anyone could have scientific discussions with Lan- dau and get his advice. Only a few of those who passed the minimum became his graduate students. The right and simultaneously the responsibility of a Landau student was full-fledged participation in his seminar. But, again, anyone could participate in the seminar, ask questions and make comments. The duties of “full-fledged” seminar members comprised regularly making summary reports in alphabetical order at the seminar. After each seminar, Landau took the most recent issue of Physical Review (the journal wasn’t divided into sections then) and marked the articles the next speaker was to report on at the seminar. Typically there were 10 to 15 articles from very diverse branches of physics. Mainly these were experimental or half- experimental, half-theoretical articles. Sometimes there were short theoretical articles, such as letters to the editor. I remember how I gave an account of a Physical Review letter to the editor from Marshak and Tamor which presented the results of calculations of photoproduction of muons on the nucleon and the capture of muons in hydrogen in perturbation theory. The speaker not only had to summarize the article, i.e., present its basic idea and primary results, but also clearly understand how these results were obtained, cite all the necessary formulas and even experimental techniques and explain them to the audience. Most importantly, the speaker had to have his own opinion as to whether a given work was correct. In short, speakers bore the same responsibility for the works they reported on (and for these works’ errors!) as the authors. That held true for works in the most diverse of physics May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

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fields, from elementary particle physics and nuclear physics to the properties of metals and liquids. Landau had a special love for alum. He always marked articles on the properties of alum in Physical Review. So for us (at ITEP) “alum” became a catch-all word to refer to any less-than-interesting Landau seminar topic. (But I reported on alum-related articles conscientiously.) Landau knew each report topic thoroughly (despite the fact that he scarcely read any articles at all, only listened to their presentations) and asked questions requiring immediate and definite answers: generalities like “the author argues that...” were forbidden. The audience always included experts in the field, and they also asked questions and made comments. So making a survey of Physical Review was no easy task. Fortunately, this had to be done about twice annually. Sometimes, if Landau thought the speaker hadn’t given a sufficiently qualified account of the article, he interrupted him and asked him to go on to the next one. If this happened two or three times in the course of the report, Landau would exclaim: “You didn’t prepare for the lesson! Who’s next, Alyosha?” Alexei Abrikosov, the seminar’s secretary, was charged with following the list of speakers. In the worst case, if the same speaker was driven from the podium a few times, he faced ostracism: he was omitted from the list of participants and Landau refused to discuss anything with him, but of course he could still attend the seminar. I recall two such cases, and in one of them the speaker was the well- known physicist V. G. Levich, a future corresponding member of the Academy of Sciences. Other Landau students were also subjected to ostracism: Berestetsky, Ter-Martirosyan and even Pomeranchuk, but for different grievances, not for failings at the seminar. I’ll tell of this later. Only after much time had elapsed – about a year or even more – and only after one or two of the more respected participants had interceded for him, would the offender receive a pardon. Theoretical works were presented differently. A person, not necessarily a seminar participant, who wanted to speak at the seminar about a theoretical work (his own or from the literature) started by describing it to Landau. If Landau agreed with its main proposi- April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

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tions, the report was included in the seminar. During the report Landau made clarifying remarks, and quite often his explanations of the work strongly differed from the author’s perspective. A noisy debate ensued. Landau could often be heard to say: “The author himself doesn’t understand what he’s done!” In all cases Landau had a completely original understanding of the work, and it wasn’t easy for a typical person to follow his reasoning. I wasn’t the only one to find it took several hours, sometimes days, for me to understand the depth of his statements, which often shed light on a problem from a completely different side. A theoretical report freed a seminar participant from mandatory surveys of Physical Review. Pomeranchuk, for instance, never made the surveys and always reported on theoretical works. Reports on theoretical works were made not only by physicists from the Landau school but also by Tamm, Bogolyubov, Gelfand and many others. In the postwar period and until 1955 not one foreign physicist ever came to Moscow. Among the seminar participants were two exceptional people who didn’t fit the usual rules: Ginzburg and Migdal. Landau once said of Ginzburg, “Ginzburg isn’t my student, he just stuck to me.” And indeed, Ginzburg thought of himself as a student of Tamm. Nonethe- less, he was one of the Landau seminar’s most active participants. He didn’t subordinate himself to the standard rules for presenting surveys and so on. But he spoke often, and his every speech abounded with new facts and new ideas, presented with brilliance and wit. I still remember his report on supernovae with a historical preface about their observations in ancient Babylon, Egypt and China. And it’s no coincidence that the well-known phenomenological theory of superconductivity, the forerunner of many contemporary models of spontaneous symmetry breaking, was created by Ginzburg and Lan- dau. Another exceptional person was Migdal. He isn’t in the list of Landau’s students – he didn’t pass the theoretical minimum – but he was a full-fledged seminar participant. Only Migdal was allowed to be late for the seminar and still enter the hall through the front door. Typically the seminar began at the set time precisely down to May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

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the minute, but sometimes Landau said, “Let’s wait five minutes – these are the five Migdal minutes.” Once in the middle of a seminar the auditorium’s front door opened and a figure in a firefighter’s suit and firefighter’s helmet appeared in the doorway. “To the exits! Clear the premises, we’re holding fire-fighting training here!” the man said in a firm tone. Lifshitz jumped up from his seat: “Our seminar meets here every Thursday! You have no right!” “To the exits!” the man commanded still more firmly. People began rising from their seats and went to the doors. Then the fireman removed his helmet and the thread that tugged his nose upward – it was Migdal! In 1958, Landau and certain other seminar participants were highly enthusiastic about the new Heisenberg theory in which all particles arise from a universal fermion field. (Others, however, took a highly skeptical view of this theory.) At one seminar Landau received a letter through Pontecorvo, supposedly from Pauli, and Lan- dau read it aloud. In the brief letter, Pauli wrote that he liked Heisenberg’s theory, that he’d found new arguments in its favor and found it highly plausible. Moreover, wrote Pauli, the latest experiments with Λ hyperons confirm Heisenberg’s theory. No details were given about these experiments, though. There was great excitement: after all, Pauli was known as a person with a critical turn of mind, far from gullible. Different hypotheses were advanced; one young theorist even went up to the board and tried to imagine what the experiment could be that Pauli wrote of. Meanwhile, Migdal took the letter, read it carefully and said, “Something’s strange here. If you read the first letters of all the lines from top to bottom, it spells the Russian word ‘fools.’ What could that mean?” The secret was simple: The letter was written by Migdal and Pontecorvo.

Stories of the Creation of Some Works Work by Landau, Abrikosov and Khalatnikov

Immediately after enrolling at ITEP (1950) I started studying renormalization theory, Feynman’s technique. A. D. Galanin had tried to calculate radiative corrections in quantum electrodynamics April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

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(QED) using the old technique. He switched to the new Feynman technique and served for me as a kind of senior teammate. We learned how to calculate radiative corrections in QED and a meson theoryf – first in the lowest order of perturbation theory, and then in higher orders as well. I managed to build a precise system of coupled equations for the Green function in the meson theory. Then in a joint paper by A. D. Galanin and myself, the mass and charge renormalization was carried out in this system. We showed that the solutions in this system don’t have to contain infinities – they must be finite. However, when trying to truncate this system at any finite order, infinities appeared again: eliminating them required summing the entire infinite series. So this attempt wasn’t crowned with success, but we learned a lot. In calculating the first orders of perturbation theory, Galanin and I saw that in polarization operators and vertex functions at large virtualities p2, logarithms of the type ln(p2/m2) arise. In the first order it was ln(p2/m2), in the second order there were terms proportional to [ln(p2/m2)]2, in the third order [ln(p2/m2)]3, etc. Edwards’ article [1] was very instructive for us. Edwards built an equation for the vertex function in a ladder approximation and found that in the n-th order of perturbation theory there arise terms [e2 ln(p2/m2)]n. In the 1950s, Landau used to come to the Teplo-Technical Lab- oratory (TTL, now ITEP) every Wednesday. He took part – very actively – in the Wednesday experimental seminars held there, led by Alikhanov. After the seminar, Landau used to drop by a room of theorists where Galanin, Rudik and I were sitting then. All the other theorists gathered there as well, and discussions began, lasting about two hours. In one such discussion, Pomeranchuk, Galanin and I explained to Landau the situation with radiative corrections in quantum electrodynamics. From these conversations Landau got the idea of summing the leading logarithmic terms, that is, the terms containing [e2 ln(p2/m2)]n in QED. This was why Pomeranchuk, Galanin and I were acknowledged in the first Landau, Abrikosov and Khalatnikov’s

f Apparently the author means the scalar QED. May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

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paper. (Landau was sparing with acknowledgments and only expressed them to those who’d really contributed something significant to his work.) Initially, when Landau formulated the idea, his concept was that summing the leading logarithms in QED gives rise to what is now called asymptotic freedom – interaction decreasing with the growth of p2. These expectations were formulated in the first of the series of works by Landau, Abrikosov and Khalatnikov, sent to press even before the final results were obtained. When Landau came to the Teplo-Technical Laboratory on Wednesdays, he talked about how the calculations were going. The main ideas (turning the integration contour, the introduction of a cutoff, choice of an appropriate gauge, etc.) belonged to Landau, but technically Abrikosov and Khalat- nikov did all the calculations – Landau himself had a poor grasp of Feynman technique. Their results confirmed expectations: the effective charge in QED decreases with increasing energy. Galanin and I decided to repeat these calculations. We wanted to apply the same idea in our system of renormalized equations. (We did this with Pomeranchuk later on.) However, the calculation of the very first loop led to the opposite result: the effective charge didn’t decrease but grew with the growth of energy! The next Wednesday we told Landau about this and convinced him we were right. The last in the series of Landau, Abrikosov and Khalatnikov’s works, which the authors already planned to send to press, contained a sign error that radically changed all the conclusions – instead of asymptotic freedom there appeared a zero charge. According to S. S. Gershtein (who worked at the Institute of Physical Problems then), upon returning from the TTL after this seminar, Landau said, “Galanin and Ioffe saved me from disgrace.” Gershtein described this episode in his recollections. A year or two after the publication of the Landau, Abrikosov and Khalatnikov works, following the publication of the Landau and Pomeranchuk article containing a more general proof of zero charge, Landau received a letter from Pauli. It said that Pauli’s student Wal- ter Thirring had found an example of a theory without zero charge: a scalar theory of the interaction of mesons with nucleons. The letter April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

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was accompanied by Thirring’s manuscript. Dau gave this article to Chuk and Chuk to me, with a request to look into it. I studied the article and came to the conclusion that it was incorrect. The mistake came from using the Ward identity, which arises in diﬀerentiation of the mass of the nucleon, and which was broken by renormalization. I told this to Chuk. “You found a mistake, you should write Pauli about this,” said Chuk. It scared me to think of writing to Pauli himself that his student had done incorrect work and that he, Pauli, hadn’t noticed! But Chuk insisted, and in the end I wrote Pauli a letter. I got an answer not from Pauli but from Thirring. He fully acknowledged his error. The article never appeared in print.

Works on nonconservation of C, P ,andT

In 1955-1957 everyone was excited about the mystery of θ-τ.The decay of K-mesons into two or three pions was experimentally observed. Given the conservation of parity, which was then considered sacred, the same meson couldn’t simultaneously decay in two or three pions. Therefore most physicists thought these were different mesons, θ and τ. With refinement of the experiments, however, it became clear that their masses coincide. In the spring of 1956, Lee and Yang presented their revolutionary article putting forth the hypothesis on the parity nonconservation of weak interactions, explaining the θ-τ mystery and calculating the effects of parity violation in the β decay and the decay chain π → μ → e. Landau categorically denied the possibility of parity violation, saying, “Space cannot be asymmetric!” Pomeranchuk had a greater liking for the hypothesis of parity-degenerate doublets of strange particles, rather than P violation. A.P. Rudik and I decided to calculate some other effects based on the assumption of parity nonconservation, apart from those examined by Lee and Yang. Our choice settled on β-γ correlation. I made an estimate and found that the effect should be large. Rudik began detailed calculations. After a while he came to see me and said, “You know, the effect is zero.” “That can’t be!” I said. We sat down to figure things out, and I saw that Rudik, as an educated theorist, had imposed a condition of May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

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C invariance when he wrote the weak interaction Lagrangian, which caused the constants in the parity-nonconserving terms to be purely imaginary. Lee’s and Yang’s constants were arbitrary complex numbers. (If the constants are assumed to be purely imaginary, all these parity nonconserving effects are lost.) The question of a connection between C and P invariance came up. I discussed this question with Volodya Sudakov, and as we talked we recalled a work by Pauli. I had read this work before, but had completely forgotten about it. This was partly due to Landau’s skepticism about the given work: he saw the CPT theorem as a kind of trivial relation satisfied by any Lagrangian. I would like to note that the Lee and Yang paper says not a word about the CPT theorem or the connection between C, P and T invariance. I read the Pauli article again, carefully now, and it immediately became clear that along with the parity violation, there must also be a violation of either C or T , or both. Then came the following idea: two K0 mesons with strongly different lifetimes can only exist given that at least one of the symmetries, C or T , is valid at least approximately. Rudik and I considered a number of effects and saw that P -odd pair correlations of spin and momentum (the terms ∼ σp) appear given C violation and T conservation; otherwise they are absent. (In a subsequent work I proved this theorem in a general form, and also found the type of P -odd terms corresponding to T -violation.) We wrote a paper, and I described it to L. B. Okun. Okun very helpfully remarked that analogous effects, differ- entiating between C-invariant and T -invariant theories, also appear in K0 meson decay into π mesons. We included this remark in the article, and I suggested that Okun become a co-author. He at first refused, saying that such a remark deserves only an acknowledgment, but in the end I persuaded him. After this, Pomeranchuk was told of our work. Pomeranchuk decided we had to tell Dau about the work right away, the next Wednesday. On Wednesday Dau initially refused to listen: “I don’t want to hear about parity nonconservation. It’s nonsense!” Chuk persuaded him: “Dau, be patient for just 15 minutes, listen April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

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to what the young people have to say.” Dau reluctantly agreed. I spoke for a short time, perhaps half an hour. Dau kept silent, then left. The next morning Pomeranchuk phoned me: “Dau’s solved the problem of parity nonconservation. We’re meeting with him right away.” By then both of Landau’s works – on the conservation of combined parity and on the two-component neutrino – were ready with all computations and formulations. Our paper and Landau’s papers were sent to press prior to the experiments by Wu et al. with the discovery of electron asymmetry in the decay of polarized nuclei, i.e. this was the discovery of parity nonconservation. Our results implied that charge parity was not conserved in the β decay either. A corresponding statement was added as our work was being proofed for publication. A similar assertion was made in the work by Wu et al., where the authors cited a work by Lee, Oehme and Yang done later than ours. In their Nobel lectures, Lee and Yang noted our priority in this matter. Unfortunately, the tale of the creation of these Landau works on parity nonconservation ended with a distasteful episode, unpleasant to mention, but without which the story is incomplete. Literally a few days after Landau sent his articles to Journal of Experimental and Theoretical Physics, he gave an interview to a correspondent of Pravda,g which immediately published it. In this interview, Landau talked about the problem of parity (non)conservation and how he had solved it. There was no mention of the work of Lee and Yang (not to mention our own). All the TTL theorists were outraged by this interview. Berestetsky and Ter-Martirosyan went to Landau and let him know what they thought about it. The result of their actions was that they were both expelled from the seminar. I didn’t voice my opinion directly to Landau, but expressed it in conversations with his colleagues, who apparently relayed it to Landau. Landau punished me diﬀerently: he removed my name from his article’s acknowledgments, leaving only Okun and Rudik. This was more than Pomeranchuk could take. He went to Landau and told him (as Chuk

gThe main Soviet newspaper associated with the Central Committee of the Communist Party of the Soviet Union. May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

Lev Davidovich Landau 19

himself told me): “Boris explained everything about C, P and T to you. You wouldn’t have done your work without him, and you’re removing his name from the acknowledgments!” I don’t know Landau’s reply, but he settled for a compromise: he restored my name to the acknowledgments, although not in alphabetical order, but second. Landau considered CP conservation to be a precise law of nature and wouldn’t accept its violation. He said the same thing about CP and space asymmetry as he had earlier about parity violation. I constructed an example of a Lagrangian in which CP was violated but nothing happened to the vacuum, and tried to change his mind, but he didn’t want to hear about it.

The range of applicability of the theory of weak interactions

Starting in 1958, when Gell-Mann and Feynman, and Marshak and Sudarshan formulated a universal four-fermion theory of weak interactions, I became interested in the issue of higher-order corrections in this non-renormalizable theory. The idea was that due to higher-order corrections in the weak interaction, a series of observable effects ought appear, while their absence in the experiment would make it possible to establish the upper limit of the range of applicability of the theory of weak interactions. It was assumed that the momentum integration in loops with virtual hadrons converges due to a strong interaction, making it unnecessary to consider diagrams with virtual hadrons: their contribution was presumed to be small. In my 1960 work [2] one such effect was considered: the decays μ → eγ and μ → 3e, as well as corrections violating the equality of the β-andμ-decay constants. At the time people believed in the existence of a single neutrino and that the μ → eγ decay was not forbidden. The strongest constraint on Λ ≤ 50 GeV arose namely from this decay. However, when it became clear that electron and muon neutrinos are different, this constraint disappeared. Since no constraints appeared in the examination of purely leptonic processes, and since it was commonly thought that the cutoff in virtual hadron April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

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loops occurs through strong interactions, there was an impression that this path held little promise. In my 1966 work [3] I established that, given the current algebra, strong interactions do not cut off amplitudes with virtual hadrons in certain cases (this concerned corrections to the β-decay constant due to weak interaction in a theory with an intermediate boson). E. P. Shabalin set a question before me: couldn’t this technique be used for examining weak neutral currents, where the experimental constraints are very strong? Jointly with Shabalin, in a theory featuring only ordinary and strange particles (i.e. only u, d and s quarks) + − we examined the KL → μ μ decay amplitude and the KL − KS mass difference; we showed that, given the current algebra, the weak interactions loops could not be cut off by strong interactions. We − calculated the KL → μ+μ amplitude and the KL − KS mass difference in the order G2Λ2. The strongest constraint on the cutoff parameter Λ ≤ 5 GeV arose from the KL − KS mass difference. In quark language this meant that the theory of weak interaction with u, d and s quarks changes its form at very low energies E ≤ 5GeV. This assertion was the starting point for the Glashow, Iliopoulos and Maiani hypothesis on the existence of a charmed quark c,aswas mentioned by Maiani in some historical talks. Glashow, Iliopoulos and Maiani introduced it in such a way that the c-quark contribution compensated for the divergent terms coming from the “old” u, d and s quarks (the so-called GIM mechanism). We reported on our work at a seminar in ITEP, released a preprint, and the article was published in the Soviet Journal of Nu- clear Physics. Some time later, L. B. Okun traveled to a conference in the United States. Upon his return, he spoke at a theory group seminar on the new things he had learned at this conference. The main news was a relation for the KL − KS mass difference obtained by Gell-Mann, Goldberger, Low and Kroll who carried out a calculation of weak interaction corrections. In the formula, which he wrote on the board, I recognized our formula; they coincided exactly. (Strictly speaking, both our formula and theirs presumed a vacuum state saturation. Besides that, we had calculated the next- to-leading contribution due to a single-pion state and shown that it May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

Lev Davidovich Landau 21

was small.) After the seminar, I showed Lev Borisovich our already published work and reminded him he had been present at the seminar where I had talked about it. He advised me to send a letter and a copy of the article to Low, who had presented the work at the conference. In his reply, Low acknowledged that we had done the same thing they had done, but significantly earlier. As a result, the Gell-Mann, Goldberger, Low and Kroll article never appeared in print. In his survey article on the subject, Low cited our work without mentioning his own. In connection with this activity, I received an invitation from Marshak to present a paper at the international conference “Particles and Fields” in Rochester in 1967. There was an intriguing story behind this invitation. In the summer of 1967, Marshak participated in a conference organized by the Ukrainian Academy of Sciences and held in Yalta. The Chairman of the Organizing Committee was N.N. Bogolyubov and the conference organization was high-end in the sense of comfort, service, etc. At the same time, a strict hierarchy was maintained among the guests: who got black caviar, who got red, and who got exclusively cervelat. Gribov and I also took part in this conference, and we had many discussions with Marshak. (I had known Marshak since 1956, when he had first come to Moscow.) During one of these discussions, Mar- shak said he would send us both invitations to the “Particles and Fields” conference, which he was organizing. “But we won’t be allowed!” we said. “I’ll also invite Bogolyubov and set a condition that all three of you have to come. If you’re not allowed, I’ll revoke Bogolyubov’s invitation.” Marshak’s trick worked. I started going through the formalities and reached a very high level, which I’d never reached before. I wrote a conference paper in which I presented our results on the + − KL → μ μ amplitude and the KL − KS mass difference and a number of other things. At the last minute I was barred from going to the conference, but Gribov was allowed to go. Marshak found himself in a difficult position: he could revoke Bogolyubov’s invitation, but then Gribov wouldn’t go either. He compromised: Gribov went, and I didn’t. Gribov agreed to present my paper on my behalf. However, April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

22 B. Ioﬀe

he didn’t like the part concerning the KL − KS mass diﬀerence, particularly the hypothesis on the vacuum state saturation – so he set a condition that this part had to be discarded. I had to consent. As a result, this part remained less well-known in the West, which led to an analogous work being done by Marshak, Mohapatra and Rao, albeit much later.

Landau’s Personality Many have written on Landau (see, e.g., [4-9]). Seeking to avoid repetition, I’ll try to say here only what, in my opinion, not enough has been said about. The thing is that for Landau, creating a school, the seminar and much more had one aim: supporting the scientiﬁc level of physics. What was important for him was not his school, not having a large number of students who revered him as a “maestro” (as Pomeranchuk sometimes called him), but having his students always at the forefront of science. He felt no need at all – moreover, this ran counter to his nature – for any of his students to have top science careers, to move into directorial posts. Even after his accident, when Landau was ill and reacted weakly to everything around him, someone once came to see him and said, “Dau, your student has become a director.” “My student,” answered Dau, “could never be a director.” Outward signs of servility toward the Teacher were alien to Landau, so much so that I can’t even imagine how he’d have responded if someone had displayed them – probably he’d have shown him the door. In this he was the direct opposite of certain heads of other schools. Landau felt his personal responsibility – a kind of “white man’s burden” – for maintaining science at a high level. He didn’t keep silent, as the majority do now and as is accepted in the West, when a speaker made inaccurate statements in his presence. Landau’s very existence supported this level: few would risk coming forward with a raw and ill-conceived idea, fearing Landau’s criticism. Pomeranchuk once said: “You can’t imagine the tremendous sanitation work Dau did in theoretical physics.” If for some reason Dau didn’t want to publicly criticize a lecturer, May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

Lev Davidovich Landau 23

he simply didn’t come to his lecture. This was the case with Rumer’s lecture on 5-optics, which Rumer gave upon returning to Moscow after many years spent in prisons and exile. Dau liked Rumer, but he viewed the works on 5-optics as incorrect and didn’t come to his lecture. E. L. Feinberg gives a marvelous description of this episode [7]. Landau’s exactingness toward keeping science at a high level was not incompatible with a relatively modest self-assessment. He saw himself as a second-class physicist and clearly distinguished between problems he could and couldn’t solve. A typical Landau aphorism was: “How can you solve a problem when you don’t know its answer in advance?” In the class of problems to which he limited himself, Landau had no difficulty in solving problems: the difficulties were only in their formulation. In the fact that Landau wouldn’t take on problems whose answer he couldn’t know in advance lay not only his strong side but also a weak side. By the same token, he would refuse to try to solve problems he saw as out of his league. It seems to me that as a result of such a modest self-assessment Landau didn’t do all he might have done (particularly in quantum field theory). Landau’s whole demeanor didn’t conform to the commonly accepted image of a solid Academician. Pomeranchuk could tell him, “Dau, you’re talking nonsense!” and Dau would take this quite calmly, but of course would demand convincing proofs. Since the founding of ITEP (which started off as Laboratory No. 3 of the USSR Academy of Sciences, then became the Teplo-Technical Laboratory), Landau made regular visits to ITEP on Wednesdays for the experimental seminar led by Alikhanov, and then would stay for an hour and a half or so to talk with the theorists. Throughout 1946 he was head of the Theory Laboratory, then Pomeranchuk became head while Landau stayed on, moonlighting as a part-time employee. This continued until 1958, when moonlighting was banned and Lan- dau was let go. (Zeldovich, who had also been moonlighting, was let go at the same time.) The Wednesday talks, in which all the theorists took part (there weren’t many of us then, just five to seven in April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

24 B. Ioﬀe

all) were highly varied and free, touching on a broad range of issues, from physics to politics and literature, and for us young people they were utterly captivating. I remember once in 1950 the conversation turned to the rules of voting in the UN Security Council (none of us had a copy of the UN Charter). Landau suggested, “Let’s bet for cake!” I agreed, with Chuk as witness. The following Wednesday I brought the UN Charter andshowedittoDautoprovemyselfright.ButDauimmediatelyre- torted, “That’s just what I said!” Chuk diplomatically said he didn’t remember who’d claimed what. Some time later Dau and I argued again, and he again proposed betting for cake. “But you won’t give it up,” I blurted out. Quite unexpectedly Dau took offense, and he nursed this offense for quite some time. Then I rued my words: I’d crossed some kind of limit. Back to characterizing Landau’s personality: I think that inner modesty, or rather, even timidity, may have typified his character. He understood his weakness and tried to fight it, especially in his youth, but this spilled over into shock tactics. I agree with E. L. Feinberg [7] that it was as if he had two essences (I dislike the word “mask” in Feinberg’s book [7]): the outward one was sharp and cocky, and the inner one was soft, timid, easily wounded. This duality in Landau influenced his relationships with women, which were described (albeit with extreme distortions) in his wife Kora Drobantseva’s book [8]. (In my opinion, the book is revolting. To characterize the author, I’ll mention the following. After Landau’s car accident, when he was between life and death, physicists formed a brigade whose members kept watch around the clock in the hospital and organized delivery of medicines, doctors, special nutrition, etc. They received instructions from Evgeny Mikhailovich Lifshitz and his wife Elena Konstantinovna, who both essentially led the fight for his life. Each shift was headed by a responsible attendant. As one of those with this responsibility, I kept watch at the hospital once every three to four days. I can categorically state that during the first month and a half Kora never appeared at the hospital. Not once! She showed up the first time a month and a half after the accident, when it became clear that Landau would live.) May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

Lev Davidovich Landau 25

In her book, Kora portrays Landau as a sort of Don Juan or something worse. It seems to me that although she lived with Dau for many years, she never managed to understand her husband’s nature. A. S. Kronrodh succeeded much better with this. He once introduced Landau to a lady who, if not a woman of easy virtue, in any case came close to that deﬁnition. Some time later Kronrod inquired, “So, did you get anywhere with that lady?” “What do you mean?” Dau replied. “She was untouchable!” Explaining this story, Kronrod said, “It wasn’t that the lady was untouchable, but that Landau was inwardly timid, and the experienced lady immediately felt this.”

***

Now on to other subjects. In conversations and seminars, Landau liked to speak aphoristically. These were his own aphorisms, and he sometimes repeated them. Many took a scornful view of his aphorisms: “Ah, playing the same old record again!” In fact, his aphorisms held a deeper meaning. Landau understood that it’s hard to argue with an aphoristic expression, and that this is the best way to end a useless debate that otherwise would go on indefinitely. Here are a few such aphorisms. Landau thought there was a lot of stupidity out there (in science and life) and not much intelligence. One aphorism thus went as follows: “Why are singers stupid? It’s a different principle of selection.” Here’s another, a good fit for the present day: “People who hear of some extraordinary phenomenon start proposing to explain it with improbable hypotheses. First consider the simplest explanation: that it’s all nonsense.” Finally – and with great relevance for today – Landau believed that a leader in science absolutely has to have his own generally accepted scientific results. Only then does he have the moral right to lead people and set problems before them (and, I’ll now note, to give recommendations to the political administration). Landau used to say:

hAlexander Kronrod (1921-1986) was a Soviet mathematician, Head of the ITEP Math- ematical Department in the 1950s and ’60s. April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

26 B. Ioﬀe

“No scientiﬁc career can be based on decency alone – this will inevitably lead to a lack of both science and decency.” One wants to expand on these words now: No scientiﬁc career can be based solely on organizational skills without like consequences.

The Leaflet On April 27, 1938, Landau was arrested. After spending exactly a year in the NKVD’s Lubyanka prison, he was released on April 28, 1939, after Pyotr Leonidovich Kapitsa courageously interfered.i In Landau’s file, which science historian G. E. Gorelik [9] managed to read in the KGB archives, the main charge against Landau concerned “participation in an anti-Soviet group that existed at the Kharkov Institute of Physics and Technology, and subversive activity.” But another part of the case involves a leaflet written by Landau’s friend M. A. Korets and approved by Landau. He acknowledges this in his depositions made in prison. The leaflet was written (in late April of 1938) on behalf of a non-existent Anti-Fascist Labor Party. It was supposed to be distributed during May Day celebrations. The leaflet’s content is astounding. It says the “Stalinist clique has carried out a fascist coup d’etat,” compares Stalin with Hitler and Mussolini, calls the workers to overthrow the fascist dictator and his clique, and to join a (non-existent!) Anti-Fascist Labor Party. (Gorelik [9] gives the leaflet’s full text, Feinberg [7] provides an abbreviation.) Landau’s case contains only a typewritten copy of the leaflet; Gorelik saw no original. Such a leaflet in those days presumed immediate execution; executions took place for much less, and here Landau was released after a year, while Korets also got a relatively light sentence (10 years in the camps, plus an extension for another 10 years) and lived up to the 1980s. In Landau’s case, the leaflet

iP.L. Kapitsa wrote the following statement addressed to the NKVD authorities: “I ask you to release from custody, under my personal guarantee, the arrested Professor Lev Davidovich Landau. I guarantee to NKVD that Landau will not engage in any counter- revolutionary activities in my Institute, and I will take all reasonable measures to prevent him from counter-revolutionary work outside the Institute. If I notice that Landau makes any statements aimed at harming the Soviet government, I will immediately inform the NKVD authorities.” May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

Lev Davidovich Landau 27

doesn’t figure as the main grounds for the accusations (the main charge is subversive activity), but in supplement to them. A question arises: was the leaflet fabricated through NKVD forgery? No one doubts, of course, that the NKVD were great masters at this kind of thing. Gorelik [9] answers this question in the negative, and Feinberg [7] agrees with him, while for Ginzburg [6] the question remains unclear. Gorelik’s main argument was that in the 1930s Landau had a Communist vision: he believed that science could only develop successfully under the Communist system, and that the way to science was open to all young talents from all layers of society. According to Gorelik, in 1937, after seeing the mass arrests, Landau realized the existing system had nothing in common with the one he, Landau, had imagined, and he decided to fight this system. This account strikes me as naive. Landau was above all a rational person. He introduced a rational approach to everything, even where it was totally unwar- ranted; the whole story of his life speaks of this. He knew perfectly well that his closest friends – M. L. Bronshtein, L. V. Shubnikov and many other physicists – had been arrested in 1937 and vanished without a trace in the NKVD torture chambers. Landau moved from Kharkov to Moscow in February 1937 to save himself from inevitable arrest. (He suspected that he was being monitored in Moscow as well; see [9].) He couldn’t help but realize that the leaflet, if distributed (it basically existed in a single copy, if it existed at all) could lead to nothing but its authors’ arrest. As for what would become of them afterward, there would have been nothing to hope for. Only someone set on martyrdom could have elected to prepare and distribute such a leaflet. Landau wasn’t that kind of person; he was more like a hedonist. And of course Landau was hardly stupid enough to not foresee all the consequences. I thus don’t think Landau could have taken part in preparing the leaflet in even the slightest degree. I also don’t think Korets could have approached him with any such proposal: based on evidence from people who knew Korets, he loved Landau and of course would have understood the danger he was exposing him to. The following possibility seems more plausible to me. In prison, April 5, 2013 14:4 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioffe-Landau-Mant

28 B. Ioﬀe

Korets was forced to sign a confession that he had written the leaflet and that Landau had approved its text. It’s also probable that the leaflet was actually written by the examiner. Then the leaflet and Korets’ confession were shown to the already broken Landau, and he also confessed his part in preparing the leaflet. This doesn’t seem at all surprising, since in his own handwritten deposition Landau con- fesses his anti-Soviet activity and much, much more. (The masters at the NKVD knew how to extract confessions. There’s a known instance of one prisoner confessing that he blew up a bridge over the Volga. Many years later, set free and having gone there, he saw the bridge intact and unharmed: no one ever blew it up.) In the 1970s, already released, Korets got to talking: he said that yes, he had written the leaflet. Possibly, though, it was easier for him to say this than to confess he’d signed the deposition under torture. When Korets was released in the 1950s, Landau helped him. There’s no contradiction in this, either: Landau knew from his own experience how a confession was beaten out of Korets. I myself once heard Lan- dau say, “If I’d spent another two months in jail, I wouldn’t have survived.” The question remains: why did the NKVD need a leaflet that didn’t figure as the main grounds of accusation? There may be varying hypotheses. Here is one. At first, one alternative for a case was examined that could have involved a large open trial of scientists. Such a trial would have needed tangible proofs. Then these ideas were abandoned. Perhaps the letters Stalin received from Western scientists in Landau’s defense played a role here. A policy shift may have occurred with the brief thaw during Yezhov’s replacement by Beria; Landau was arrested under Yezhov, his testimony is dated Au- gust 8, 1938 (still under Yezhov) and his case was apparently to be considered later. (For comparison, Beria was appointed head of the NKVD in November of that year.) What is the truth? The secrets of Lubyanka remain secrets today.

References 1. S. F. Edwards, Phys. Rev. 90, 284 (1953). 2. B. L. Ioﬀe, JETP 38, 1608 (1960). May 13, 2013 15:33 WSPC/Trim Size: 9in x 6in for Proceedings 2c˙Ioﬀe-Landau-Mant

Lev Davidovich Landau 29

3. B. L. Ioﬀe, JETP Lett. 4, 332 (1966). 4. Memories of Landau, Ed. I. M. Khalatnikov, (Nauka, Moscow, 1988). 5. A. Livanova, Landau, (Znaniye, Moscow, 1983). 6. V. L. Ginzburg, On Science, Myself and Others, (Fizmatlit, Moscow, 2003). 7. E. L. Feinberg, Epoch and Personality, (Nauka, Moscow, 1999). 8. K. Drobantseva-Landau, Academician Landau: How We Lived,(Zakharov ACT, Moscow, 1999). 9. G. E. Gorelik, My Anti-Soviet activities... One year in the life of Landau, Priroda, 1991, 11, 93-104. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

LANDAU AS I KNEW HIM∗

S. S. GERSHTEIN Institute for High Energy Physics Protvino, 142281 Moscow Region, Russia [email protected]

An “Ardent Communist” Landau was never a member of the Party.a He was called an “ardent Communist” by the father of the American hydrogen bomb, Edward Teller, who became acquainted with Lev Davidovich during their joint visit to Copenhagen with Niels Bohr. Explaining his intention to work on the hydrogen bomb, Teller named among his reasons the “emotional emphasis when my good friend, the excellent physicist, Lev Landau, was jailed by Stalin. I had known him in Leipzig and Copenhagen as an ardent Communist. I was pushed to the conclusion that Stalin’s Communism was not much better than the Nazi dictatorship of Hitler” (see [1], Vol. 1, p. 547). Teller had every reason to consider Landau an “ardent Commu- nist.” In private conversations, in a speech at the student dormitory, in newspaper interviews, at that time Landau spoke admiringly of the revolutionary changes in Soviet Russia. He told of how in Soviet Russia the means of production belonged to the state and the workers themselves, freeing the USSR from exploitation of the majority by the minority, with each person working instead for the whole country’s benefit, with great attention paid to science and education, with an expanding system of universities and scientific institutions, and significant amounts of funding for student stipends (see the articles

∗This is the second part of the paper published in Priroda, 2008, Issue 1, p. 15. Trans- lated from Russian by James Manteith. For the ﬁrst part see p. 451. aCommunist Party of the Soviet Union, the only party that existed in the USSR.

30 April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

Landau as I Knew Him 31

by H. Casimir and J.R. Pellam in [2]). He sincerely believed the revolution would eradicate all bourgeois prejudices, which he treated with great contempt, as well as undeserved privileges. He naively thought humankind faced a bright future, such that each person was simply obliged to organize his life to be happy. And he asserted that happiness lies in creative work and free love, where both partners have equal rights and live without any bourgeois holdovers, pettiness and jealousy, going their separate ways if love has passed. He thought the family should be preserved, though, for the sake of child-rearing. Such views were actively disseminated in the 1920s by certain revolutionary intellectuals like the well-known Alexandra Kollontai.b Landau also retained the enthusiasm of a builder of a new society after returning to his country, although the reality of his surroundings could have caused doubts. After all, he moved to Kharkov in 1932 and lived there during the terrible famine in the Ukraine. But namely at this time he set himself the task of making Soviet theoretical physics the world’s best. Pursuing this goal, he conceived and began writing his wonderful “Course,”c gathering talented youth and creating his famous school. At the time he also wanted to write a physics textbook for schoolchildren. This unfulfilled wish stayed with him for the rest of his life. He attributed the repressions of 1937 entirely to the dictatorship of Stalin and his clique. “The great cause of the October Revolution has been vilely betrayed. The country is awashinfloodsofbloodanddirt”–sobeginstheleaflet,composed, as stated in the Landau case file,d with his participation [3]. Fur- thermore, “Stalin... has become like Hitler and Mussolini. To save

bAlexandra Kollontai (1872-1952) was a prominent Communist radical revolutionary. In 1923, Kollontai was appointed Soviet Ambassador to Norway. Also known for her unflinching advocacy of free love. cKarl Hall, “Think less about foundations: A Short Course on the Course of Theoretical Physics of Landau and Lifshitz”, in Pedagogy and the Practice of Science: Historical and Contemporary Perspectives, Ed. David Kaiser, (MIT Press, 2005), p. 253. dOn April 27, 1938 Landau was arrested by the NKVD. He was released a year later thanks to Kapitsa’s appeal to Stalin, see footnote, p. 26. Landau’s arrest and interrogation file was declassified and became available to historians only 60 years later. A KGB briefing concerning Landau prepared for the Central Committee of the Communist Party in the early 1960s was found in Central Committee’s secret archive and published a few years earlier. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

32 S. S. Gershtein

his power, Stalin is destroying the country and making it easy prey for rabid German fascism.” The last words are prophetic. The Stalin system’s obliteration of the Red Army’s top command personnel, of industrial leaders and talented structural engineers was paid for by the country with the tragedy of the initial stages of the Great Patriotic Ware and the loss of millions of human lives. The leaflet summoned the laboring class and all working people to a decisive struggle for socialism against Stalin’s and Hitler’s fascism. The leaflet clearly reflects Landau’s convictions. However, some people who knew him doubt that he actually took part in composing it. Essentially, they argue that Lev Davidovich, with great successes in science, seeing it as his vocation, could hardly be unaware of the deadly danger of taking part in fighting Stalin’s regime. In my view, these arguments are misguided. I think the case file for the most part correctly reflects the history of the leaflet’s appearance. Landau’s longtime friend and former assistant M. A. Korets approached him with the text. Landau made revisionsbutrefusedtohaveanythingtodowithwhatevercame next. Although the text of the leaflet shown to Landau during his questioning is in Korets’ handwriting, its formulations’ clarity and conciseness are typical of Lev Davidovich’s style and convincingly attest to his co-authorship. A different matter is whether Korets had the moral right to draw Landau into this hopeless and deadly escapade. Was he aware that he was putting the life of a genius at risk? Could all this have been a provocation that Korets himself was mixed up in? (Landau and Korets were arrested five days after the leaflet was written.) The term in jail, which lasted exactly a year, led Landau to ex- ercise greater caution but in no way altered his socialist views and national loyalty. He actively participated in the military buildup during the Great Patriotic War (this earned him his first decoration, in 1943). Starting in the first half of 1943 (that is, practically from the very start of the atomic project), he began to perform different

eThe term Great Patriotic War is used in Russia to describe the period from 22 June 1941 to 9 May 1945 of World War II. Germans invaded Soviet Union on 22 June 1941. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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tasks for this project ([1], Vol. 1, p. 31), and in 1944, I.V. Kurchatov wrote a letter to Beria indicating the project’s need for Landau’s full involvement ( [1], Vol. 1, p. 244). A memo from A. P. Aleksandrov shows that in March 1947 Landau had completed the theory of “nuclear piles” and jointly with Laboratory No 2 f and the Institute of Chemical Physics was doing work on developing critical-mass reactions. It’s also noted that he was directing a theoretical seminar at Laboratory No 2 ([1], Vol. 2, p. 90). Some historians of science of the post-perestroika era speculate that Landau was forced to participate in the atomic project solely for the cause of self-preservation. This may have been the case in the final years before Stalin’s death, when tensions were mounting inside and outside the country and Lev Davi- dovich had to work on other people’s orders. But this wasn’t true of the first post-war years. There is evidence of this in speeches made by Landau himself, whom no efforts could make say other than what he thought. In a speech prepared for central radio broadcast in June 1946, Lev Davidovich, not usually prone to rhetoric, writes, “Russian scientists have contributed to solving the problem of the atom. The role of Soviet science in this research is continuously increasing. The new five-year plan and the program of economic recovery and development include experimental and theoretical projects which should lead to nuclear energy’s practical use for the good of our country and the benefit of all humanity” [4]. After Stalin’s death, Landau hoped the country would revive the socialist principles he believed in. “We shall see the sky sparkling with diamonds,” he quoted Chekhov. “Dau, where are the diamonds?” he was teased several years later by his sister Sofia Davi- dovna, an incredibly smart and beautiful woman, a true Leningrad intellectual who graduated from the Institute of Technology and helped establish titanium production in our country. Landau supported Khrushchev’s criticism of Stalin. He said, “Don’t blame Khrushchev for what he didn’t do before, during Stalin’s life, but

f Laboratory No 2 was the code name for a nuclear research institution in Moscow. Later it became the Laboratory of Measuring Devices, then the I. V. Kurchatov Institute of Atomic Energy. Currently the Russian Research Center Kurchatov Institute. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

34 S. S. Gershtein

praise him for what he’s determined to do now.” At a reception in the Kremlin, Aleksandrov took Lev Davidovich to speak with Khrushchev, and as Dau told it, they showered each other with compliments. One well-known physicist, close to Landau’s circle, said several years ago that Landau had been “cowardly.” I couldn’t believe this newspaper interview, taking the statement to be a journalistic error. But soon I heard the same appraisal expressed by the same person on broadcast television. This literally put me in shock. Indeed, Landau would bitterly speak of himself as a coward. But those who knew him realized the high standard he had in mind. Didn’t Dau intervene for the convicted Korets in the Kharkov period (and secure his release)? Didn’t he dare to chase off the person who claimed, in the Korets trial, that Landau and L. V. Shubnikov were forming a counter-revolutionary group at the Kharkov Institute of Physics and Technology [5]? This claim later brought L.V. Shub- nikov’s and L. V. Rosenkevich’s arrest and, based on the testimony thrashed out of them, Landau’s own arrest [3]. Are there really so many examples of simple thoughtless bravery leading to a role in writing an anti-Stalinist leaflet in the years of mass terror? Of course, after his return to freedom, Landau grew more cautious. Apart from everything else, he knew P. L. Kapitsa had gotten him out on bailg and that he shouldn’t compromise him. Nonetheless, Lev Davidovich did what his more prudent colleagues sought to avoid. He went to the post office and sent money to the exiled Rumer;h he showed concern for Shubnikov’s widow, O. N. Trapeznikova; he regularly visited the disgraced Kapitsa, confined to his dacha.i At the height of various ideological campaigns, he signed a letter against the ignorant criticism of the theory of relativity and in defense of a colleague accused of cosmopolitanismj (the same per-

gSee footnote, p. 26. hYuri Rumer (1901-1985) was a Soviet physicist known in the West as Georg Rumer. In the early 1930s he worked as an assistant of Max Born in G¨ottingen where he investigated the basics of quantum chemistry in collaboration with Walter Heitler. Rumer was arrested in Moscow in 1938 as an accomplice of the public enemy Landau. iCountry cottage. jThis is a euphemism. Oﬃcially called “the struggle against cosmopolitanism,” it was April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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son who later called him cowardly). There were also other acts which Dau never spoke of. “Dau’s character, along with certain elements of physical timidity (he was afraid of dogs, and so am I, by the way), was marked by a rare moral firmness,” recalls Academician M. A. Styrikovich, an old friend of Landau’s and his sister’s. “Both earlier and especially later on (in hard times), if he thought he was right, it was impossible to convince him to compromise, even if this was necessary in order to avoid serious real danger” [2]. This side of Dau was also evident during his stay in prison. Ac- cording to a note which the investigator apparently prepared for high- ranking officials [6], during interrogation, Landau stood for seven hours and sat for six days in a room with no conversation (and apparently with no sleep); investigator Litkens “persuaded” him for 12 hours at a time, investigators “took swings but didn’t beat” him, threatened him with transfer to Lefortovo (where the prisoner knew there was torture), showed him confession statements from his Kharkov friends, who by then had been shot. He then called a hunger strike and, contrary to the investigator’s assertion that he “named Kapitsa and Semyonov as the members of the organization who directed my anti-Soviet work,” didn’t sign the interrogation protocol before making “clarifications” according to which he had “merely counted on Kapitsa and Semyonov as anti-Soviet assets, but never decided whether to be totally forthright with them, since I wasn’t close enough to them, while moreover my dependence on Kapitsa left no room for taking risks.” At the first opportunity, during the interrogation conducted by Beria’s deputy Kobulov, “he refuted all his testimony as fabricated, stating, however, that during the investigation no physical force was used against him” [3]. The words of Lev Davidovich’s favorite poet, Gumilev,k from the poem “Gondla,”

in fact a ferocious campaign by Stalin against the Jews in the Soviet Union in the late 1940s and early 1950s. At this time all Jewish schools, theaters, publishing houses and newspapers were shut down. Arrests and dismissals of the Jews followed. kNikolai Gumilev (1886-1921) was an inﬂuential Russian poet. In 1921 he was arrested by the Cheka on (false) allegations of participation in a monarchist conspiracy. Executed shortly after, he was banned and never published until the demise of the Soviet Union in 1991. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

36 S. S. Gershtein

involuntarily come to mind: “Yes, nature laced the substance of his bones with steel as well,” describing a man physically weak but strong in spirit. Landau tried to stay out of philosophical discussions, never going so far as to accuse the creators of quantum mechanics, for example, of recognizing the “freedom of will of the electron” [7]. In autumn 1953, when Stalinist practices remained alive, Landau gave some of his close colleagues a scare. After the successful test of the hydrogen bomb, he was given the title Hero of Socialist Labor, and the government decided to assign him a security guard. At this Dau rebelled. He said he had written a letter to the government which stated, “My work is hard on the nerves and doesn’t toler- ate any foreign presence. Otherwise, the guard will be for a corpse, scientiﬁcally speaking.” People around him feared the reprisal that might follow his refusal of the guard. E. M. Lifshitz even made a special trip to Leningrad and tried to persuade his sister to inﬂu- ence Dau to relent. But she categorically refused. In connection with Lev Davidovich’s letter, he was received by the Minister of Medium Machine Building and Deputy of the Council of Ministers V. A. Malyshev. In private, Dau told a small group how the conversation had gone. Malyshev had said a guard was an honor, that members of the Central Committee had guards. “Well, that’s their personal business,” Dau replied. “But there’s a crime wave in the country now; you’re highly valuable, you need guarding.” “I prefer a stabbing in a dark alley,” said Dau. “But maybe you’re afraid the guard will keep you from chasing women? Don’t worry, on the contrary...” “Well, now, that’s my personal life, and it needn’t concern you,” Dau replied. Listening to this story as a young mathematician from the Teplotechnical Laboratory,l A. Kronrod exclaimed, “Well, for that conversation, Dau, you should be made not Hero of Socialist Labor but Hero of the Soviet Union.”

lThe nuclear research institution headed by A.I. Alikhanov originally had the code name of Laboratory No. 3. Then it became Teplotechnical (Thermo-Technical) Laboratory (TTL) although it had nothing to do with thermal technologies. Currently, Institute of Theoretical and Experimental Physics (ITEP). April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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Landau also protested against not getting clearance to attend international scientific conferences. On this subject he also wrote to somewhere “higher up.” He was able to meet with N. A. Mukhitdi- nov (the then-secretary of the Central Committee of the Communist Party), who promised to settle the matter. Apparently this was connected with the Central Committee science division’s request to the KGB and the briefing documents now known to have been received.m From the testimony of agents – secret service employees tracking Landau – and wiretapping data cited in the KGB briefing, clearly, while preserving certain illusions, he eventually reaches this conclusion: “I deny that our system is socialist, because the means of production don’t belong at all to the people, but to bureaucrats.” He foretold the inevitable downfall of the Soviet system. And he discussed the ways this might happen: “If our system can’t collapse in a peaceful manner, a third world war is inevitable... So the question of the peaceful elimination of our system is a question of the fate of humanity, basically.” These predictions were made by the “ardent Communist” in 1957, some thirty years before the Soviet Union’s collapse.

Landau as I Knew Him During my study at Moscow State University, academic science was expelled from the Faculty of Physics. My thesis adviser was Professor Anatoly Aleksandrovich Vlasov – a brilliant lecturer and remarkable physicist with a tragic (in my opinion) fate in science. It was Vlasov who acquainted me with Landau. This was in 1951 at our class’s graduation party. For some reason I demonstratively didn’t attend the diploma presentation ceremony, which took place at the so-called Great Communist Auditorium in the old MSU building on Mokho- vaya Street. Walking on the balustrade around the auditorium, I met Vlasov, who also hadn’t gone to the ceremony. We were standing with my classmate Kolya Chetverikov when Vlasov exclaimed, “There, climbing those stairs, it’s Lev Davidovich himself! Come, I’ll introduce you.” It turned out that a group of students who had

mSee the last footnote on p. 31. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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completed their thesis work at the Institute of Physical Problemsn had invited Landau to our graduate party, and he had come. Vlasov took Kolya and me up to him and introduced us: “Our theorists.” I was assigned to work as a teacher at a technical school of hy- drolysis in Kansk, Krasnoyarsk Krai. But they wouldn’t have me. Vlasov made many attempts to find a job in science for me somewhere, all to no avail on account of my background (fifth pointo plus repressed parents). Eventually I was sent to a rural school in the Kaluga region, 105 kilometers from Moscow. Proximity to Moscow left me hoping to continue research work with Vlasov. But he firmly said, “I think it would be better for you to try to start work with Landau.” Subsequently I was very grateful to Vlasov for this advice, which I now realize he gave because he liked me. In the autumn of 1951, when I started working at the country school, I had a visit from my close university friend Sergei Repin. He was engaged to Natalya Talnikova, who lived in the apartment next door to Landau. “You should take Landau’s exams,” he said. “Here’s his phone number. Call him.” With much hesitation, after studying for the first exam (which I thought would be “Mechanics”), I phoned Landau, introduced myself and said I’d like to take his theoretical minimum tests. He agreed and named a time, asking whetheritwouldworkforme. At the agreed hour, having taken time off from the school, I rang Landau’s doorbell. The door was opened by a very beautiful woman, who I understood to be Landau’s wife. She greeted me warmly, saying that Lev Davidovich would come soon, and led me to the second floor to a small room which I will always remember. After waiting about fifteen minutes, I noticed with horror that a puddle had dripped from my boots onto the shiny parquet floor. As I tried to dry it with my papers, voices sounded from downstairs. “Daulenka,

nCurrently P.L. Kapitsa Institute for Physical Problems of the Russian Academy of Sciences. The Institute was founded in 1934. The founder of the Institute, Pyotr Kapitsa, served as its head for many years. The head of the theoretical division of the Institute was L. D. Landau. The theoretical division later separated and became L.D. Landau Institute for Theoretical Physics in Chernogolovka. o“Nationality” (i.e. ethnic origin) was entry number 5 in all Soviet identiﬁcation documents. Entry number 5 or ﬁfth point became a euphemism for “Jewish.” April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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what’s got you running so late? The boy’s been waiting for you a long time already,” I heard the female voice say, followed by some explanations from the male voice. Coming upstairs, Lev Davidovich apologized and said the first exam would cover mathematics. I hadn’t specifically studied for that, but because at the physics department it was taught very well (unlike physics), I said I could test in math right away. In a way it was even good that I hadn’t studied for math, as I found the integral which Landau assigned easy to handle without using Euler substitutions (I later learned that Lev Davidovich was known to send examination takers packing for using them in simple cases). After I solved all the problems, he said, “All right, now study for mechanics.” “That’s the test I just came to take,” I said. Landau started assigning me mechanics problems. It bears saying that Landau was easy to test with. His friendly attitude was heart- ening, as was, I might say, his sympathy for the person taking the examination. After assigning the next problem, he usually left the room and, occasionally coming in and glancing at the examination taker’s scribbled sheets of paper, would say, “Well, well, you’re doing fine. Wrap up quickly.” Or, “You’re doing something wrong; do it all scientifically.” I was the last person to take all nine exams with him. Lev Petrovich Pitaevsky, who took the theoretical minimum after me, took all but two with Landau, and the last two exams with E. M. Lifshitz. Lev Petrovich said Lifshitz was usually only interested in checking whether the final answer was right. After successfully passing “mechanics,” I told Lev Davidovich (not without faintheartedness) that I’d noticed quite a few typos in his book. He wasn’t at all offended, and on the contrary thanked me and jotted down in his notebook the mistakes I’d found which hadn’t been spotted before. Only after all this did he start asking me who I’d studied under at MSU before this. I expected this question and was ready to defend Vlasov in case Landau spoke badly of him. To my surprise and joy, he said, “Well, of course, Vlasov might be the only one in the Physics Department it’s possible to have anything to do with. True,” he added, “Vlasov’s latest idea about a single-particle crystal holds purely clinical interest, in my opinion.” It was hard to April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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argue. In early 1953, I passed all the theoretical minimum exams, and Lev Davidovich recommended me to Yakov Borisovich Zeldovich – the time when he spoke the phrase that many later repeated, “I don’t know anyone but Zeldovich with so many new ideas, except maybe Fermi.” In August 1954, after at last finishing the required term of employment, I managed to leave the school and come to Moscow to seek a position at some research institution or university. But Stal- inist practices remained intact in many respects. Nobody hired me, despite the brilliant references signed by Landau and Zeldovich. Af- ter going several months without work, I started falling into despair. What saved me from this was Lev Davidovich’s and Yakov Boriso- vich’s caring and the support of fellow classmates: V. V. Sudakov’s family and A. A. Logunov’s family. I had already started thinking of leaving Moscow. But in early 1955, Landau told me, “Hang on a little longer. There’s talk of Kapitsa returning. Then I can accept you to the graduate program.” Indeed, in the spring of 1955, Pyotr Leonidovich again became director of the Institute of Physical Problems, and after the trial exam arranged for me by Kapitsa, I was accepted to the graduate program. As my adviser Landau appointed A. A. Abrikosov, who became a friend. True, I didn’t find the proposed task very enticing: determining the shape and size of superconducting regions in an intermediate state in a charged conductor. I was attracted to particle physics. The discovery of parity nonconservation and muon catalysis gave me the opportunity to address these problems. Because Landau himself started working on problems of weak interaction, he became my direct adviser and instructed me to clarify certain issues. For example, he immediately asked me to check the degree of electron polarization in β decays. At the time, β interaction was regarded as a symmetric combination – with respect to particle permutation – of scalar, pseudoscalar and tensor terms, with the neutrino’s helicity unknown then. For the sake of definiteness, Landau assumed this combination to be right- handed. I found confirmation that electrons in β decays are polarized in the direction of their momentum (in the case of a right-handed April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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neutrino) and obtained the absolute value of their polarization to be v/c, the ratio of the electron velocity to the speed of light. An intriguing nuance for me was the fact that an electron and proton participate in β interaction only with their left-hand components, in contrast to the right-hand components of the neutrino and neutron. Landau also found this intriguing. But we went no further. Lev Davidovich had me solicit theory advice from experimenters at the present Kurchatov Center who were preparing to measure electron polarization, and I had the pleasure of talking over issues with one of our best experimenters, P. E. Spivak. I remember the following episode from that time. After advancing the left-handed neutrino hypothesis, Landau immediately wanted to point out its implications. He asked me if I’d ever calculated the muon decay. “How did you integrate over the phase space? In the elliptical coordinates?” “Yes, the elliptical,” I replied. Lev Davidovich said nothing. He apparently didn’t know about the invariant calculation method, but felt that the old method was cumbersome and not very elegant. Therefore in his article he presented only results without giving the calculations. I think there were many other cases when the general approach to various kinds of problem-solving which Landau was so praised for, resulted from extensive and painstaking work which he kept silent about. Landau’s seminars figure in many memoirs. I’ll only talk about two of the ones I remember. A mathematician friend of mine once mentioned that I. M. Gelfand had decided to study quantum field theory, because in his view all its difficulties stemmed from physicists not really knowing mathematics. A while later my friend said, “Gelfand’s done everything.” “What’s he done?” I asked. “Every- thing,” the mathematician replied. This rumor spread far and wide, and Israel Moiseyevich was invited to give a lecture at Landau’s seminar. Gelfand allowed himself an unprecedented slip – he came 20 minutes late. There was already another lecturer at the blackboard. But Lev Davidovich asked him to yield his place to Gelfand. Going against custom, Landau didn’t permit Abrikosov and Khalatnikov to make objections during the report, but dealt Gelfand a literally April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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crushing defeat after its end. Reportedly after the seminar Israel Moiseyevich said that theoretical physicists weren’t nearly as simple as he’d thought, that theoretical physics was very close to mathematics, and so he’d better start working on something else, maybe biology. Subsequently, when Lev Davidovich was hospitalized at the Insti- tute of Neurosurgery after the accident, it turned out that Gelfand had a job there. “What’s he working on?” one of the physicists asked the head doctor, Yegorov. “You’d better ask him yourself,” he replied. The other episode, truly historic, was the seminar where N. N. Bo- golyubov lectured on his explanation of superconductivity. The first hour was fairly tense. Landau just couldn’t understand the physical meaning of the mathematical transformations Nikolai Nikolayevich was making. During the break, though, as Bogolyubov and Landau continued their conversation while walking down the hallway, Niko- lai Nikolayevich told Lev Davidovich about the Cooper effect (the pairing of two electrons near the Fermi surface), and Landau immediately understood everything. The second hour of the seminar, so to speak, was a smash hit. In a manner quite unlike him, Landau effu- sively praised the work accomplished. In turn, Nikolai Nikolayevich praised the expression Lev Davidovich wrote on the board, advising him to publish it without fail. They agreed to hold a joint seminar. I welcomed this cooperation, not understanding (and I still don’t understand) Landau’s wariness toward Bogolyubov. Perhaps it came from Nikolai Nikolayevich maintaining relationships with people whom Lev Davidovich neither respected nor cared for: “What did he leave D. D. Ivanenko and A. A. Sokolov at his department for?” But maybe this was due to the Central Committee’s Science Department patronizing Bogolyubov’s school while accusing Landau and his school of numerous sins. Relationships also became more strained as some members of both schools sought to be greater royal- ists than the king himself. Because I had friends among Bogolyubov’s students, who talked about him, I tried to persuade Dau that it basically would go against Bogolyubov’s nature to plot anything against him personally or against anyone else. But a big article by Aca- April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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demician I. M. Vinogradov appeared in “Pravda,” saying that the mathematician N. N. Bogolyubov had solved problems theoretical physicists couldn’t solve, explaining superﬂuidity and superconductivity (moreover, Landau’s name wasn’t even mentioned in connection with superconductivity). The joint work by the two schools never happened. After none of Landau’s students managed to take notice of L. Cooper’s article, the seminar operations were reorganized. “I admit that I’m a parasite, that I don’t read and only listen to what you tell me. But I see that I’ve been a parasite on bloodless organisms. You aren’t reading anything either,” said Lev Davidovich. Now every participant was assigned a specialty which he had to report on. This was much easier than surveying two issues of Physical Review, which then covered all branches of physics. Moreover, Landau decided he should take an attentive approach to works he’d previously refuted. There had been a surge of interest in Heisenberg’s non-linear theory.p LandauevencorrespondedwithW.PauliandW.Heisenbergonthe subject. (A. B. Migdal exploited this for his next prank. He composed a letter to Landau from Pauli, with contents that no one at the seminar could understand.) Upon further investigation, though, Lev Davidovich saw the Heisenberg theory’s futility. Landau had a totally uncompromising attitude toward works and judgments that seemed wrong to him. And he expressed this attitude openly and quite sharply, without respect of persons. The Nobel prize laureate C. V. Raman, for instance, was infuriated by the remarks Landau made during his lecture at Kapitsa’s seminar, and literally shoved Landau out of the seminar room. I knew of only one instance when Lev Davidovich refrained from criticizing an incorrect work. This happened when N. A. Kozyrev was to speak at Kapitsa’s seminar about his wild hypothesis on energy and time. Landau knew that Kozyrev, having started out as a talented astrophysicist, had then spent many years imprisoned at a gulag camp, and he pitied him but couldn’t stand to hear nonsense.

pSee W. Heisenberg, Introduction to the Uniﬁed Field Theory of Elementary Particles, (Interscience Publishers, London, 1966). April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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Therefore, despite his custom, he simply didn’t go to the seminar. I heard that once he didn’t attend a lecture by his close friend Yu. B. Rumer, hosted by physicists as a way to solicit permission for him to stay and work in Moscow. Rumer had lost this right after many years of imprisonment – spent in a “sharashka”q along with A. N. Tupolev and S. P. Korolyov – and then in exile. Landau’s support could have been significant. But Landau didn’t believe in the idea Rumer was developing, and he was organically incapable of speaking falsely. Sometimes Lev Davidovich judged wrongly. He was critical when Bogolyubov lectured on his work on weak nonideal Bose gas – that is, work subsequently considered an outstanding accomplishment. I remember how he criticized a lecture by the remarkable physicist F.L. Shapiro (who had extended, based on his experimental data, the theory of effective radius) but then, convinced the result had been correct, apologized to him and included the result in his “Quantum Mechanics” course. Landau’s critical mindset sometimes kept him from accepting new ideas until he completely understood their physical basis. This was the case, for instance, with the nuclear shells and the latest developments in quantum electrodynamics. I remember the following episode. In summer 1961 I came to Yakov Borisovich Zeldovich to discuss the problem of the second (muon) neutrino. New data were accumulating in favor of this hypothesis. “Let’s go see Dau,” said Zeldovich after our discussion. We found him in the garden at the Institute of Physical Problems. He said he was savoring the warm day. At that moment he apparently didn’t much want to talk science. “There’s no accurate way to calculate the processes that favor having two different neutrinos. And really, why multiply the number of elementary particles; there’s enough of them as it is,” said Dau, brushing off all our objections. “Too bad you didn’t speak up about all this in 1947. That would have been a great help to the Alikhanov brothers,” joked Yakov Borisovich. (The Alikhanov broth-

qSharashka was an informal name for secret research and development laboratories in the Soviet Gulag labor camp system, staﬀed by highly educated political prisoners. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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ers had “discovered,” thanks to errors in their experimental methods, a large number of unstable particles – “varitrons”– and received the Stalin Prize for this in 1947.) Dau made no reply to this joke. “Why did Dau believe the Alikhanovs?” I asked Yakov Borisovich when we were alone. “Dau was skeptical about the meson theory of nuclear forces – almost nothing in it can be calculated with any accuracy. Then Ivanenko comes along and advertises it in every way. So since it’s turned out that there are many mesons, varitrons, that means – Dau’s decided – mesons don’t relate to nuclear forces.”r Of all the modern great physicists, Lev Davidovich most reminded me of Richard Feynman. Subsequently I was able to conﬁrm this. In 1972 in Hungary, at a conference on weak interactions, V. Telegdi introduced me to Feynman, who presented his famous “Quarks as Partons” lecture there. After one of the lectures, at which I made a comment on the possible existence of a third lepton (apart from the electron and muon) and its properties, Feynman approached me and said he believed in the existence of a third lepton. He also asked me

rThis passage contains a subtext probably unclear for an uninformed reader. Landau and D.D. Ivanenko started as very close friends in their student years. At Leningrad University, Landau, Ivanenko and G. Gamow were nicknamed the “three musketeers.” All three graduated from the Leningrad University in 1927, and all began their careers with famous papers: Gamow’s theory of α decays (1927), Landau’s diamagnetism (1930), and Ivanenko’s proton–neutron model of the atomic nucleus (1932). It was Ivanenko who coined the nickname Dau. In 1933 Gamow was allowed to travel abroad to a physics conference from which he never returned to the USSR. All ties with his former friends were severed. The friendship between Ivanenko and Landau lasted until the late 1930s. Its collapse is attributed to a silly joke by Ivanenko, who insisted on Landau’s participation in the 1939 Soviet Conference on Nuclear Physics in Kharkov. Landau did not want to go. Then Ivanenko sent a cable to Dau: “I am very sick, come at once,” signed Kora (Landau’s wife, who was then in Kharkov). Their relationship further deteriorated to the level of open animosity in the 1940s. In 1949 Ivanenko participated in the Organizing Committee of the so called “All-Union Conference of Physicists,” which was supposed to proclaim the guiding role of Communist principles in physics research and the need to combat bourgeois “physical idealism,” inﬂicting a crushing blow to “cosmopolitanism” (see footnote, p. 35). (Incidentally, the latter conference was canceled in the last minute, allegedly due to Kurchatov’s complaint to Stalin: “Comrade Stalin, what do you want? Do you want to inﬂict a crushing blow to bourgeois idealism and cosmopolitanism, or you want to have the A bomb in time?”) After this, the majority of leading Soviet physicists ostracized Ivanenko. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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what I was working on at the time. I told him about the problem of supercritical nuclei, which Zeldovich and I had worked on several years before and which was finally solved by Yakov Borisovich and V. S. Popov from ITEP. Feynman was interested in this, and he and I talked in the lobby of the restaurant after lunch on until dinner. He even wrote down the problem Z>137 on a special card he took out of his wallet. During this discussion, he strongly reminded me of Dau. I told him so. “Oh, for me that’s a great compliment,” he replied. Feynman greatly admired Landau. I remember during my graduate studies there was talk of a letter Feynman had written him. In theletterheacknowledgedthatwhenhe’dstartedworkingonsu- perfluidity, he hadn’t believed certain results Landau had obtained, but that the more he delved into the problem, the more he grew convinced that Landau’s intuition was correct. Accordingly, Feynman asked Landau what he thought about the situation in quantum field theory. Dau, in his reply, wrote about the zero charge. Feynman reminded me of Landau in the style of his behavior. I think that for him, as for Landau, shock tactics were a means to overcome natural shyness. I was glad to learn that V. L. Ginzburg had also seen their similari- ties. However, I completely disagree with Vitaly Lazarevich’s opinion that Landau harbored no feelings of warm friendship toward anyone. “For some reason I think, although I’m really not sure, that Landau basically harbored no such feelings,” Ginzburg recalled [2]. Perhaps Vitaly Lazarevich never witnessed anything like this. But his friend and colleague E. L. Feinberg was touched when Landau showed these feelings toward Rumer [2], and quoted Kapitsa: “Those who knew Landau closely were aware that behind these harsh judgments was hiding a kind and compassionate person.” And could a callous person who harbored no warm feelings toward anyone find such moving words to begin his article: “With deep sadness I send this article, written in honor of the sixtieth birthday of Wolfgang Pauli, for a collection devoted to his memory. Memories of him will be kept sacred by those who had the good fortune to know him personally.” Many couldn’t help but notice how warmly Landau felt toward I. Ya. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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Pomeranchuk, toward N. Bohr, whom he revered as his teacher, or toward the friend of his youth R. Peierls. I felt Dau’s sympathy and support at the most difficult moments of my life: when I worked at the rural school with no chance to do science, when I couldn’t find work after returning to Moscow, and later, in autumn 1961, when my wife left me, leaving me our three- year-old son at my request. Dau, who always took an interest in his friends’ and students’ family lives, was upset by this. He asked how I was coping with the child. I explained that my son had a nanny and that we were handling the situation in keeping with his own theory, like intelligent people. But this apparently didn’t reassure him, and he started to show me particular attention. Usually I tried to come to Kapitsa’s seminar on Wednesdays in order to attend the theoretical seminar the next morning. Dau started inviting me home to supper after the Kapitsa seminar. Before this, I’d visited his home relatively rarely. We talked of science and of life. I remember Kora was worried because Kapitsa wanted to write a letter to Khrushchev about Dau not being allowed to travel to international conferences. “What he writes might go over the top,” she said. “After all, he wrote a letter to Stalin complaining about Beria!” Dau argued with her and praised Kapitsa in every way. On Wednesday, January 3, 1962, Yu. D. Prokoshkin and I were invited to deliver a lecture at Kapitsa’s seminar, discussing the area of research later called “meson chemistry.” Our talk was after the break. The first hour was devoted to a lecture by the renowned Linus Pauling, twice a Nobel laureate: for chemistry and for peace. After the seminar, Kapitsa, as usual, invited the lecturers and his closest colleagues to his office for tea. He entertained the guest by talking politics: de Gaulle, Churchill’s scientific advisers, the Swedish king, and so forth. At some point Dau rose from the table, went to the door and motioned to me. We went out to the foyer. “Well, how are things with you?” Dau asked. “Fine,” I replied, “come to Dubna. Some interesting experiments are being prepared there now. A lot of people would like very much to talk with you.” “Oh, well, I’m slow on my feet and lazy,” Dau said. And we went back to Pyotr Leonidovich’s office. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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But a day later, I got a call in Dubna from an old classmate, married to a friend of mine who’d been one of Landau’s most talented young students, Vladimir Vasilyevich Sudakov. “Dau was at TTL and came to see us,” she said. “He said you invited him to Dubna, andhedecidedtogowithus.”Atfirsttheyplannedtotravelby the commuter train, but then it bothered Day that I lived quite far from the station, and they decided to go by car (not knowing that I planned to meet them at the station in an institute car). I was waiting for them on Sunday, January 7. On the advice of my housemate at the cottage, S. M. Shapiro, I even fixed lunch. At about one in the afternoon I started to worry. It was windy outside, snow was gusting and there was black ice on the roads. I went to a nearby cottage to see A. A. Logunov, whose telephone had a direct line to Moscow, and tried to reach Dau at home. His phone was busy. Then I phoned Abrikosov. He didn’t know anything. More and more disturbed, I started continuously dialing Dau’s number. At some point the line was free, and Kora said, “Dau is in the hospital, near death. I can’t talk now. I’m expecting a call.” She hung up. I immediately reported this to Abrikosov, knowing he would make every effort to help Dau. After contacting Abrikosov again and learning there had been a car accident and Dau was at Hospital No. 50,s I hurried to Moscow. At the hospital were already several highly qualified doctors, found on Sunday and invited there by Dau’s regular doctor (Kar- mazin, I think). Fortunately, Sudakov knew his phone number and told him about the crash. They gave Dau immediate attention. In the hospital waiting room, I learned of Dau’s terrible injuries. The next morning, the hospital was filled with an unusually subdued crowd of physicists who’d found out about the catastrophe. Kremlin doctors arrived and immediately started writing a protocol about the terminal nature of Dau’s injuries. Much has been written on Lan- dau’s sufferings and the efforts made to save him. I won’t describe this. I remember the team of physicists, which included many people who didn’t know Dau. It was a moment of truth which revealed the

sA hospital on the fringes of Moscow. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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inner natures of a wide range of people. I’d like to write of what I saw after Landau’s release from the academic hospital. In the summer he was taken to a country house in Mozzhinka. Not knowing what state he was in, I went there. Kora’s sister was caring for Dau. She told me Dau, realizing his position, was in despair that he couldn’t work as before. He didn’t sleep, and said he’d become so worthless he couldn’t even kill himself. I involuntarily recalled one of Dau’s favorites among N. Gumilev’s poems: “Even glinting guns, even hissing waves may no longer freely break these chains.” From then on, Dau’s life was mainly spent between home and the academic hospital. People who came to see him tried to tell him physics news, not realizing that he couldn’t concentrate like before, and that for him this was torture. Still, he clearly remembered things from the past. He was said to have lost his operational memory. But this wasn’t quite true. He hadn’t lost his operational memory, or lost his humor, despite the pain. Once,justbackfromatriptothemountains,IcametovisitDau at the academic hospital, without shaving off the beard I’d let grow in the mountains. Dau didn’t like people with beards: “Why wear your stupidity on your face?” When he saw me, he asked, “Syoma, have you really signed up for the castrati?” “What do you mean, Dau?” “Just that now you’re a follower of Fidel Castro,” he said. The next day, after I’d shaved, when I went to see him, by the gate of the hospital garden I ran into E. M. Lifshitz and V. Weisskopf, whom Evgeny Mikhailovich had taken to see Dau. It turned out Dau had told them, “Yesterday I had a visit from Semyon, with his hideous beard. I told him to shave it off immediately.” We rejoiced together that Dau also had an operational memory. Time passed, and many of those who’d selflessly saved Lev Davi- dovich started to forget about him. Once when I went to visit him at the hospital, I found him walking in the hospital courtyard with Irakly Andronnikov,t who was also going through treatment at the

tIrakly Andronnikov (1908-1990) was a well-known Russian literature historian, philol- ogist, and media personality. April 5, 2013 14:7 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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hospital and was a friend of Landau’s. A nurse, Tanya, was walking behind them. She told me that almost no one came to see Dau and that this pained him greatly. Only Alyosha (Abrikosov) appeared regularly. I tried to entertain Dau with diﬀerent funny stories. Then I made a careless blunder, telling him that the theorists at the Insti- tute of Physical Problems wanted to organize a special theoretical institute at Chernogolovka. “What for?” said Dau. “Theorists should work beside experimenters.” (Later I read that Landau and George Gamow had tried to organize an institute of theoretical physics. Ap- parently Dau didn’t want the theorists divided from the Institute of Physical Problems, given his sense of gratitude to Kapitsa.) After leaving the hospital, I immediately went to the Institute of Physical Problems and reprimanded my friends for not visiting the invalid. The typical response: “I can’t stand seeing our teacher in this state.” I couldn’t understand this: “So if, for example, your father was in such a state, you wouldn’t be able to see him, either?” Khalatnikov chided me for telling Dau about Chernogolovka: “We were trying not to say anything to him about it.” By the way, the Landau Institute for Theoretical Physics became one of the world’s best research centers, and is worthy of bearing Landau’s name. I once had an opportunity to joke about this. What happened was that when Khalatnikov and Abrikosov were “forcing” one of their articles upon Dau, he turned it down several times and, entering our graduate studies room, repeated, “After my death, Apricot and Bathrobe (Abrikos and Khalat) are going to create a world center of pathology.” So when Isaak Markovich Khalatnikov told me the organizers had succeeding in naming the institute after Landau, I replied, “Dau predicted many times that you and Alyosha would organize this center, but what he never guessed (although he could have) was that you’d give the center his name!” Landau’s sixtieth birthday was approaching. Concerned about this, I phoned A. B. Migdal, who had enjoyed a wonderful celebration of his ﬁfty-year jubilee. “There’s no need to make any arrangements,” he said. “Dau’s in bad shape now.” On January 22, 1968, Karen Avetovich Ter-Martirosyan, Vladimir Naumovich Gribov and I met at the Institute for Physical Problems, May 10, 2013 11:35 WSPC/Trim Size: 9in x 6in for Proceedings 2d˙Gersh-Priroda˙Land˙One

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and after some hesitation decided to visit Landau at home to con- gratulate him on his sixtieth birthday. He was alone with Kora. He seemed to me to be glad we had come. We sat for a long time with him and Kora at the table, having tea with homemade pastries and making some kind of small-talk. Dau seemed calm and sad, occasionally smiling. One of his last family photos gives a good idea of his appearance. He had a birthday visit from A. K. Kikoin – his friend since the days of work in Kharkov, and the brother of I. K. Kikoin.u Majestic in a general’s greatcoat, A. A. Vishnevsky, the renowned surgeon and remarkable man who had been a great help in Landau’s treatment, arrived as another birthday visitor. We stayed on and on, and just couldn’t manage to leave. We said goodbye only at six o’clock, when Pyotr Leonidovich Kapitsa and his wife Anna Alekseyevna arrived. That’s how Lev Davidovich met his sixtieth birthday. When Khalatnikov, the Landau Institute’s director, returned from India, he organized a celebration of Landau’s jubilee in March at the Institute of Physical Problems. A lot of people came, Nobel laureates were present, and Alexander Galich sang in the conference room (then later in Kapitsa’s oﬃce). Dau sat with a detached air, smiling weakly at those who congratulated him. Less than a month later he was gone.

References 1. History of the Soviet Atomic Project, Ed. V.P. Vizgin (Moscow, Yanus-K Pub- lishers, 1998). 2. Memories of Landau, Ed. I.M. Khalatnikov (Moscow, Nauka, 1988). 3. Izvestiya of the Central Committee of the CPSU, 1991, No. 3. 4. TheAtomicProjectoftheUSSR, Eds. L.D. Ryabev and G.A. Goncharov, (Moscow, Fizmatlit – Sarov, Russian Federal Nuclear Center, 2000), Vol. 2, p. 529. 5. Yu. N. Ranyuk, L. D. Landau and L. M. Pyatigorsky, Voprosy Istorii, Es- testvoznaniya i Tekhniki, 1999, No. 4. 6. G. E. Gorelik, My anti-Soviet activity, Priroda, 1991, No. 11. 7. A. S. Sonin, Physical Idealism: The Story of a Ideological Campaign,(Moscow, Fizmatlit, 1994).

uIsaak Konstantinovich Kikoin (1908-1984) was a close associate of I.V. Kurchatov in the Soviet atomic project. April 5, 2013 13:31 WSPC/Trim Size: 9in x 6in for Proceedings 3a_Chap2-divider

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ARKADY BENEDIKTOVICH MIGDAL∗

N. O. AGASYAN, S. T. BELYAYEV, L. B. OKUN, and E. E. SAPERSHTEIN

The outstanding theoretical physicist Arkady Benediktovich Mig- dal was one of the pioneers of theoretical nuclear physics in the Soviet Union, the founder of a major scientific school, a man of diverse gifts and irresistible personal charm. A. B. Migdal was born on March 11, 1911, in Lida (Belarus). In the 1920s his family moved to Leningrad. Migdal produced his first scientific work at age 17. He then enrolled at the physics department of the Leningrad State University (LSU), but studied there only a short while: arrested, he spent over two months under investigation, then was released (releases were still granted sometimes then). From 1931 to 1936, while working at the factory “Electrical Appliance,” he produced several scientific works. At this time he managed to recover a place at the LSU extension division. After graduation in 1936 A. B. Migdal enrolled in graduate school at the Leningrad Physical-Technical Institute, where he formed his research interests and his own research style. His thesis adviser was M. P. Bronshtein.a Despite the briefness of this contact with Bronshtein – in 1937 Matvei Petrovich was arrested and executed – this bright, talented and deep person played a major role in Migdal’s scientific development. Migdal’s first mature works examined the interaction of neutrons with matter, including atom ionization by neutron nuclear impact (1939). To solve this problem, he created an original method, the so called “shake-off.” Later, while in Moscow in the doctoral program at the Institute of Physical Problems, he successfully applied this method to calculate the probability of atomic processes that ac- company α and β nuclear decays. These works made their author

∗Published in Vospominaniya ob Akademike A. B. Migdale, Ed. N.O. Agasyan et al., (Fizmatlit, Moscow, 2003), p. 5. Translated from Russian by James Manteith. aSee footnote, p. 171.

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widely known and are described in detail in quantum mechanics textbooks; the shake-off method itself has become firmly entrenched in modern theoretical physics. To this day it has not only completely kept its relevance for phenomena involving nuclear particles, but is also widely used in the physics of purely atomic processes, in which “fast” transitions in inner electron shells cause sudden changes in the screening of the nuclear field, and with it the shake-off relative to the slow electrons of outer shells. A little later, A. B. Migdal began working on the theory of pho- toabsorption of atomic nuclei. He predicted the existence of the giant dipole resonance associated with neutron oscillation relative to protons and calculated the resonance’s position through the parameters of the Weizsäcker mass formula. This work, together with works describing phenomena accompanying α and β nuclear decay, served as the basis for the doctoral dissertation (1943). It was published in 1944 and brilliantly confirmed experimentally in 1947. Today the physics of giant resonances have become an intensively developing branch of nuclear physics, with origins in Migdal’s work. In 1945, A. B. Migdal moved to Laboratory No 2 (later the Labo- ratory of Measuring Devices, then the Kurchatov Institute of Atomic Energy, and currently the Russian Research Center Kurchatov In- stitute) and began working on the atomic problem. At this time, after the well-known work of I.I. Gurevich and I.Ya. Pomeranchuk, the idea of a heterogeneous reactor was being intensively developed. Migdal made a significant contribution to the development of a realistic theory of a finite heterogeneous reactor. Based on the idea, stated by L. D. Landau, that a uranium block can be considered as a source of fast neutrons and an outlet for thermal and resonant neutrons, Arkady Benediktovich jointly with G.I. Budker developed a calculation method for such a reactor. This method was later used by A.D. Galanin and S.M. Feinberg for constructing a theory of a finite heterogeneous reactor. Another important result obtained by Migdal at the time was the exact solution for the absorption of gamma quanta by an infinite medium, taking into account multiple scattering. This work proved very significant for the reactor’s bio- logical shield. But Migdal was most fascinated by general physics April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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problems. Fortunately, Kurchatov understood the role of fundamental science and the value of the scientific atmosphere that always arises around people like AB. He placed Migdal at the head of the theoretical sector (the famous Sector 10), allowing him to deal mainly with fundamental problems. A. B. Migdal’s work on the theory of nuclear reactions with the formation of slow nucleons is well known. It was reported at Lan- dau’s seminar in 1950, but due to limitations associated with clumsy “secrecy” was published only in 1955. One of the first works in the theory of strong interactions, it was essentially based on using analytical properties of the S-matrix and on identification of its most significant singularities. Subsequently this approach was called dispersion; the effect of the final-state interaction (the Migdal-Watson effect) is presented in most textbooks on quantum mechanics and the theory of nuclear reactions and remains one of this approach’s most important achievements. To this day, clear identification of the “Migdal-Watson factor” accompanies any calculation of the cross section of a multiparticle nuclear reaction, whose end products are two nucleons with small relative momentum. The exceptions are few-nucleon reactions, where the problem can have an exact solution with the effect of the final-state interaction factored in automatically. In 1951-1953, a group headed by Migdal took part in researching the problem of controlled thermonuclear fusion, participating in the studies then begun at the Institute of Atomic Energy. In work carried out in 1951 together with V.M. Galitsky, a pioneering study was made of the extremely important issue of the distribution of cyclotron radiation in magnetized thermonuclear plasma, while work with S.I. Braginsky (1953) developed a qualitative theory of the basic physical processes accompanying the inertial pinch effect (ionization, skin effect, cumulation, etc.). These works, along with other Soviet works on plasma physics, were declassified and published only in 1958 in the well-known collection Plasma Physics,whichcameasa complete surprise to the West. Notably, in those same years, simultaneously and independently from D. Bohm and D. Pines, A.B. Migdal together with V.M. Galitsky developed a method of collective variables to describe plasma. These works by Migdal have completely re- April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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tained their foundational significance for the subsequent development of the corresponding parts of the theory of thermonuclear plasma and moreover in many ways contributed to addressing the broader problem of establishing a modern plasma theory as a physics of collective processes. In the early 1950s there was interest in the influence of the amor- phous medium on the bremsstrahlung of relativistic electrons. Qual- itative analysis was performed by L.D. Landau and I.Ya. Pomer- anchuk, who investigated the suppression of bremsstrahlung due to multiple scattering, and M.L. Ter-Mikaelyan, who examined how polarization of the medium influences this process. They obtained approximate expressions for the bremsstrahlung spectrum in two frequency ranges. However, a quantitative relativistic theory seemed impossible because of the extraordinary complexity of the process. Migdal made a bet that he would solve this problem, then won it with the new method he created in 1954-1955: the quantum kinetic equation. This method subsequently found wide application not only in the theory of particle passage through matter, but also in other fields of physics. A.B. Migdal was one of the creators of the modern theory of many- body systems based on the use of quantum field theory, or Green’s function method. His 1957 work on the jump in momentum distribution at zero temperature for a Fermi system with an arbitrary interaction played a crucial role for understanding Fermi system physics (“the Migdal jump”). This was contrary to a then-prevalent belief that the jump in the filling number np of an ideal Fermi gas at a momentum equal to the Fermi momentum pF issmearedbyanarbi- trarily weak interaction. Migdal, based on the analytic properties of a single-particle Green’s function of a Fermi system, showed that the jump is retained at any (arbitrarily strong) interaction. The location of the np jump serves as a strict definition of pF for systems with interaction. It later turned out that in the case of attraction between fermions near the Fermi surface there is a Bose condensate of Cooper pairs, leading to superfluidity and smearing of np at a width proportional to the gap Δ; however, for normal Fermi systems Migdal’s jump theorem is valid and has been confirmed experimentally. April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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Another classic, produced jointly with V.M. Galitsky, was a 1958 work on the formulation of the method of Green’s functions for Fermi systems. Analytical properties of the Green’s functions, spectral decomposition and dispersion relations for the Green’s functions, an exact formula for the energy – this is far from a complete list of the results obtained in the work. These works are presented almost verbatim in textbooks and monographs on the many-body problem. A work of 1958 containing the solution of the problem of electron- phonon interaction in normal metal is also widely known. It was one of the first applications of Green’s function method to real systems and one of the first analyses of electron interactions in metal without the use of perturbation theory. The concrete results, including singularities in the phonon spectrum caused by phonon interaction with electrons (Migdal-Kohn singularities), are classic in the theory of metals. Tellingly, in J. Bardeen’s Nobel lecture this work is mentioned eight times. AB’s works on the theory of solids, although few in number, have played a very large role in the development of this field of physics. As a whole, these works by Migdal (along with Landau’s Fermi liquid theory) made it possible to understand that the presence of electron interactions in normal metal leads only to quantitative, not qualitative changes in their behavior compared to the case of non-interacting particles. This fundamental statement formed the basis for the further development of the theory of normal metals. A.B. Migdal’s work on the theory of normal metals was extended by G.M. Eliashberg to superconductors. This resulted in the creation of a theory of superconductors with strong electron-phonon interaction. A. B. Migdal’s works on the theory of solids are of great methodological value, although A. B. Migdal never set himself a goal of obtaining methodological results. These works have the following history. In the 1950s, Migdal grew interested in the phenomenon of superconductivity. Early on (before G. Fröhlich’s work) he realized the importance of electron-phonon interaction, assuming that the single-particle excitation spectrum must contain a gap. How- ever, the perturbation theory calculations failed to allow for a gap. He therefore developed a general method for the excitation spectrum April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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using Green’s functions and constructed a theory of strong electron- phonon interaction. Arkady Benediktovich saw these works as only the foundation for the theory of superconductivity. They were therefore only published two years after they were done, but by then Bardeen-Cooper-Schrieffer theory had appeared. The next stage of A. B. Migdal’s scientific work concerned the use of quantum field theory methods in nuclear physics. The work “Superfluidity and the nuclei moments of inertia” (1959) was one of the first to develop a theory of atomic nuclei accounting for nucleon superfluidity. It showed (as S. T. Belyayev’s work did independently) that the difference between the moments of nuclei inertia and the solid core values is a consequence of the effects of superfluidity. To this day it is one of the most striking manifestations of the Cooper phenomenon in nuclei. Also of fundamental importance was the 1961 work “Single-particle excitations and superfluidity in Fermi systems with arbitrary interaction. Application to the nucleus.” It developed a diagram technique for finite Fermi systems with superfluidity and gave a rigorous formulation of the nuclear shell model. Migdal’s next major series of works (some in collaboration with students) culminated in the monographs “Theory of finite Fermi systems and properties of atomic nuclei” (1965) and “Method of quasiparticles in nuclear theory” (1967). Both monographs were translated in the United States and became standard reference books for nuclear theoreticians worldwide. They developed an approach – based on using methods of many-body theory and close to ideas of Fermi-liquid theory – which represented a key stage in the creation of a quantitative theory of the nucleus. In place of the many models in which individual constants were introduced for each phenomenon, and often for each nucleus, there was now a method in which by introducing several phenomenological parameters universal for all nuclei and all nuclear phenomena it became possible to describe a large range of nuclear phenomena: the spectra of low-lying states and the transition probabilities between them, magnetic and quadrupole moments of the nuclei, probabilities of β decay and μ capture, isotonic and isomeric shifts of atomic and mesoatomic lines and much more. In years to come, A. B. Migdal’s students developed a self-consistent April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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finite Fermi system theory in which the same parameters also allow calculation of such global characteristics of nuclei as binding energy, density distribution of nucleons, average field of the nucleus, elastic and inelastic scattering and other particles. Thus it became possible to describe almost all nuclear characteristics on the basis of a unified approach employing several universal parameters. These changes in the theory of finite Fermi systems are reflected in the book’s second edition (1983). In the late 1960s in connection with discussion of possible experiments with collisions of heavy ions, interest revived in the electrodynamics of strong Coulomb fields corresponding to the critical nuclear charge zcr = 170. Various authors, including Ya. B. Zeldovich and V. S. Popov, performed a detailed analysis of the situation when the electronic level approaches the boundary of the lower continuum 2 E = −mc as z approaches zcr. A slight increase of z over zcr would lead to the production of an electron-positron pair. Intrigued by this problem, A. B. Migdal immediately addressed a similar problem for bosons. He realized that in the boson case the situation is fundamentally different: as the well deepens above the critical value, bosons, unlike fermions, can be produced indefinitely, if no repulsion comes into play between them, impeding further development of instability. In 1971, A. B. Migdal (at this time he moved to the L. D. Landau In- stitute of Theoretical Physics) pointed out the possible consequences of such a restructuring of the ground state of the atomic nucleus: a phase transition of the nuclear matter with the formation of a pion condensate. These ideas gave the impetus for the development of an entire field of science: in subsequent years there were large numbers of works devoted to the problem of the pion condensate; the most important of them were by A. B. Migdal and his students. Although these works showed that the pion condensate is absent in ordinary nuclei, they played an important role in the development of modern nuclear physics. These studies developed a consistent theory of pion degrees of freedom (or closely related to them) in nuclear matter. Explicitly accounting for pion degrees of freedom not only improved the theoretical description of a large number of experimental data (magnetic moments, probabilities of magnetic transitions, etc.), but April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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also led to a series of qualitative effects. It thus turned out that pion modes in nuclei are strongly softened – that is, pion production with large momentum in a nuclear medium demands much less energy than in the vacuum. Accounting for this effect makes it possible to understand such nuclear phenomena as the enhancement of the soft pion production in collisions of heavy ions of intermediate and high energies. A. B. Migdal’s works on this subject have many followers worldwide. They alone are among the most cited works in nuclear physics. The absence of a pion condensate in ordinary nuclei doesn’t rule out the possible existence of abnormal nuclei: superdense or with an unusual charge-to-mass ratio. A goal of producing such abnormal nuclei was among the main incentives for creating relativistic heavy ion accelerators. Although these searches have yet to yield results, a large, intensively developing field of nuclear physics has arisen. Softening of the pion degrees of freedom must play an important role in pulsars – neutron stars whose central density can vary, depending on the mass of the star, within a range from a density of the order of nuclear ρ0 to ∼ 10ρ0 . This effect thus naturally explains the rapid cooling of more massive neutron stars after their formation. The superfluidity explanation of the “starquakes” of neutron stars, manifested in disruptions of their periods, is generally accepted. Data for some pulsars doesn’t accord with the normal mechanism of superfluidity. If superfluidity is associated with the pion condensate in this case, theoretical interpretation of the above pulsars becomes much easier. Moreover, within an evolving neutron star, a phase transition may occur with the formation of a pion condensate accompanied by a large discharge of energy, including neutron radiation. The progress in the study of the physics of pion degrees of freedom in nuclei and stars, achieved in the 1980s found reflection in a book written by A. B. Migdal together with his students, which was released after his death by the publisher “Nauka.” In the 1980s A. B. Migdal became fascinated by quantum chromodynamics. As always, he set himself large tasks. Here his “top priority” was to create a theory of confinement. While working on April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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this problem, A. B. Migdal stated some original ideas. In particular, he noted that due to the growth of the effective constant of interaction, the “Coulomb” field of a quark is unstable with respect to the production of “charged” gluons. He began to develop a phenomenological approach to QCD and, together with his students, created a model of hadrons based on QCD concepts, an alternative to bag models. In this model most of the hadron’s energy is concentrated in an extended gluon droplet, at whose ends are a light quark and antiquark (for mesons) or a quark and diquark (for baryons). This model naturally explains why the Regge trajectories for hadrons remain linear all the way to the vanishing angular momentum. This approach stayed incomplete, and AB worked on it until his last days. In his scientific work Migdal, a “born physicist,” always moved from the phenomenon to the most adequate method of its theoretical study. With a superb grasp of the whole arsenal at theoretical physics’ command – from transparent qualitative evaluations to complicated mathematical apparatus – he practically always achieved an impressive balance between ends and means. All of Migdal’s scientific work was very harmonious. Namely a drive for harmony accounts for such characteristic traits of Migdal’s scientific style as the masterly use of phenomenological approaches, the relatively rare employment of standard perturbation theory and, accordingly, his invention of qualitatively new, essentially nonperturbative approaches (shake-off, final state interaction, etc.), and finally, his rate of errors, very low for a highly productive scientist. Migdal the scientist is inseparable from Migdal the teacher. He worked very artistically, and like any artist he needed an audience. In this role there was usually one or several young colleagues (or students) who followed AB’s reasoning and calculations and learned to work in theoretical physics. A. B. Migdal thus trained dozens of active theoretical physicists. His students included future Academicians and corresponding members of the Academy of Sciences (among them the late A.M. Budker, V.M. Galitsky and A.I. Larkin), doctors and of science working in the most diverse fields of modern physics, such as elementary particles, atomic nuclei, condensed matter, plasma, reactors, accelerators... This is the “Migdal school.” April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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A. B. Migdal’s teaching work is connected with the Moscow Engi- neering Physics Institute (MEPI), where he worked since its founding. For over forty years he lectured at MEPI on nuclear theory and approximate methods of quantum theory; his seminars invariably attracted bright students to him. Teaching work in many ways helped Arkady Benediktovich writing the monographs Approximate methods of quantum mechanics (with V. P. Krainov) and Qualitative methods in quantum theory, as well as the previously mentioned books translated into English. Readers’ quiet but indisputable appraisal of the scientific significance and practical usefulness of Migdal’s books lies in the simple fact that they were scooped up almost immediately. In his last 10 or 15 years Migdal took a very enthusiastic and serious approach to extensive work that can only conditionally be grouped under the name of science popularization. This includes numerous articles and books – some belonging to the classic popular science genre (for instance, the little book Quantum Mechanics for Big and Small), as well as books containing important thoughts and observations on the psychology of scientific creativity, the aims of science and its role in society. It suffices to mention the fascinating book Searches for Truth (1978; 1983), the deep conceptual articles “Niels Bohr” and “Physics and Philosophy.” The broadest possible audience always took an interest in Migdal’s TV presentations. In these presentations, as well as in articles in Lit- erary Gazette, he many times voiced his position as a citizen. A typical instance was in 1986, when the TV program “I Doubt the Obvi- ous, Believe in Miracles...” was filmed on the basis of A. B. Migdal’s popular articles and presentations. In this program, he expressed his joy about Andrei Dmitrievich Sakharov’s return from exile (at the time, that name remained under a strict ban). This part was censored by the TV administration, and Migdal had to appeal to A.N. Yakovlev, who was then a member of the Politburo. He argued effectively, and for the first time, the still half-disgraced Academi- cian’s name sounded from TV screens without offensive epithets. A.B. Migdal’s relationship with A.D. Sakharov deserves separate discussion. Migdal always saw Andrei Dmitrievich as model citizen. It was no accident that in 1981 Migdal was among those who helped April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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save Sakharov’s life during one of the most difficult periods of his exile in Gorky. Migdal himself, who had a markedly public temperament, nonetheless shunned direct political activity throughout his life. However, when it was a question of choice, he always behaved with great decency and in the most difficult times didn’t taint himself with even one ignoble act. He is known for his role in fighting to preserve a spirit of free thought in the USSR Academy of Sciences. Andrei Dmitrievich paid tribute to AB with deep respect and after returning from exile recruited him for the founding of Moscow Tri- bune, rightly thinking that AB’s high public reputation and intellect would help in forming this public organization. For such a great creative personality as A. B. Migdal, science was not enough. He can be spoken of in Pushkin’s words: “...an Academician, and a hero, and a seafarer, and a carpenter...” Artists know him as a sculptor and woodcarver, jewelers as a jeweler and collector of stones, underwater divers as one of the creators of the Soviet aqualung, as the organizer and first chairman of the USSR Federation of Underwater Sports, and skiers and mountain climbers justly consider him one of their own, while physicists can only shrug... The meaning of life, according to AB, “is not to reach a goal by the shortest route, but to feel and see as much as possible along the way.” In each of his many “hobbies,” A. B. Migdal reached a professional or near-professional level. As a MEPI professor, in the 1950s, he was a member of the institute’s swimming team. A. B. Migdal created a group for amateur underwater photography and filming, and organized expeditions of divers to the Kuril Islands, during which three underwater films were shot about marine life. Two of them, “Above Us is the Sea of Japan” and “At the Rocks of Moneron,” were screened for general public among the best amateur films in the country. AB was a first-rate teller of humorous stories, which he presented very artistically. Migdal’s many funny “pranks” are well known. For the rest of their lives AB’s friends will remember his 1986 75th birthday celebration, which he moved to April 1 and held at a cafe in the center of the riotous and jubilant Arbat, the former site of the First Moscow Fools Day. The guests were greeted by a polite April 5, 2013 14:20 WSPC/Trim Size: 9in x 6in for Proceedings 3b˙Migdal˙Intro

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doorman who eagerly accepted tips, with only his eyes betraying Migdal, unchanged by makeup. Migdal started off all his lectures, even the most important ones, with a joke. These jokes, like the brilliant Migdalian pranks, would travel around by word of mouth, always supporting the vivacious atmosphere that surrounded Migdal. A. B. Migdal was a great, loyal friend. He not only was always ready to help his friends in difficult times, but always tried to share his joys with them. So, having loved mountains all his life, visiting them in winter and summer, he always tried to initiate his friends into this as well. All these qualities made Migdal the center of any company, bringing him love and admiration. A. B. Migdal’s life and works naturally lead to broader reflections on the role and self-worth of a major, highly gifted personality in science and society. It seems that a key to understanding Migdal’s essence as a person and scientist may be found by paraphrasing the title of his own book Searches for Truth as “searches for harmony.” After all, namely harmony synthesizes truth with the beauty and happiness that were so much a part of Migdal’s view of the world. Scientific and artistic creativity, interaction with people, striving for harmony, striving to be in harmony with the self – all this led Migdal to develop his own holistic perception of life and ways to address the problems of choice along life’s path, the concept of human happiness. He learned of his fatal illness after traveling professionally to Prince- ton University in 1990. He endured his suffering with courage and dignity, delivering a number of brilliant lectures and continuing his scientific work until his very last days. He told the friends who came to see him, “I’m not afraid of death. I’ve lived not one but several happy lives, and I’m happy now. I’m very glad that I learned about my illness early enough to go to mountaineering camp one last time.” A. B. Migdal died at Princeton. The urn with his ashes is buried at Novodevichy Cemetery in Moscow. Through the whole course of his life, Migdal earned the deep respect, sincere sympathy and often even adoration of a great many people of all ages. The unique charm of Migdal’s personality will remain forever in the grateful memory of his many students, friends and admirers – everyone who had the rare good fortune to spend time with this Scientist, Teacher, Man. April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3c˙Migdal-Belya-Mant

REMEMBERING AB∗

S. T. BELYAYEV Division of General and Nuclear Physics National Research Center Kurchatov Institute Moscow 123098, Russia [email protected]

In 1947 I became a second-year student at Moscow State Uni- versity’s Physics and Engineering Department, where a part of the week’s classes were taught at base organizations. Our group’s base was the future Kurchatov Institute, at that time known as the mysterious “Laboratory N o 2,” and later as LIPAN.a Besides group lectures and practical work at the experimental laboratories, we also had access to the general seminars which Igor Vasilyevich Kurchatov tried to hold, with Leonid Vasilyevich Groshev ﬁlling in when he was absent. At the seminar, theorists spoke as welcome co-presenters and commentators. In 1949 I felt ready to approach A. B. Migdal to ask if I could transfer to his theoretical sector. In response, he suggested a number of simple qualitative problems, which I then successfully solved. (Incidentally, AB used the very same “introductory problems” for screening many generations of students.) So I wound up among AB’s students. From 1952 on (for 10 years) I also served as an employee of the Migdal Sector. My memoirs here are mainly inspired by these years of constant communication with AB. After my departure for Novosibirsk in 1962, although our meetings still took place, they became occasional.

∗Published in Russian in Vospominaniya ob Akademike A. B. Migdale,Ed.N.O. Agasyan et al., (Fizmatlit, Moscow, 2003), p. 14. Translated from Russian by James Manteith. aRussian acronym for Laboratory of Measuring Devices of the Academy of Sciences. Currently the National Research Center Kurchatov Institute.

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By the time I arrived at “Sector 10,” headed by AB, B.T. Gelik- man, A. M. Budker, and V. M. Galitsky were already there; later Grechukhin and Strutinsky appeared, then Vaks and Larkin. I can’t say whether AB personally took part in selecting employees, but the composition of the sector clearly stood out as a mix of characters and temperaments, as well as broad interests. The atmosphere was quite liberal and free, even in the choice of research problems. Apparently Kurchatov deliberately gave AB thematic freedom, only occasionally tossing goal-oriented problems his way. AB was simply incapable of working on “necessary tasks”; he needed to “catch fire.” AB also gave others freedom and had little interest in his employees’ specific activities, if these activities lay outside the range of his direct interests. AB was a very unusual boss; he found administrative duties bur- densome and gladly entrusted them to others. Some employee would usually sign bureaucratic document instead of him, and when a document happened to be brought in his presence, he would ask jokingly beforehand, “Now show me how I sign.” The room viewed as his office was typically used for general discussions. If AB appeared and the discussion didn’t quiet down, AB would listen a while, then might say, “How about this: you do some f...cking work for me here, and I’ll f...ck off and go home.” Only after that would everyone go back to their rooms. AB viewed monitoring subordinates’ research activities as unnecessary, apparently believing that the main thing was the sector’s scientific atmosphere and his own example. Only when receiving direct assignments or questions from Kurchatov would he arrange for their discussion. But when a basic approach to a solution was clarified and the last step was to calculate everything painstakingly, he lost interest and passed the initiative to others. He usually worked at home, viewing his sector as a kind of discussion club and appearing there a couple times a week, mainly to tell about his recent results or new ideas. A theorist’s work always includes periods of searching for approaches to a problem and ways to solve it. AB passed through these stages of “trial and error” on his own and rarely brought them up for discussion. All that was April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3c˙Migdal-Belya-Mant

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discussed was the details of the solution, concrete steps. The main thing wasn’t up for discussion. He found it important to have actively interested partners in conversation, but only for honing his own logic and argumentation. This role could be far from easy and far from pleasant. The conversational partner had to offer questions and critique details without offering any alternatives. For instance, it was impossible even to imagine having Budker as part of these conversations. He would immediately propose something original: “Kadya, why don’t you...?” – at which point AB would shoot back, “Andrei! I’ve been thinking this through for weeks, and you only heard about it five minutes ago. Are you really hoping to tell me something new?!”’ Most tried to play the role of passive listeners, while cultured intellectual Galitsky usually wound up as a victim. AB particularly appreciated discussions with him, and only with him did a joint paper ever come to fruition. I can imagine it wasn’t easy to work with AB at this time. A couple of times he asked me about doing work together. This happened at his home. AB picked up a pack of blank paper and started laying out the idea, writing out formulas. My role wasn’t very clear; I tried to make comments or offer alternatives, but AB was absorbed in his own thoughts. But when he felt stuck and needed to reassess something, he would switch to something else: we would discuss his new sculptures, new books or movies. In the late 1950s AB asked me and Galitsky about writing a book on the quantum many-body theory. We agreed to disconnect ourselves from the outside world, sequestering ourselves by winter at his artist friend’s country cottage. This resulted in our having a grand time together, but the work got no farther than a couple of pages of a general outline. In scientific discussions AB appeared very self-confident. He really did have a high estimate of his own ability; he only took on complex problems and developed original methods. He thought following scientific periodicals was a waste of time. For many years his main problem was superconductivity. He analyzed the landmark articles as they appeared, and each time would prove the futility of models proposed by others. He became convinced that a solution was possible only in the framework of the April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3c˙Migdal-Belya-Mant

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fundamental theory of solids. The triumph of quantum electrodynamics pointed the way forward, and by 1957 the primary apparatus of the quantum theory of many bodies and electron gas in metals had been created. But at the finish line, others – not Migdal – attained success. I remember a seminar at the Institute of Physical Prob- lems, where the new BCS theory of superconductivity was discussed. During the break Landau scolded me and Galitsky: “I know AB doesn’t follow journal publications, but why didn’t you point out Cooper’s note to him? After that, AB would have had no problem doing the rest. He had everything ready.” We didn’t argue with Landau, but later Galitsky told me: “I told AB about that work; it made no impression on him.” In a broad sense, AB saw himself as part of the Landau school and discussed his major works with Landau, but AB’s attitude toward Dau was peculiar. Prizing his independence and autonomy, AB kept himself somewhat detached and tried to emphasize the differences in the styles of their work. Landau is known for his amazing intuition. He often qualitatively “guessed” the solution to complex problems without calculations. AB was drawn to an approach with greater mathematical rigor. More than once AB appeared at the sector and excitedly started talking about how Landau was of course mistaken and how he would prove it. But as a rule, a while later, AB would announce, “It turns out Dau was right. I don’t understand how he came up with it; after all, he couldn’t have done all my calculations.” Both the difference in styles and the fruitfulness of their combination can be seen by comparing the pioneering works by Landau and Pomeranchuk on bremsstrahlung of relativistic electrons in a dense medium and these works’ development in subsequent fundamental work by AB. Part of this work was done by AB jointly with a N. M. Polievktov- Nikoladze, a seeker of the doctoral degree recommended to him from Tbilisi. (AB had very warm relations with Adronikashvili, the director of the institute in Tbilisi, and apparently they both coordinated on this issue with Kurchatov). Polievktov-Nikoladze was a good mathematician, and along with this one could feel in him a special interethnic intellectual culture inherited from the two family lines, April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3c˙Migdal-Belya-Mant

Remembering AB 71

well-known in Georgia. The latter factor clearly played a significant role for AB. AB had an unusual way of working with Polievktov. He immediately recognized his higher qualifications in mathematics and spoke openly about this. The work proceeded more traditionally, with a division of tasks and subsequent synthesis. At the time, for AB this was a special case. One of AB’s many pranks was also connected with Polievktov. After his arrival, AB took him to introduce him to Kurchatov. After reaching an agreement beforehand with the secretary, AB entered the office alone with his appearance slightly altered (nose tugged back with a thread, ruffled coiffure) and started introducing himself with a Georgian accent. Partway through the conversation, Kurchatov saw through the ruse and burst out laughing. AB told the story of this prank many times with pride. AB broke new ground in his works. Even when facing trails blazed repeatedly by others, he didn’t bother with preliminary acquaintance with existing models and results. The main thing was being certain that his method was original and correct. When superconductivity’s star faded, he created a new direction: the theory of finite Fermi systems, where he started developing original approaches to describing the properties of nuclei. Once after a lecture at an international conference in Dubna he was asked how his theory of finite Fermi systems related to existing theories. In response, AB recalled an anecdote about an old Gypsy, who, coming out of the tent, saw a bunch of filth-smeared children and thought, “I should give them a bath.” But then he waved his hand and said, “Aw...it’s easier to make new ones!” In this finite Fermi system period, AB noticeably changed the style of his work. At this time a large group of students surrounded him, with many joint publications, both in journals and as monographs. For me, having known him mainly in his “superconductivity period,” this came as a stunning metamorphosis. But I observed this stage from the side, only rarely discussing certain general problems with AB. In the mid-1970s AB phoned me in Novosibirsk and proposed a trip with him to the United States. I said no; I was very busy. But during our meeting in Moscow, AB revisited this suggestion: for a April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3c˙Migdal-Belya-Mant

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long time he hadn’t been allowed to go abroad, but now seemingly the ban was lifted, and he had many interesting offers from America. But he faced restrictions as to his travel companions, and he could get permission to go with me. “Spartak, surely you can’t refuse to pay tribute to your old teacher!” Our month of traveling around America was very intense; AB was tireless, never missing any opportunity for new acquaintances and discussions. Along with this, he took pains to satisfy his thirst for travel and adventure. The first visit was to Los Alamos. After this, over a three-day weekend (including Labor Day) in the car of a local young theorist, the three of us, taking shifts at the wheel, drove about two thousand kilometers to the north. After this, the two of us went on by plane to Berkeley. After that came Santa Barbara, Chicago, Illinois, New York, Long Island. In Santa Barbara, AB asked for a phone call to Feynman at Cal- tech to arrange a meeting. Apparently this wasn’t easy, but a meeting was scheduled, and after a car trip from Santa Barbara to Los Angeles and Pasadena, the meeting took place. I no longer remember the details of the conversation, but recall an impression of mutual probing of shared interests. The initiative belonged to AB; he talked about his general ideas, about pion condensate, and tried to arouse the interest of his partner in the conversation, to provoke discussion. Feynman, though, didn’t directly “turn on” to this, making only as- sociative remarks. From the side, it was quite intriguing to follow this “duel” between two scientific leaders, both absorbed in their own problems. They obviously felt each others’ power, but realized a working relationship was impossible. The meeting with Feynman was a special event. The rest of the work meetings were more traditional. Everywhere there were seminar lectures, discussions, but AB made sure that the rest of the time was filled with a “cultural program” to his taste. His authority was very high, and hosts tried to fulfill all his wishes. The route by car from Los Alamos through the desert passed through desert with a lunar landscape and Indian reservations; we spent the night and met the sunrise at the Grand Canyon. But AB also wanted to hire a small plane for an hour-long flight in the canyon. We made a special side-trip to a place for hot-air balloon April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3c˙Migdal-Belya-Mant

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ﬂight contests. In Santa Barbara we of course swam in the ocean and tried learning to surf. And when one new professor acquaintance turned out to have a yacht and another had an airplane, AB couldn’t turn down either invitation. On the yacht, he asked to sail to a nude beach, and upon learning that this was forbidden, he proposed dropping anchor and swimming to the beach. In the six-seat plane, AB sat next to the owner-pilot, and I sat behind them. AB asked if it was hard to steer the plane, at which he was invited to try his own hand at this. AB, without hesitation, took over the controls and even attempted some kind of maneuver. On the East Coast it was already cold, but AB insisted on swimming in the ocean: “When else willwegettoswimintwooceans?” AB was very many-sided in his interests and hobbies. Art, sports, conversation with people who interested him seemed to take up all his time. Moreover, he gave himself over to any hobby with a passion. I can vividly see him on a mountain slope, ﬂying downhill on poorly controlled skis to the cries of his young friends, “AB, save yourself for science!” But he couldn’t save himself only for science. All the more amazing, then, how much he did for it. April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

A. B. MIGDAL IN MY LIFE∗

ANATOLY LARKIN W.I. Fine Theoretical Physics Institute University of Minnesota Minneapolis, MN 55455, USA

My memory has a better grasp of first impressions. I will try to recreate how I saw my Teacher when I was a young graduate student in the late fifties, and to convey his remarks as I’ve remembered them. I became one of AB’s students because of getting drunk. On November 7, 1955, our group of theorist diploma students gathered at Lenya Rudakov’s in Khimki to observe the day of the GOSR (the Great October Socialist Revolution). Drinking heavily, I proposed a toast to the liquidation of post office boxes. Post office box (POB) was a general term for numerous secret enterprises.a At the time I was a diploma student at Andrei Dmitrievich Sakharov’s POB. Immediately the most sober part of our group gathered in the kitchen and began to discuss not how to liquidate boxes but how to pull me out of the box. My friend Valya Vaks promised to talk with his adviser, A. B. Migdal. Two days later I was at AB’s home on Chkalov Street. At the end of the conversation, AB said he would accept me for correspondence postgraduate study, but that this wasn’t an effective method

∗Published in Russian in Vospominaniya ob Akademike A. B. Migdale,Ed.N.O. Agasyan et al., (Fizmatlit, Moscow, 2003), p. 28. Translated from Russian by James Manteith. aNumerous institutions conducting classified research for the military. Since many of them had no official unclassified names, they were known as PO box number such and such. Eventually in the Brezhnev era “post-office box” or just “box” came to indicate a low-efficient technical research institute with a monstrous number of personnel and virtually no scientific output.

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of instruction and that I should try to get out of the box on my own. AB later said he’d decided to accept me because he thought I bore a resemblance to Stalik Braginsky, whom he liked. (Stanislav Bra- ginsky was a theorist in Leontovich’s group.) I never met Braginsky, but I’m very grateful to him. After an early defense of my diploma under A. D. Sakharov, I started working for AB. AB had an original and very effective manner of teaching begin- ners. You had to spend the entire day, sometimes staying late into the night, at home with AB, sitting beside him and watching the Teacher at work. In this way I quickly mastered diagram technique in solid state theory. There was no way to learn it from books and articles – these simply didn’t exist. The technique took shape before my eyes. (I think that diagram technique, like geometry in ancient Greece, is an oral science and develops only through communication.) Such observation of the Teacher’s work was still more useful for the development of my physics intuition. As I saw it, my role was to stand watch in case AB made a mistake. At first I understood little, but didn’t want to interrupt the creative process with stupid questions. I had to guess whether my lack of understanding came from ignorance, meaning that I could figure things out later on, or whether there was an error in the calculations or logic. Apparently I guessed successfully. Valya Vaks said that once when he was sitting beside AB he missed an important error, and AB told him, “That’s an error Tolya would have caught...” I think now that the reason we were needed wasn’t really for finding errors. Any work, especially creative work, should bring positive emotions not only in the future but every day. It gave AB pleasure when he was able to teach someone. It brought him special joy if his successful techniques were a source of genuine delight. And maybe we made it a little harder for him to be distracted from science by other interesting things. His teaching was very tactful. A typical working day began with the words: “Let’s warm up by getting the known result.” In 1956 AB developed a theory of superconductivity. Sometimes he said, “I came a little late to physics – all of quantum mechanics was already done – but never mind, we’ll do a theory of superconduc- May 13, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

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tivity.” Here he was twice mistaken. His quantum mechanics problem on ionization in beta-decay is now in textbooks. AB said he found the problem’s solution in a dream. He thought about the problem for a long time, couldn’t sleep, and then had a dream where a circus rider jumped off a horse. In the morning he realized that the nucleus runs away like the horse while the electrons remain. Earlier than Fröhlich’s work, AB realized that the exchange of phonons leads to attraction between electrons. The discovery of the isotopic effect confirmed his guess that phonons are important for superconductivity. It remained to prove that the interaction leads to a gap in the spectrum of single-electron excitations. Spectrum calculation based on perturbation theory didn’t yield a gap. But in real metals, the interaction isn’t weak, and it’s necessary to abandon perturbation theory and develop a theory of strong interaction. The fortress didn’t yield to the first assault; a siege had to be laid. Diagram technique was designed for just this. By the time I came along, Migdal and Galitsky had already completed their work proving that the excitation spectrum is determined by Green’s function poles. That meant it was necessary to calculate a Green’s function. Migdal succeeded in obtaining a closed system of equations for Green’s functions. In the process, he discovered that amplitude in Landau’s Fermi-liquid theory depends on which approaches zero more rapidly: the frequency or the wave vector. In addition, he calculated the phonon Green’s function and discovered a singularity in the phonon spectrum (the Migdal-Kohn effect). AB didn’t attach much importance to this effect – it only interfered with solving the system of equations. In the end, the system was solved, but no gap in the spectrum appeared. To me, a beginning graduate student, diagram technique seemed to offer a method for all future discoveries. The only thing needed was to make a summation of all the needed diagrams, and all effects would be explained. But it has remained a mystery to me why Migdal became so engrossed in technique, seeking a Green’s function and not a physical phenomenon. Perhaps he was influenced by Landau’s superfluidity work, which asserted that the excitation spectrum, not Bose condensation, matters for superfluidity. April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

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AB kept searching for an error in his calculations, and I had to go to work at the POB. (The law making it a criminal offense not to report for work was abolished that year, but I didn’t know this.) I asked AB for advice about what to work on. He replied, “Let’s meet tomorrow at the Kaluzhskaya subway station (now the Octo- berstation).WecangoonfoottotheLandauseminarandtalk along the way.” On the way, he said Brueckner had come to Moscow and that logarithmic divergences were arising in the Coulomb interaction problem. Such divergences arise in the collision integral in the Landau kinetic equation for plasma. Diagram technique is a good method for eliminating these divergences. Arriving at my POB, I started looking for Brueckner’s work, but couldn’t find it. (The work by Gell-Mann and Brueckner appeared only a year later.) On account of my youth, I took slight offense at the Teacher, wondering why he hadn’t told me that the density of states needed consideration. Knowing diagram technique, I could have done this task earlier and better than Gell-Mann and Brueck- ner.) Still, I found a work by Matsubara. It had been published in a Japanese journal and was little known then. In the work, Matsubara had devised a temperature diagram technique and, as an example, found Debye screening in plasma. I realized that Matsubara hadn’t proved Wick’s theorem – the basis of any diagram technique – but with youthful daring, in the Migdal-Galitsky formula for the two- particle Green’s function I replaced the Fermi distribution functions with Boltzmann functions and started calculating the collision integral. After many errors, I succeeded in calculating the sublogarithmic factor in this integral. When I arrived and showed Migdal this result, he showed no particular interest and asked me to tell Belyayev and Galitsky about it. They immediately noticed that Wick’s theorem wasn’t proved and didn’t listen. (Vitya Galitsky later told me he thought that a kinematic interaction would arise at the final temperature, as with spin waves.) Only two years later did I succeed in justifying my results and publishing the work. In 1957, Andrei Sakharov helped me transfer to graduate school under Migdal, and I was able to work entirely on diagrams. At this time the theory of superconductivity was developed, not by Migdal May 13, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

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but by Bardeen, Cooper and Schrieffer (BCS). Before this Migdal had said that he usually didn’t worry if something he had been working on was done earlier by others: “That means the task wasn’t difficult and wasn’t worth working on.” He couldn’t say that about superconductivity. AB relayed his conversation with Bogolyubov: “What a pity that I didn’t think to make your canonical transformation when I realized that phonons cause attraction between electrons.” Bogolyubov replied: “And I did the canonical transformation in 1947, but didn’t know about phonons, and with Coulomb repulsion I obtained a zero result.” AB immediately began to seek an application of BCS theory in nuclear physics. All day he and I sat together and worked out a table of isotopes, counting even-odd mass differences between nuclei. For almost all heavy nuclei these differences were identical. That meant this was a property of nuclear matter. AB recalled Landau’s superfluidity model for the moments of inertia of nuclei. In this model, the moments of inertia were too small. Migdal phoned Landau and said, “Dau, we’ve never done a collaborative work together; let’s do a work on moments of inertia.” Apparently Dau replied evasively; I don’t remember any further contact between them. I stayed busy with my plasma, while AB’s work went slowly: summer was approaching, and scuba was taking up more and more time. Next I will describe how a random event can change the fate not only of one person but of a whole direction in science. On the first Thursday in September 1958, after the seminar, I was packed into Landau’s office along with his students. (That spring I had reported on my work at the Landau seminar and received approval, and I felt at ease in his office.) Landau came in and said, “The problem of moments of inertia of nuclei is up for grabs; it needs solving.” Someone answered, “All right, we’ll do it.” I’m a slowpoke, and I was already back home when it struck me: “What about the Teacher? He’s working on this problem; I have to tell him.” I hesitated as to whether it was appropriate to relate what I had heard in private, but decided that Migdal and Landau were close April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

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friends and would figure things out. The next day, the first Friday in September after vacation, the sector met and AB called on everyone to band together and develop a theory of elementary particles, or, more precisely, a theory of multiple production. (September had begun the same way the year before and two years before. AB had a good idea: while there are many mesons, they can be described by the classical field, whereas particles are quantum fluctuations of this field.) I arrived late, and when I came in, I said that Landau had told his students to solve the problem of the moment of inertia. Immediately elementary particles were forgotten; Valya Vaks and I took turns standing watch, and in two weeks AB finished his work and described it to Landau. Later a certain cooling occurred in my relationship with AB. There were no objective reasons for this. On the contrary, AB showed the utmost concern for me. I needed employment, needed help getting an apartment. But apparently I showed less enthusiasm. I remember once Vitya Galitsky called me and Valya Vaks together and said the Teacher was offended at us; apparently we needed to tell him we loved him more often. Another time, in a small circle, I spoke my mind about a trait of Migdal’s that I didn’t like, and immediately got a reproof from Vitya: “You know, Tolya, you should love people more – not closing your eyes to how they fall short, but loving them along with their shortcomings.” In my life and in these memoirs I’ve tried to follow this commandment of Galitsky’s. Apparently there was this same cooling effect in other students’ relationships with AB when they grew up, and he developed a theory for this effect. Much later, in 1976, AB gave a speech of response at the Landau Institute’s Scientific Council, in honor of his jubilee birthday. It was a memorable speech: “To teach a person anything, the student has to love the teacher. That’s why I always tried to make beginning students fall in love. But after falling in love, there always comes a time of cooling. If people are intellectually developed, they don’t push things to the breaking point, but keep friendly relations.” I am glad that Migdal and I kept friendly relations. We took trips together to the mountains, to Leningrad, to Uzhgorod, to Nor- Amberd, to Kiev. I remember how when we flew to Uzhgorod the May 13, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

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Lvov-Uzhgorod flight was canceled, and AB and I slept on benches at the Lvov airport. But when we traveled to Kiev and Misha Urin bought us all second-class tickets, AB fumed, “When I needed to speak with Landau during a trip, I bought tickets for a two- person compartment; Misha wants to talk with me in the second- class coach.” In the summer of 1962, AB invited me to spend two weeks with him at a country home at Nikolina Gora and do work on superfluid Fermi liquid applied to the nucleus. We worked very hard, sometimes arguing late into the night. Falling asleep, I would think that maybe AB was right, then in the morning the argument would start again with changed sides. I remember one general remark from AB when I told him, “Why are we fighting; we’ve settled this question and already made a notation. You have a lot of energy, but if I start discussing old stuff, I won’tbeabletomoveontoanythingnew.” AB replied, “Tolya, you’re wrong. Energy doesn’t need saving; what’s needed is constant self-invigoration.” In two weeks we did two major works, then over several months finished them and wrote articles. I was in a hurry to switch to other work, but AB discussed the completed work again and rewrote already written pieces. He treated all his work like this: he would redo finished work for several months and sometimes years. AB believed that everything in life, including scientific work, should be beautiful. I remember his indignation at a plumber who laid a pipe crookedly in the bathroom: “How could he have done it? This means he doesn’t like his work.” AB wanted me to keep studying the nucleus, but didn’t pressure me. I liked working with Valya Vaks more, though. Besides, I liked discussing my work with friends my own age, or slightly older. I had friends like that at the Institute of Theoretical and Experimen- tal Physics and the Institute of Physical Problems, and I took turns working on either field theory or solids. I had no friends in nuclear physics. AB gathered many talented young guys in his sector (they were called “Migdalites”), but I disliked the role of chief, even temporary acting chief. April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

A. B. Migdal in My Life 81

At this time, Belyayev and Galitsky left for Novosibirsk.b Iwas infected by their romanticism and told AB I wanted to go and join them. AB’s temper flared, and he said that even if I had decided I could go, he thought this was bad for me, for him, and for the sector. Ultimately I didn’t go to Novosibirsk. But when in 1965 I was invited to the newly organized Landau Institute, AB approved of this move. Perhaps he foresaw that his son Sasha and he himself would be at the Landau Institute, but more likely he just understood how well things would go for me at this institute and wanted what was best. When AB moved to the Landau Institute in 1970, I was afraid that he would find it difficult to exchange an atmosphere of adoring students for the Landau Institute’s democratic atmosphere. I even told my student Dima Khmelnitsky that he’d corrected my Teacher too freely at the seminar and that eggs don’t teach the chicken, especially when the eggs are grandchildren. But AB felt comfortable at the institute. He said he realized how much it had poisoned his life that at the Institute of Atomic Energy he had to go through a checkpoint and show the guard a pass.

LAST CONVERSATION

In 1990 I returned from a business trip and learned that AB was in the U.S. and had an incurable disease. I think a person in that state wants to hear that someone needs him. And I really did need his advice. I called AB and asked, “Should I leave the country?” Many of my friends had left the country, but I didn’t want to go. I hoped AB would strengthen me in this conviction. When his son Sasha left, AB said he didn’t want to go. Our arguments were diﬀerent. I believed that a person should die in the same country he was born in, while AB thought life in the Soviet Union was more interesting. But it turned out that AB had thought through my

bIn 1957 Khrushchev launched a large-scale project for the development of science in Siberia. The Siberian Branch of the USSR Academy of Sciences was created. Many new research institutions were founded in Akademgorodok, a suburb of Novosibirsk. A number of outstanding scientists from Moscow and other cities in the European part of the USSR were relocated there. Among them was, for instance, G.I. Budker, the founder of the world-famous Institute of Nuclear Physics currently bearing his name. May 13, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

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problems better than I had. He replied, “Tolya, I don’t understand how you’ll be able to get your large family out, but I think leaving is necessary.” Overcome, I didn’t ask him why. I always thought of my Fate as loving me. The one thing needed is not to reject Fate’s gifts. One of the best of these gifts was my Teacher, A. B. Migdal.

WHAT MIGDAL LOVED

1. AB loved science. Obviously, without love of science, work in science is impossible. But what did he love about science? Roughly speaking, most of all he loved himself in science. He was one of those scientists for whom seeking truth is more interesting than truth itself. AB said he read others’ work like this: he would read the title and sometimes the abstract, then would stop reading and would think about how he’d have done the work. He didn’t like reading or listening about others’ work, but the work process delighted him. He especially liked a result if it could delight his friends, as when he derived a quantum kinetic equation during a debate with Landau. AB dreamed of winning a Nobel Prize, but I think this wasn’t for the sake of eternal or worldwide glory, but for delighting his friends. In 1966 Moscow hosted the 10th Low-Temperature Conference. One report was called “The Migdal-Kohn Effect.” I told Migdal about this. He responded, “Give me the program, and I’ll show it to the Journal of Experimental and Theoretical Physics employee who reg- isters participants. Otherwise, she tells me I’m a nuclear physicist and have no business going to a low-temperature conference.” 2. AB loved practical jokes. I remember Ya. A. Smorodinsky visiting AB at home and saying, “Tomorrow is April Fool’s Day, and here you are doing something scientific.” After long preparation, supposedly an employee of the foreign department of the Academy of Sciences had phoned Landau and said, “The Japanese physicist Kikuchi has flown in to Moscow; he wants to meet with you. Is it all right to give him your phone number?” Then Smorodinsky, in Kikuchi’s voice, phoned Landau and said that he and his co-author Yamoguchi had made a further develop- April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

A. B. Migdal in My Life 83

ment in Fermi liquid theory and noticed that amplitude depends on the order of the limiting transition. An hour or two later, Landau phoned Migdal and said, “Kikuchi has flown in; he’s not so dumb, he made the observation about amplitude like you did. Tomorrow he’s coming to Physics Problems.” The next day (April 1) everyone assembled, but Kikuchi never showed up. When an irate Landau planned to phone the Academy, Migdal said, “Maybe Kikuchi is here?” A year later, AB and B. M. Pontecorvo composed a letter which Pontecorvo had allegedly received in Dubna from Pauli. In the letter, “Pauli” told about his new results, supposedly supporting the theory recently published by Heisenberg and Pauli. Pontecorvo phoned Landau, and the next day, Thursday (April 1), E. M. Lifshitz read this letter aloud at the Landau seminar. Landau remarked, “I’ve long led a parasitic life: I don’t read others’ works but ask to be told about them. But now I realize I’ve been a parasite on a corpse. How could such great people’s work have gone unnoticed?” During the break, Pontecorvo convinced Lev Okun to clarify that the data described by “Pauli” could also be explained without the Heisenberg- Pauli theory. At the end of the seminar, AB couldn’t take any more and said that the first letters of the paragraphs in the “Pauli” letter formed the word “Idiots.” Later AB said, “I’m glad Okun fell for it. Lyovareactstoeverythingveryquickly;letthisbealessontohim.” AB enjoyed good pranks, even if he was their object. He loved to tell of how friends had once slipped the Moscow phone book into his backpack with a note: “Telegraph the sign and magnitude of the difference between the number of Ivanovs and the number of Rabinoviches.” Such books were a rarity then. AB was proud of the book; it would have been a pity to throw it away. He had to carry it through high mountain passes. Much later, AB received a letter from a “foreign physicist”: “I was told that you’ve been speaking badly of my work. Accordingly, I’m forced to revoke my invitation.” AB fumed, “Who could have told him?” – until Sasha said, “Happy April Fool’s Day, papa!” I seem to have done little to show my delight. I remember AB May 13, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

84 A. Larkin

once asked me, “So, Misha Urin thinks my tomfoolery undermines my authority. What do you think?” I replied that in my eyes his tomfoolery only caused his authority to grow. 3. AB loved the sea and mountains. I remember in 1956 Vitya Suetin, a student at the Bauman Institute, came to AB, and they started to design an underwater rifle, a mask, a snorkel. They decided to make the snorkel from toothbrush holders. For some reason they wanted to make the valve from a ping-pong ball. A year later, they had already designed a scuba set and made drawings of the gear. Scuba took a lot of time and money. I remember how Migdal’s wife, Tatyana Lvovna, reacted to the reduction in income: “Never mind, there’ll be one less dress and one less scuba set.” AB suggested that it would be better to do without Beck, their beloved dog. Beck, a huge black Great Dane, loved to come up from behind, lay his head on a student’s shoulder and join him in looking at what the Teacher was writing. Apparently it was possible just to make do without the dress. Still, there was much excitement after he brought back his underwater film. The hall at the Institute of Atomic Energy club, where AB showed the film, was packed solid; there was no room for the director of the institute, and AB later phoned Aleksandrov and apologized. I thought scuba was a sport for the gods and made no effort to learn it. But hiking in the mountains has greatly enhanced my life, and this was AB’s doing. He took me to the Uzunkol alpine camp, and he walked roped up with me to my first summit. I was later in the mountains many times with AB and without him. AB’s delight was transmitted to me as well. But not only the mountains themselves appealed to AB in the mountains. He sought to meet with good people there. Once in the mountains I was a witness to AB arguing with Vizborc about flying saucers. AB had many friends among the first-class climbers. Once I came to the director of the Arkhyz tourist base who was a good friend of AB. I was carrying a letter from AB to the director of this base attesting me as a good personal friend of AB. The scene was almost

cYuri Vizbor (1934-1984) was a well-known Soviet poet, song-writer, and actor. April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

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like in Golden Calf : d “Wow,” exclaimed the director, “the fellow sitting over there is also a friend of Migdal’s!” All these mountain climbers were his friends. At age 79, Migdal spent the last summer of his life in the mountains. Once I invited Migdal to go canoeing on the Sherna River, near Moscow. AB was as happy as a child: “What a beautiful place! I didn’t know there were such untouched places so close to Moscow. It’s as if I were back in my childhood.” This episode showed me what life was like for AB as a child in the little Belarus town of Lida. 4. AB loved art. In art, as in science, AB loved most what he could do himself. And there was much he knew how to do: carving wood, cutting precious and semi-precious gems, making jewelry from gold, silver, glass, gemstones. And all this at an inspiring level. I remember his indignation when someone at the JETP offices told him, “Ah, a cameo...” – “What’s that supposed to mean? I’ll write an opera and they’ll say, ‘Ah, an opera...’” But he didn’t much care for opera. I remember asking him for time off to go to the Bolshoi Theater. AB said it’s better to listen to symphonic music and only released me when I said that my Tanya was waiting for me at the theater. I didn’t understand sculpture very well, but it was pleasant to watch AB at work. He didn’t see carving as work; science was work. Sometimes while working he would say he was tired and needed to rest, and for half an hour he would carve. Around then, in 1956, ABcarvedastickofboxwoodintoasculptureofTatyanaLvovnain the image of Venus. This came out as a small statuette. Many years later, in a tangle of boxwood windfalls in the Caucasus, I salvaged Migdal a large chunk of a boxwood log as a gift. He responded, “I have so much material, I may never have time to work with all of it.” This was a rare occasion when he thought about life’s finiteness. But most of all he wasn’t very happy about the boxwood because by that time his wood-carving hobby had given way to a metal-carving

dA satirical dilogy Golden Calf and Twelve Chairs written by Ilya Ilf and Evgeny Petrov in the 1930’s with an intelligent con artist as the main character was very popular in the Soviet Union. May 13, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

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hobby. At this time he received a set of very good cutters for his lathe as a gift, and AB was happy about this gift, but worried that it was too valuable a present from someone he wasn’t very close to. Moreover, AB recalled that when another person sent him a case of good Georgian wine, along with a request for a review of his work, AB refused to review the work, but the wine needed drinking to keep it from spoiling. 5. AB loved his family. He wanted his son Sasha to work in science. I remember two disputes between AB and B. T. Geilikman. When Sasha got his passport at age 16, AB said that Sasha should decide on his own which nationality to choose,e but that he advised him to register as Russian based on his mother, because he wanted to Sashatoworkinscienceandthe“fifthpoint”f would interfere with this. Much later, when Geilikman remarked that Sasha’s main stimulus for work in science was ambitiousness, AB replied that the taste for science would come later, and for the time being, if ambitiousness helped with learning science, let him be ambitious. Always cheerful, AB was distraught for several months when Sasha was applying to the Moscow Institute for Physics and Technology. The institute had announced that the school students who took the first three places in a special competition would be accepted without examinations. The first three places went to students who had finished the ninth grade and still had no certificates of graduation, and the institute refused to accept them. AB was indignant: “I wouldn’t argue, but after all, they promised to accept them. How can they go back on their word?” The institute agreed to accept only Sasha, but AB managed to get all three boys accepted to the institute on probation. After they’d passed the school examinations for a matriculation certificate,

eIn Russian the word “nationality” is used to mean ethnic origin. What is known as nationality in the West is called citizenship. Each Soviet citizen, upon receiving a passport at the age of sixteen, had to indicate his “nationality.” If both parents had the same nationality this would be the one; if not, he/she could choose between the two nationalities of the parents. f Soviet “passport” (which was in fact an internal ID card) carried extensive information such as home address, marital status, etc. “Nationality” — was entry number 5. It was mandatory to disclose these data in all oﬃcial documents. Entry number 5 became a euphemism for “Jewish.” April 5, 2013 14:21 WSPC/Trim Size: 9in x 6in for Proceedings 3d˙Migdal-Larkin-Mant

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outside the regular program, they transferred to the institute as students. 6. AB valued friendship. I remember a comment AB made about French Communists. Once when Professor Sliv from Leningrad paid AB a visit, AB told him about a friend of his, a French physicist. Sliv remarked, “Did you know that your friend is the secretary of the district committee of the French Communist Party?” AB replied, “I know, but I think the secretary of the district committee in France isn’t at all the same as the secretary of the Krasnopresnensky district committee.” I agreed with AB, but was surprised. I disapproved but understood why people joined the Soviet Communist Party for various reasons. But I couldn’t understand why physicists would join the French Communist Party. I asked AB about this. He answered, “Se- curity.” To my surprise, he clariﬁed this as follows: “In this world you need to have friends, and French Communists are very friendly people.” This explanation greatly shook my conﬁdence in my principle: “No one owed, a member of nothing.” I decided that my Party was the school of Migdal, the school of Landau. April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

MEMORIES OF A. B. MIGDAL∗

V. A. KHODEL Russian Research Center Kurchatov Institute 1, Akademika Kurchatova pl., Moscow 123182, Russia and McDonnell Center for the Space Sciences and Department of Physics Washington University, St. Louis, MO 63130, USA [email protected]

These notes record things that live in my memory connected with Arkady Benediktovich Migdal. He entered my life when I was 17, and became my teacher. “You meant all in my fate” – Boris Pasternak said these words as if speaking for me. Fate is a chain of phase transitions from one state to another, which happen to a person throughout his life. A teacher determines much in this chain – choice of path, professional training. A teacher gives guidance at the path’s beginning, and comes to help in difficult times. My first meeting with the Teacher occurred after I graduated from school with a gold medal (at the time, this came with a serious in- dulgence: there was no need to take entrance exams, only to have an interview) and planned to apply to the Moscow Engineering Physics Institute (MEPI). It was a warm summer day when I came to the interview, opposite the main post office, in the yellow building which housed MEPI then. Entering the fairly large hall, where teachers from the institute sat at little tables and examined prospective students, among them I saw two strikingly different people. The shorter one, with dark, sad eyes, spoke rather slowly and softly, as if afraid of disturbing colleagues at other tables. The second one, gray-eyed and

∗Published in Vospominaniya ob Akademike A. B. Migdale, Ed. N.O. Agasyan et al., (Fizmatlit, Moscow, 2003), p. 49. Translated from Russian by James Manteith.

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burly, with the face of a boxer and an athletic haircut, basically led the conversation, which bore little resemblance to an examination. The questions they asked had very little to do with the school program, and at first I proceeded shakily; then because they were nice, I grew bolder, began to think out loud, and gave an intelligible answer to the last of their questions. Apparently this final point – whether it’s possible to draw a line on a sheet in a grid-ruled notebook in a way avoiding all the intersections of the notebook’s horizontal and vertical lines – decided everything. Then closer to winter our dean’s secretary phoned and gave me a number I was meant to call. As a result, one autumn day in 1956, I stood on the threshold of an apartment on the fifth floor of a building on Chkalov Street, and the door was opened by that same athletic- looking person who had spoken with me in the summer. That’s how at 17 I became a student in the school of A. B. Migdal. This school’s main feature was the figure of the Teacher himself. He taught there basically alone from morning to evening. For many years, along with his other students, I was a spectator of plays in this theater with one actor – plays where the actor didn’t know the script, as the plays themselves were written right before our eyes. As a rule, the plays’ material came from problems that comprised the contents of his future works. But sometimes he would depart from the usual nuclear physics and attack world-ether theory, trying to find a mechanism to eliminate friction experienced by elementary particles moving through this ether, or quantum electrodynamics, attempting to deduce a closed equation for finding the world constant e2/hc. Lively figurative language – “We’ll walk singing songs around singular points!”, “One-sixth is of the order of one-tenth, which is much less than 10 percent,” “The integration’s done and... face-down in the dirt!” – was among the important parts of the play, where “from nothing... suddenly a new world arises and acquires flesh and blood.” This world was born in the author’s and performer’s grueling struggle with himself: AB (as he was often called by those who knew him well) liked to repeat: “You need to look for arguments against yourself – arguments “for” will always find themselves on their own”... And April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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he sought these with incredible tenacity until he either overturned the initial assertion or became convinced, after a huge number of attempts, that everything was OK. Namely this explains why his works contain almost no errors. True, the OK came very rarely – after all, it’s well known that the efficiency index of even the most talented creative minds adds up to only a few percent. Ultimately because of this self-torture the young spectators made it their own habit not to go easy on themselves and to analyze problems honestly – not only in science, by the way. The Teacher never wasted words, knowing full well that he would be understood subtly. I remember the 1960s and the battle between the pack of “Marxist biologists” and the scant group of scientists, mostly physicists, over Lysenko’s theory of the inheritance of acquired traits. I remember how funnily AB mimed the face of Lysenko after M. A. Leontovich asked him, at a meeting of the Academy of Sciences, “Can a frost-covered mare give birth to a frost-covered foal?” That alone was enough. As AB often liked to say in the circle of his students, “I’m happy that among us there are no bastards.” I think this wasn’t only because of the initial selection. The school also played its part. In those years, a tremendous number of “ordinary” people, encouraged by a system that promoted hatred in all its forms, were obsessed by the struggle not only against genetics but also against theoretical physics – especially quantum mechanics and the general theory of relativity – flooding scientific institutes with their works along this line. “Letters from the workers” needed answering. And AB responded: “Before considering such work, let’s first find out what else the author has done in physics besides the proposed ‘night- marish discovery.’ Nothing? Then most likely we’re dealing with the paranoid syndrome and it’s probably not worth wasting time.” The first book AB gave me from his library was Bridgman’s famous book Dimensional Analysis. From it I first learned that the period of a pendulum’s oscillation can be found without making any calculations, just by using the fact that it oscillates under the influence of gravity. But it’s impossible to calculate the mass of an electron from electrodynamics. AB loved this book and planned to April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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write something in the same vein, even finding a title: Calculations without Calculations. Later he did what he had wanted, but “took wider,” with his book including qualitative evaluations of the characteristics of phenomena in different areas of physics. This book was translated into English by A. Leggett, one of the best theoretical physicists working in the U.S. AB would ask his students, “How should you solve a new problem?” And he answered his own question: “Based on common sense.” His favorite saying in those years was a parable about Jesus Christ walking with his disciples on the water as if upon dry land. Christ, addressing a freshly made disciple, says, “Walk like everyone else – on the rocks. Stop showing off!” One of the main components in common sense as AB understood it was a kind of principle of correspondence. The essence of this principle was that any research results, even the most unexpected ones, should be put to a test: is it consistent with results already known to science in the same range of parameters and under the same conditions, where the said results have already undergone the relevant expert examination? And if the new theory successfully passed this test but “the experiment disagrees with the theory, then so much the worse for the experiment, because such work is protected by four hundred years of experience in theoretical physics, and an individual experiment – by nothing.” In general, AB reflected a lot on the psychology and technology of scientific creativity, going on to write a whole book on the subject. He saw pursuit of truth as the main engine of creativity. As for himself, besides this, the fuel for his “engine” was often polemical fervor, with which the Teacher was excessively endowed, and which he lent to many of his students. Thus the quantitative theory of multiple scattering of particles in a medium, now called the Landau- Pomeranchuk-Migdal effect, was devised by AB after the appearance of a work by Landau and Pomeranchuk, because of his dissatisfaction with how his two colleagues, more famous than him at the time, had solved this problem. The method of solution proposed by AB enabled solving a whole series of important problems in theoretical physics and was highly regarded by Landau and Pomeranchuk, among others. April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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Indeed, in the fate of the theory of finite Fermi systems, which later became one of the most significant developments in the theory of interacting Fermi systems, polemical fervor also played a far from minor role. Once AB came to work and told Tolya Larkin: “Landau told a pack of lies with his Fermi-liquid theory – his formulas don’t fit my phonons!” This was in reference to AB’s famous work on the study of electron-phonon interaction, which had a gigantic impact on the diagram approach to many-body theory and was mentioned by Bardeen in his Nobel lecture. I no longer remember Tolya’s answer, but afterward there came a pause of a few weeks, and then suddenly AB brought the text of his new article, which generalized Landau’s formulas into a system of two types of particles. This was the first experiment with applying Landau’s ideas in atomic nucleus theory. Later works on this subject flowed like a river and formed the substance of a new method in the theory of nuclear phenomena – a method based on using effective nucleon-nucleon interaction, universal for all nuclei, rather than a set of parameters varying from one nucleus to another, as was earlier the case. Originally AB called this the Saint-Laurent method, writing in the preface to one of the main articles that the famous fashion designer had once declared that he’d make women wear coats in the form of sundresses. The preface’s polemical fervor didn’t fall on deaf ears: the “nuclear community” read the article and started actively citing the new theory, but, rather than a coat sewn in the shape of a sundress, preferred a coat in the shape of a kimono, its “cut” designed by Vauterin and Brink. They borrowed AB’s idea of the universality of effective nuclear interactions, and, blowing off all ideology, bundled the idea into the Hartree-Fock method with effective forces and used it to calculate global characteristics of nuclei – their binding energies, radii – doing as the Teacher had originally forbidden. I found all this particularly offensive. I spent a lot of effort attempting to show, and ultimately showed even before their work appeared, that the then- popular Strutinsky method of calculating the shell correction to the total binding energy of nuclei, fit flawlessly into the scheme of finite Fermi system theory. AB long resisted, saying there’s no way to reliably calculate a few MeV correction if the total energy of the nucleus April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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is a thousand times greater than the correction. The real cause of his resistance was that Landau’s Fermi-liquid theory had no suitable tool to calculate the total energy of the system. Alas, following Strutinsky, I parametrized the droplet part instead of building an effective functional for its calculation using consistency conditions between the mass operator and density. Then the theory of finite Fermi systems would have been completely finished. Later we did this with Edik Sapershtein, and AB agreed with us, including our work’s main results in the new edition of his book on the theory of finite Fermi systems, but, in chess terms, the time had elapsed. AB held common sense in great esteem not only in the analysis of new phenomenon. Soon after the war’s end, when he headed Sector 10 at the Academy of Sciences Laboratory of Measuring Devices, abbreviated to LIPAN (the name given to the Institute of Atomic Energy at the time, for the sake of secrecya), one day a provincial- looking, no longer very young man came by, artillery captain Budker. He didn’t elicit much sympathy from AB, and to put a final dot on the “i” AB asked him, “What is the spin of the deuteron?” AB later said that Budker’s eyes showed he was hearing the word “deuteron” for the first time. But Budker’s answer stunned him: “Well, what can it be, anyway? Either zero or one!” “I realized instantly,” AB recalled later, “that this man would go far.” And he wasn’t mistaken. Budker not only became the most famous member of AB’s team but was elected to the Academy of Sci- ences before anyone else.b Of course, at that time nobody could foresee Budker’s distant future. However, his talent was clearly visible. Having become an employee of the sector, Budker gushed out a stream of ideas on his boss, sometimes driving Migdal into a state of white heat. But the examination which these ideas thus had was

aCurrently the National Research Center Kurchatov Institute. bGersh Itzkovich Budker (1918-1977) was an outstanding Soviet physicist, Academician of the USSR Academy of Sciences since 1964. Founder and ﬁrst director of the Institute of Nuclear Physics of the Siberian Branch of the USSR Academy of Sciences, he authored numerous discoveries and inventions in the ﬁeld of plasma physics and accelerator physics. April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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so flawless and fruitful that there’s now no way to imagine the experimental physics of elementary particles without them. And when, having left hearth and home to head up the creation of a new physics center in Siberia, Budker was elected to the Academy, he put a lot of energy into seeing that his former boss also became an Academician at the next elections. AB treated students like his children, and maybe even more passionately. He was free of jealousy toward others’ success, because he himself was extremely talented, and not only in science. His attitude toward the problem of fathers and children can be characterized, better than many other things could, by the gift inscription on one of his own books, given to a “child”: “The teacher who loses a competition to his student has actually won.” He recalled that once in his youth he had to take up a shovel alongside a professional digger, who, encouraging the “young soldier,” said, “Take wider!” And when AB would hear something sensible, he too would tell the student, “Take wider!” AB liked to tell this joke. There was a man with a tomcat who disappeared somewhere every evening, returning toward morning. When the owner got sick of this, he went and had the cat castrated. Indeed, for some time the cat spent the night at home, but then he started slipping away again in the evenings. The surprised owner asked the cat, “Just what’s going on now?” “I’m working as a con- sultant,” the cat replied. And AB said he foresaw a time when he himself would no longer be able to do anything worthwhile. “Then I’ll start consulting for students.” Indeed, his mind was so overloaded with his own scientific questions that he almost never had room to burden it with some secondary problem, so at times it was senseless to discuss anything of your own with him. But everything changed when it came to matters that were more prosaic, but were important for his employees. In those years – really, just as at any other time under Soviet power – the most critical issue was the “housing problem,” which “ruined many.” AB helped many with these issues. In my case, by the time I’m speaking of, I had already worked at the Institute for more than 15 years and been a doctor of science for five, but I continued to live with my wife and two April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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children in a room in a communal apartment, although based on the position I held at our institute then, I should have gotten separate housing. It was promised to me a few times, but then it turned out that my time hadn’t yet arrived. There was a system in place through which an employee who received an apartment in a new building was meant to work a while at his construction site – usually at the final stage, when the frame was ready and there was something to paint, wallpaper and the like. The last time I worked there for the allotted term, but in the building’s settling I again got nothing. Learning of this, AB, who by that time had already worked for several years at Chernogolovka, became indignant. At a meeting of the Academy of Sciences, he approached V. A. Legasov, who oversaw affairs at the Institute then. I don’t know what he said, but a few days later I was summoned to institute’s management office, where I was handed the keys to an apartment, vacant for almost a year, in the institute’s building in the Sokol District. Once AB and I traveled to a nuclear conference in Leningrad. In the evening you board the train, then you sleep through the night and in the morning wake up already in the city on the Neva. We sat opposite each other in the dark compartment and talked about something, wrote some kind of formulas. Suddenly he picked up a clean sheet of paper and started drawing. I didn’t immediately realize what he was doing. The portrait of a fairly young man, with a resemblance to me, is now among my most precious relics. Did conflicts arise between AB and his students? Rarely, but they occurred. I won’t try to delve into those with non-scientific or pseudo-scientific causes. But there were also sharp work-related conflicts. One of them – between the Teacher and one of his students, our teammate, turning out to have different understandings of the role of quadrupole-quadrupole forces in the big picture of low-energy phenomena – proved quite distressing and lasted several years. But more often the guilty parties in such conflicts turned out to be the students themselves, and the conflicts’ cause to be that same abun- dance of polemical fervor which the Teacher awakened in students. Fortunately, such conflicts, which everyone tried to settle, always ended with the sides reconciled and were never recalled again. April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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Youthfulness accompanied AB throughout almost his entire life. For many years he was a professional swimmer and underwater diver. The Diving Federation issued him certificate number one for good reason. In the 1980s, we spent the two weeks of spring holidays at almost the same place on the Black Sea in the Caucasus: I in the coastal mountains, he in Sukhumi. The sea is regularly exposed to sudden storms during this season. He later told me that once while swimming, after spending some time in the water, he tried to make it to shore and couldn’t immediately do so – the waves had gotten so strong that they simply washed him back to sea. He then swam away from the shore to a relatively safe distance and started looking for a way out of this bind. He spent about an hour in the cold spring sea and then, when the right moment came, struck out like lightning until he was safely on shore. And he was about 75 then. He loved the mountains and spent several weeks there each year in winter and summer. He once said, “Difficult problems are either solved within a month or not solved at all. And then you just need to stop thinking about them and go to the mountains for a couple of months; then after coming back you’ll find it turns out the problem is already solved.” Indeed, usually when he returned from mountaineering camps in the Caucasus, he would bring a load of new ideas. True, there was a case in his life when these words needed a completely different interpretation. This was in 1940. AB was working then at the Institute of Physical Problemsc and studying the theory of liquid helium-4. In the summer, before leaving for the mountains, he told his boss L. D. Landau about the results concerning the long- wavelength part of the excitation spectrum and its contribution to the thermodynamics of liquid helium-4. A draft of this work has sur- vivedtothisday.ThenintheautumnwhenABreturnedfromthe mountains the problem really had been solved: rotons were added

cCurrently P.L. Kapitsa Institute for Physical Problems of the Russian Academy of Sciences. The Institute was founded in 1934. The founder of the Institute, Pyotr Kapitsa, served as its head for many years. The head of the theoretical division of the Institute was L. D. Landau. The theoretical division later separated and became the L.D. Landau Institute for Theoretical Physics in Chernogolovka. April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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to Migdal’s phonons, and furthermore, the corresponding article had already gone to press. To be fair, it should be said that the author acknowledged his predecessor’s achievement. This can be confirmed by glancing at the text presented on page 361 of volume one of L.D. Lan- dau’s works. As a bonus AB received the incontestable right to do anything he wanted at Landau’s seminars – a right he put to brilliant use for staging his famous pranks. And in 1958, after solving the problem of electron-phonon interaction, when he showed Landau the work, Landau played a direct part in preparing the article for print. Knowledgeable people say the article noticeably improved in quality. Once after my return from the Pamirs I told him about the Fort- ambek glacier, and he was seized with a wish to travel to the region. This is no simple matter, and can only be done with the help of a helicopter. When he succeeded, he begged the helicopter pilots who took him there to fly as close as possible to the blue two-kilometer face of Communism Peak. The face’s beauty and power stunned him so greatly that as he later said, he cried during the flight, unashamed of his tears. Reflecting on beauty, AB often recalled N. Zabolotsky’s lines: “And what is beauty, then? Why is it lifted as a god by people? A vessel bearing emptiness? Or the fire that glistens in the vessel?” This fire of beauty glistens in dozens of his works. He was the first to use the Thomas-Reiche-Kühn sum rule to calculate the position of the dipole resonance in atomic nuclei, even before this resonance was discovered. Now on the basis of other sum rules theorists successfully calculate the masses of elementary particles. He invented polology, becoming the first to use the so-called deuteron pole to calculate the scattering cross section of slow neutrons – the famous Migdal-Watson effect. How many times since then has this work been reproduced in new fields of particle physics, and not there alone! Nobel laureate R. Schrieffer honestly rewrote AB’s work on electron-phonon interaction, publishing an article in Physical Review in which he simply replaced the acoustic phonon spectrum in AB’s formulas with Einstein’s spectrum. AB stood at the forefront of the most powerful trend in the modern theory of condensed matter, re- April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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lated to the application of the methods of quantum field theory, with his 1958 joint publication – with V. M. Galitsky, also his student – of one of the first and best works on the subject. The impetus given to the theory of condensed matter proved so strong and fruitful that by now, a half century later, its terms are widely used in describing the nucleon structure in field-theoretic framework. How did Migdal become known to the general public? AB himself never sought popularity, and everything came about almost by accident. He bought a new Volgad and left it overnight, still without plates, by the entrance to his building on Vystavochny Lane. Ap- parently sensing that something was wrong, at 11 in the evening he went down to check on the car – it was still there. But when AB went outside again an hour later, the car had been stolen. In the morning, the whole school was on its feet. The working hypothesis was that some kids had stolen the car to go for a ride and then ditch it – which meant it was somewhere nearby. That day is now impossible to recall without a smile. From the morning on, young people in groups of two or three wandered the Shabolovka neighborhood, meticulously examining all parked cars. We even reached the “Kanatchikov Dacha” hospital,e but the search failed there, too. The psychos were innocent. As we later learned, nothing could have turned up anyway, because the car had been targeted by a well- known repeat offender for his personal use back when it was still parked in the garage of the Academy of Sciences, where this repeat offender had accomplices. The story only came to light a few years later, when this repeat offender, entering a “Beryozka” hard currency store, raised a scandal there for some petty reason and accidentally showed the wrong passport to the police officer who appeared on the scene. He was “raked in,” and during the investigation, he admitted that he was driving the car of an Academician. The car was returned to its rightful owner. But just as soon as it was stolen and AB was left without this

dA Soviet style “luxurious” car unavailable to general public. eMoscow Psychiatric Hospital, located on a suburban road. The name “Kanatchikov dacha” is given by the area in which the hospital was build: in the middle of the 19th century this area was a suburban possession of the merchant Kanatchikov. April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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favorite toy – simultaneously a means of transportation – he borrowed money and bought a Zhiguli.f “What a wonderful car,” he later enthused. “How well it handles! And after all, the Lord tried to enlighten me many times – switch to a Zhiguli! Once at night He even laid a telegraph pole across the dirt road I was driving, but I ignored his teachings and replaced the wrecked Volga with a new one. God simply had to resort to extreme measures, and only then, thanks be to Him, I saw the light.” As for the borrowed money, AB decided to return it by earning an honest living on the side. This led to the appearance of the book In Search of Truth and a cycle of programs in S. P. Kapitsa’s show Incredible But True.Inthiswaythe general public grew acquainted with the man it called Academician Migdal. What drew a large audience to TV screens when he spoke? I think it was the inimitable tone of a man honest in every way, who sought the truth and had the ability, in television’s brief instants to make the viewer a participant in this search. This was his way long before he became a TV star. I remember his report at a scientiﬁc seminar at the height of the Brezhnev era. He started this report by contemplating God, saying that “Physics can neither conﬁrm His existence, nor reject it. It just remains for us to hope that God doesn’t interfere with experimental results.” Those in the audience who considered themselves hereditary atheists were delighted by the remark all the same. On another occasion he said, “I used to be proud of never producing incorrect work. But what’s the good in that? Can a professional motorcyclist really be proud of never getting injured even once in his career? That just means he hasn’t worked at the limit of his ability. Apparently I haven’t either...” Moscow had great respect for this man. When he turned 75, it was decided to celebrate his jubilee in a restaurant on Novy Arbat. His students tried to do everything possible to make this jubilee a success. A large number of people often wholly unacquainted with the day’s hero also took part in preparing and holding what turned out to be science’s last ball, after which it turned back into Cinderella

f A mass-produced Soviet car mimicking FIAT-124. April 5, 2013 14:22 WSPC/Trim Size: 9in x 6in for Proceedings 3e˙Migdal˙Khodel˙Mant

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in our country. In late October 1990, I accompanied him and his wife Tatyana Lvovna to Sheremetyevo Airport. AB flew to the United States to treat the disease that had struck him. He had a constant temperature, and really the Teacher’s whole appearance showed his suffering. How carefully the Aeroflot staff looked after him in the waiting area! Alas, he never returned to Moscow – the disease turned out to be incurable. At home I have a sculptural portrait of Einstein done by AB, in a copy made by the author himself. He said once that the first version hadn’t satisfied him – Einstein came out too young – and then he decided to chisel deeper wrinkles on the forehead of the finished portrait. When he brought the chisel near, suddenly it seemed to him that Einstein’s face had contorted, and AB blurted out, “Hold on a little while, I won’t hurt you.” In completing my notes, I’d like to repeat these words: “Don’t be angry, Teacher, if anything’s wrong; I didn’t want to hurt you.” April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

MEMORIES OF AB∗

V. G. VAKS Institute of General and Nuclear Physics Russian Research Center Kurchatov Institute 1, Akademika Kurchatova pl., Moscow 123182, Russia [email protected]

I had the good fortune to be a student of A. B. Migdal – AB, as we called him in person or in his absence – and to work in the sector he headed at the Kurchatov Institute, along with his other students and my friends, including Vitya Galitsky, Spartak Belyayev and Tolya Larkin. I was especially close with AB in the second half of the 1950s, the years most important for my formation, and AB’s contribution to this formation was very great. To this day, I’ve often quoted AB on various occasions, as it’s hard to put things better or more precisely than he did; I tell friends stories heard from AB, because these stories enhance life as AB himself enhanced it; my daughter is named Tanya after AB’s wife Tatyana Lvovna, and so on. In what follows, I’ll recount a few episodes in my life in which AB played an important or decisive role, and then will share some other memories of AB. I met AB in 1954 when he began to teach a course on theoretical physics (quantum mechanics, I think) for our group of fifth-year theorists at Moscow Engineering Physics Institute (MEPI). As far as I can remember, he taught very freely, with digressions on other scientific and non-scientific topics, often recalling and presenting various equations right there in the lecture, before our eyes. Later, when we got to know each other better, he said many times that he didn’t prepare for lectures ahead of time; he only did this en route, on the

∗Published in Vospominaniya ob Akademike A. B. Migdale, Ed. N.O. Agasyan et al., (Fizmatlit, Moscow, 2003), p. 28. Translated from Russian by James Manteith.

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subway – not out of lack of organization, but intentionally, because he also considered it useful for students to observe the process of scientific thinking. Still later, when my friends and I entered the stage of the “skepticism of students growing up,” we sometimes grumbled that AB had just thought up this “theory of improvisation” as a way to justify his laziness and disinclination to spend time on tedious lecture preparation. Now, though, I think this theory was more likely sincere, because AB always liked to show “how to” – the way to do whatever sort of work well and beautifully, especially in science – and he really did consider this useful for learning. During one of the aforementioned lecture digressions, AB invited us to solve a certain hydrodynamics problem (primarily mathematical), saying that if properly developed, this could also hold scientific interest. I took a greater interest in this problem than others did, and several days later brought AB its solution. After this he started paying attention to me, and some time later I began to visit him at home and learn theoretical physics by watching him work. In his article in this volume, Tolya Larkin has written well and in detail on what it was like to study with AB at this time, so I won’t write about that. The only thing I would add here is a typical, almost obligatory phrase used by AB at the end of every work day, often late in the evening: “We did a good job today, Valya!” (He said the same thing to other students.) Meanwhile the actual content of the “good job” could vary widely, including discussion, say, of problems of literature and art or amusing episodes from AB’s life, and often, as far as I could tell then, with no success to speak of. With time, though, I came to appreciate this cheerful phrase, and I like to quote it to my students, especially when a day’s work yields nothing sensible: “As my teacher would say in such cases, you and I did a good job today!” Now I’ll describe one event that took place in our group in the spring of 1955, when we were finishing our fifth year. Once all of us were called to the dean’s office and with little explanation were told to go to a certain lecture hall for a “scientific interview.” There we found two unfamiliar examiners – one younger and taller, the other older and shorter – who proceeded to “chase” us through different branches April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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of theoretical physics. All of us followed our habits as students, trying to display ourselves as well as possible, and many of us, including Tolya Larkin, Igor Kobzarev, Yura Chizmadzhev and me, apparently succeeded. Visiting AB as usual that evening, I told him about my probable “success,” expecting praise. Instead, he asked a few questions about the examiners’ appearance and then exclaimed, “Valya, what have you done! That was Sakharov and Zeldovich, came to recruit you for their top-secret base where they make atomic bombs and where they never let you out! You should have pretended to be a complete idiot!” That’s how I first found out about Arzamas-16 and Sakharov (I’d heard the name Zeldovich before that), whom AB told me much of later on. Then began the campaign for relief from the prospects AB had named. This was waged by our research advisers, which some of us already had by then: I. A. Pomeranchuk worked with Kobzarev, V. G. Levich with Chizmadzhev, and AB with me (Larkin didn’t yet have an adviser then; he indeed wound up at Arzamas-16, and only got out of there to work with AB a year later, as Tolya recounts in his article in this collection). I was then for the first time able to appreciate AB’s energy and irrepressibility when a person he felt responsible for needed help. After about a week of his assorted visits and conversations, which he told me nothing of at that time, he invited me to meet with him again and said, “Well, Valya, consider that because of you I’ve eaten my fill of shit for the rest of my life!” (this of course was a vain hope: there was a lot of “shit” to come related both to students and to other people he felt obliged to help, such as when he prevented Sakharov’s hunger strike from having a tragic outcome. Later AB said that his negotiations with A. B. Zeldovich about me were long and difficult, and that one of the key phrases was, “Yasha, don’t deprive me of a talented student, maybe one of my last: after all, I’m not young anymore!” Here AB was stretching the truth: he was just 44 then and had many wonderful students to come, such as Tolya Larkin, who appeared a year later. That’s how I didn’t go to Arzamas-16, avoiding a turn of events I now understand could hardly have ended well for me, given the makeup of my character at that time. April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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The next episode I want to relate is connected with the start of my employment. In the second half of 1955, AB, having supervised my thesis work, invited me, after MEPI graduation, to start working at the sector he headed at the Kurchatov Institute. At that time, for secrecy, the institute was called the USSR Laboratory of Measuring Devices – LIPAN – later the Kurchatov Institute of Atomic Energy, and now the National Research Center “Kurchatov Institute.” I told AB then that I might have problems getting hired at LIPAN as the son of someone who had been repressed. (My father, Grigory Isakovich Vaks, was arrested in April 1938, tortured by the NKVDa in January 1939 and didn’t live to appear in court. We received word of this from a woman who had witnessed his death; officially he was “deceased while under investigation for articles 58.10 and 58.11.) Before that I had never talked about politics with AB and didn’t know whether he would want to bother making a case for an “inconvenient” student; rehabilitations had only just begun then, and we received a certificate of my father’s rehabilitation only in 1957. After this conversation, though, AB seemed to start treating me with greater care. He spoke about me (apparently in superlatives) to I. V. Kurchatov, who headed LIPAN, and Kurchatov arranged for my acceptance. Kurchatov’s phone conversation about me with an official from the personnel department took place in AB’s presence. At that time these officials usually also served in the KGB and had a double subordination. The official apparently expressed caution about hiring a “son of an enemy of the people” to work at a secret institute (dislike for a Jewish surname was another possibility). At this, Kurchatov, repeating words suggested to him by AB, said that “at the moment of his father’s arrest, the son was only five years old, and he can’t answer for his father,” that he was “this much and that much” (there followed laudatory compliments from AB) and that he,

aThe Soviet acronym for the name of the secret police at that time. The Soviet secret police has changed acronyms like a chameleon. It started out as the Cheka, and then became the GPU, the OGPU, the NKVD, the NKGB, the MGB, and ﬁnally the KGB. Even today, however, people often simply refer to the secret police as “the Cheka” and the secret agents as “the Chekists.” April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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Kurchatov, insisted on his hire. As a result, in 1956 I was hired at the Kurchatov Institute, where I work to this day. The next episode relates to my scientific work with AB, and may also be of interest in that it involves three very worthy men: AB (Migdal), Ya. B. (Zeldovich) and I. B. (Khriplovich). I must say that despite having a very warm personal relationship, AB and I on the whole never managed to do joint scientific work, and we have no joint scientific publications. This is mainly because early in my scientific career I sought to deal only with the theory of elementary particles (in that day’s accepted sense of the term), while AB himself didn’t work in this area at all then. However, with the tact characteristic of him in such matters, he strongly encouraged my leanings of that time. Among other things, as a thesis he suggested that I consider the topic of radiation deviations from the Coulomb law at short distances. Moreover, his basic physics idea seemed beautiful and attractive (it’s described in my 1959 article on this in Journal of Experimental Theoretical Physics), but it turned out that these effects are small and barely observable. His second proposal, discussed below, related to the 1956 discovery of parity nonconservation in weak interactions. AB suggested that I think about whether parity nonconservation can lead to macroscopic consequences – for instance, whether it can be used to explain spiral galaxies taking the form of “left” or “right” screw configurations. At the same time, his main idea was to investigate the possibility that the effects of a parity nonconserving interaction that is weak but qualitatively different from others, may increase due to their accumulation at large, for instance, astronomical scales. At first I really did devise a phenomenological model of such an “increase,” but then, mainly through discussions with AB, it turned out that this model contradicts gauge invariance of the electromagnetic interaction and therefore must be rejected. Ul- timately as a dry remnant there remained only the qualitative model of a parity nonconserving electromagnetic interaction, later called “anapole.” It corresponds to a distribution of electric current (such as electrons) which at the same time can be imagined in the form of a quasisphere (or torus) on which the current flows out from one “funnel” (at, say, the north pole) definable by spin direction, then April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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spreads over the sphere, and finally is absorbed by the second funnel at the south pole. However, the parity violating electromagnetic field is non-zero only inside the particle-quasisphere. Therefore no macroscopic effects arise from these unusual objects’ existence, despite AB’s initial idea. In the absence of such effects, a description of the model without any calculations seemed to AB to be insufficient for scientific publication. The story continued as follows. A few months later AB and I attended L. D. Landau’s seminar at the Institute of Physical Problems and heard Ya. B. Zeldovich report on two works he had done. One related, it seems, to hydrodynamics, and the other outlined notions of parity nonconserving electromagnetic interactions quite similar to ours. AB grew very excited and dragged me up to Zeldovich during the break: “Yasha, Valya did everything you talked about several months ago, but I discouraged him from publishing!” Ya. B. reacted very calmly and benevolently: “Which work, the first or the second?” “On parity nonconservation.” “Good, let’s write a joint article.” Scared, I refused, finding Ya. B.’s work much deeper and more substantive than my simple model; beyond that, it seemed awkward to impose my co-authorship on a distinguished scientist so “scandalously.” Then in his 1957 JETP article (where the name “anapole” was proposed) Ya. B. wrote as a separate paragraph, “As I learned after the work’s completion, results analogous to ours were obtained independently by V. G. Vaks.” In a 1997 article in So- viet Physics –Uspekhi on the experimental discovery of the anapole, I.B. Khriplovich repeated this citation, showing no less tact than Zel- dovich: after all, forty years had already passed, and few in scientific literature show such scrupulousness. Later on, AB also tried to make use of every possible occasion to advertise my scientific achievements (in reality quite modest). Thus at one of the USSR’s first international conferences on the physics of elementary particles, held in Kiev (I think this was in 1959) he dragged me up to Heisenberg, who had come to the confer- April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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ence, and made me outline my work on indefinite-metric schemes in quantum field theory, where I examined ideas that Heisenberg had been proposing. Heisenberg began to listen politely, but I managed not to tire the great man too much, ending the conversation fairly quickly (and G. I. Budker, a chance witness of the scene, later told me that from the side everything looked quite decent). In 1961, when I showed the internal consistency of the electrodynamics of charged particles with vanishing masses (“charged neutrinos”) and in connection with this proposed the possible existence of such particles with a very small value of charge, AB jokingly told me that he also hoped to take pride in acquaintance with a Nobel laureate after this particle’s discovery. On one of the art prints he gave me at this time, he wrote, “To the young Pushkin – from Derzhavin.” And though all these improbable compliments were of course in jest, they characterize the style of AB’s relationship with me, as with his other students. The last episode I’d like to relate here concerns a somewhat different side of AB – his life in the mountains with climbers. Mountains were one of AB’s most avid and constant passions, although of course there were others: the sea and scuba diving, sculpture, carving wood and stone, etc. There were stories of him being a good climber in his youth, and he enjoyed friendships with many famous climbers. By the time of our acquaintance, AB already preferred walking, not sporting as- cents, and usually spent several weeks with one of his students in a mountaineering camp, welcomed there as a well-loved guest. He stayed most often at the Uzunkol camp, where the host and head of the educational section was his old friend Pavel Pavlovich Zakharov (“Pal-Pal”). In his article in this collection, Tolya Larkin writes on his impressions of these trips. I went with AB to Uzunkol once in the early 1960s with Lenya Rudakov, whom I studied with in the same group at MEPI and worked with at the Kurchatov Institute. I’d like to recount an episode from this trip. One time AB, Lenya, I and Pavel Filippovich Zakharov (“Pal- Fi”), Pal-Pal’s father and also a well-known climber, who accompanied us as a senior instructor, were walking along the Myrdy glacier in April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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the Uzunkol area. This glacier is not overly complex but is “closed,” that is, it contains deep cracks – “crevasses” – covered with a layer of snow, creating a danger of falling into the crevasses. Because of this, the rules of mountaineering prescribe walking on such glaciers with safeguards, “roped up,” that is, the team members must be connected by a sturdy climbing rope and not be too close to one another, so that in case one of them falls into a crevasse, the rest can have time to gain a foothold and secure the falling person. However, moving while roped up is often inconvenient and unpleasant, because rope gets in the way. For this reason, when there’s no visible danger, this rule often goes unheeded, especially when the team leader is experienced and conﬁdent. That’s how it was this time. The glacier seemed smooth and tranquil, and, setting out in the morning from the night’s camp, Pal-Fi said, “Aw, to hell with the rope, let’s go like this.” We moved in the usual order: in front was the leader, Pal-Fi, behind him – at intervals and stepping directly in his tracks – I, Lenya, and last AB, as the second-ranked team member by experience and skill. The weather was lovely, the glacier was shining, and we walked slowly, talking about sorts of things. And suddenly, lifting my eyes from the tracks at a certain moment, I no longer saw Pal-Fi ahead of me, although all the surroundings remained quiet and blissful. And only some time later did I notice a darkening in the snow ahead and understand what had happened. Then a minute or two later from somewhere in the depths we heard a faint sound: “Oh-oh-h-ohp!” This turned out to be a groan: “Rope!” Although Lenya and I had some mountaineering experience, we both, as far as I can remember, behaved ridiculously and uselessly in these ﬁrst minutes. But AB reacted instantly and precisely. In just a few minutes, the pack with rope was stripped from one of us, the rope was unwound, AB found a reliable place at the edge of the crevasse and started “feeding” the rope into it, having also arranged me and Lenya in the positions needed for safety. Just how quickly all this was done can be judged from the fact that, as we found out later, all the while Pal-Fi was hanging in the crevasse in a braced position, depending on “friction,” pressing against the crevasse’s smooth walls with his elbows and legs; it’s physically impossible to do this very long. And April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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because he was still able to wait long enough for the rope’s end and tie himself to it, it follows that AB really did do all this very quickly. After that, the rest was easy. The three of us pulled Pal-Fi out without much effort and then, after he and all of us had come to our senses, we continued on, now with all possible precautions. It turned out Pal-Fi hadn’t broken anything, although his face and hands were badly scratched. As a result, although we tried to keep the story secret, the climbers in the camp needed barely one look at Pal-Fi to realize what had happened. He and the rest of got a strong “chewing out,” and our ventures out of camp began to be rather strictly controlled and restricted. Because of this, Lenya and I soon set out from Uzunkol through the mountains to the sea, once again with great help from AB, who appealed to Pal-Pal to give us a climbing rope and new ice axes instead of our old unreliable ones. During our hike to the sea, we found AB’s rope very useful – but that’s another story. In recounting the episode with Pal-Fi, I sought to show what AB was like when a situation called for quick and precise action. This was another of his lessons for us. I’ll now speak of some traits and sides of AB’s personality that stand out more than others in my memory. AB was a very refined and educated man who thoroughly knew and loved literature, art and history, and his always interesting “digressions” on these themes in our talks marked us deeply. I’ll always remember how in 1955 or 1956 on some occasion I first heard him quote from Gumilev’sb “Magic Violin,” and how then, seeing that I was hearing these lines for the first time, AB recited me the entire poem. For years afterward, before I first saw a samizdat edition of Gumilev, these lines heard from AB remained my single, rapturous impression of Gumilev. And when at last I read this poem, I learned it by heart right away, as later did my daughter, and now I too occasionally quote it to my students. It was the same with the poems of Pasternak, Mandelshtamc and many others I first heard from AB in quotes or in full, and only later read in one form or another. At AB’s (and also at his friend Boris

bSee the last footnote, p. 35. cFamous Russian poets of the 20th century. April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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Tovyevich Geilikman’s) I saw numerous books and art albums for the first time, and learned a lot about the history of science. AB had the rare gift of an acute, I might say musical, perception of beauty in people and life, as well as an ability to magnify this beauty. I well remember the words of I. Ya. Pomeranchuk (whom A. B. greatly loved and admired) which I once chanced to hear from him: “AB has a marvelous gift: to take a rough, unrefined slice of life and turn it into a masterpiece!” AB was always attracted to bright, talented people, and even talking about them give him joy. I clearly remember, say, his enthusiasm after meeting Vitya Suetin, then a student at Moscow State Technical University, an outstanding craftsman and inventor who later, under I. I. Gurevich, started working at our institute on AB’s recommendation, produced many remarkable inventions and became a corresponding member of the Academy of Natural Sciences. Soon these two craftsmen, AB and Suetin, became close friends; they constructed some of our country’s first scuba equipment, organized expeditions and shot wonderful films about this. When AB became the first president of the USSR Federation of Underwater Sports, he attributed one of the main accomplishments in this “career” of his (which he of course viewed rather humorously) to Suetin. I also well remember AB’s enthusiastic stories about the sculptors Vladimir Lemport and Nikolai Silis after he made their acquaintance. Later these acquaintances became close lifelong friends, and AB loved to show his friends’ works (origi- nals or copies) and share the jokes and little songs they wrote (often indeed very funny). But AB was especially drawn to people talented in science. Thus he had a great friendship with Bruno Pontecorvo, meetings with whom simply delighted him; he loved talking with Lev Okun (who was also his student) and many others. I also remember his enthusiastic account of a “very capable redheaded boy” he had discovered while conducting MEPI entrance exams. Later this “capable redhead,” Vitya Khodel, become one of AB’s talented students and my friend, and I took pleasure in telling him what I’d first heard of him from AB. It’s of course impossible to talk about AB without recalling his humor and love of life. His countless jokes, witticisms and pranks April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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were legendary. Larkin’s article describes some of them. Here I’ll tell a few of AB’s jokes, perhaps less well-known. While reading some article of his done with Pomeranchuk in the 1930s, I read at the end, “The authors thank L. Ostrover and N. Petrukhina for their great help in this work” (I give the text and names approximately) and asked AB who they were. “Oh, very sweet girls, a great comfort in our writing the article.” “So they really deserved an acknowledgment?” “It’s more complicated, Valya: Petrukhina, yes; Ostrover, no.” When AB was chosen as a corresponding member of the Academy of Sciences and he started receiving a lot of epistles addressed “To Corresponding Member...,” one proposed household name for this mail was “Member Correspondence.”d Once when AB already well- known and popular, a certain lady journalist phoned AB and started aggressively seeking an audience, inviting him to come to see her, but not at the office and not at home. AB used some pretext to decline, and, hanging up, told me, “What a fast one! My main queue is the only way to reach me.” Now I’d like to write, paraphrasing words from Larkin’s article, about what “AB didn’t like,” dividing the subject into two parts: first, what AB didn’t like to remember, and second, what he hated. Despite all the fullness and brilliance of AB’s life, of course, his life was neither easy nor unclouded. His life also included arrest in the early 1930s, as well as personal drama and indeed simply life “under the sun of the Stalin Constitution,” a life hard for a thinking and acute sensitive person to bear. Perhaps this has something to do with the fact that although AB was anything but a modest introvert and often willingly recounted different occurrences in his life, he spoke about his youth and pre-war life rarely and sparingly, at least with me. It thus happened that I only randomly learned, without details, that to gain admission to Leningrad University in the late 1920s, AB had to work as an electrician, and seemingly not only before but also after admission. He never once told me anything about his arrest. I managed to learn from him in somewhat more detail about the

dThis has a sexual connotation in Russian. April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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“brigade method” used for teaching at Leningrad State University. I don’t know the extent of people’s knowledge of this and other night- marish educational experiments conducted by the Bolsheviks right up to the mid-1930s. I myself long knew of the brigade method only from what AB said about it, and only recently learned further details from Professor V. A. Kizel, who studied at Moscow State University at about the same time as AB was at Leningrad State University (Kizel later became an outstanding climber and knew AB through meetings in the mountains). As V.A. recounts, in the late 1920s, the Bolsheviks apparently decided to “restore order” in higher education, rebuilding it based on class and ideological principles. Institutes of higher education faced a flood of the “Red Guard” – to use V.A.’s expression – people with impeccable backgrounds and Party characteristics, but who as a rule were uneducated and illiterate. This meant that for most of them, traditional teaching with lectures, tests and examinations was simply untenable. To foster conditions for these people to get diplomas (other educational goals were apparently seen as immaterial), it was decided that teaching should be “simplified,” simultaneously making it more “collective,” that is, ideologically correct. In the brigade method that was devised, it was thought that the most important thing was the team’s collective learning – for instance, simultaneously reading a book in the same room, having meetings on various themes, etc. Meanwhile, tests and exams were either canceled entirely, as at MSU, where V.A. studied, or taken on behalf of the whole brigade by one of its members, as at LSU, where AB was a student. As a result, as V.A. told it, learning in higher education was possible only for those few people who studied in spite of and not according to the official method. AB himself told me, though, that for him personally their LSU version of the brigade method wasn’t so bad, as in his brigade namely he was the sole “understander” who studied everything and took all the tests for the whole brigade. In conclusion, a little about what AB hated. AB hated Stalin, Stalinism, and all the horrors and crimes of the regime. As for Stalin himself, AB more than once called him a “bloody dog,” although harsh expressions were generally not in his character and in other April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3f˙Migdal˙Vaks˙Mant

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cases he could make do with irony. For many years, he loved proposing a toast “to Cheyne and Stokes.” “Cheyne-Stokes respiration” is a medical term associated with death agony; this term became widely known after March 1953, when it appeared in bulletins on Stalin’s health. Accordingly, this toast–sometimeswithanadded“AndmayGodgivethemgood health!” – meant a toast to being rid of the “bloody dog,” an occasion AB and all of us drank to more than once. Like most other people who had known and seen too much, AB disliked talking about this without need. From the few stories and allusions he let out, though, I know how heavily all this weighed on him. I think one of the driving forces behind his love of life, so intense and irrepressible, especially in his life’s first half, may have been a defense reaction, a conscious or unconscious effort to pit this love of life against horrific circumstances, for the survival and preservation, at least around him, of all he so loved and appreciated in life and in people. I’m happy to have had so much AB in my life. April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3g˙Migdal-Polyakov-Mant

GRAND MASTER∗

ALEXANDER POLYAKOV Department of Physics, Princeton University Washington Road, Princeton, NJ 08544, USA [email protected]

Certain questions have long concerned me: how sure is the flow of life? In what way does it depend on the decisions we make and the paths we choose? This dependence almost always seems weak and short-lived, however much pride we may take in our foresight. But there are also special points when the line of our fate leads in multiple directions and choice decides everything. For me, such a moment came early one spring morning in 1961. It was a decision to go to the physics and math Olympics at Dol- goprudny. I didn’t want to go, because the night before I’d been rattling along in a train’s sitting carriage, returning from a hunting trip (the first and last in my life). On that day, Sasha Migdal and I won first prize for the eleventh grade (while we were in the ninth). The graduate students who had organized the Olympics got permission for us to take the entrance exams at the Moscow Insti- tute of Physics and Technology. We passed the exams, but dark forces at MIPT tried to cancel our results. Then came an important event: AB decided to intervene and at the same time get to know me. My impressions were overwhelming. To me, he seemed superhuman. During the thirty years of our acquaintance, this impression faded considerably but didn’t at all disappear. AB had a mysterious ability: he was always interesting to be with, even if he wasn’t saying or doing anything interesting. Probably an inner force came bursting

∗Published in Russian in Vospominaniya ob Akademike A. B. Migdale,Ed.N.O. Agasyan et al., (Fizmatlit, Moscow, 2003), p. 58. Translated from Russian by James Manteith.

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out in his gestures, turns of phrase, gaze, and formed this electric atmosphere. Back to the dark forces. AB had to fight for Sasha and me, along with our friend Seryozha Gurvits, who also passed the exam (AB described our bid for admission to MIPT as “three Yids standing in two rows”). He went to see some high Party chief. This official said, “Don’t worry, Arkady Benediktovich, let’s accept your son and forget the matter.” AB replied, “I don’t want my son to start out in life with under- handedness.” The story sounds theatrical, but I believe it. AB loved the theater (along with theater people). When things settled into place, AB took Sasha and me to Kok- tebel. At a vacation house belonging to a friend of his, the famous art critic Gabrichevsky, cots were set out in the garden for Sasha and me. The house was filled with brilliant people from the literary and musical world. There was an atmosphere of improvisation, pranks, romance. AB was at the center of everything and seemed a part of the “Silver Age” (which our hosts indeed represented). On the beach there were varied conversations, including talk of physics. I remember AB and Bruno Maksimovich Pontecorvo discussing the theory of curved momentum space. I understood very little, but the conversation of professionals, with critical analysis of different alternatives, was fantastically interesting. This theory has stalled since then, as AB and BM foresaw. When we returned to Moscow, AB offered us a research topic. As a professor now myself, I’m struck by his intuition and boldness. We knew and could do very little. It seems our only virtue was enthusiasm. AB managed to find an interesting task lying exactly at the limit of our abilities. The task was to find the surface energy of a nucleus considered as Fermi gas in a potential well. AB explained a lot to us, and there was a lot we taught ourselves. Our equations included a very complicated and incalculable function. We didn’t know what to do, and went to see AB. He looked at the equations and said. “The function oscillates rapidly. Replace it with the April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3g˙Migdal-Polyakov-Mant

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mean.” This advice brought me to despair. It completely disagreed with normal higher mathematics. After a month of hard work, we managed to make a “normal” calculation, and of course the result was just as AB had predicted. He praised us for this small technical achievement. As a result, we believed in our abilities. Even now, reading this 1963 work doesn’t embarrass me. A little later, analogous problems were studied in mathematics (of course, without knowledge of our results), and now these heat kernel methods are an important and useful part of mathematical physics. It bears saying that childhood research impressions strongly influence future life (almost like Freud, only without the Oedipus complex). Indeed, over the next forty years, heat kernel methods have cropped up in my work more than once. After this first work, AB left us to ourselves and only occasionally gave us guiding advice. His remarkable intuition revealed itself here as well. At this time, Vaks, Larkin and Nambu proposed the idea of spontaneous symmetry violation in elementary particles based on an analogy with superconductivity. Experts viewed this idea more than a little skeptically. AB wasn’t afraid, and he advised us to work on this. We then wrote a work which the experts laughed at while forgiving us on account of our youth. Subsequently, spontaneous violation became a central theme in particle physics. In general, physical intuition was AB’s main strength. Many years ago I reread Landau’s great work on the theory of superfluidity. And I whistled when I read a small footnote. Landau starts with the hypothesis that the main elementary excitations in quantum helium are phonons, whose heat capacity he calculates. This hypothesis is fundamental and far from trivial; its direct result is superfluidity. The footnote says that this calculation was done by A. B. Migdal a year earlier. Of course, Landau goes on to develop this theory with ingenious forcefulness, but the start was made by AB. I asked him what had happened. He said Landau had advised him not to publish this result, given that there was no complete theory and, besides, the answer was inconsistent with experiment (as we now know, for a trivial reason). Apparently Landau had an idea for a complete theory and grew nervous (a feeling familiar to professionals). Unfortunately, April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3g˙Migdal-Polyakov-Mant

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as AB told me, the reference didn’t make it into the article’s German version. Geniuses also have weaknesses. It’s interesting that a similar intersection with Landau took place again in Fermi liquid theory. In the mid-1950s, AB wrote his own work – maybe his most important – on Fermi systems. He introduced a precise definition of quasiparticles, using the methods of quantum field theory – already quite a revolutionary achievement. He proved that quasiparticle distribution has a jump on the Fermi surface. This meant complex Fermi systems could be examined as a gas of quasiparticles. Landau developed this idea to a dizzying degree; his theory forms the basis of the modern theory of solid bodies. AB couldn’t have done this. But he was the pioneer. The next work of that era was the theory of electron-phonon interaction. AB overcame enormous technical difficulties and built a remarkable theory. But he recalled it sadly. He actually had aimed for a theory of superconductivity. This phenomenon relates to the properties of electron pairs (as we now know). AB managed to consider only individual electrons and planned to develop his own methods for examining pairs. Meanwhile, Bardeen, Cooper and Schrieffer used crude (but ingenious) methods to build a correct theory. Caught up in the beauties of formalism, AB was unfortunately too late. It’s some comfort that the methods AB devised then are now widely used in the theory of superconductivity, and in general this was a classic work. His story taught me an important lesson. The lessons were many. One day I visited AB at home on Chkalov Street. His apartment was being renovated. AB appeared, along with some little paint-smeared man, apparently the head contractor. AB spoke with him in a friendly, even respectful manner. I (silently) applauded AB’s show of democracy and at the same instant was introduced to Isaak Yakovlevich Pomeranchuk. The conversation turned from painting walls to physics. Isaak Yakovlevich gave me several pieces of advice on what to study. This was very instructive, even though I didn’t follow the advice. AB maintained friendships with many brilliant people from different generations and different professions. It seems to me that he consciously created his own isolated world over many years and by April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3g˙Migdal-Polyakov-Mant

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force of personality kept it from dissolving in his surroundings. This “rational egoism” had important consequences for Russian science. Many worthy people found work, received medical care, were elected to the Academy thanks to AB. And a lot of jerks were thwarted. True, some lapses occurred. Once I was visiting AB when a certain fox came to see him before elections and said, undeterred by my presence: “Arkady Benediktovich, I don’t care how you vote, but I want you to know that you’re the beacon of my whole life.” When he left, AB turned to me thoughtfully and asked, “Listen, Sasha, maybe he’s not such a bad person?” I burst out laughing, and a second later AB joined me. In the bleak years, AB met with A. P. Aleksandrov, trying to help Sakharov and Orlov, whose courage he admired. I don’t know what came of this. Once I received a request from Journal of Experimental and Theoretical Physics to review an article by Sakharov. I wrote something highly positive (and as far as I recall, the article was published). But I didn’t like the work very much, and I shared this opinion with AB (as usual, not holding my tongue). AB became very angry and said, “Sasha, that’s the wrong tone for speaking of great men and saints.” Another side of AB’s life involved art. I liked his wooden sculptures, which conveyed his internal energy. He wrote popular books, which I liked less; his mind was too original for him to make a good popularizer. AB had interesting views on literature. In the 1960s, the novel Master and Margarita was published. We were delighted and learned it almost by heart. AB also liked the novel, but found it somehow “Soviet” and even obscene. Among other things, he took oﬀense at the scene with handing over foreign currency, where the author clearly sympathizes with jail keepers. In his youth, AB spent time in prison because of his parents’ foreign currency. I think this inﬂuenced his literary taste. In 1990, AB came to Princeton already ill. While he could walk, we walked a lot together on the quiet lanes of Princeton. He said he felt not fear but rather curiosity. I almost believe that was true. Here are two episodes separated by thirty years of our acquaintance. April 5, 2013 14:23 WSPC/Trim Size: 9in x 6in for Proceedings 3g˙Migdal-Polyakov-Mant

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That ﬁrst year in Koktebel, we joined AB’s old friend Lev Mikhailovich Rubinshtein, a master climber, for an ascent of one of the local mountains. These mountains are small but quite treach- erous, and more than one person has died there. At some point AB lost his footing and started sliding downwards. I saw this and was horriﬁed. In a perfectly calm voice, as if relating an interesting fact, AB said, “Lyova, I think I’m falling.” Then he found something to seize hold of, and all ended well. In the last weeks of his life, when AB stayed lying down, my wife Dasha went to visit him and Tatyana Lvovna. Dasha and Tatyana Lvovna sat in the kitchen and drank cognac. AB heard the clinking of shot glasses and asked who had arrived. “Angel Dashenka brought food and drink,” said Tatyana Lvovna. “That angel’s a drinker,” said AB. This seems to be the last turn of phrase from AB that we often call to mind. He was just as calm as back then on the mountain. Memoirsaresadtowrite,andsadtoread,infact.We’recon- fronted with images of a lifetime of incredibly interesting events and complex interactions. Is there some kind of “long-term order” in all this, or just a moment’s random combination, like spirals in a turbulent stream? April 5, 2013 13:31 WSPC/Trim Size: 9in x 6in for Proceedings 4a_Chap3-divider

CHAPTER 3 May 10, 2013 11:7 WSPC/Trim Size: 9in x 6in for Proceedings 4a_Chap3-divider May 13, 2013 15:48 WSPC/Trim Size: 9in x 6in for Proceedings 13˙Index

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ON THE PATH TOWARDS UNIVERSAL WEAK INTERACTION∗

S. S. GERSHTEIN Institute for High Energy Physics Protvino, 142281 Moscow Region, Russia [email protected]

I will always remember my ﬁrst meeting with YaB.a In the autumn of 1951, after my graduation from Moscow State University, I ended up as a teacher of physics and mathematics in a high school in a village called Belousovo in the Kaluga Region, 105 km from Moscow. Sitting in the evenings at dinner with the old peasant woman who kindly took care of me, and in whose izba (loghouse) I lived, I looked at my university notes and, listening to the rain beating on the window, beyond which was pitch darkness, I consciously bade farewell to the scientiﬁc activity for which I had prepared at university. However, my friends who graduated in the same year didn’t leave me to my fate. One of them, Sergei Repin, asked, “Why not try to pass Landau’s minimum?”b and gave me LD’s [Landau’s] telephone number. I called ‘Dau’c and began to take his exams. At the beginning of 1953, when I had passed the last of them, LD said, “Think of a theme for your work and try to go to the seminar. Unfortunately,

∗Originally published in Russian in Yakov Borisovich Zeldovich, Eds. S.S. Gershtein and R. A. Syunyaev, (Moscow, Fizmatlit, 1993; Second edition, 2008). A slightly abbreviated English edition is Zeldovich. Reminiscences, Ed. R. A. Syunyaev, (Chapman & Hall/CRC, 2004). Translated from Russian by Denise Gabuzda. aYaB (pronounced in Russian as Yaah Beh) – that’s how his colleagues would address Yakov Borisovich Zeldovich. b Landau’s ‘theoretical minimum’ or simply ‘minimum’ was a sort of qualifying exam, which he insisted that anyone who was to have professional contact with him must pass. –Translator c A widespread nickname for Landau used among Soviet physicists. Sometimes people would address Landau as LD, an abbreviation from Lev Davidovich. – Translator

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I can’t accept you in my group. I’ve already looked into it, and it’s impossible.” It is easy to say ‘think of a theme.’ I was able to read fresh journals only in fits and starts when I came to Moscow, and at that time we didn’t study nuclear physics and elementary-particle physics at all at the university (these subjects were taught only at the secret nuclear section of the Physics Department). Nonetheless, I tried to set aside one free day at the school – Thursday – to go to LD’s seminar (this was far from simple with a workload of 44 hours per week in two shifts), and I came to my first seminar two weeks after my conversation with LD. Before the beginning of the seminar, I sat somewhere in the middle of the hall and began to look through a fresh issue of Physical Review, which I had been loaned for a couple of hours. Unexpectedly, a strange man sat down in the free seat next to mine; he was of modest height, wearing round glasses, and struck me with a sort of unusual internal energy. This energy could be felt in his unusually lively eyes and impatient motions. He seemed to find it hard to stay in his place, looking around at the people gathering for the seminar and searching for a glance from someone he knew. In passing, he unceremoniously looked at my open journal and turned away disappointed, having convinced himself that he had already seen that issue. Soon, the seminar began. I don’t remember who the speaker was. I think the talk was about some article on kinetics. Unexpectedly, my neighbor got up and started arguing with the speaker. LD also got involved in the argument, which immediately turned into a discussion between Dau and my neighbor, who rapidly moved to a place in the front row. “Who in the world is that?” I thought, knowing that it was rare that someone could hold their own for very long in a discussion with LD. I was even more surprised by Dau’s words: “Yes, I think you’re right.” That was an extremely rare event. None of my acquaintances were sitting near me, so I couldn’t ask who my neighbor had been. After the seminar, Dau went out into the corridor, then, returning to the hall, came up to me, asked me to follow him, led me to that same stranger who had so interested me, and presented me with the following words: “Here’s the young man I told you about. Take him April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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on, he is in every way thirsty for activity.” His short companion said, “Let’s go,” and we went to his home together with two other people, whom he had already invited. From the conversation, I understood that they were both from Leningrad (they were I.M. Shmushkevich and L.S. Sliv, who later became my friends). Entering the flat, our host briefly gave a command to the woman who opened the door – “Sasha, something to eat” – and, turning to us, said, “All discussions after lunch.” When we had eaten, we went into the small room that served as his office, and he began a scientific conversation with my two new acquaintances, and extended to me some typewritten pages with the words, “You have a read for now.” I read the name of the author of the article, and only then realized that I was talking with Zeldovich. I suddenly felt shy. At that time, YaB’s name was surrounded by a blanket of secrecy. Studying at Moscow State University, we heard about the pre-war work of Zeldovich and Khariton on uranium-fission chain reactions, about his research on combustion and detonation; therefore, we didn’t doubt that he had become involved in work on the atomic bomb. This was confirmed by a story told by one of the older students, of how he had seen YaB making a presentation in defense of N.N. Semenov at a discussion in which Semenov had been accused of forcing through idealism in the theory of combustion (this type of discussion was common at that time). YaB arrived at the gathering with the star of a Hero of Socialist Labor on his chest. It was clear that he had not put it on by chance. The appearance on the podium of a speaker with a piece of regalia so rare at that time exerted a significant influence on the results of a ‘scientific’ discussion of this sort, and the fact that the decree ordering the decoration had not been published lent even more importance to the presentation. Knowing all this, I was struck by the simplicity of YaB’s relations with us, and his democratic attitude. Having finished his conversation with the two Leningraders, YaB called me to his desk and began to tell us about his new theory of β decay. It was clear that he was very enthused by and satisfied with this result. When we parted, he gave me several typewritten copies of his papers and said that I should read them and come again in two weeks, when he would be in Moscow again. In this way, I first became April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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acquainted with YaB and, having been to his home, wholeheartedly took a liking to that home and its inhabitants. When I next appeared at Landau’s seminar, he asked, “Well, how do you like YaB?” and, without waiting for an answer, said, “He won’t let you be idle. I don’t know of anyone else with so many ideas in his head. Maybe only Fermi. In addition, YaB has an iron grip, and he’ll force you to work at full steam.” This coincided with my impressions. The articles that YaB gave me were dedicated to several very different issues. There was a paper on baryon charge (which YaB rediscovered, not knowing about the earlier work of Wigner and Stückelberg, and which subsequently served as an example for his scheme for lepton charge), another on the Compton effect in polarized electrons (enabling the measurement of circular polarization of γ rays), and finally, one on various types of β decay. This last article interestedmemost,andIdecidedtoworkinthisarea. Later, I reflected more than once on how lucky I was: I met YaB precisely when he became attracted to elementary-particle physics. It is well known that, during his years of scientific activity, YaB changed the main area of his interest several times: from chemical physics (catalysis, combustion, detonation) to nuclear physics, the theory of elementary particles, and then to astrophysics, gravitation, and cosmology. These shifts in interest were not undertaken by chance. Possessing broad views and an amazing intuition, YaB chose the most interesting and pressing problems of his time. In the beginning of the 1950s, one such problem was the physics of weak interactions. After the discovery at the end of the 1940s of the π → μν, μ → eνν¯ decays and of μ capture, it became clear that these processes occur under the action of forces that have the same order of magnitude as that for the known β decay. In this way, the idea arose that all these processes are due to a special ‘weak’ four-fermion interaction bearing a universal character. It is evident that the hypothesis of the existence of a new elementary interaction (together with the strong, gravitational and electromagnetic interactions) was of fundamental importance; however, verifying it required first and foremost a good understanding of the weak, four-fermion interactions for all known processes. And these had not been reliably established, April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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even for the long-studied β decay. Of the five possible types of four- fermion interaction (scalar S, vector V ,tensorT , axial-vector A,and pseudoscalar P )inβ decay preference was given to type T ,andit was also supposed that one of the so-called Fermi types (V or S) existed. Beginning to work in a new research field, YaB tried first of all to distinguish the main problems in this field and search for general principles for solving them. In doing this, he often revealed new problems that had not previously been known to experts in the field, but which subsequently became fundamentally important. This was the case, for example, with the problem of the observed limit to the magnitude of the cosmological constant. YaB decided that the general principle that should be used as a basis in searches for types of β decay was whether the theory could be renormalized. As is known, this principle subsequently played an important role in the creation of a theory for the electroweak interaction. However, this was done in a different form to that which YaB proposed. At the beginning of the 1950s, it was known that, in addition to electrodynamics, theories with scalar and pseudoscalar particles were renormalizable. Based on this, YaB proposed that the intermediary particles in the β decay were precisely these particles, and obtained a (V + T )formofβ decay, which, as it then seemed, was in agreement with the experimental data. Therefore, it is easy to understand his joy. Striving to derive further experimentally observable consequences of his theory, which could either confirm or disprove it, YaB noted that, in his scheme, taking into account the Coulomb field of the nucleus should lead to a mixture of various types of β interactions, which should be visible in the β-decay spectra of electrons. He assigned to me the calculation of this phenomenon. We usually met as follows: YaB, coming to Moscow for a short time, would send me a telegram to Kaluga Region and give the time when I should come to his place (as a rule, at 6 am). It was not easy to get to Vorobiev Road on time: public transport was only beginning to operate at that hour. There I would find YaB half- dressed, but already sitting at his desk. Occupied primarily with his ‘special business,’ YaB set aside rare hours for doing purely scientific May 10, 2013 11:46 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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research. Sometimes our meetings occurred only a few hours before YaB’s departure for the ‘object,’ and in that case, the door was opened by the ‘secretaries,’ who, as I guessed, were his escorts. After our discussions, he insisted that I join his family for breakfast, and I, at first shy, was struck by the atmosphere of kindness that ruled in the Zeldovich home. It was clear that this was a deeply work- loving family, where each conscientiously went about his business, be it scientific work or studying at school. I didn’t see any trace of the ambitions or feelings of exclusivity that were so characteristic of the wives and children in many highly placed families. There was no lacquered furniture, nor expensive things set up on display, and the housekeeper Sasha was essentially a member of the family. I will never forget the kindness and sympathy exhibited by Varvara Pavlovna. For many people who came into contact with YaB, it was a mystery how, when he changed his field of interest, he managed to both get oriented very quickly in the new area and remain up-to-date on developments in former fields of work, from time to time returning to them and obtaining spectacular results. Through my work with YaB, I came to understand that this was no mystery. Apart from his talent (of the sort that can be said to be God-given), this ability was connected with YaB’s working methods. When he began to work in a new area of physics, he first and foremost sought out young specialists; talking with them ‘as equals,’ he could rapidly get acquainted with the most important results obtained in that area.d In many ways, the learning process was aided by YaB’s democratic nature and lack of professorial conceit. He was never too shy to ask ‘stupid’ questions in any situation, and often got condescending answers from the specialists (I remember a joke that certain ‘serious’ young people liked to repeat: “YaB wants to apply physical chemistry methods to elementary particle theory.”) However, it usually soon turned out that some of these ‘stupid’ questions left the specialists stumped – that they, indeed, represented new formulations of a problem or

dFor example, Landau recommended V. Sudakov when YaB wanted to ‘study’ β decay. –S.G. April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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completely new problems that had not been considered previously. In addition, an active approach to the ‘learning’ process was characteristic of YaB. When he came across unclear questions or new problems, he educated himself in the very process of solving them. I remember his words when he learned that I was studying the renormalization theory: “What use is it to study abstract theory? You should find and solve some problem, that way you’ll really learn.” As he accumulated new problems, YaB assembled around him young physicists who were just starting their careers, and, working together with them, rapidly became familiar with areas that were new to him. In this way, a new school was also formed, which continued its investigations after the interests of the teacher had shifted to another field. The personal contact, attention, and concern demonstrated by YaB toward his former students meant that he was always up-to-date on developments connected with his former research. Young researchers constantly came to him for advice or to discuss new results. He got drawn into discussions that frequently led to new ideas in some ‘old’ field. YaB experienced the need to discuss his new research with various people, listen to their criticism, find counterarguments, and thereby test the soundness of his own ideas. These discussions were very fruitful and educational for his students. We involuntarily became infected with the joy he experienced when he discovered some new, unknown effect, solved some new problem, or understood the possibility of a simple, ‘first principles’ explanation for some phenomenon. He usually gave his students the manuscripts of his own papers to read and asked them to make comments, for which he unfailingly expressed thanks in his articles. This stimulated deeper study of a subject, and increased one’s confidence in one’s own abilities. YaB usually discussed the contents of his scientific talks with his students. I remember one episode in particular in connection with this. In 1954 to 1955, I. V. Kurchatov decided to organize a cycle of lectures on the most topical problems of physics, in order to expand the horizons of his researchers and their possibilities for choosing new directions of scientific activity. He asked YaB to read several lectures on β decay and weak interactions. YaB’s attitude toward April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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this request was serious, since he quite correctly believed that physicists, especially experimentalists, could make large contributions to these problems. (These hopes were shown to be fully justified only a few years later, when the brilliant research of P.E. Spivak’s group on β decay of neutron and of I.I. Gurevich’s group on μ → e decay appeared.) Therefore, he tried to make the material in his talks as accessible as possible to experimentalists who hadn’t worked in these fields before. I should say that YaB could master this art like no one else. Preparing for lectures, he invited Sudakov and myself to help him, and we had long discussions together, not only about the contents, but about the best way to present individual questions. Our sort of reward for this was that YaB took us to his lectures, and, after they were finished, presented us to Kurchatov as his assistants.e By that time, I was already living in Moscow again. Having worked through my required three years at the village school, I moved to Moscow in order to be closer to science; I hoped to find a position as a teacher at one of the universities or, if I was lucky, at a scientific institute. YaB and Dau recommended me for several places, but each time, when the question got to the personnel department, they would drag it out for a month or two, and I would then receive a rejection on some more or less plausible pretext. I made ends meet by giving lessons. I didn’t want to go back to work at a school, all the more so because hope was dawning ahead. Times gradually changed, and at some point, Landau told me, “There is talk that Kapitsa will be re-appointed director of the Institute of Physical Problems.f In that case, I’ll be able to take you on as a postgraduate student.” However, weeks and then months passed, and my situation didn’t change. I don’t know what I would have done without the help of my friends.

e As science becomes more bureaucratic, there are fewer and fewer high-ranking scientists who are willing to learn in public, thereby acting to motivate lower-ranking ‘bosses’ in their own investigations. Therefore, I often remember sadly the over-full hall, and Kurchatov sitting in the front row with the notebook in which he wrote YaB’s lectures, asking questions from time to time when something wasn’t clear to him. f Currently P.L. Kapitsa Institute for Physical Problems of the Russian Academy of Sciences. The Institute was founded in 1934. The founder of the Institute, Pyotr Kapitsa, served as its head for many years. The head of the theoretical division of the Institute was L. D. Landau. April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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YaB, interested in my affairs, offered me money on many occasions, which I, naturally, refused, saying that I didn’t need it. The circumstances highlighted the delicacy with which YaB could insist on his own way (subsequently, I often encountered similar actions toward both myself and other people). He once asked if I would agree to give private lessons to the daughter of a friend, a schoolgirl who had survived a serious disease in her earlier childhood. I accepted this offer, and worked enthusiastically with the capable girl, who was keen to learn in spite of the serious after-effects of her disease. After a while, YaB, asking about my activities, asked, “Since you’re giving lessons, I’d like to ask you to work a bit with my girls.” I began to refuse, saying that this was quite unnecessary for them, their studies were going fine, they got straight A’s in school, and would only be embarrassed if they were assigned a tutor (at that time, it was considered shameful). However, YaB found the following objection: “At school, they don’t teach experimental skills. Buy some instruments, and let them do some experiments.” I had no choice but to agree (I had some experience in this area, having tried to establish a similar physics laboratory at the village school, so that each student could carry out experiments). I was able to obtain some rather good equipment in educational supply stores – an optical bench, lenses, galvanometers, and so forth. I also found a small Wilson chamber. And so Olya, Ma- rina, and I began to set up various experiments and solve problems connected with them. At times, these experiments ended in embarrassment for me – several times, I burned out sensitive electronic instruments. YaB gently made fun of me; sometimes he himself took part in the experiments, and I, together with my students, listened with interest to his commentaries about the applications of the phenomena being studied in various technical devices. I was surprised by YaB’s experimental skills and his ability to work with his hands. “After all, I began as an experimentalist,” he told me, “and before that I worked as a lab assistant” (at that time, I didn’t yet know that YaB had not continued his formal education beyond high school). I don’t know if my lessons (thought up by YaB, as I understood, as a way of helping me) were of any use to my students; but they taught April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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me many things, and helped me support myself until May 1955, when Landau was finally able to realize his plan and take me on as his postgraduate student at the Institute of Physical Problems. In the meantime, my scientific discussions with YaB continued. The calculation of the effect that I carried out proved to be useless, since the experimentalists had by that time established with certainty that the β interaction was a sum of the scalar and tensor types (and not the vector and tensor types, as followed from YaB’s theory). I could feel that he was sorry that my work had turned out to be for nothing, and was looking for a new problem for me to work on. Once, when discussing the experimental data, he told me: “Experiments show that the ratio of the Gamow-Teller and Fermi constants does not greatly exceed unity. It would be very beautiful and important for our understanding of the nature of weak interactions if these two constants were the same for a “naked” nucleon, and the small difference between them arose because the nucleon was immersed in a pion cloud. Let’s calculate this effect.”g Remembering YaB’s comment that the best way to learn was by working on problems, I proposed that we perform calculations for all possible versions of the interaction. YaB agreed to this. When we independently concluded our calculations and began to check over our results, we discovered that there was a significant divergence between our results for the vector case. I, working as a student, had carefully used the isotopic spin matrices, while YaB, trying to obtain his results more quickly, had acted somewhat primitively, using the same constant for interactions of a neutral pion with protons and with neutrons (while, in fact, the

g I’ll mention in connection with this that an important element of YaB’s natural philosophy was a belief in the existence of beauty and internal connections between various phenomena. In addition to this guess, which turned out to be completely correct, I remember that even back then, he told me more than once, “Note the following: the constant for weak interactions of fermions with intermediate bosons has units of electrical charge. It would be very beautiful and natural if it were simply equal to the electric charge. This could be used to estimate the mass of the intermediate bosons.” Having forgotten that it was necessary to use Heaviside units for the charge, he obtained a mass √of about 30 GeV for the intermediate bosons. If this is multiplied by the omitted factor 4π the resulting value is very close to the experimentally measured mass for the W boson. – S.G. April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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constant has different signs for these two cases). When he discovered the reason for the discrepancy between our results, YaB exclaimed: “Now I understand how a symmetrical theory differs from an isotopic invariant theory!” However, unexpected results awaited us in the future. Taking into account in the vector case the possibility of β decay of a charged pion (which YaB earlier calculated based on the Fermi-Young model, using, in essence, only the isotopic invariance of this model), we discovered that pion corrections didn’t change the constant for the weak vector interaction. This result immediately interested us, although it seemed not to be related to the real behavior of the β interaction established in experiments. First, we thought that the result was associated with a specific structure of the perturbation theory with which we were working. However, after some discussions, we understood that our result was an analog of the conservation of electric charge of the proton, which does not change during strong interactions with pions, and we even saw some possibility of rigorously proving this using the Ward identity. We were very excited about our discovery, and regretted very much that it remained a simple mental game, and did not exist in Nature. We understood that, in the vector case, possibilities would open for the precise experimental verification of the behavior of the universal weak interaction. From a pragmatic point of view, we were able to gain satisfaction only in the confirmation of YaB’s guess. Our result for the scalar and tensor cases showed that the observed ratio of the Gamow-Teller and Fermi constants was completely consistent with the proposal that these constants were equal for a ‘naked’ nucleon. “We should write a paper,” said YaB. However, a new hindrance arose. When I arrived at YaB’s home at the appointed time, I found a note warning me that he had been delayed and asking me to wait for him. The note began with the words, “Woe to us,” and beneath it lay a new issue of Physical Review with an article by Finkelstein and Moshkovsky, where they considered the same problem for the scalar and tensor cases and came to the same conclusions. The novelty of our work was lost. Furthermore, their calculation had been based on the model of Chew and Low, which, it stands to reason, took into April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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account the strong interaction more accurately than our perturbation theory, from which we expected only a qualitative confirmation of the hypothesis. I was upset, and thought that YaB would also be distressed, and to an appreciable extent because of me. But YaB wasn’t depressed. When he returned home, he proposed that we work through Finkel- stein and Moshkovsky’s paper together, and we discovered several inaccuracies. They did not change the main conclusions, but were important for comparisons of β and μ decays. “This is the subject for a short note,” said YaB, “At the same time, we’ll note the properties of the vector case. It’s important that your first published work comes out soon.” By the time of my next visit, he already had a draft of the article. After reading it through and making several corrections, I asked, “Won’t Dau criticize our treatment of the vector case? After all, he doesn’t like abstract discussions about things that don’t actually exist.” – “It’s impossible just to walk by such a beautiful possibility,” answered YaB, “And if you’re afraid of Dau, let’s add the words ‘does not have practical importance, but is me- thodically very interesting’ before the paragraph on the properties of the vector case.” And we sent the article off to the publisher. A few years later, the law of conservation of vector current was rediscovered by R. Feynman and M. Gell-Mann in their famous work, in which they proposed almost simultaneously with Marshak and Sudarshan their theory of the universal (V−A) weak interaction. As later noted by Feynman, neither he nor Gell-Mann knew about our work (but in the future always referenced it). Numerous experimental studies performed after the work of Feynman and Gell-Mann confirmed that precisely the vector and axial-vector types of weak interaction exist in nature. Returning to our work many years later, YaB always expressed satisfaction that, in spite of the experimental situation at that time, we had noted the properties of the vector interaction, which played an important role in the experimental verification of the universal character of weak interactions, and stimulated the development of gauge theories. This, in my view, showed YaB’s characteristic striving for a thorough analysis of any question he considered. His scientific un- April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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inhibitedness and the fact that he never worried about looking silly enabled him to widely discuss effects that would seem to be unrealizable in nature.h Many such comments, made as if in passing, later proved to be very important. I’d like to present two examples in connection with this. A. M. Budker recalled that his desire to work on colliding beams was initiated by something YaB said during one of his talks: “This question could be elucidated in experiments with colliding beams, however it is probably impossible to create them.” Budker said that the word ‘impossible’ cut him to the quick, and he began to search for ways to realize the idea technically. Subse- quently, when this became possible and prominent discoveries were made in colliding-beam experiments, Budker frequently referred to this comment by Zeldovich. Another example is a comment made in the classical pre-war work of Zeldovich and Khariton on fission chain reactions. Discussing the possible realization of fission reactions in natural uranium, the authors noted that approximately a billion years ago, when the percent- age content of 235U was substantially higher, this would have been comparatively easy. The importance of this comment was demonstrated after the discovery of a natural reactor that operated in Africa about two billion years ago. YaB was very distressed that, having made this comment, he hadn’t gone on to predict the existence of natural reactors in the past. By the way, I should note that YaB, a very sincere and direct person, never hid his annoyance with himself in situations when,

h It is characteristic that Landau also loved to talk about such things within a narrow circle of colleagues, but tried not to refer to them in his published work. In my opinion, this sometimes led to certain losses to science. There are few now who know that, in the well known work by Landau, A. A. Abrikosov, and I. M. Khalatnikov, there was initially a sign error in the formula relating the physical and seed charges. The situation that arose because of this was very pleasing to Landau, and he fully developed a philosophy of asymptotic freedom, which now is realized in quantum chromodynamics. However, when A. D. Galanin and B. L. Ioﬀe pointed out the error to Landau and he was able to correct the article before its publication, this ‘philosophy’ was omitted in the new version (which led to zero charge). Not many people knew about this. If it had been known, this would undoubtedly have helped subsequent researchers in the ﬁeld of quantum chromodynamics. (In any case, Yu. B. Khriplovich, who changed the sign in quantum chromodynamics told me that he was not aware of this event.) – S.G. April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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having embarked on the right path to solving some problems he had set himself, he bypassed some consequences or the final solution for a question. However, this did not prevent him, like a true scientist, from being delighted with the results obtained by other investigators, and from praising them in every possible way. I remember how YaB criticized himself for the fact that, having considered the creation of pairs in the field of a rotating black hole, he didn’t think of the general effect of black-hole evaporation, and was delighted with the results of Stephen Hawking. I also recall the following words of Dau at the end of the 1950s: “YaB has amazing flair and luck.” This is no longer a secret, so I can tell you about it. When YaB first raised the question of thermonuclear reactions, it became clear that it would not be possible to realize them in deuterium, since the effective cross section for dd reactions measured experimentally was too small. Then, YaB began to present, as it then seemed to me, a completely unfounded suggestion that the cross section for the reaction of deuterium with tritium should be substantially larger. When it was measured, this cross section, indeed, turned out to be 100 times higher than the dd cross section, due to the resonance of the 5He nucleus, which we hadn’t considered. However, even before this, YaB’s confidence in the large cross section for deuterium-tritium reactions was so great that they had already begun to build factories. In reality, as it follows from currently declassified documents, a narrow circle of people involved in the hydrogen bomb project already knew about the large deuterium-tritium cross section from intelligence data that had been obtained in Los Alamos. The fact that YaB did not have the right to tell about it even to Landau, characterizes the situation in which they worked. By the way, V. L. Ginzburg, who suggested to use solid LiD, with the lithium-6 isotope, in the hydrogen bomb (the second idea, in the terminology of A. D. Sakharov), did not know about the large deuterium-tritium cross section, either. Initially, V. L. Ginzburg assumed that the reaction between neutrons produced in the atom bomb explosion and the lithium-6 isotope could provide an additional source of energy. He did not realize that in the neutron-lithium reaction tritium would be produced, which, in turn, May 10, 2013 11:46 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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had a large probability of a tritium-deuterium reaction.i Landau believed that it was YaB who carried out the major part of the work that led to the creation of the hydrogen bomb. According to Landau, YaB just should have kept silence, and higher authorities unavoidably would have recognized that. When Sakharov analyzed the results obtained by Zeldovich’s group he was able to find an exceedingly efficient technical solution to the problem – the so called em sloika.j After that YaB used to go around telling everyone: “What have I done? Nothing ... But look at Andrei!” As a result, in 1953 he failed to be elected as a member of the USSR Academy of Sciences and got upset and offended. My collaboration with YaB continued after my matriculation as a postgraduate student with Landau. One new push for our collaborative activities was the discovery in 1957 by Alvarez et al.of muon catalysis nuclear reactions in hydrogen, and the establishment of the universal weak interaction. We saw that these two areas were connected, since various meso-atomic and mesomolecular processes in hydrogen that determine the behavior of μ catalysis also substantially influence the capture of muons by protons. It was essential to study this phenomenon experimentally in order to comprehensively verify the theory of universal weak interactions. In the field of mesomolecular processes, we were able to discover a number of unknown mechanisms that explained the existing experimental data and predicted new phenomena. In June of 1958, when YaB was elected as a full member of the USSR Academy of Sciences, he chose precisely this theme for a talk at the Physical Mathematical Division of the Academy (since it was forbidden to speak about the results of the classified research to which YaB had devoted his energy and talent

iHistory of Soviet Atomic Energy Project, Proc. Int. Symp. HISAP-96, Dubna, 1996; Moscow, 1999; Goncharov, G. A. Thermonuclear milestones, Physics Today 49 (11),44 (1996); Goncharov, G. A. American and Soviet H-bomb development programs: historical background, Physics-Uspekhi 39 (10), 1033 (1996); Goncharov, G. A. On the history of creation of the Soviet hydrogen bomb, Physks-Uspekhi 40 (8), 859 (1997); Adamskii, V. B. and Smirnov, Yu. N. Once again on the creation of the Soviet hydrogen bomb, Physics-Uspekhi 40 (8), 855 (1997). – S.G. jA design in which ﬁssion and fusion fuel (lithium-6 deuteride) were “layered.” Sloika in Russian is a type of layered puﬀ pastry. – S.G. April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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for over 15 years). I remember that the morning before the talk, YaB asked me to visit, and we discussed some details of his presentation. And then I, having listened to his talk, spent almost the whole day worrying at the Institute of Physical Problems, waiting for the results of the vote. There was some cause for such worry. Landau, stopping into the office of his graduate students, had talked about various pre-election academic intrigues. He feared that YaB’s independent character, for whom work always occupied first place, might arouse discontent among certain academicians. In this way, I first came up against the ‘wrong side’ of the Academy, and suffered deeply for YaB. Happily, it all ended favorably, and YaB was elected by the majority as an academician. (Dau described how Kurchatov’s presentation in support of YaB had made a large impression on those present.) Under the influence of YaB, muon physics determined the area of my scientific interests for many years. With his approval, I moved to work in Dubna, where several experimental groups of the Lab- oratory of Nuclear Problems (including those of B. M. Pontecorvo and V. P. Dzhelepov) had begun to study μ capture and μ catalysis, while the group of Yu. D. Prokoshkin had begun to design experiments for the detection of pion β decay. YaB’s idea about the possibility of resonance amplification of the formation of mesomolecules (when they have a level with a small binding energy)k served for us as a guiding thread for the interpretation of the unexpected results from the groups of Dzhelepov and Ermolov, who detected an increase in the output of μ catalysis during deuterium fusion reactions as the temperature increased. The possibility I noted for the existence of a vibrational-rotational level of deuterium mesomolecules with a binding energy of several electron volts led the Estonian physicist E. Vesman, then my graduate student, to the discovery of a peculiar mechanism for the resonance formation of deuterium mesomolecules; subsequent very refined calculations by L. I. Ponomarev’s group not

k This idea was contained in the work published by YaB in 1954 (before the discovery of Alvarez’s group), with the ﬁrst estimates testifying to the possibility of observing μ catalysis in a mixture of hydrogen isotopes. – S.G. April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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only confirmed the existence of this level in the deuterium mesomolecule, but also established the presence of an analogous level in the deuterium-tritium mesomolecule. This last result proved to be very important, and led to the prediction in 1977 that a single muon could give rise to about 100 nuclear fusion reactions in a deuterium-tritium mixture. Subsequent experiments conducted in the USSR (Dubna), USA, and Switzer- land confirmed these predictions and put forth (in accordance with the idea of the Leningrad Institute for Nuclear Physics researcher Yu. V. Petrov) μ catalysis as an alternative method for the processing of nuclear fuel. In the course of this work, it was elucidated that the most important restriction on the efficiency of μ catalysis was the ‘sticking’ of muons to helium nuclei indicated by YaB, which arises as a result of nuclear fusion reactions. Currently, more than fifty groups in the world are working in the area of μ catalysis, international conferences regularly take place, and a specialized international journal is published. In 1960, YaB and I wrote a review dedicated to μ catalysis for Uspekhi Fizicheskikh Nauk. During our work on this, YaB gave me his notebooks from 1957, after Alvarez’s discovery. Reading these notebooks allowed me to penetrate more deeply into YaB’s creative laboratory. Judging from their contents, the notebooks were written during his time off work at the ‘object’ and in Moscow. They demonstrated how YaB worked and thought: he set himself a problem, made estimates, rechecked them using various methods. He didn’t shun routine calculations, computations of integrals, extrap- olations, or numerical estimates. The notebooks include brief sum- maries of Alvarez’s work (together with a derivation of his results done by YaB himself), and also Frank’s work, published in Nature in 1947, and Sakharov’s report, published in 1948 (YaB learned about these last two papers only in 1957). One also encounters traces of discussions between YaB and Sakharov from that time: “ADS pro- poses. . . ,” “the very deep idea of ADS,” and so forth. One of the notebooks contains a manuscript for some joint work by YaB and Sakharov. In our review, I tried to develop some of the ideas expressed in April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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YaB’s notebooks, guided by certain beliefs about how, in his opinion, a review should be. “In a review,” said YaB, “there must be, first of all, a good introduction, which presents a clear formulation of the problem that is accessible to any physicist, even if he hasn’t worked in this area. Furthermore, it must be complete. Don’t be afraid to explain general questions when this is necessary in order for the maincontenttobeusefulbothtospecialistsandtothosewishing to enter work on the problem in question.” I tried always to be guided by these instructions, and when now, after 40 years, I still encounter references to our review, I remember these instructions with gratitude. I presented L. I. Ponomarev with YaB’s notebooks, for use in the education of his students, who, in essence, are YaB’s scientific “great grandchildren.” One of the most important and acclaimed accomplishments of modern physics is undoubtedly the understanding of the deep internal connection between the theory of elementary particles and cosmology. YaB was at the source of this flow of research. In the 1960s, when his interests had shifted toward astrophysics and cosmology, he entered these fields enriched with knowledge of the latest problems of elementary-particle physics, and immediately began to obtain interesting results at this junction of different scientific disciplines. Since those years were marked by major discoveries in each of these fields, YaB worked in two directions simultaneously. He enthusiastically adopted the idea of quarks and estimated (together with L. B. Okun’ and S. B. Pikelner) the possible concentration of free quarks in the surrounding medium in the framework of a hot theory of the universe. After this, he initiated experiments to search for free quarks in matter. I remember that he took me to the laboratory of V. B. Braginsky in order to acquaint me with such experiments, and to discuss them. To a large degree, the negative results of these experiments allowed modern concepts on the impossibility of the existence of free quarks to be established, and gave a push to the search for mechanisms for quark confinement. In 1966, YaB and I were invited to Hungary by Professor Marx. It was the first trip to a foreign country for both of us. YaB was, as they say, a hit. Many people who hadn’t known him earlier were April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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enchanted not only by the depth and breadth of his knowledge, but also by his energy, brilliant wit, and resourcefulness in discussions. It was during discussions on Lake Balaton that our idea about the possibility of obtaining restrictions on the total mass of all types of stable (or quasi-stable) neutrinos from cosmological data was born. YaB loved Hungary very much, and visited it again several times. He much regretted that he was not able to go to the ‘Neutrino-72’ conference in Balaton, which brought together many eminent West- ern physicists, including R. Feynman. I had the pleasure of talking with Feynman for several hours. He was interested in work on supercritical charge begun by YaB and me and then continued by YaB with V. S. Popov, who discovered one rather important error in our earlier work. Feynman wrote the problem for Z>137 on a special card, which he placed in his pocket. He said that a desire to meet YaB had been one incentive for him to come to the conference, since he learned from V. Telegdi that Zeldovich often attended neutrino conferences in Hungary. The possibility of traveling outside the ‘socialist camp’ for contact with major Western physicists (which could have been so fruitful for science) was opened to YaB only at the end of his life. Under YaB’s influence, I also began to become interested in astrophysics. M. Yu. Khlopov and I joined the group of my university friend V. S. Imshennik, who was working on the problem of supernova explosions. We were able to find a mechanism for neutrino ignition of thermonuclear reactions in stars. In self-consistent calculations, this mechanism could provide an explosion of a star with either the formation of a pulsar or the complete destruction of the star, with the release of a large amount of energy consistent with that observed. YaB was interested in our work and clarified many points in connection with it. It turned out that our mechanism for combustion and heating of material ahead of a front had been considered by YaB while he was still in his youth. In this way, it was remarkable that several of YaB’s various fields of interest came together in a single phenomenon: the physics of stars, the weak interaction with participation of the neutrino, combustion, and explosions. My acquaintance with YaB has allowed me to learn of several April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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episodes from his life, about which I’d like to write. In the pre-war years, and especially at the beginning of the Great Patriotic War,l he expended a lot of effort and energy on strengthening the defense of our country. In this area, his activities certainly weren’t reduced to purely theoretical investigations, and frequently involved large risk to his life. Once, when we were traveling together to Dubna and the driver of our car turned out to be a middle-aged woman, YaB recalled how, at the beginning of the war, a woman driver had taken him and a colleague to a test site for experiments with high-explosive shells, with which the car was heavily loaded. At some point, the woman, exhausted by lack of sleep, fell asleep at the wheel, and the car veered off the road and turned over. Fortunately, the detonators, which were in his colleague’s pockets, didn’t react upon the impact, and there was no explosion. Another time, YaB and his colleague were miraculously saved during an explosion that took place when they were conducting research aimed at ensuring the stable burning of powder in reactive shells intended for the well known ‘Katyusha’ rockets. And here’s another episode in YaB’s activities, about which I learned by chance. Looking over the just-published two-volume collection of Landau’s works, YaB pronounced with respect: “Dau has almost no incorrect papers.” Then, after a brief silence, he added: “However, we did get stung on one of them. Landau proved that a tangential break of a supersonic flow was stable. Based on this, Khariton and I began to experiment with supersonic flows of hydrogen. We hoped to create on this basis flamethrowers capable of igniting Nazi tanks. However, it turned out that instabilities arose in supersonic flows in virtually the same way as in subsonic flows. At that time, we had many other problems to work on, and we didn’t have time to spend on sorting out the theoretical side of this question. This was later worked out by S. I. Syrovatskii.” Listening to this story, I again was struck by YaB’s phenomenal ability to apply

l The part of World War II beginning from the onset of Nazi aggression toward the USSR in June 1941. – Translator April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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the results of fundamental science to applied problems, and thought about the stupidity and incompetence of the bureaucrats who had forbidden work in multiple organizations, even for scientists of YaB’s rank. (With the announcement of the official position banning multiple workplaces in scientific institutions, both Landau and Zeldovich were forced to leave the Institute of Theoretical and Experimental Physics, where they had worked part-time). YaB never talked with me about what he called his “special business.” For me, there is no doubt, however, that his role in the solution of the atomic problem includes far more than just his personal contribution. I believe that the breadth of his scientific interests was of invaluable importance, since it meant he knew people with various specialities, whom it was possible to attract to work on solving the huge number of specific problems that arose. In recent years, I’ve had occasion to meet some people inclined (after the event) to be skeptical about the value of this aspect of YaB’s activity. I consider this to be deeply wrong and unjust. It is not possible to judge the past based on the moods and situations in the 1990s. In the first place, all this activity began during the war, in years of deadly peril. In the second place, in the post-war decade, many people working on the ‘problem’ (not only YaB, but also I. E. Tamm and A. D. Sakharov) sincerely believed that establishing a nuclear equilibrium could be the only way of preserving peace. They served this goal to the full measure of their talent and ability, devoting the best and most productive years of their lives. The situation changed at the beginning of the 1960s, when the danger of militarization and the opposition between global powers became clear. Here, I must again refer to words of Landau, spoken in the autumn of 1961. Dau talked about how he, perturbed by our new nuclear tests, which had resumed after a long moratorium, literally threw himself at YaB with the words: “Is it your organization that has put the government up to these new tests?” “No,” answered YaB, “we didn’t need this. We had people opposing it.” The recently published excerpts from Sakharov’s memoirs shed some light on this story. As far as I know, it was at the beginning of the 1960s that YaB tried to move away from ‘special’ work. He himself let slip in his conversations with me that this was April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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far from easy. With the years, I developed a need for regular contact with YaB, calling him or stopping by to see him, in order to talk about scientiﬁc news, consult with him about my work, learn what he was currently working on. Sometimes, YaB wrote me letters (in general, he wrote easily – like he talked). Some of these contain funny drawings. These letters are very dear to me: the very personality of YaB is evident in them. Once, on a Monday, returning home from lectures, I felt an irresistible desire to stop in to see YaB at the Institute of Physical Problems. There, I met S. I. Anisimov, who told me that YaB had left twenty minutes earlier. “No problem, I’ll stop by another time,” I said. There was no other time. Two days later, I learned about YaB’s illness and sudden death. He loved verses, knew and quoted many, and could himself compose them impromptu in both Russian and English. When I now think of YaB, I involuntarily recall the verses of D. Samoilov, written upon the death of Akhmatova: That’s all. The eyes of genius are closed. And when the heavens dimmed and blurred, As if in a deserted abode, Our voices could be heard.

Afterword 1993 The desire to write an afterword arose after I was able to become acquainted with the full text of A. D. Sakharov’s memoirs, thanks to E. G. Bonner. It shows clearly what a huge role the mutual attraction between Sakharov and Zeldovich played in Sakharov’s scientiﬁc activity, along with the support that Zeldovich gave him, both in the early stage of his ‘speciality’ and in later years, when he was caught up in the problems of elementary-particle physics, gravitation, and cosmology. AD spoke about this also in his valedictory address at YaB’s funeral service. At the same time, in AD’s memoirs, which were written during the most diﬃcult years of exile, under conditions of almost total isolation, one encounters reproaches, and sometimes even open hostility, towards YaB. These parts of the text upset many people who knew both Sakharov and Zeldovich well. It seems to me April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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that some of AD’s reproaches stem from mutual misunderstanding (which under other circumstances could have been simply resolved by talking). This has prompted me to write an addition to my memoirs about YaB. Of course, relations between people of the caliber of Zeldovich and Sakharov are often not simple. However, throughout my acquaintance with YaB, I was constantly aware of his delight with AD’s talent. This attitude was not at all disrupted by the Academy elections of 1953, when YaB’s nomination was unsuccessful, and, according to AD’s memoirs, Sakharov, having been elected, found himself in an awkward situation with regard to YaB. YaB’s deep belief in Sakharov’s talent and the fact that, in essence, his potential had not been realized in full, provoked in YaB a sort of anger against any circumstances distracting AD from his scientific activity. One such distraction was AD’s social activities and his struggle for human rights. I don’t discount the possibility that YaB directed his anger toward those surrounding AD, considering them guilty of distracting Sakharov from his scientific work; this, in turn, could not help but call forth an especially painful reaction from AD. I cannot say that YaB didn’t sympathize with AD’s goals and courage. Once, in the spring of 1970, in answer to a question about AD, YaB said, half joking and half serious: “There is no doubt that AD is a great man, and great men sometimes make great ‘mistakes’. For example, if somebody else had spoken out in the Academy against Lysenko, Khrushchev, no doubt, would have dissolved the Academy, but in the case of AD, Khrushchev had been removed. I think that AD should be awarded the Nobel Peace Prize: here, engaging in the activities in which he is engaging requires no less courage than that of Martin Luther King.”m YaB considered the human rights activities of Sakharov a ‘mistake’ because he didn’t believe that they could be successful under the circumstances of that time, and could influence the situation in our country and in the world. He

mIn the end, YaB’s prediction was correct, not only about AD’s Nobel Prize, but also with regard to the ‘mistakes’ of this great man. AD could easily have died in exile, if it were not for perestroika.–S.G. April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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was also not spared from anxiety about AD’s personal fate and the loss to science if Sakharov’s scientific potential were not fully developed. Once, in connection with this, YaB quoted to me the splendid verses of Pushkin: “The desert sower of freedom, I went out early, before the star. . . ,” written, in the words of Pushkin, “in imitation of the fable of the moderate democrat Jesus Christ,” and containing as a conclusion: “But I lost time for nothing, happy thoughts and labor. . . ” In a very narrow circle, YaB also expressed annoyance at individual blunders which he perceived AD to have made. For example, he was genuinely surprised that it was possible, when speaking in defense of Pablo Neruda to Pinochet – who had displaced a law- ful, liberal president and shot thousands of people – to talk of the consolidation promised by his regime. In my opinion, this, and also YaB’s concern for AD, can explain the rather sharp telephone conversation about this described by AD in his memoirs. I don’t believe that YaB used this conversation over a tapped phone line to try to demonstrate his loyalty to the regime, since he displayed ‘disloyalty’ to a much greater degree, firmly refusing to sign any letters directed against AD. YaB understood that such letters from academicians would serve as a signal for Sakharov’s general persecution, to which (as proved to be the case in reality) would be added the letters of workers, collective farmers, writers, and composers. In difficult and stagnant times, YaB himself helped and literally saved many people. I know about some cases myself, and I am sure that there are many more which I don’t know about because YaB never talked about them. He was a realist, and believed that, under the circumstances, the most effective method was ‘quiet diplomacy,’ that is, personal appeals to those on high, rather than public protests. In this regard, as YaB told me, he shared full mutual understanding with P. L. Kapitsa (several of whose letters have now been published). I won’t try to judge whether or not YaB was right; however, he well understood the limits of his own abilities – the limits that existed despite the fact that he was absolutely instrumental in the creation of the hydrogen bomb and despite his “regalia.” His possibilities were very limited. Frequently, he was not even able to hire researchers he would have liked to (if problems were posed by their personal data April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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or by the absence of a propiska,n for example). He went to great lengths to try to get these people settled in appropriate positions, in order to have the opportunity to continue working with them. (Many colleagues used him in this capacity, and he went to these lengths not only for his own students.) I believe that it was concern about the fate of the scientiﬁc ﬁelds that he had developed and about the fates of many people associated with him (rather than concern for his own position) that strongly limited YaB’s freedom of activity. Sometimes, YaB’s appeals ‘higher up’ were refused in rather unceremonious, and even humiliating ways. The following story is typical. In 1980, L. B. Okun’ received an honorable invitation to give the concluding talk at the International Rochester Conference on high-energy physics in Madison (USA). Af- ter obtaining the required permission from the Atomic Energy Com- mittee, Okun’ accepted the invitation and prepared his talk. In it, he emphasized the constant need for modern physics to search for scalar particles, including Higgs bosons. (Subsequently, this talk became famous, and in many ways determined the direction of future experimental studies, and even projects for new accelerators.) However, a highly placed bureaucrat in the Central Committeeo for- bade Okun’s trip at the very last minute for reasons which were not ‘clear’. After unsuccessful attempts by various people to try to change this decision, YaB called the secretary of the Central Commit- tee, M. V. Zimyanin. In response, Zimyanin reprimanded A. P. Alek- sandrov, the President of the USSR Academy of Sciences saying that he had let his academicians get so out of hand that they were shov-

n In the Soviet Union, each citizen had a propiska, assigning them to some particular address. A citizen was allowed to live only at the address indicated on his propiska. Without a propiska in a particular region, it was not possible to obtain work in that region; at the same time, it was usually impossible to obtain a propiska in a region without employment there. This bureaucratic catch-22 was eﬀectively used by the Soviet government to control where its citizens were living and working, and ultimately all aspects of their lives. In Russia in the early 1990s, the propiska system was oﬃcially replaced by a less restrictive system of registration, in which citizens are, in principle, free to live and work where they wish, but are required to register their addresses with the local government. Unfortunately, by the time of writing in 1999, this freedom is still at times only theoretical. – Translator o Of the Communist Party of the Soviet Union. – Translator April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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ing their noses into other people’s business, and daring to telephone the secretary of the Central Committee. I should say that Okun’s failure to appear at the conference and the disruption of the last talk became a scandal, and resulted in a substantial loss to our science.p It stands to reason that our country underwent an even greater loss due to the exile of AD and his hunger strike. However, this was impossible to explain to the higher authorities of that time, who firmly maintained a completely different view of this matter. There- fore, when AD wrote to YaB and other academicians with a request to help send a person close to him abroad (Liza Alekseeva, the fi- ancée of E. G. Bonner’s son), YaB said that he would do everything he could to try to ensure proper conditions for AD’s scientific work, but it was not in his power to send somebody abroad. This response provoked a sharp reaction in AD. In turn, YaB, the only person to answer AD’s appeal, suffered greatly when he learned of AD’s reaction to his letter (and he learned of it from a foreign radio program that quoted individual phrases from that letter). The entire affair gave YaB many bitter hours. In conclusion, I would like to consider one other question touched upon in Sakharov’s Memoirs. AccordingtoAD’sthinkinginthe 1980s, the problem of creating thermonuclear weapons, on which YaB had worked, and to which AD had contributed in 1948, was “stolen in full,” that is, based on information acquired by Soviet intelligence. AD’s reading of foreign sources made his opinion about this even more firm. Due to a series of circumstances, material shed- ding additional light on this question came into my hands several months ago. In the August 1990 issue of Priroda,whichwasdedi-

p In spite of the incomprehensible explanations of the Soviet delegates (“he didn’t show up at the airport,” “he couldn’t manage to get a ticket,” and so forth), the 1,000 participants in the international conference understood perfectly well what had happened, and unanimously made an oﬃcial protest. Understanding that they had made a mistake, high governmental oﬃcials themselves insisted on Okun’s participation in another international conference a year later. However, the consequences of the scandal could not be wiped away. Together with the protest against Sakharov’s exile, the Okun scandal served as an additional argument against having the next Rochester Conference in the Soviet Union (though this had been planned earlier). In this way, a large number of Soviet physicists were deprived of the opportunity to participate in it. – S.G. May 10, 2013 11:46 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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cated to Sakharov, I found in an article by Yu. A. Romanov a reference to the fact that the question of creating a hydrogen bomb was first raised in the USSR in 1946, in a special report presented to the government by I. I. Gurevich, Ya. B. Zeldovich, I. Ya. Pomeranchuk, and Yu. B. Khariton. Interested by this, I stopped by to see Gurevich and asked him, if possible, to tell me about this report and to comment on AD’s suggestion. Isai Isidorovich said that, in 1946, they had no indication that scientists in America were working on this question. It was simply that the deuteron and nuclear reactions between light nuclei were among his interests and those of I. Ya. Pomeranchuk, since they provide information about nuclear forces and represent the source of energy in stars. In their joint discussions, Zeldovich and Khariton noted that it was, in principle, possible to bring about thermonuclear fusion under terrestrial conditions by heating deuterium in a shock wave initiated by an atomic explosion. Their estimates showed that, under these conditions, it was possible to avoid the transfer of a large fraction of the energy released into electromagnetic radiation, and thereby to obtain an explosion of an unlimited quantity of the light element. This is how their joint proposal, which they made to Kurchatov, arose. “It’s possible that I can even show it to you,” said Gurevich, “It’s probably preserved in the archives of the Institute of Atomic Energy.” Indeed, a few weeks later, I held in my hands a certified copy of this proposal, containing seven pages of typewritten text, with the formulas written in by Gurevich’s hand and with the note ‘1946’ made on the last page by Kurchatov. “Here’s your clear proof that we didn’t know about any American projects,” said Gurevich, indicating the title page of the text. “Imagine how deeply classified it would be, and behind how many seals it would have been preserved otherwise.”q

q This report is published in full in Uspekhi Fizicheskikh Nauk, 1991, vol. 161, iss. 5, p. 170. Apparently, I. I. Gurevich was not aware that, as early as in the middle of 1945, Klaus Fuchs had issued reports about discussions of possibilities for creating a hydrogen bomb at Los Alamos. He didn’t know that a report he was involved in was preserved with the highest secrecy stamp in the archive of the Ministry of Medium Machine Building (see I. I. Gurevich, Ya. B. Zeldovich, I. Ya. Pomeranchuk, and Yu. B. Khariton, Soviet Physics- May 15, 2013 10:43 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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I agreed, though it remained unclear to me why it was not given any secret status at all, and was simply put in an archive. Gurevich explained this as follows: “I think that, at that time, they simply waved us away. Stalin and Beriya urged on the creation of an atomic bomb. We didn’t yet have an operational experimental reactor, and here the scientific ‘sages’ show up with new projects that it might not even be possible to carry out. I didn’t work on this any further, and how events developed after that, I don’t know.” Judging from Sakharov’s Memoirs, in the middle of 1948, theoretical calculations in connection with this proposal were already being developed under the supervision of Zeldovich and A. S. Kompaneets in the Institute of Chemical Physics of the USSR Academy of Sci- ences. Tamm’s group, which included AD, was created in order to verify them. Later experimental studies were conducted at the ‘object.’ They yielded extremely interesting scientific results; in particular, temperatures of about a billion degrees were achieved.r The fact that, in 1948, all work on nuclear fusion was carried out in the deepest secrecy (even the innocent report of AD on μ catalysis was classified) indicates that the government understood the importance of the problem by that time. It is possible that it was Khariton and Zeldovich who were able to convince the government of this (Landau once said with irony: “YuBs and YaB are our Soviet saints. For the sake of the cause, they are prepared to argue with the big bosses, and to persist when the bosses don’t understand.”). However, it is also possible that the government received intelligence data about similar projects in the USA. This is quite probable, given the iner-

Uspekhi 34 (5), 445-446, 1991; Goncharov, G. A. On the history of creation of the Soviet hydrogen bomb, Physics-Uspekhi 40 (8), 859 (1997); Adamskii, V. B. and Smirnov, Yu. N. Once again on the creation of the Soviet hydrogen bomb, Physics-Uspekhi 40 (8), 855 (1997)). Ministry of Medium Machine Building of the USSR was a code name for the agency (established by Decree of the Presidium of the Supreme Soviet of 26 June 1953), that supervised Soviet nuclear industry, including production of nuclear warheads. Before 1953 it was known as the First Chief Directorate (nuclear industry) and the Third Chief Directorate (development in the area of controlled missiles, aircrafts, rockets and long range missiles) established in September of 1942. – S.G. r See L. P. Feoktistov, Abornleader,inZeldovich. Reminiscences, Ed. R. A. Syunyaev, (Chapman & Hall/CRC, 2004), p. 121. sYulii Borisovich Khariton (1904-1996), the chief designer of the Soviet atomic bomb. April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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tia of the state machine, which was not inclined to especially trust its ‘smart guys.’ (It is clear, for example, that no desperate letters from G. N. Flerov to Stalin about the need to make an atomic bomb could have been effective if there hadn’t been intelligence data about similar work outside the country.)t Afterword 2006 Declassified documents on the history of the Soviet atomic project show that the work on the hydrogen bomb in the USSR was indeed initiated in 1945 by a dispatch from Klaus Fuchsu reporting on discussions of this problem in Los Alamos. Fuchs informed Soviet intelligence of the Edward Teller’s project under the code name “Classic Super,” which in our country was known as “Tube.” I. I. Gurevich, undoubtedly, did not know about this. Most probably, the above work of four authors was initiated by Igor Vasilievich Kurchatov himself who could have asked: “What do you think, could one ignite the deuterium fusion reaction by an atomic bomb explosions? Isn’t it an interesting question?...” According to recollections of the participants of the nuclear project, Igor Vasilievich used to use this trick to direct their attention towards problems of which he knew from intelligence but could not mention this. This way of actions had some advantages. First, Kur- chatov’s coworkers (those who got a problem from him in this way) often were able to find a more efficient solution. Second, this provided Kurchatov with an independent check of the intelligence information. It seems that the situation with the work of four authors was similar. In addition with the results that coincided with Fuchs’s data, this work contained new and original suggestions. I.V. Kurchatov seemingly kept this work in his archive. For I.I. Gurevich this was an argument convincing him in the absence of predecessors. In fact, as was discovered by Professor G.A. Goncharov, the work of I.I. Gure-

t This calls to mind a not altogether decent comparison made by YaB: “There is a sort of impotence when a person can’t become aroused until he sees that somebody else is already acting.” – S.G. uKlaus Fuchs (1911-1988) was a German-British theoretical physicist and atomic spy supplying information from the Los Alamos National Laboratory to the USSR during and shortly after World War II. April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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vich et al. was in the Ministry of Medium Machine Building sealed with the highest secrecy stamp. Andrei Dmitrievich Sakharov knew, but could not tell, that the device known as Tube, on which Zel- dovich and his colleagues worked so hard, was motivated by Teller’s Classic Super. When Zeldovich’s suspicions of Tube’s failure grew into certainty he insisted on shutting the project down. Sakharov did exactly the same by rejecting his own project of a Large Sloika which, as he wrote in his memoirs, was imprudently announced by him and approved by the government. It turned out to be a deadend. Exactly after this, as a result of a brain storm organized by Ya. B. Zeldovich, A. D. Sakharov, and the team of their talented colleagues, an idea of the radiation implosion was born (the third idea, in the terminology of A. D. Sakharov). V.A. Davidenko who repeatedly called upon theorists to think how to use the “device” (A bomb) to ignite the “superdevice” (H bomb), played an important role. I remember that once, when we met, YaB told me with great sadness: “Davidenko died a few days ago. He was the author of that idea.” I thought that Zeldovich had in mind the use of lithium- 6 deuterite. That it was Davidenko who suggested lithium-6 deuterite. I already knew about this clever idea, but was not aware that V.L. Ginzburg was its author. The importance which YaB attributed to Davidenko’s words, rather vague and qualitative at best, shows, time and again, how appreciative YaB was – appreciative of thoughts of other people which led him to new discoveries. It is remarkable how one and the same scientific thought can develop in different places. In Los Alamos it was a mathematician, Stan Ulam, who realized that Classic Super is doomed to failure and suggested to exploit the nuclear fission energy from the atomic bomb explosion to ignite, through hydrodynamic lenses, nuclear fusion. Somewhat later in Soviet Union the same thought came to Davi- denko’s mind. However, Edward Teller understood that radiation implosion – i.e. squeezing the fusion material by soft γ rays resulting from the explosion of the atomic bomb – is most suitable for this purpose. The atomic bomb was supposed to be located in the heavy shell of the “device.” Something similar had been previously discussed by K. Fuchs and J. von Neumann, but only in applica- April 5, 2013 14:34 WSPC/Trim Size: 9in x 6in for Proceedings 4b˙Gershtein˙o˙Zeldoviche

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tion to the initiating block of Classic Super. The same solution was found by Zeldovich, Sakharov and Yu.A. Trutnev. A massive effort of brilliant physicists, mathematicians, designers and engineers led to a remarkably speedy implementation of the two-stage construction, outlined above. An outstanding physicist, Lev Petrovich Feoktistov, recollects:v “In essence, we worked on this construction only in 1954 and early 1955. In November of 1955 the first test of the hydrogen bomb of this new type was carried out. The result turned out to be overwhelming. All other versions of the project were immediately abandoned. The two-stage construction described above served as a basis for all further developments of thermonuclear explosives used in various types of weaponry, as well as for the peaceful applications.” Of course, today it is very difficult for people who grew up in the post-Stalin era, and especially outside the Soviet Union, to understand how such noble and extremely honest people as Tamm, Sakharov, Pomeranchuk, Zeldovich, and many of their colleagues could work so selflessly on the creation of a horrifying weapon, devoting all their knowledge and talent to this work, displaying extraordinary initiative, persistence and creativity, and not acknowledging what danger such weapons posed for the fate of the entire world in the hands of a totalitarian system. This was not simply the interest of researchers in an unusual physics problem (although this was also very important). The motives driving these people are clearly laid out in Sakharov’s Memoirs. Here there is nothing to add or remove. This afterword does not in any way aim to somehow make excuses for YaB. He does not need this. After YaB’s death, Sakharov wrote about the fact that all the disagreements between them seemed to him “no more than foam carried by the flow of life.” I would like it if people’s memories could preserve the creative collaboration between Sakharov and Zeldovich, which was so fruitful, and the fact that their signatures often stood side by side (as in the case of the manuscript of their joint paper “On Reactions Caused by μ Mesons in Hydrogen,” which is preserved among my documents).

vSee L. Feoktistov, The Weapon that Exhausted Itself, (Moscow, 1999). – S.G. April 5, 2013 14:35 WSPC/Trim Size: 9in x 6in for Proceedings 4c˙Shiryaeva

ASIMPLELOVESTORY∗

ANNA SHIRYAEVA [email protected], [email protected]

Mother and Father My mother, Olga Konstantinovna Shiryaeva, was born in 1911 and had a clear memory of pre-revolutionary times. After high school she enrolled in textile institute, where she encountered some problems because of her family background: Olga Konstantinovna’s father was a Russian officer and had served in the Imperial Army, and her mother came from a family of Russified Swedes. As a result, she was allowed to transfer, ostensibly for health reasons, from textile institute to the architectural institute then called Vkhutemas.a She was lucky: she wound up working in Shchusev’s studio and acquired a good education. Examples of this can be seen in works she carried out while still a student: the drawings at the Komsomolskaya subway station in Moscow and the design of the Aragvi restaurant. After graduation, Olga Konstantinovna married, and in 1937 she gave birth to a son, Sergei. From 1939 to 1941 Olga Konstantinovna was in Riga on business, returning from there literally just days before the war. From the war’s first days she wanted to go to the front, but couldn’t, due to the small child. During the war, she lived in evacuation in the town of Buzuluk in the Orenburg region. In late 1945 she was denounced and repressed. She was charged with spy- ing, if not for the Japanese, then for the Poles. Then came various camps, and in the late 1940s she wound up working on the construc-

∗Published in Russian in Yakov Borisovich Zeldovich,Eds.S.S.GershteinandR.A. Sunyaev, (Fizmatlit, Moscow, 2008, Second Edition), p. 155. Translated from Russian by James Manteith. See also O. K. Shiryaeva, Istoriya Odnoy Zhizni, Ed. Alina Chertilina, http://zhurnal.lib.ru/c/chertilina a s/istoriaodnoj.shtml . aThe Russian acronym for Higher Art and Technical Studios founded in 1920 in Moscow.

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tion of Sarov, the secret “city of physicists.”b Olga Konstantinovna was always saved, including in the camps, by her profession, which enabled her to stay alive. After release in 1949, she continued to work at the city’s construction sites: she did finishing work on cottages, made scenery for theater productions, painted murals in the cathedral, which at first was the “general’s dining room” and then became the theater. Be- neath the dome is still preserved her mural: an endless blue sky, and clouds. My mother met my father, Yakov Borisovich Zeldovich, on a tennis court. She was always passionate about sports, and started playing tennis as soon as conditions permitted. One day she saw a short man with bright eyes. This was Yakov Borisovich. Mother’s appearance, Nordic and intriguing, made an impression. The man watched her very closely. She didn’t like this, and left, unfortunately forgetting the balls, which were in terrible deficit. By the time she returned for the balls, he’d changed clothes. He immediately walked her home. That was the start of their acquaintance. Acquaintance grew into love. This meeting played a cruel trick on my mother. Soon she was called to a “special place” and invited to “give reports,” but she refused to “snitch.” It was a difficult choice. First she spent a month in jail. She could receive visits only from her son Sergei. He brought packages, including clothing and money sent by Yakov Borisovich. Obviously his influence was unable to change anything at that time. Thank God, no measures of physical coercion were used against her. Family legend has it my father was very distraught while going through my mother’s disappearance. He knew she had been “locked up,” but could do nothing. He was denied some sort of promotion then, seemingly as punishment. Mom was accompanied to the train by the KGB agent who had wanted her to give information, to “write reports.” Just a few days before her departure she learned she was pregnant. This was also

bFrom 1946 to 1991 it was called Arzamas-16, a closed town in Nizhny Novgorod Oblast, the site of the Russian center for nuclear weapon research. Soviet analog of Los Alamos. April 5, 2013 14:35 WSPC/Trim Size: 9in x 6in for Proceedings 4c˙Shiryaeva

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known to the agent, who tried to persuade her up to the last moment, warning her that out there she was certainly done for. Up to the last minute he hoped my mother would cooperate. They both understood she was heading into the unknown, if not to her death. There was no court verdict. She was simply “shipped off” to Kolyma.c The transfer lasted five months. At the gold mines lived exiles and criminals; it was a “last stop” on the road to extinction. Pregnancy saved my mother. She was settled behind the stove in the bakery. I was born in January 1951, my mother said, at a temperature of −42oC.d My mother and I spent our first year together in Kolyma, while my father struggled in Sarov, trying somehow to save us. Again as family legend has it, Yakov Borisovich reached Beria and met with him. Since there had been no verdict, there was no ruling on a release. Simply somebody had been in one place and showed up in another. Suddenly we received a money transfer and instructions to leave. In six days my mother reached Magadan, terribly tired. Years went by. I grew up. My father was always around. I found him shocking: terribly cheerful, spring-loaded with energy, one might say. I was quite embarrassed that he was shorter than my mother, that he liked noisy games, that he would always have to kick a ball in the courtyard, that he loved to dance although he didn’t know how. To me, an insecure teenager, this seemed awful. I always liked being with my father. He said, “A daughter’s demand is a command. Done.” In my case, of course, this policy led to pampering. If I was vacationing in the south with friends and ran out of money, I sent my father a telegram and the money came right away. When I wanted to study at the famous Physics and Mathemat- ics School No. 2 (in fact, not very reasonably), right away a phone

cKolyma is an extremely remote region located in the far north-eastern area of Russia, part of which lies within the Arctic Circle, with very cold winters. Under Stalin’s rule, Kolyma became the site of many Gulag labor camps. A million or more people died on route to the area or in the Kolyma camps between 1932 and 1954. d −72oC in the Russian original. This seems to be a misprint. April 5, 2013 14:35 WSPC/Trim Size: 9in x 6in for Proceedings 4c˙Shiryaeva

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call was made and I got a transfer. He tried to teach me something. I actively resisted. But nonetheless, probably under pressure from father, I went to study at the Moscow Engineering Physics Institute. Even as a schoolgirl, I studied under Israel Khaimovich Sivashin- sky: he prepared me well for institute. I liked everything and studied all right, but when I applied to the faculty of computer science at MEPI, out of fear I made every possible dumbest mistake in the written exam and became terribly upset. Retaking exams wasn’t allowed then. My father said, “Never mind,” and I took the exam again, performed all the assignments and got a perfect score. I just stopped freaking out. Once father came to the institute to lecture. Mostly likely the administration knew whose daughter I was, but among the students I didn’t stand out. Naturally, I went to the lecture hall along with everyone else. But my father yanked me out like a turnip and said, “This is my daughter.” And at the break we walked together hand in hand in plain view of everyone... After this incident, for a long time I had a sense of hearing “rustling” from behind. For ﬁve years I was a fairly average MEPI student. One day I told my father I didn’t want to study in the computer science department, which had, I said, lots of girls. I wanted to go to the theoretical department. I was immediately transferred there. When I said I didn’t want to study at MEPI, my father asked, “Well, where do you want to go?” I said, probably to the Plekhanov Economics Academy or somewhere else. I successfully transferred to the Plekhanov Academy, where I demonstrated a knowledge of mathematics absolutely incredible for that time. I now think that this form of upbringing was not very correct, but nonetheless, that’s how it was. I can’t imagine my father being strict, because he never lived with us, but father’s pampering is easy for me to imagine. True, we never took a vacation together. And father and I never went to the theater...

“Scat” and the Family Name Once my mother became seriously ill, and my father went to fetch a doctor. I was used to riding in the front seat of my father’s car, April 5, 2013 14:35 WSPC/Trim Size: 9in x 6in for Proceedings 4c˙Shiryaeva

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and climbed in the front. He told me, “Scat, shoo, this isn’t for you now.” I immediately began to pout. But I don’t remember any other scolding. He expressed himself quite simply: if it was time for “scat,” he said “scat” without hesitating. If it was time for “here, kitty kitty,” he said, “here, kitty.” Because I’d didn’t particularly climb into things, most often I was a good kitty. When at 16 I chose my surname, I adopted my mother’s. My father said, “Well, whatever you want, of course. If you don’t want to be Zeldovich, don’t be.” But he was disappointed, noticeably so. National connotations caused me much more fear then. I didn’t think about my father’s authority as a scientist. It was just that with a Jewish surname, everyone knew things would be harder. Besides, I went and got married literally at age 17 and successfully changed my surname, so the issue went away on its own. My mother told me in broad terms what exactly my father studied in science. At the time, I was probably too focused on myself, but that “rustling,” which accompanied me through all my student years, forced me to reflect. I realized that in science not only would my level never reach father’s heights, but that I wouldn’t even be his weak reflection. I should never have gotten involved in this business... After the Plekhanov Academy I became an economist and mathematician; I had my first husband and child. I met my current husband there as well – he was my term-paper adviser. Since then, I haven’t worked and haven’t studied: I’ve moved smoothly from one person’s pampering to another’s. I remember how upset father was when I had health problems before giving birth to my third child: I was getting on in years, at 37. He ran around, made phone calls, tried to help somehow. Father supported our family materially for a long time.

Brothers and Sisters, Children and Grandchildren My younger brother Lyonka and I met each other in a funny way. I was going to see my father and had taken the number seven streetcar, which goes along Kosygin Street even today. Seeing a young man, I thought, “He’s my brother”; I saw him and just knew. After that we April 5, 2013 14:35 WSPC/Trim Size: 9in x 6in for Proceedings 4c˙Shiryaeva

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walked on the same sidewalk, up the same stairs, reached the same door – that’s how we met. Lyonya, like me, was born out of wedlock. His mother died prematurely, and his older brother Borya took care of him. Lyonka also graduated from Physics and Mathematics School No. 2. He had his own apartment, and studied at the Moscow Institute of Physics and Technology. I remember that just before father died I came to visit him with my youngest son, who was a month or two old, and my husband. At this time Marina came by. And I met Sasha, Borya and Olya when father died, at the funeral, although they had known of my existence, just as I had known of theirs. Life had just never brought us together. In 2000, my husband and I moved to Prague. I have one daughter in Moscow; the other sometimes lives there and sometimes here. Our youngest, Sergei, is still young, 16 years old. He’s studying in the Czech Republic to be a chemist. My eldest daughter already has three children of her own, boys. My middle daughter did well and graduated from that same Physics and Mathematics School No. 2 and the Department of Automation and Microelectronics at MEPI; she has a good grasp of computers. She’s just passed the “candidate minimum” exams in sociology. From what she says, now she’s more interested in other things: she’s studying solutions to “women’s” issues. Quite unexpectedly, almost all the younger generation – grandchildren and great-grandchildren – are fascinated by chemistry. My son Seryozhka simply preferred any technical subjects – physics, math, chemistry – just nothing humanitarian. My eldest grandson Albert plays chess at the Botvinnik School and is studying successfully in an English school. My grandson Denis is also still in school and doing well in swimming. Yashenka is still little, and a year-old grandson, Seryozhenka, was just “tossed” my way. Life goes on. April 5, 2013 13:32 WSPC/Trim Size: 9in x 6in for Proceedings 5a_Chap4-divider

CHAPTER 4 May 10, 2013 11:7 WSPC/Trim Size: 9in x 6in for Proceedings 5a_Chap4-divider May 13, 2013 15:48 WSPC/Trim Size: 9in x 6in for Proceedings 13˙Index

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YAKOV ABRAMOVICH SMORODINSKY

NOEMI SMORODINSKAYA Institute for Theoretical and Experimental Physics Moscow, Russia [email protected]

My father Yakov Abramovich Smorodinsky (Ya.A. hereafter) was born on December 30, 1917 in a small town of Malaya Vishera located about 100 miles south-east of St. Petersburg. His mother Roza Smorodinsky (Fitingof) originated from a big family. She married a young railroad engineer and a dance competition winner named Abram Smorodinsky, who died of typhus in 1921, when little Yakov was four years old. So, he was brought up solely by his mother. After graduating with honors from the Physics Department of the Leningrad State University in 1939, Ya.A. started his graduate studies under the supervision of L.D. Landau at the Institute of Physical Problems in Moscow.a He received the Candidate of Science degreeb in 1941, just before the beginning of World War II in the USSR. A month after the German invasion of the USSR (on June 22, 1941) the Soviet Academy of Sciences was evacuated to the city of Kazan to carry out research for the war eﬀort. Ya.A. performed calculations needed for the construction of ice-based lines of communication such as ice roads, ice bridges, and other similar structures on the surface of bays, rivers, lakes, or seas. His supervisor for this project was Academician Aleksey Nikolaevich Krylov, a famous naval architect andanexpertinmechanicsandmathematics. In 1944, when Ya.A. returned to Moscow from Kazan, Igor Vasi- lyevich Kurchatov oﬀered him a position at the newly created Labo- ratory N o2 (now the Russian Research Center Kurchatov Institute)

aCurrently P.L. Kapitsa Institute of Physical Problems. bEquivalent to PhD in the US.

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to work on isotope separation by the gaseous diffusion method in the group of Isaak Konstantinovich Kikoin and Sergey Lvovich Sobolev. This Laboratory was created as a part of the Soviet atomic project with the task of developing Soviet atomic weapons. Therefore, most of its activities were associated with applied sciences. However, Kur- chatov realized the importance of collaboration between theorists and experimentalists, between fundamental and applied science. He had a strong opinion that, in order to work efficiently, physicists should be aware of all news in science, especially in nuclear physics. To this end, he organized a seminar which took place every Tuesday morning and attracted physicists from many other organizations. This seminar was an excellent school for young people, a forum for discussing new results and gaining experience. Ya.A. was responsible for invited speakers. He had already worked with L.D. Landau on the theory of nucleon-nucleon interactions and thus was well known in the physics community. When Kurchatov asked him to arrange a series of lectures on the theory of atomic nuclei, Ya.A. invited L.D. Landau. More than 500 physicists attended Landau’s lectures on a regular basis. Later, in 1955, my father and Landau expanded this lecture course and published it as the famous Landau-Smorodinsky textbook “Lectures on the Theory of Atomic Nucleus.” In 1948 Kurchatov initiated the construction of a new laboratory 125 km north of Moscow in the place now known as Dubna. For secrecy reasons this Laboratory was officially called Hydrotechnical Laboratory of the Academy of Sciences of the USSR, although its research program had nothing to do with water.c Then, upon Kurcha- tov’s request, four young theoretical physicists, who were considered to be the most advanced experts in nuclear theory – I.Ya. Pomer- anchuk, A.B. Migdal, Ya.A. Smorodinsky, and B.T. Geilikman – began weekly trips to Dubna to deliver lectures on nuclear and elementary particle physics, to participate in theory seminars, to help plan the experimental program, and to analyze fresh results from the five- meter synchrocyclotron accelerator which was launched in Dubna in

cCurrently this is the Joint Institute for Nuclear Research. April 5, 2013 14:42 WSPC/Trim Size: 9in x 6in for Proceedings 5b˙Smorodinsky˙Naya

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December 1949. This synchrocyclotron accelerated protons up to then unheard of energy, 480 MeV! At the same time Ya.A. taught at the Moscow Institute for Physics and Engineering. His lectures soon became famous among students from other institutions, so the audience swelled with each lecture. At that time the study of the low-energy nucleon-nucleon strong interaction was thought to be the most important part of nuclear and elementary particle physics. The only source of information was the experimental exploration of nucleon interactions with the simplest nuclei and, first and foremost, nucleon-nucleon scattering data. The theory of strong interactions had not been formulated yet, and therefore phenomenological analysis of the above collisions reigned practically uncontested. Ya.A. began his career in physics with nucleon-nucleon scattering problems – his first publications were devoted to the scattering of light off mesons (and generally to electromagnetic interactions of particles with integer spins). In 1944 he turned his attention to the yet unformulated theory of strong interactions. In an elegant work with Landau, Ya.A. considered phenomenological nuclear forces in the proton-proton scattering, with a constant (parametrizing boundary conditions) represented as a linear function of energy. This approach allowed them to describe strong interactions in terms of two constants: scattering length and effective radius. The corresponding normalization of the asymptotic expression of the deuteron wave function is now called the Smorodinsky normalization. Smorodinsky’s subsequent papers dealt with the nucleon-nucleon scattering at high energies (at that time high energies began at a few hundred MeV). The goal of such experiments was to obtain information on the asymptotic behavior of the wave functions of colliding nucleons. In other words, the goal was the reconstruction of the nucleon-nucleon scattering matrix. The main question was: what and how many experiments must be done to identify this matrix? This question is now referred to as the complete experiment problem. A nice example that illustrates the need for complicated experiments with several targets is provided by the isotropic scattering 0 0 dominated by two states, 3P and 1S . How can one separate the April 5, 2013 14:42 WSPC/Trim Size: 9in x 6in for Proceedings 5b˙Smorodinsky˙Naya

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contributions of these two states? There is no polarization in such 0 scattering, but it is known that in the 1S state the spins are always 0 opposite, whereas the 3P state is characterized by almost parallel spin orientations. Hence, these states can be distinguished by measuring polarization correlations. However, such an experiment must include scattering off three targets: the pp scattering in addition to coincidence measurements of polarizations of the scattered and recoil particles using two extra targets. To solve the complete experiment problem, Ya.A. considered all possible types of nucleon- nucleon scattering experiments for different polarizations of the incident beam and the target and different quantities measured (cross sections, polarization of scattered or recoil particles, and polarization correlations). It turned out that the simplest complete proton-proton experiment involved the measurement of five judiciously chosen quantities performed at one energy and all scattering angles, or at least nine such experiments performed at a given energy and angle. These experiments did not need any polarized target, but if a polarized target was used, the number of targets decreased by one. Ya.A. was fascinated by the complete experiment idea and attempted to apply it to various other processes, e.g. to β decays. He formulated general relations for phase shift transformations which do not affect observ- ables (cross section, polarization, etc.) and can lead to ambiguities in the phase analysis. Ya.A. was always extremely enthusiastic about symmetry methods in physics. One could say that he was fascinated by such methods. His subsequent works were devoted to symmetries in physics. He was among the first to recognize the importance of the unitary symmetry in elementary particle theory, i.e. the necessity of reaching beyond the Wigner multiplets, related to isotopic spin, to the “su- permultiplets” of Gell-Mann’s “eightfold way.” He became an expert in group theory methods and their applications. Ya.A. believed that symmetry could act as a powerful tool in theoretical physics, providing guidelines leading to beautiful results. All his students and colleagues remember Ya.A.’s passionate discussions of the role of symmetry in nature. Ya.A. was one of the first physicists to fully realize the importance of unitary symmetry in April 5, 2013 14:42 WSPC/Trim Size: 9in x 6in for Proceedings 5b˙Smorodinsky˙Naya

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elementary particle physics. He particularly appreciated the importance of combining the intrinsic SU(3) symmetry with space-time symmetries. His original contributions – important papers on the representation theory of SU(3) in different bases and two very influential review articles – followed shortly. One review article was devoted to SU(3) symmetry, the other to SU(6). These two articles very clearly explained the underlying mathematics as well as numerous applications to strong, weak, and electromagnetic interactions. At that time they attracted many physicists, both senior and younger physicists, to this area of research. The next big project of Ya.A. was devoted to the Lobachevsky geometry, representations of the Lorentz groups and invariant expansions of the scattering amplitudes. He realized that the Lobachevsky geometry of the velocity space provided a very efficient tool for description of relativistic kinematics. A seminal article of Ya.A. (with N.Ya. Vilenkin) laid the basis for a new direction in mathematical physics which is actively pursued to this day. Ya.A.’s original idea was to develop a mathematical basis for relativistic expansions of scattering amplitudes, i.e. relativistic energy- dependent phase shift analysis. The two-variable expansions he developed were later generalized by Ya.A’s colleague and close friend Pavel Winternitz to the case of reactions with four particles having arbitrary spins. These methods were applied to analyze distributions on the Dalitz plots and nucleon-nucleon scattering data. The mathematical apparatus incorporated in this study proved to be useful in a number of other related areas. After this digression into relativistic kinematics, Ya.A. returned to the Lie groups. He determined the basis functions for representations of O(p, q), SU(p, q), and similar groups. The classification of subgroups of the Lie groups and separation of variables in the Hamilton-Jacobi and Laplace-Beltrami equations followed as a natural logical step. The “method of trees” invented by Vilenkin and developed by Ya.A. is now widely used in various applications ranging from nuclear physics to quantum groups. Finite-dimensional integrable and “superintegrable” systems became Ya.A.’s next major research program. At that time only two April 5, 2013 14:42 WSPC/Trim Size: 9in x 6in for Proceedings 5b˙Smorodinsky˙Naya

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“superintegrable” systems were known: the hydrogen atom with its O(4) symmetry and the harmonic oscillator with its SU(3) symmetry. Ya.A., with co-authors, found many more such systems. By today the theory of integrable systems has been fully developed and plays a significant role in physics. For many years Ya.A. was interested in analyzing the quantum- mechanical three-body problem by using the hyperspherical method. Needless to say, this problem was studied many times in celestial mechanics, but only those systems which had the Newtonian interaction potential were investigated in detail. As far as quantum mechanics was concerned, a general case of the three-body problem had never been considered before the 1960s. A number of works written by Ya.A. (with J. Nyiri, V. Pustovalov, and V. Efros, et al.) were devoted to the development of the general theory of harmonic functions for a three-body system and the construction of a complete set of hyperspherical functions as a basis. This part of Ya.A.’s activity is described by Julia Nyiri, a coauthor and close friend, in her memoir paper in the present book. In the 1980s Ya.A. switched to a new direction in weak interaction physics: neutrinos in media. Before that he had published several articles with Ya.B. Zeldovich and B. Pontecorvo on neutrinos. Later, in the 1980s, seven papers with V.N. Oraevsky and V.B. Semikoz appeared. The 1957 discussion with Ya.B. Zeldovich of the neutrino anapole moment in vacuum inspired Ya.A. to work out the complete electromagnetic structure of neutrino in medium. He found that the emergence of a geometrical phase in neutrino interaction with a magnetic field is similar to the Aharonov–Bohm effect. This observation gave rise to a number of follow-up papers. His deep understanding of various parts of theoretical physics – from unexpected quantum mechanics analogies to the cutting-edge mathematical concepts – was instrumental. His colleagues remember how helpful Ya.A.’s ideas were, especially at the initial stage when his control of symmetry breaking patterns, through the limiting case of the known electromagnetic structure in the vacuum, allowed them to successfully deal with unavoidable questions arising, as usual, in the beginning of each research project. April 5, 2013 14:42 WSPC/Trim Size: 9in x 6in for Proceedings 5b˙Smorodinsky˙Naya

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In the early 1990s Ya.A. started to work on quantum groups. This term – quantum groups – was born in 1986 in connection with the inverse quantum problem. He hoped to report on his results in the then near future, but unfortunately his expectations did not come true. He passed away on October 16, 1992 in Dubna while discussing the quantum group technique with V.G. Kadyshevsky, then the director of the Joint Institute of Nuclear Research. Ya.A. was a great bibliophile. He not only loved and collected rare books, but invested a lot of effort in translating and publishing books of the best foreign scientists. Four volumes of Albert Einstein’s collected papers, Collected Scientific Papers of Wolfgang Pauli, and Collected Papers of Werner Heisenberg are among the most significant books from Smorodinsky’s list. He initiated the Russian Journal Physics of Atomic Nuclei and was its Deputy Editor-in-Chief. A big collection of Martin Gardner’s books in Russian were translated and published owing to Ya.A. Every physicist is familiar with his pref- aces and introductions to more than 30 books translated in Russian. His comments on Lewis Carrol’s “Alice’s Adventures in Wonderland” and “Through the Looking Glass” are in fact literary essays about life, nature, and science. Ya.A. was an extraordinary human being. He was broadly educated in various sciences and had the reputation of a genuine connoisseur of the arts, architecture, and history. Deep knowledge and broad erudition permeated his immediate reactions to what he saw around him. Among many of Smorodinsky’s stories one deserves special mention. In 1986 he found out that no expert could determine when the Russian painter Filonovd had created his famous painting “Shostakovich’s Symphony.” One of the inscriptions on the canvas said “19 January... eclipse 15-39 18 total eclipse.” Smorodinsky looked up the dates and times of the eclipses which could be observed in Russia during Filonov’s life; the lunar eclipse of 1935 attracted his attention because it fit the date and time written on the

dPavel Nikolayevich Filonov (1883-1941) was a Russian avant-garde painter, art theorist, and poet. He died of starvation during the Nazi Siege of Leningrad. April 5, 2013 14:42 WSPC/Trim Size: 9in x 6in for Proceedings 5b˙Smorodinsky˙Naya

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canvas. Thus, he managed to establish the exact date. Since then the painting is attributed to 1935, but there is no reference to the discoverer of this date. Now I want to add a few words about the human side of my father. He was always our family’s heart; he never missed a chance to participate in all family activities. When my mother (very briefly) took Chinese language lessons, my dad often sat beside her to see what she was doing. Very soon I noted a funny picture: he was left alone at the desk trying to learn by heart Chinese hieroglyphs, whereas my mom was already deeply involved in chatting on the phone with her friends. As a child I constantly felt his very special care for everything I was doing. It could be collecting butterflies, assembling planes from wooden sticks and paper, playing cards, cooking, etc... – everything. Father introduced a spirit of professionalism to any part of our life. When he saw that I or, later, my daughter started doing something – be it a school home assignment, sport exercises, or just a game – my father would immediately bring a pile of books which we had to read before the beginning. Then he would join us at all stages. It is not that we read all of these books, nor that we mastered all he tried to teach us (mostly to no avail), but we inherited his general attitude: every job must be done properly, making use of all possible sources of knowledge and skills, and in as perfect of a way as possible. I am not sure we always follow this guideline, but we never forget about it. My father’s life, devoted to physics, profoundly affected various fields of this beautiful science. His most lasting and important legacy is the community of scientists, his former students, who now populate the best research centers worldwide. It is up to them to recall and pass along to new generations some of Smorodinsky’s enthusiasm, devotion, and passion for both science and life. April 5, 2013 14:43 WSPC/Trim Size: 9in x 6in for Proceedings 5c˙Smor-Komarov

YAKOV ABRAMOVICH SMORODINSKY AT LENINGRAD STATE UNIVERSITY∗

I. V. KOMAROV Physics Department, St.-Petersburg State University Ulianovskaya 2, St. Petersburg 198904, Russia

Ya. A. Smorodinsky studied at the Leningrad State University from 1934 to 1939. When he entered the Department of Physics at the Leningrad University, this was the only department of physics in the Soviet Union, and continued as such for some time. Smorodinsky’s first scientific adviser was Matvei Petrovich Bron- shtein.a In 1935 M. P. Bronshtein published a paper titled “On the scattering of neutrons by protons” in the journal Doklady Academii Nauk [1]. It was a variation on the theme of the classical paper by H. Bethe and R. Peierls. M. P. Bronshtein contributed to many fields of theoretical physics. In 1935 he defended his doctoral thesis on the quantization of the gravitational field. Under the guidance of M. P. Bronshtein Ya. A. Smorodinsky began working on problems of low-energy nuclear physics. In October of 1936 arrests began in the Department of Physics,

∗Published in Physics of Atomic Nuclei 72, 889 (2009). aMatvei Petrovich Bronshtein (1906-1938) was a brilliant young Soviet theoretical physicist, a rising star, known for classical works in the field of relativistic quantum theory, astrophysics, cosmology, and gravitation, see e.g. G. Gorelik and V. Frenkel, Matvei Petrovich Bronshtein,(Birkhäuser Verlag, 1994). Arrested in August 1937 by NKVD, he was included in a special list: “Leningrad – 1st category” (death by firing squad) of February 3, 1938, signed by Stalin. On February 18, 1938 he was formally sentenced to death by the Military Collegium of the Supreme Court of the USSR, and executed on the same day. The Military Collegium of the Supreme Court was the highest judicial body in the Soviet Union; during two years (1937 and ’38) it sentenced to death 30 thousand people. In fact, all sentences were predetermined in accordance with the lists drawn up by the NKVD and signed by the top leadership of the USSR.

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and they continued for two years. The Department was deprived of its Dean and seven of the 11 sectors within the Department lost their Heads. In the spring of 1937 no lectures were given, because many of the lecturers were arrested and new ones were not ready to lecture. During that time Ya. A. Smorodinsky was a third- and fourth-year undergraduate student. M. P. Bronshtein was arrested in August of 1937. Even his wife, Lidia Korneevna Chukovskaya, did not know what he was accused of. In December 1938 V. A. Fockb wrote a letter defending M. P. Bronshtein. However, he did not know that Bronshtein had already been executed in February 1938. The heads of all three theoretical divisions were arrested. Only one of them, V. A. Fock, was released after P. L. Kapitsa’s intervention. There was an attempt to establish one Department out of the remaining two and M. P. Bronshtein was supposed to be its Head. However, after his arrest this position was ﬁlled by L. E. Gurevich. Soon after that all three theoretical divisions were merged into the “Joint Department of Theoretical Physics.” The word “joint” was then lost and up until 1962 our University had only one Department of Theoretical Physics. Ya. A. Smorodinsky completed his Diploma thesis under the supervision of L. E. Gurevich. The report of the Department reads: “On April 1, 1939 a ﬁfth-year student Y. A. Smorodinsky gave a lecture on the Modern Status of the Theory of Nuclear Systems (adviser L. E. Gurevich).” Thus, Ya. A. Smorodinsky at that time was not only a student but also an unintentional participant in the tragedy he witnessed in the Department of Physics of the Leningrad State University. Needless to say, this was only a small episode in the tragic fate of our country. After that Ya. A. Smorodinsky started his graduate studies under the supervision of L. D. Landau. Landau had been released from prison in the summer of 1939. Ya. A. Smorodinsky continued working on the problem formulated by M. P. Bronshtein. In 1944 Landau and Smorodinsky published their famous paper on proton-proton

bVladimir Aleksandrovich Fock (1898-1974) was an outstanding Soviet physicist who did foundational work on quantum mechanics and quantum electrodynamics. April 5, 2013 14:43 WSPC/Trim Size: 9in x 6in for Proceedings 5c˙Smor-Komarov

Smorodinsky and Leningrad University 173

scattering [2]. On a personal note, I should mention that J. Ny´ıri and Ya. A. Smorodinsky in their paper on the eigenfunctions in the three-body problem [3] stressed that the quantum analog of the Kowalevski’s topc was unknown. In many respects my own scien- tiﬁc interests were deﬁned by this observation.

References 1. M. P. Bronshtein, Doklady Academii Nauk 8, 75 (1935). 2. L. D. Landau and Ya. A. Smorodinsky, ZhETF 14, 269 (1944). 3. J. Nyiri and Ya. A. Smorodinsky, Sov. J. Nucl. Phys. 12, 109 (1971).

cSofia Vasilyevna Kovalevskaya (1850-1891) was an outstanding Russian female mathematician, responsible for important original contributions to analysis, differential equations and mechanics, and the first woman appointed to a full professorship in Northern Europe. She herself used the pen name Sophie Kowalevski for her academic publications. May 10, 2013 11:54 WSPC/Trim Size: 9in x 6in for Proceedings 5d˙Smorod˙Ryndin

ABOUT HYDROTECHNICAL LABORATORY, PROFESSOR SMORODINSKY, AND NUCLEON–NUCLEON SCATTERING∗

R. M. RYNDIN Petersburg Nuclear Physics Institute Gatchina 188000, St. Petersburg, Russia

... for you, Michelangelo, Barma, Dante burnt alive by the lightning of your own incandescent talent. Andrei Voznesensky, “Masters”a

Yakov Abramovich Smorodinsky... memory brings me back to those far-off days when we first met in March 1952. We saw each other for the first time at the Hydrotechnical Laboratory (GTL) of the Academy of Sciences of the USSR,b where I obtained a position after graduation from The Physics Department of Leningrad State University. Already a well known professor, Yakov Abramovich (Ya.A.) was only eleven years older than me, a beginning physicist. Today, I would say that we were almost of the same age. We immediately liked each other, and worked closely together for 18 years until I moved back to St. Petersburg, at that time Leningrad, of course. I

∗Published in Ya.A. Smorodinsky, Selected Papers, Eds. Yu.A. Danilov, V.G. Kadyshev- sky, and A.N. Sisakyan (URSS Publishers, Moscow, 2001), p. 71. Abbreviated version. aTranslated by Max Hayward. bGTL is the Russian acronym for Hydrotechnical Laboratory. For secrecy reasons it had another name – POB 1326, where POB stands for “Post office box.” That’s how numerous institutions conducting classified research for the military were referred to in the USSR. Later GTL became JINR (Joint Institute for Nuclear Research), in Dubna, officially an independent nuclear research center run jointly by several Soviet block countries. In fact, JINR was run by The Ministry of Medium Machine Building.

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Professor Smorodinsky ... 175

learned a lot from Ya.A. during those years: his intrinsic desire and ability to share his knowledge was a peculiarity of his talent. GTL was a first-class equipped laboratory with excellent staff. Its experimental base was formed by the synchrotrone which accelerated protons up to the then maximal energy reached at the world accelerators. Located in the vicinity of a silent, tiny town which arose at the place of the former village Novo-Ivankovo, the laboratory became the best place for work, a sort of island of the scientific community. How- ever, it should not be forgotten that in the close vicinity there was located another island belonging to a different archipelago named GULAG. There, convoyed columns of prisoners walked the streets to do construction work, and the prisoners’ cemetery became the first cemetery of the town. It was located on a meadow overgrown with grass on the bank of the river Dubna. Walking around one day, we suddenly came across it. I have no idea if it is still there. The Novo- Ivankovo symbiosis of a research institution and a prisoner camp was notatallauniquecaseatthattime. I.Ya. Pomeranchuk volunteered as the Head of the Theory De- partment. Every Saturday, he came to Dubna together with Ya.A. Smorodinsky, B.T. Geilikman, and A.B. Migdal to participate in the seminar and discussions. Sometimes they were joined by L.D. Landau. The importance of these discussions and conversations for young theorists and experimentalists can hardly be exaggerated. These meetings continued for a pretty long time, but all good things end sometime. So our idyll ended too. One day Pomeranchuk stopped his visits to Dubna. We asked puzzled questions, but Boris Toevich Geilikman, who accepted the appointment as the Acting Head of the Theory Department, provided rather evasive answers, saying that a new nomination for the theorists’ Head was being discussed. In the subsequent discussions of the forthcoming changes, the name of Ya.P. Terletsky appeared all of a sudden. Soon he showed up as a new boss. A person less appropriate to be an expert in high energy or elementary particle physics could be hardly found. I know nothing exactly and can only guess as to how and in what circles this name surfaced. The only thing I can say is that the new appointment obviously caused a great loss to the labora- April 5, 2013 14:44 WSPC/Trim Size: 9in x 6in for Proceedings 5d˙Smorod˙Ryndin

176 R. M. Ryndin

tory. The reality was that Pomeranchuk was just squeezed out. The theoretical “quartet” – Pomeranchuk, Smorodinsky, Geilikman, and Migdal – ceased to exist, and only Ya.A. continued his weekly visits. Under such circumstances his role and responsibility significantly increased. It was he who became a real, rather than formal, successor of Pomeranchuk, and it was not an odd decision. His amazing physical intuition, ability to perceive, with sort of probably a sixth sense, new and still obscure phenomena, and his experience in the phenomenological analysis of collision processes were indispensable when planning accelerator experiments or analyzing experimental results. Ya.A. made a significant contribution to the future triumph of the laboratory. He was the center of the group, which included L.I. Lapidus, S.M. Bilenky, and myself. Very soon it was called Smorodin- sky’s group. To be fair, it should be mentioned that Terletsky barely tried to influence our activities. At that time, the study of strong interactions between nucleons was one of the most important tasks of nuclear and high energy physics. The main source of gaining information on such interactions was experimental investigation of the simplest nuclear reactions with protons: first of all, nucleon-nucleon scattering data. Since the consistent theory of strong interactions had not been developed by that time, the phenomenological analysis of collision processes played a dominant role. Nucleon-nucleon scattering turned out to be Ya.A.’s first love in physics. It was true love rather than a fleeting feeling. Actually, this love started during the war time and had been flourishing for at least fifteen years. It first manifested in Ya.A’s remarkable article in which he described nucleon-nucleon low-energy scattering by introducing a new concept of the effective radius of strong interactions which modified the Bethe-Peierls zero-range approximation. This work was inspired by an elegant paper by Ya.A. and L.D. Landau on phenomenological account of nuclear forces in the proton-proton scattering with a certain constant (parametrizing boundary conditions) in the form of a linear function of energy. This approach allowed them to describe strong interactions in terms of two constants: the scattering length and the effective radius. April 5, 2013 14:44 WSPC/Trim Size: 9in x 6in for Proceedings 5d˙Smorod˙Ryndin

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Yakov Abramovich was a nontrivial person with broad interests. Among physicists he was an outstanding theoretcian; among biblio- philes he was not simply a bibliophile, but rather a connoisseur who read books and shared them with others; among teachers he was a born enlightener. Suﬃce it to remember The Complete Papers of Albert Einstein, The Collected Papers of Wolfgang Pauli, The Feyn- manLecturesonPhysics, etc. He had something borrowed from Renaissance people. His fantastic, indefatigable energy was incredible. When coming to Leningrad in the 1970s-1980s, he would always rush somewhere. It could be participating in a seminar or meeting interesting people or seeing something curious. Once, he went to see the collection of rare manuscripts in the Library of the Academy of Sciences, and another time he could go to see an art exhibition at the Hermitage or Russian Museums, or he could just have fun playing with puzzles and engaging others into his play. Books, speciﬁcally art books, were his profound and eternal love. He not only knew and loved art, but enjoyed generously sharing this love with everyone who wanted to listen, look, and understand. He had a similar deep knowledge of poetry and helped those who were ignorant or not well-enough educated in poetry to get access to a huge part of it which had not been published in the USSR in the 1950s-1960s (for instance, Marina Tsvetayeva, Osip Mandelstam, Nikolai Gumilev, Rudyard Kipling, John Dos Passos, etc.). Ya.A. lived, and taught others how to live, a full life. He was full of a curious interest in life, in all its manifestations.

This dewdrop world – It may be a dewdrop, And yet - and yet ... Kobayashi Issa April 5, 2013 14:44 WSPC/Trim Size: 9in x 6in for Proceedings 5e˙Smor-Calogero

REMEMBERING YAKOV ABRAMOVICH SMORODINSKY∗

F. CALOGERO Dipartimento di Fisica, Universit`a di Roma “La Sapienza,” Italy Istituto Nazionale di Fisica Nucleare, Sezione di Roma [email protected], [email protected]

This is a very brief contribution reflecting my intervention at the Conference on Symmetries in Physics dedicated to Yakov Abramovich Smorodinsky, held on March 27-29, 2008. I met Yakov Abramovich probably more than thirty years ago in Dubna, where I used to come in the context of my collaboration with Yuri Simonov and his wife Alla Badalyan on the approach to nuclear physics based on the expansion of the many-nucleon wave function in hyperspherical harmonics. At that time contact among scientists living in the Soviet Union and those of us living in the “capitalist world” were still quite complicated: my visits to the Soviet Union were certainly carefully monitored by the KGB, and I had to respect many rules, though most of them pertained to my Russian colleagues, whose behavior these rules meant to constrain. As a consequence, social contact with my fellow physicists was, as a rule, difficult, although this did not prevent me – and my family, when we spent the academic year 1969-1970 in Moscow – to develop a strong and lasting bond of friendship with a few colleagues who were prepared to take some risks and ignore the rules which were indeed primarily meant to prevent just such friendships to flourish. Having become at least partly aware and accustomed to this situation, I was rather surprised and greatly heartened by the friendly and open disposition of Yakov Abramovich when I met him for the first time in Dubna: he immediately invited me to his home for dinner, where I

∗Published in Physics of Atomic Nuclei 72, 886 (2009).

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Remembering Yakov Abramovich Smorodinsky 179

met his family and enjoyed a warm and most cordial hospitality. His conversation was moreover quite fascinating, due to the very broad range of his interests, in science and, even more so, in just about every field of intellectual endeavor. The freedom from any ideological conformity which he displayed in these interactions was remarkable and unusual. I seem to remember that he was particularly interested in literature, especially the contemporary literature in the rest of the world which was difficult to access in the Soviet Union, where foreign writers were usually translated into Russian or (occasionally) published in their original language only if they passed some test of ideological acceptability to the Soviet regime. Indeed I remember that Yakov Abramovich did not hesitate to offer me a kind of bargain: I was to provide him with literary works (mainly new novels in English), and he would in exchange give me art books published in Russia which were relatively inexpensive, albeit to have access to them generally required having good relations with the official artistic and publishing establish- ments, connections which Yakov Abramovich evidently did master. As it happens, circumstances – including probably my laziness – did not allow our bargain to flourish, and I became particularly sorry for this when I received the sad news of his untimely death. I am happy to take part in this collection, paying thereby my tribute to the memory of an individual remarkable both for his scientific achievements and for his congenial personality. As for the scientific substance of my contribution to this conference, I reported recent findings obtained in collaboration with Fran¸cois Leyvraz. Since these results are already published – see [1] as well as Section 5.5 of the monograph [2] – I limit my report of them here to an extremely terse description of their essence. Taking as starting point the Hamiltonian describing the most general many-body problem respecting overall translation-invariance, we have shown how it is possible to manufacture a modified (albeit not too different) Hamiltonian depending on a positive parameter T (which can be chosen arbitrarily, and is, dimensionally, a time). This modified Hamiltonian features – in the classical context – the following two properties: April 5, 2013 14:44 WSPC/Trim Size: 9in x 6in for Proceedings 5e˙Smor-Calogero

180 F. Calogero

(i) Starting from generic initial data, the dynamics yielded by the modiﬁed Hamiltonian – up to a rescaling of the independent variable (“time”) by a constant real factor (which might however have either sign) – is essentially identical to that yielded by the original (un- modiﬁed, “realistic”) Hamiltonian, over times which are short with respect to T, t T,

(but let us emphasize that T can be assigned arbitrarily). (ii) The time-evolution yielded by the modified Hamiltonian is isochronous with period T, namely, from any initial data it yields closed trajectories in phase space which are periodic in all degrees of freedom with period T. The simultaneous validity of these two properties has obviously remarkable implications, especially regarding the statistical mechanics and thermodynamics associated with these Hamiltonians. In the quantal context, the modified Hamiltonian features an (infinitely degenerate) equispaced spectrum, consistent with its property of isochrony.

References 1. F. Calogero and F. Leyvraz, New J. Phys. 10, 023042 (2008). 2. F. Calogero, Isochronous Systems, (Oxford University Press, Oxford, 2008). April 5, 2013 14:45 WSPC/Trim Size: 9in x 6in for Proceedings 5f˙Smor-Frenkel

REMEMBERING YAKOV ABRAMOVICH∗

A. FRENKEL Research Institute for Particle and Nuclear Physics Wigner Research Center for Physics, Budapest, Hungary [email protected]

Shortly after its foundation in 1956 the Joint Institute for Nu- clear Research in Dubna became an important training place for young physicists from Eastern-European countries. In those years I, too, was much younger than now, and from the late 1950s until the mid-1980s visited the Laboratory of Theoretical Physics many times for a few weeks. Discussions with Yakov Abramovich about particle physics and field theory were always interesting and instructive. When flavor SU(3) symmetry was discovered, his Dubna reprint review on the subject for me – and I think not only for me – proved to be a very helpful handbook during many subsequent years. Let me also tell you about an episode which I remember with gratitude. In the late 1970s I released a preprint on the reformulation of the theory of the relativistic Dirac magnetic monopole. I mentioned this to Yakov Abramovich. He asked a few questions and then said he would like to have a copy. I did not expect he would read it, because this was a long paper and I knew that he was not working on the subject. But he did read it, made helpful critical comments, and encouraged me to publish the paper. Among the many young physicists from Eastern Europe who spent a few years in the Laboratory of Theoretical Physics there were at least five from Hungary, and they all benefited from their contacts with Yakov Abramovich. The first two were Gabor Domokos and Peter Suranyi. They spent four years in Dubna in the early 1960s.

∗Published in Physics of Atomic Nuclei 72, 888 (2009).

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182 A. Frenkel

They now live in the United States, and I know from them that they learned a lot from Yakov Abramovich on various subjects, the most important being the systematization of the Regge poles based on the representations of the Lorentz group. The first Hungarian physicist who not only had discussions with Yakov Abramovich but also worked with him was Julia Nyiri. They published 8 papers together over a period of more than ten years, the last one in 1979. In the late 1960s and early 70s Miklos Huszar and Kalman Toth spent three years in the Laboratory of Theoretical Physics. Huszar has two group-theoretical papers published together with Yakov Abramovich, and Toth told me that discussions with Yakov Abramovich on the transformation functions between the bases of scattering amplitudes in the s, u,andt channels led to one of his best papers. Yakov Abramovich was not only an outstanding physicist, but was also a man of exceptionally wide culture. His Moscow apartment, where he used to invite many of us in spite of the fact that this was not allowed in those years, was full with books of high literature in various languages and with splendid art books containing magnificent reproductions. We had no idea how he obtained them, since he was not allowed to travel to the West. When in the late 1980s he visited our institute in Budapest, in response to the question of what he would like to see, he answered that he would like to go to the Christian Museum of Fine Arts in Esztergom. I think there are not many people abroad who know that there is a town in Hungary called Esztergom harboring a first-rate museum of fine arts, but Yakov Abramovich knew. We all felt deep sorrow when we learned in 1992 that Yakov Abramovich had passed away, and I feel honored that I can remember him. He was one of the leading scientists of his time and helped many generations of young colleagues find their way. April 5, 2013 14:46 WSPC/Trim Size: 9in x 6in for Proceedings 5g˙Smor-Winternitz

YAKOV ABRAMOVICH SMORODINSKY AND HIS INFLUENCE ON MY LIFE

P. WINTERNITZ Centre de Recherches Mathématiques and Département de Mathématique et de Statistique UniversitédeMontréal, Canada [email protected]

Next to my parents, Yakov Abramovich was the person who had the greatest influence on my life. I would like to use this opportunity to say a few words about this influence, and mainly about him and his work. The influence started before I met him personally. I was working on my MSc diploma under the supervision of Professor G.F. Drukaryev at the Leningrad State University. Among the first scientific documents I was given to read were the book “Lectures on Nuclear Theory” by Landau and Smorodinsky [1] and an article by Puzikov, Ryndin, and Smorodinsky [2] in which they introduced the concept of a “complete experiment” in the scattering of particles with spin. A complete experiment is really a set of experiments from which it is possible to reconstruct the scattering matrix (up to an overall ambiguity in the phase). This article became very influential, determining the direction of experiments on nucleon–nucleon scattering for many years. My reading of this book and the article affected not only my MSc thesis but also quite a bit of my later work on polarization phenomenology. In a certain sense this 1957 article was written before its times. Indeed, a complete nucleon–nucleon experiment at a given energy and scattering angle requires the measurement of at least 9 independent quantities. Experimentally that requires the use of a polarized beam and polarized target, unavailable at the time. The first proton–proton complete experiment was

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performed at the University of Chicago in 1968, while those subsequent experiments at the PSI Institute in Zurich (1981 and 1989), at LAMPF in Los Alamos (1985 and 1990), at Saturne II in Saclay (1990 and 1998), and at Argonne (1986). The first complete neutron- proton experiment was realized at Saclay in 1986. My direct and personal interaction with Ya.A. Smorodinsky started in 1963 when I came from Czechoslovakia to join his research team in Dubna and did my PhD work under his guidance. It lasted till 1968 when I returned to Prague and subsequently emigrated (ultimately to Canada). By the time I arrived in Dubna, Ya.A. had embraced the topic of symmetries in physics. He had just finished a very influential paper [3] in collaboration with the well known mathematician N.Ya. Vilenkin on the representation theory of the Lorentz group and its applications in relativistic particle scattering theory. This article gave rise to several research programs that many theoretical and mathematical physicists all over the world (including myself) worked on and some are still working on. The general theme is the study of the representation theory of compact and specially noncompact Lie groups in specific bases. Different bases for representations of the same group, e.g., the homogeneous Lorentz group O(3, 1), are usually related to different chains of subgroups, both continuous and discrete ones. Very different special functions appear as basis functions in different bases. Different subgroup chains have different physical applications. For instance, the O(3, 1) ⊃ O(3), O(3, 1) ⊃ O(2, 1), and O(3, 1) ⊃ E(2) two-variable expansions incorporated partial-wave analysis, Regge-pole expansions and eikonal expansions, respectively [4]. Two- variable expansions were later generalized to the case of reactions involving four particles with arbitrary spins and applied to analyze distributions on Dalitz plots and nucleon–nucleon scattering data. The group-theoretical and special-function-theory aspects of this research program induced several lines of further mathematical research. One was a series of papers on basis functions for representations of O(p, q), SU(p, q), and other groups. Others are ongoing series of articles on classifying subgroups of Lie groups [5] and on the separation of variables in Hamilton-Jacobi and Laplace-Beltrami equations [6]. The April 5, 2013 14:46 WSPC/Trim Size: 9in x 6in for Proceedings 5g˙Smor-Winternitz

Smorodinsky and His Inﬂuence on My Life 185

“method of trees” proposed by Vilenkin and further developed by Ya.A. Smorodinsky and collaborators [7] is now being applied in areas varying from nuclear physics to quantum groups. It provides a graphical interpretation of different types of coordinates and of their relation to subgroups of isometry groups, or conformal groups of various homogeneous spaces. A very natural question to ask is whether the basis functions arising in the representation theory of various Lie groups are related among each other. The answer is given by the theory of Lie group and Lie-algebra contractions. Indeed, the use of “analytic contractions” has made it possible, for instance, to connect special functions related to “trees” on O(n) spheres and on O(n − 1, 1) hyperboloids and to obtain new asymptotic formulas for these special functions [8]. A related but different research direction started in Dubna in the 1960 was what we then called dynamical symmetries in quantum mechanics [9, 10]. It now goes under the name of superintegrability in classical and quantum mechanics [11]. The problem originally posed was to find all potentials in two and three dimensions that can be inserted into the Schrödinger or Hamilton-Jacobi equation and that would allow a “dynamical” symmetry group. A useful way of distinguishing between kinematical and dynamical symmetries for the Schrödinger equation was proposed. Namely, kinematical symmetries correspond to the Lie point symmetries and are generated by sets of first-order differential operators, commuting with the Hamiltonian. Dynamical symmetries, on the other hand, are generated by sets of higher order operators, commuting with the Hamiltonian. They correspond to generalized symmetries, or Lie–Backhand symmetries, in the theory of differential equations. Second-order operators in quantum mechanics, or integrals of motion in classical mechanics that are quadratic in the momenta, turned out to be specially interesting. Indeed, Hamilto- nians in n dimensions, allowing n commuting quadratic integrals of motion, will also allow the separation of variables in the Schrödinger and Hamilton-Jacobi equations. Such a Hamiltonian system will be integrable, both in the classical and quantum-mechanical senses. A further question that was posed was that of finding “superintegrable” April 5, 2013 14:46 WSPC/Trim Size: 9in x 6in for Proceedings 5g˙Smor-Winternitz

186 P. Winternitz

systems with more than n integrals of motion. In classical mechanics, a system can have up to 2n−1 functionally independent integrals of motion. In quantum mechanics the same is true, but the integrals are operators, and their independence must be more carefully defined. When articles [9, 10] were written, only two superintegrable systems were known: the hydrogen atom (or the Kepler system) with its O(4) symmetry, discovered by V. Fock, and the harmonic oscillator with its SU(3) symmetry. This very brief list was significantly extended in [9, 10], where a complete classification of superintegrable systems with integrals of motion that are second order operators in the momenta was given for two- and three- dimensional Euclidean spaces. Superintegrable systems are still exceptional among classical and quantum mechanical systems; however, in 2009 it was shown that infinite families of superintegrable systems exist with integrals of motion that are polynomials of arbitrary order in the momenta [12]. The study of superintegrable systems is currently a very active field of research. Indeed, the articles [9, 10] have received 246 and 227 citations, respectively, among them about 60 each since 2009. The prestigious Journal of Physics A: Math- ematical and Theoretical (IOPscience Publishers) awarded its Best Paper Prize to articles on superintegrability in 2011 and 2012 conse- qutively [12, 13]. Superintegrability could also be called “non-Abelian integrabil- ity.” The integrals of motion all commute with the Hamiltonian, but amongst each they form a non-Abelian algebra. This may be a finite or infinite-dimensional Lie algebra, or a polynomial algebra. In this sense all soliton systems described by integrable nonlinear partial differential equations are actually infinite-dimensional superintegrable systems, rather than just integrable ones. They all have infinite non- Abelian algebras of integrals of motion with (infinite-dimensional) Abelian subalgebras. This article does not attempt to be a complete review of the scientific activities of Yakov Abramovich Smorodinsky. As the title states, these are the reflections of one of his students on the influence that Yakov Abramovich had as a scientist and a teacher. For a more balanced and objective view I refer to the Selected Papers of April 5, 2013 14:46 WSPC/Trim Size: 9in x 6in for Proceedings 5g˙Smor-Winternitz

Smorodinsky and His Inﬂuence on My Life 187

Ya.A. Smorodinsky cited in [5], in particular, the introduction to each section of this book. The influence of Yakov Abramovich on my life did not end when I left Dubna in 1968. Indeed, my emigration was facilitated by my association with him. Papers we had written together were known in the community and served as an excellent introduction for me. We interacted again personally during the last years of his life in 1990–1992 when he was finally able to travel, and visited me in Montréal. At that time, he was very interested in the new topic of quantum groups. We discussed a possible collaboration but unfortunately Yakov Abramovich passed away before this reached fruition. There are many things that I learned from Yakov Abramovich in addition to theoretical and mathematical physics. I came to appreciate (and share) his opinion that mathematical physics must involve the use of “real” mathematics at the cutting edge of the discipline. On the other hand, he loved and practiced “real” phenomenology: the art of extracting the maximal possible information from well- performed and well-planned experiments. One conversation with Ya.A. that made a lasting impression on me was about the difference between the work of an accountant and that of a scientist. The work of an accountant is very useful at the moment it is done and only then. The work of a scientist is supposed to have a lasting value. The implication was that one should not try to “chase the mainstream” but should develop his or her own scientific direction. If you are lucky, the mainstream will come to you. In the case of Yakov Abramovich Smorodinsky it can certainly be said that his contribution to physics has stood the test of time. Much of his work is more appreciated now than it was at the time of the first publication.

References 1. L.D. Landau and Ya.A. Smorodinsky, Lectures on Nuclear Theory, (GITTL, Moscow, 1955). 2. L.D. Puzikov, R.M. Ryndin, and Ya.A. Smorodinsky, Nucl. Phys. 3, 436 (1957). 3. N.Ya. Vilenkin and Ya.A. Smorodinsky, Sov. Phys. JETP 19, 1209 (1964). 4. P. Winternitz, Ya.A. Smorodinsky, and M.B. Sheftel, Sov. J. Nucl. Phys. 8, April 5, 2013 14:46 WSPC/Trim Size: 9in x 6in for Proceedings 5g˙Smor-Winternitz

188 P. Winternitz

485 (1969). 5. P. Winternitz, in Ya.A. Smorodinsky, Selected Papers, Eds. Yu.A. Danilov, V.G. Kadyshevsky, and A.N. Sisakyan (URSS Publishers, Moscow, 2001), p. 473. 6. W. Miller, Jr., Symmetry and Separation of Variables (Addison-Wesley, Reading, 1977). 7. N.Ya. Vilenkin, G.I. Kuznetsov, and Ya.A. Smorodinsky, Sov. J. Nucl. Phys. 2, 645 (1966). 8. A.A. Izmestyev, G.S. Pogosyan, A.N. Sissakian, and P. Winternitz, J. Math. Phys. 40, 1549 (1999). 9. I. Fris, V. Mandrosov, Ya.A. Smorodinsky, M. Uhlir, and P. Winternitz, Phys. Lett. 16, 351 (1965). 10. A.A. Makarov, Ya.A. Smorodinsky, Kh. Valiev, and P. Winternitz, Nuovo Cimento A 52, 1061 (1967). 11. P. Tempesta et al., Superintegrability in Classical and Quantum Systems (AMS, Providence, 2004). 12. F. Tremblay, A.V. Turbiner, and P. Winternitz, J. Phys. A. Math. Theor. 42, 242001 (2009). 13. E.G. Kalnins, W. Miller Jr., and S. Post, J. Phys. A. Math. Theor. 43, 035202 (2010). April 5, 2013 14:47 WSPC/Trim Size: 9in x 6in for Proceedings 5h˙Smorod-J-nyiri

YAKOV ABRAMOVICH AS I REMEMBER HIM∗

JULIA NY´IRI Research Institute for Particle and Nuclear Physics Wigner Research Center for Physics, Budapest, Hungary [email protected]

I first heard of Yakov Abramovich when (being a student of the Leningrad State University) I read his papers written with Pomer- anchuk and Landau [1]. Later, in my last year at the university, thinking about a possible future working place, I met G. Domokos who at that time was a researcher in Dubna. He gave me the advice to go to Dubna for a while and look for the possibility to work with Professor Smorodinsky who was the broadest-minded physicist he had ever met. As it happened, after four years of work at the Central Research Institute for Physics in Budapest, I went to Dubna. I did not really dare to think about a joint collaboration with Yakov Abramovich. From what I knew about his results, he seemed to be such a great man that I could not imagine myself in this role. On the other hand, since my diploma thesis was devoted to dispersion relations, it was natural to continue on this topic, so I spent my first year in Dubna working on current algebra. People meet each other unavoidably in the narrow corridors of the Laboratory of Theoretical Physics. Yakov Abramovich stopped me several times and we talked about different things. His knowledge and the fields of his interests were quite amazing – from Hungarian poetry to the latest achievements in physics. He closely followed new results, appreciated their significance, and immediately saw their relevance from the point of view of already known phenomena. His day

∗Published in Physics of Atomic Nuclei 72, 891 (2009).

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seemed to be much longer than 24 hours. He thought about various problems at the same time, such as nucleon–nucleon interactions, symmetries in physics, non-relativistic systems with dynamical symmetries, integral representations for relativistic amplitudes, unitary representation of the Lorentz group, Poincaré and Lorentz invariant expansions of relativistic amplitudes, the Regge trajectories. It was clear that, working on a problem, he knew that there was an answer and he could foresee what it was. I feel fortunate that he finally persuaded me to join him in the work on the three-body problem. During those years – from 1968 to 1970 – I learned not only what was possible about the subject, but I got acquainted with a whole new world of physics, where facts from the most different fields were all interconnected. In Budapest, I had already worked on group theory, but it became a new experience for me to apply it to the classical and the quantum mechanical three-body problems. As it turned out, the three-body problem in quantum mechanics in general, and in nuclear physics in particular, provided an extremely interesting field for investigations, and the developed techniques were useful for the solution of various, sometimes quite unexpected, problems (see, for example, [2]). I defended my PhD thesis on this subject in Dubna in 1970, but we continued to work together after my return to Budapest, and later, being again in Dubna, until 1979 [3]. In classical mechanics or, more precisely, in celestial mechanics, the three-body problem was the subject of several rather successful theories. But, naturally, only systems with Newtonian interactions were considered in detail. The case of other forces was practically not investigated. In quantum mechanics, the three-body problem was almost not taken into consideration at that time, or if, then only for practical purposes – calculations of energy levels in He3, neutron-deuteron scattering – without formulating the problem, in general. A consistent way to handle the problem was to construct a basis for non-interacting particles and then develop a perturbation theory in the framework of which the functions of the interacting particles could be expanded over this basis. April 5, 2013 14:47 WSPC/Trim Size: 9in x 6in for Proceedings 5h˙Smorod-J-nyiri

Yakov Abramovich as I Remember Him 191

From a group-theoretical point of view, the most interesting questions are related to the fifth quantum number Ω. This has to be introduced because the quantum numbers describing rotations and permutations are not sufficient to characterize the states in the three- body system. A complete set of basis functions for the quantum mechanical three-body problem was chosen in the form of hyperspherical functions, characterized by quantum numbers corresponding to the chain O(6) ⊃ SU(3) ⊃ O(3). Then equations were derived to obtain the basis functions in an explicit form. The problem of constructing a basis for a system of three free particles, realizing representations of the three-dimensional rotation group and of the permutation group, conceptually was quite simple. However, to solve the problem in practice turned out to be rather hard: it was very difficult to obtain a general solution for the calculated set of equations to determine the eigenfunctions. Fortunately, the eigenvalue equations could be simplified considerably, the solution was derived in a closed form, the coefficients were calculated in different ways, and numerical results were obtained. Since the quantum mechanical problem that we have considered had the same symmetry properties as the classical one, it was interesting to investigate the classical problem from the group-theoretical point of view. The equations of motion were obtained very easily for both the case of free particles and that of different potentials. The classification of a three-body system could be used for the analysis of three-particle decay processes too. For example, dealing with the Dalitz plot for decay processes, it turned out to be useful to expand the point density inside the physical region into a series of orthonormal functions. (Such an expansion is similar to the usual phase analysis for two-particle decays. It was helpful in analyzing experimental data, in calculating different correlation functions, etc.) The set of basis functions chosen as K-harmonics was especially suitable for the description of correlations between the particle momenta. Also, from a practical point of view, it was essential to develop a method to calculate matrix elements of two-particle interactions introducing different potentials and to obtain a proper approximation April 5, 2013 14:47 WSPC/Trim Size: 9in x 6in for Proceedings 5h˙Smorod-J-nyiri

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for bound states as well. It was not just the physics that was interesting and beautiful. I think the most important fact for me was that (especially in the first years in Dubna) with the help of Yakov Abramovich I got a feeling of a country and a culture I had not known. Smorodinsky’s place was always interesting, friendly and warm, the food was nice, and I had the opportunity to meet remarkable people – and not only physicists. And, of course, there was the fantastic library of Yakov Abramovich which gave me a lot of pleasure and knowledge. Our connection remained quite close for many years, when I already switched to the quark model and high energy physics. Yakov Abramovich visited us often in Moscow; to our delight, he dropped in every time when he had something to do in the vicinity of our apartment. We – he, my husband V.N. Gribov and myself – had long discussions on new achievements in physics and astronomy, on literature and arts, and on events in the world around us. My little son Pali had very nice company in his early childhood: Masha, Yakov Abramovich’s granddaughter, and Seryozha Filippov (the parents of both are my close friends till now). Pali enjoyed toys and puzzles invented by Yakov Abramovich – as he recollects in his article below.a He often had the feeling that they were of the same age. When my son began studying chemistry, he was amazed by the fact that Yakov Abramovich seemed to know everything about the latest research results in chemistry. It is, in a way, significant for me that the article of Yakov Abramovich which was the first I read [1] influenced the only paper on which I worked together with my husband [4]. I deeply regret that I could present this work [5] only after the death of Yakov Abramovich, at the conference which was devoted to his memory in 1993. This was so long ago; remarkably, the Smorodinsky conferences continue to take place on a regular basis. Yakov Abramovich remains with us, those who were fortunate to know him. His personality and his results will inspire generations of physicists to come.

aSee p. 194 of the present Collection. April 5, 2013 14:47 WSPC/Trim Size: 9in x 6in for Proceedings 5h˙Smorod-J-nyiri

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References 1. I.Ya. Pomeranchuk, Ya.A. Smorodinsky, J. Phys. USSR 9, 97 (1945); L.D. Landau, Ya.A. Smorodinsky, Zh. Eksp. Teor. Fiz. 14, 269 (1944). 2. J. Nyiri, Ya.A. Smorodinsky, Preprint JINR E4-4043 (1968); Sov. J. Nucl. Phys. 9, 515 (1969); Materials of Symposium on the Nuclear Three Body Prob- lem and Related Topics, (Budapest, 1971)); Preprint JINR E2-4809 (1969); Sov. J. Nucl. Phys. 12, 109 (1971); Materials of the Second Problem Sympo- sium on Nuclear Physics, (Novosibirsk, 1970); Materials of the XV Interna- tional Conference on High Energy Physics, (Kiev, 1970). 3. J. Nyiri, Preprint KFKI-72-3 (1972); J. Nyiri, Acta Phys. Hung. 32, 241 (1972); J. Nyiri, Acta Phys. Slovaca 23, 81 (1973); J. Nyiri, Ya.A. Smorodin- sky, Sov. J. Nucl. Phys. 29, 429 (1979). 4. V.N. Gribov, J. Nyiri, Perturbative QCD Workshop Meeting, Lund preprint LU-TP-91-15 (1991). Also in: V.N. Gribov, Gauge Theories and Quark Con- ﬁnement (Phasis, Moscow, 2001). 5. J. Nyiri, Proceedings of the International Workshop on Symmetry Methods in Physics, (Dubna, Russia, 1994) Vol. 2, 378. April 5, 2013 14:48 WSPC/Trim Size: 9in x 6in for Proceedings 5i˙Smor-Pale

ABOUT YAKOV ABRAMOVICH∗

PAL´ NY´IRI Department of Social Sciences Vrije Universiteit, Amsterdam, the Netherlands [email protected]

I knew Yakov Abramovich mostly as a child. That is to say, I was a child; Yakov Abramovich was over sixty. Years later, when I had to take charge of constructing my own intellectual environment, I realised what a luxury it had been to socialize with the adults who populated my childhood and for whom substantive conversations had been the norm, not an exception worthy of celebration. Among the many intellectual lighthouses who surrounded me, Yakov Abramovich was one of the brightest and most constant. Yakov Abramovich behaved the same way with children as he did with adults, to the point that I sometimes felt solidary with him. This was related to his unmatched curiosity and ability to pay attention to and be surprised by all sorts of things and phenomena around him. Once in Dubna, he and his wife Valentina Aleksandrovna visited us, and he gave me a tyre from a toy car that he had picked up in the street. That tyre hung on my keychain for many years. Another time he brought a plastic ﬂy for ﬁshing, which turned out to be perfect for annoying my mother when left on various windowpanes. I think he liked the wonderful pointlessness of these objects deprived of their contexts. Later, Yakov Abramovich started sharing puzzles, which he con- sumed in inordinate quantities. The puzzles could be problems (mathematical, linguistic or other), which I rarely had the patience

∗Published in Ya.A. Smorodinsky, Selected Papers, Eds. Yu.A. Danilov, V.G. Kady- shevsky, and A.N. Sisakyan (URSS Publishers, Moscow, 2001), p. 535.

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About Yakov Abramovich 195

or intelligence to solve, or objects that had to be transformed, un- hooked, joined, or combined, from Tangram to varieties of Rubik’s cube and all sorts of locks. Occasionally, my mother would bring him such things from Hungary. Later, in the West, when I came across shops full of these objects, it made me sad to think how much Yakov Abramovich would enjoy them. But he could also fabricate equally interesting gadgets himself, using whatever was at hand. Once, from a bottle of Hungarian brandy, a cork, four forks and the pin, he created something like a merry-go-round that would go on spinning very long because of its low friction and large weight. Another time, bored at a conference banquet in Odessa, he made a series of elephants from the wires holding the corks in champagne bottles. Later still, when I was studying chemistry at the university, Yakov Abramovich amazed me by bringing up some of the latest articles published in organic chemistry and biochemistry. I had never heard of most of them – although sometimes I would pretend I did, but I took the opportunity to talk to him about the chemistry of crown ethers, which I was then getting interested in and which he was quite familiar with. How he managed I did not understand, but I was even more surprised by the fact that he – though not allowed to travel to the West – was aware of so many art books that had just been published there. Amazingly retaining this perspective of a cosmopolitan polymath in Soviet conditions, Yakov Abramovich could be quite intolerant of what he perceived as displays of parochialism or orthodoxy, banal though they may have seemed in a political system that made such displays part of its oﬃcial ideology. Like his teacher Landau, he hated beards, and when I asked him why, he replied: because it’s idiotic savagery. Since Yakov Abramovich was not otherwise a stick- ler for grooming, I was surprised. Perhaps he saw beards as signs of religious or national conservatism that, though hardly present in the late Soviet Union, harked back to earlier times and preﬁgured times to come. April 5, 2013 13:32 WSPC/Trim Size: 9in x 6in for Proceedings 6a_Chap5-divider

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For a more technical review see pp. 488–523. April 5, 2013 15:2 WSPC/Trim Size: 9in x 6in for Proceedings 6c˙Karen-Intro

KAREN AVETOVICH TER-MARTIROSYAN∗

One can say that Karen Avetovich Ter-Martirosyan was one of the stars in the brilliant constellation of theoretical physicists dating back to the golden era of Soviet physics: a disciple of Yakov Frenkel and Lev Landau, he was one of the creators of the theory of (soft) strong interactions at high energies. Ter-Martirosyan was born on September 28, 1922, into an Arme- nian family in Tbilisi, Georgia (former Soviet Union). At that time Tbilisi was a truly cosmopolitan city, with a huge and influential Armenian community. In 1943, at the age of 21, Karen Avetovich Ter-Martirosyan graduated from the Tbilisi State University. After two years of teaching physics at the Tbilisi Railroad Institute, he enrolled as a graduate student at the Leningrad Physical Technical Institute (PTI, now the Ioffe Physical Technical Institute in St. Petersburg). He completed his Candidate (PhD) thesis under the supervision of Yakov Frenkel. In 1949 Ter-Martirosyan accepted a position in the Theory Division of PTI. Landau had left PTI and moved to Kharkov and then Moscow in the 1930s; however, once in a while he would come PTI, as a visitor. That’s where Ter-Martirosyan and Landau first met. Their active working relationship continued in Moscow, where Karen moved in 1955 to join the Theory Division of Institute of Theoretical and Ex- perimental Physics (ITEP) led by Isaak Pomeranchuk. Two years later Karen received the Doctor of Science (Professor’s) degree in theoretical physics. One of Karen’s colleague’s recollects:

∗This compilation is based on the following materials: Yuri Abov et al., Sov. Phys. Usp. 45, 999–1000 (2002), and Yuri Abov et al., Phys. Usp. 49, 881–882 (2006), and http://www.famhist.ru/famhist/landau/0005ba79.htm.

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“Karen Avetovich Ter-Martirosyan appeared in the field of view of Landau as a meteor. Later Lev Davidovich [Landau] regarded him as one of the most talented of his disciples. Once Ter-Martirosyan called him in the evening and said that he would like to try to pass the theoretical minimum examination. ‘Come to my place tomorrow at nine in the morning. I have to have a completely clear head to speak on scientific topics,’ - said Landau. Karen passed the exam with flying colors. Lev Davidovich kept repeating to his wife after the departure of Ter-Martirosyan: ‘What a capable young man! Extremely capable!’ ” In his scientific career, Karen used to select problems that others had not worked on, addressing them in his own style which would frequently become a general standard in the given range of questions. The beginning of his half-century career in theoretical physics was devoted to nuclear physics. In 1952 he created a theory of the Coulomb excitations of atomic nuclei, which led to the discovery of nonsphericity in certain heavy nuclei. Soon after, in 1952-54, he solved the quantum-mechanical three-body problem with a point-like interaction – the so-called Skornyakov–Ter-Martirosyan equation. It was later generalized by Ludwig Faddeev and became a major tool in nuclear and atomic physics. In quantum field theory Ter-Martirosyan formulated (with Igor Dyatlov and Vladimir Sudakov) a method of “parquet” equations for summing planar diagrams. The parquet equations in quantum electrodynamics were regarded by Landau as an unsolvable problem. This method, which seemed to be of a purely academic interest in 1957, subsequently found applications in analyzing the scalar sector of electroweak models. After his move to Moscow Karen Avetovich decided to change the focus of his research. Influenced by Landau and Pomeranchuk, he turned to field theory and elementary particle physics. In collaboration with Vladimir Gribov and Pomeranchuk, he developed the theory of bifurcation points in the plane of complex angular momentum, studied the multi-Reggeon kinematics processes (which he in fact discovered), developed a theory for describing the hadronic cross-section growth at high energies, and, finally, built the theory of the critical and supercritical Pomeron (with Alexander Migdal and April 5, 2013 15:2 WSPC/Trim Size: 9in x 6in for Proceedings 6c˙Karen-Intro

Karen Avetovich Ter-Martirosyan 201

Alexander Polyakov). He invested much effort in the supercritical Pomeron. In these explorations of soft hadronic interactions at high energies, a profound theoretical understanding came hand in hand with the thorough analysis of a huge amount of experimental data from accelerators at Brookhaven, Serpukhov, and CERN available at the time. Later on, Ter-Martirosyan constructed a theory of multiplicity distribution of hadrons at high energies. It formed the basis for the theory of multiple particle production in hadron-hadron and hadron-nucleus collisions at high energies. Ter-Martirosyan’s theory, developed and extended by his followers, survived till this day as the main phenomenological approach for describing soft hadron interactions at high energies. Karen Avetovich was so deeply immersed in soft hadronic interaction, inspired by the beauty of the Regge theory and its applications, that the ideas of quarks and gluons, and quantum chromodynamics (QCD) in general, were alien to him till the November revolution of 1974, the discovery of the J/ψ particle. After the November revolution his research interests changed again. In the 1980s Karen Avetovich developed a model of quark-gluon string production and fragmentation. B-meson physics and possible Standard Model extensions were the major focus of Karen’s interests in the 1990s. His last talk at the ITEP seminar, in 2005, was devoted to neutrino physics. Ter-Martirosyan was the recipient of the 1968 USSR State Prize for his work on the Coulomb excitations of atomic nuclei, and in 1999 he received the Pomeranchuk Prize “for his fundamental contribution to quantum mechanics and quantum field theory.” In 2000, he was elected as the Corresponding Member of the Russian Academy of Sciences. Pedagogical activities occupied a huge place in Ter-Martirosyan’s life. He founded the Elementary Particle Physics Chair at the Moscow Institute of Physics and Technology and headed it for many years. He helped to train dozens of young physicists who became experts not only in nuclear and elementary particle physics but in other areas as well. He developed excellent courses in quantum electrodynamics, quantum field theory, and elementary particle theory. April 5, 2013 15:2 WSPC/Trim Size: 9in x 6in for Proceedings 6c˙Karen-Intro

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Many years of teaching in combination with his creative – sometimes, explosive – personality produced a unique Ter-Martirosyan’s cohort of young theoretical physicists. Among his students were three famous Sashas (Alexander Polyakov, Alexander Zamolod- chikov, and Alexander Migdal), Vladimir Gribov, Alexei Anselm, Alexei Kaidalov, Yan Kogan, and many others. In the 1960s Ter-Martirosyan was a mastermind behind the well- known Nor-Hamberd school of physics in Armenia. Later he participated in organization of almost every ITEP winter school of physics. Karen Avetovich was a deeply sincere man of highest moral standards, both in science and in life. His principle was to tell the truth, as he understood it, under any circumstances, at any time, and to anyone; he just could not understand how anyone could play the hypocrite to comply with a dubious situation. He made mistakes, of course, but these were sincere mistakes “straight from the heart.” He was loved by many ... April 5, 2013 15:3 WSPC/Trim Size: 9in x 6in for Proceedings 6d˙Shifman-Karen-Mant

KAREN AVETOVICH∗

M. SHIFMAN William I. Fine Theoretical Physics Institute University of Minnesota Minneapolis, MN 55455, USA [email protected]

I was never a student of Karen Avetovich (Karen, as everyone called him behind his back) and never collaborated with him. I’ve never worked on Reggeistics – the area of high-energy physics that was close to his heart. For an understandable reason – a thirty-year age difference – I couldn’t be his close friend. And yet I decided to write a few kind words about Ter-Martirosyan for a reason which will soon become clear. I won’t talk about his scientific career. That can be found on the Internet. These few lines speak of him as a person. Physics was his life, passion and refuge. It filled his soul with colors bright as a Martiros Saryan canvas, colors which burst forth from him into the world. Their glow tinted everyone his life touched. Karen was easily excited, sometimes blowing up at seminars when he thought the speaker was talking nonsense. A couple of times, I personally had occasion to bear the force of these explosions. But later, when he cooled down, he always asked for forgiveness, and with such childlike sincerity that there was no way not to forgive him. Many trials beset him on his course in life. His children suffered from sort of genetic ailment that affects only Armenians and Jews (that’s in his own words). His son died young. I can still see Karen Avetovich’s face on that day, and the fact that I didn’t attend the funeral – a terrible sin – pains me to this day. But he didn’t grow

∗Translated from Russian by James Manteith.

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bitter. His temper was the temper of a person infinitely good and very emotional, in the southern manner. Karen’s attitude to female graduate students had a touch of pa- ternal feelings; in their presence Karen always stayed gallant. In my memory he had two – Olya and Anya – and he tinkered endlessly with each of their theses. He always loved to feed young people, in the literal sense of the word. Sometimes in the evening in his office he opened a box of delicious cookies and set out tea for everyone who’d stayed late at the old Menshikov mansion after working hours. Needless to say, these were almost entirely young people... The Menshikov mansion offices were set up by dividing the old bedrooms with plywood partitions. There was no soundproofing. For some time my seat was in Sudakov’s office, adjacent to Karen’s office. Discussing physics issues with colleagues is my favorite pastime, and my voice, unfortunately, isn’t very quiet. No matter how I tried, I obviously irritated Karen (and I understand him completely). Finally he kicked me out of Sudakov’s office. Clearly, though, it bothered him to do this, and soon he came to me with some version of a multi- part exchange through which I wound up in Simonov’s office. Karen was happy to have provided for me, and as for what Simonov thought of this, we’ll leave that unsaid... One time Karen, along with Berestetskii, helped me in a difficult situation (when I went several months without a job), even though I hadn’t asked him about anything. He decided on his own... I know he generously gave his assistance to other people as well, without expecting anything in return. And what pupils he had! The crème de la crème of Soviet theoretical physics in the late “Soviet ages.” Karen’s attitude toward young physicists appearing at ITEP was friendly and encouraging. Young theorists trying to pass Landau’s notorious theoretical minimum could always be seen around him. The process of passing these examinations could take months. De- spite his southern temperament Karen was a patient and thoughtful examiner. He loved discussing physics with young people. Often in these discussions he would play the role of the “devil’s advocate” – his natural role – since Karen had a conservative mindset and cautious attitude to “new physics” and the early speculations and conjectures April 5, 2013 15:3 WSPC/Trim Size: 9in x 6in for Proceedings 6d˙Shifman-Karen-Mant

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that come with it. However, after an initial stage of deep reflections and hesitations, new theories could evoke Karen’s sincere admiration and exuberant enthusiasm. I think that the book The Theory of Gauge Interactions of Elementary Particles [1] was written in this kind of happy time. In 1977, the international conference Neutrino-77 was held in Bak- san. The contemporary reader is unlikely to grasp this, but at that time special permission was needed to attend such a conference, because it involved foreigners. The Institute had compiled an attendee list, which included me, because the topic fascinated me at the time, and I had things to say about it. As a rule, attendee lists for conferences within the Soviet Union were approved without problems. But in this case something unforeseen happened. My name and Zuckerman’s were removed. Although no reasons were given, everyone understood: some official had disliked the too obviously Jewish- sounding surnames. To say this offended me says nothing. The evening of the next day, Karen called me into his office. He poured me and himself a cup of tea with lemon, and we kept silent for a while. Then he said, “You see, Misha, over the years I’ve realized our life is full of injustices. What can you do if God decided for you to be born in a ... country?” (I remember which word Karen used, but won’t say it.) We fell silent again. Then he continued: “Thinking about all the injustices and insults we go through just because, for no reason at all, weekly if not daily, a person could go crazy. My advice to you is to think only about good things. You do good work. Think about that. I hear you have a lovely newborn daughter. Think about that. It also helps me to read books about history – Armenian or Georgian, for instance. Would you like me to bring you something?” The last time I saw Karen was five years before his death. We had both come to Paris for a conference, he from Moscow, and I from America. During the first day’s meetings we sat in different parts of the auditorium and were unable to talk. But then there was a banquet, he came up, hugged me, said how glad he was. We talked a little about science. Karen soon left, while April 5, 2013 15:3 WSPC/Trim Size: 9in x 6in for Proceedings 6d˙Shifman-Karen-Mant

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I stayed to the end. I left the restaurant after midnight. The night was beautiful, a light, gentle breeze was blowing, and all the stars spilled out across the sky. I decided to walk. Suddenly in the middle of a square, I don’t remember which, I saw the proﬁle of a perplexed man who struck me as familiar. It was Karen. I walked over to him. He turned and said, “Misha, I’m so happy for you. I remember my students, Sasha Polyakov, Sasha Zamolodchikov... Ah, one more thing, I’ve forgotten the way back to the hotel...”

Reference 1. M.B. Voloshin and K.A. Ter-Martirosyan, Teoriya Kalibrovochnyh Vzaimod- eystvii Elementarnyh Chastits, (Moscow, Energoatomizdat, 1984). April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6e˙Smilga-Karen

K. A. TER-MARTIROSYAN AS I REMEMBER HIM

A. V. SMILGA SUBATECH, Universit´edeNantes 4 rue Alfred Kastler, BP 20722 Nantes 44307, France [email protected]

Karen Avetovich Ter-Martirosyan was a remarkable physicist, one of the creators of the great ITEP a theoretical physics school. He was a teacher of many brilliant theorists. The most known of them are probably three Alexanders: Alexander Polyakov, Alexander Migdal and Alexander Zamolodchikov. He was also one of my teachers and it is an honor and pleasure for me to write these notes. Let me start, however, with two disclaimers. i) This is not a biography. I cannot write it without a special research simply because I do not know well enough many facts of life of Karen Avetovich (K.A. hereafter), especially of his youth. I am sharing with you my personal recollections of K.A. meaning that I will not be able to avoid mentioning myself, sometimes. ii) This note is intended for publication in English, and, therefore, I am writing it in English even although my English style is considerably worse than the Russian style. Please, excuse inevitable barbarisms. I ﬁrst met K.A. in July 1970, while passing the entrance examinations to Moscow Institute of Physics and Technology (MIPT). To be more precise, by this date I had already passed the regular exams: written and oral math, written and oral physics and the Russian composition. But, following the special procedure set up in MIPT, I had, in addition, to pass a kind of interview where the professors looked at their future students, asked them all kind of questions

aInstitute for Theoretical and Experimental Physics in Moscow.

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208 A. V. Smilga

about physics and life. The impression they got played a role in the final selection and in distributing the admitted students over different specializations (in MIPT, this was done already at the freshman level, although could be changed later). I was asked which branch of physics I liked the best. I answered – elementary particles –and was sent to K.A. I saw a man with an expressive flexile face who briskly asked a few questions (I remember, it was something about electron going simultaneously through two holes in the barrier and thus producing an interference pattern), and I was accepted. MIPT was a special university. The best in physics in the So- viet Union and, maybe, the best in the world. During the first two years, all students studied together on the university campus in Dol- goprudny (a small city very close to Moscow). But starting from the third (sometimes, from the second) year, they spent more and more time at the “base” – a research Institute with this or that specialization. In our case, it was ITEP. There we had to take many special courses (strong interactions, weak interactions, theory of accelerators, nuclear electronics, ...). In addition, we had to work for one of experimental laboratories. By default,wewereassumedtowriteamasterthesisonsomeexperimental subjectandthencontinuetoworkashighenergyexperimentalists. Those who wanted to become theorists had to pass some extra and very special examinations – theoretical minimum. This routine was established by Landau and was to some extent preserved in ITEP (as well as in the Institute of Theoretical Physics in Chernogolovka). Landau’s theoretical minimum involved two exams on math and 9 exams on all branches of theoretical physics. There were only about 20 people who passed the whole set of these examinations to Landau himself, and this list can be considered as Who is Who in Soviet theoretical physics. Ter-Martirosyan is there. In the 1970s, after Landau’s death, K.A. and some other former Landau’s students carried out this initiation ceremony in an alleviated form. Rather than eleven, I had to pass only three exams – on quantum mechanics, quantum electrodynamics and on the modern field theory (whatever was modern back in 1975). The first exam was on quantum mechanics. Its program basically April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6e˙Smilga-Karen

K. A. Ter-Martirosyan as I Remember Him 209

repeated Landau & Lifshitz’s (L & L) textbook, but with some sections omitted. Thus, the typewritten program I got from an elder student consisted of a list of sections that had to be omitted from L & L in preparation. But it had a typo. Instead of “113, 147” it read “113–147” and I understood that there was no need to study all sections from 113 to 147 – the whole scattering theory! I happily called K.A., we met, he quickly understood my audacity and ignorance and sent me home. In several months I came to him again having already learned the sections 114, 115, etc. This time, I was more fortunate. After posing some more simple questions, he suggested a problem to me: to find the shift of the Coulomb levels in the pp¯ atom due to strong interactions. This problem is not so simple. According to the routine set up by K.A., I first spent several hours in his office trying to solve it, then he listened to what I was able to babble after that and sent me home: come back when you solve it! It took me about a week. To find the shift, one had to write a solution of the radial Schrödinger equation as a generic hypergeometric function (of course, a hypergeometric function — commented K.A. - this is known from high school curriculum) and to impose proper boundary conditions. Later I learned that this problem was based on an unpublished paper of K.A. He solved it, found too simple to publish, but suggested it instead to prospective students. While passing two other theoretical examinations, my examiner was not K.A. but Boris Lazarevich Ioffe who became my adviser in Master’s thesis and then PhD. Meanwhile, I was following the regular course of K.A. on the theory of strong interactions. That was the spring of 1974, QCD was just invented and not yet established itself as the true and indisputable fundamental theory of strong interactions. The course of K.A. was not about quarks and gluons, but rather about the Regge theory developed by Gribov and Ter- Martirosyan himself. That was the subject where he was the leading world expert. K.A. wanted to write a book on the basis of his course (it did not finally work for unknown to me reasons). So he asked us to take notes of his lectures, write them up in a more or less decent literary form and give it back to him. I remember that, when it was April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6e˙Smilga-Karen

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my turn, I tried to convey exactly what he had said during the lecture and wrote: as is well known from high school curriculum and then it was, if I remember correctly, an integral representation for the Bessel function J0(x). At that time, K.A. believed in bootstrap theory rather than in quarks. I remember a certain thesis defense where K.A. was a member of the Committee. The defense subject was experimental. At some point the candidate mentioned that his data agree well with the predictions of the quark model. K.A. immediately reacted: I do not understand why you compromise your excellent experimental study by comparing it with such a speculative and suspicious model ! After the November Revolution of 1974 when charmonium was discovered, he changed his mind, of course. His scientific interests changed too. In the late 1970s and 80s, he worked not on the Regge theory anymore, but on physics of grand unification. This story illustrates well, I think, the most distinguished feature of K.A. as a scientist – his absolute intellectual integrity (combined with passionate love to physics). He never hesitated to say honestly what he thought. And when he understood he was wrong, he never hesitated to admit it! At that time, K.A. was one of the pillars of the ITEP seminar. You know, it was a genuine Russian seminar where people in the audience had a habit to ask as many questions as was necessary to clarify what the speaker said - whether it was a major scientific discovery, a pure nonsense or something in between. Sometimes, the discussion was rather heated, and K.A. (together with some other members of the ITEP theoretical department) never missed an opportunity to express his opinion. That was, I believe, the best possible (the most efficient) way to do science and to learn science. It is difficult (at least, for me personally) to learn a new subject by listening to a formal talk without questions being asked. I am missing the ITEP seminar now... Returning to K.A., his absolute integrity was his defining feature not only in physics, but in human relationships too. In some cases, people were offended by his too frank a conduct. But, I think, none could bear a grudge against K.A. for a long time. People understood April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6e˙Smilga-Karen

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that K.A. might have been careless about their vanity, but he was equally careless about the vanity of his own. Never did I meet a scientist in whose lips Pasternak’s words: “It is unseemly to be famous, celebrity does not exalt...” would so adequately express what he really thinks. K.A. was a strong theorist. His most known results refer, as I mentioned before, to the Regge approach to high-energy hadron scattering. He was the ﬁrst to consider, on top of the Regge poles, branching point singularities in the complex momentum plane, he applied the Regge theory to multiple particle production, developed the theory of the supercritical Pomeron, reggeon interactions, etc. Back in the 1950s, he obtained important results in nuclear physics: studied the Coulomb transitions in nuclei, wrote together with G.V. Sko- rniakov an integral equation describing three-body problems with a short-distance interaction ... There were other strong physicists in ITEP theory department who also obtained important results, but none of them (and nobody whom I personally had a chance to know) could match K.A. in Teacher’s quality. I guess, the explanation is simple: after physics (and, I assume, family, but I do not know personal life of K.A. well enough and cannot say much on it), his students were the most precious thing for K.A., something in his life of which he really cared about. After defending their Master’s degrees, his students were not abandoned. K.A. tried to fetch an ITEP PhD scholarship and then (or, maybe, directly after graduation, in those days that was sometimes possible) a permanent ITEP position for as many of them as he could. When it was impossible, he called all his colleagues in other research institutes asking whether they have open positions, telling them what brilliant student he happened to have right now, etc. As a father (or, maybe, even mother) trying to help as much as he/she could to his/her children ... Having made my thesis not with K.A., I cannot call myself his direct scientiﬁc son. Maybe, a stepson or a nephew. But I will never forget the lessons about physics, attitude to physics, and to life in general that I learned from him. April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6f˙Nevzorov-Karen

MEMORIES OF KAREN AVETOVICH

ROMAN NEVZOROV Institute of Theoretical and Experimental Physics B. Cheremushkinskaya 25, Moscow 117259, Russia [email protected]

Karen Avetovich Ter-Martirosyan (K.A.) was at once my teacher, scientific adviser, and collaborator. My communication with K.A. enormously influenced my life and career; he helped me to establish the basic values and principles that I try to follow in my everyday life and research activities. I met K.A. for the first time in spring of 1992, almost twenty years ago. At that time I became interested in quantum mechanics and spent a lot of time studying it. I was a third-year (undergraduate) student in the Moscow Institute of Physics and Technology (MIPT). My specialization had nothing to do with quantum mechanics, but rather was somewhat related to the formation and propagation of internal and acoustic waves. In April or May of 1992, when I had just started looking for an opportunity to change the direction of my future research, my classmates told me that a new specialization called elementary particle physics would be available in the near future, based within the Institute for Theoretical and Experimental Physics (ITEP). In order to get accepted I had to pass an interview. At that time I knew next to nothing about elementary particle physics. Nevertheless, I decided to try it and, with many other potential candidates (third-year MIPT students), arrived at ITEP where we met Karen Avetovich. He introduced himself and told us many captivating things about ITEP, Lev Landau, etc. K.A. also tried to ask us some questions. However, he spoke so fast – later I learned that it was one of his traits – that it was rather difficult for all of

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us to follow him. At the end of his lecture K.A. asked if there was anybody who would like to try to pass a special exam, the so-called theoretical minimum, on quantum mechanics. I was the only student who volunteered. I really wanted to test my knowledge of quantum mechanics. K.A. gave me a problem and left me alone. I spent a few hours working on this problem, but by the time K.A. returned I have not yet solved it. I tried to explain to him how I was attempting to proceed. He listened very carefully, and then pointed out a few issues that I had not even thought about and gave me a few pieces of advice. Then K.A. asked me to continue working on this problem at home. He also suggested to arrange another meeting in a month. That day K.A. and I left ITEP together. He talked to me the whole way after ITEP, I was overwhelmed by his energy, enthusiasm, and passion for theoretical physics. It was obvious that he was an extremely knowledgeable theorist and that he did not hesitate to share his knowledge with young people. On the other hand, I was rather disappointed with myself because after our discussion I recognized that my knowledge of quantum mechanics was not deep enough. On the way to the nearest metro station I was walking and thinking about what K.A. had told me. To tell you the truth, I did not pay any attention to where I was going. I returned back to reality only after someone stopped me and asked something; at this point I discovered myself in a neighborhood of Moscow that I was not familiar with, far away from the metro station which was my destination. After this first meeting with K.A. I decided that I had to join the ITEP group to learn quantum mechanics as deeply as I could. I was accepted, however it took me a whole year to pass theoretical minimum exam on quantum mechanics. Then I spent another year working to pass theoretical minimum exam on quantum electrodynamics and quantum field theory. K.A. was rather busy at that time. He invested immense efforts to organize the educational process for the specialization he championed, elementary particle physics. Be- cause of this he could not be directly involved in my examination process. April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6f˙Nevzorov-Karen

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Nevertheless, every time he met me he always asked about my progress, trying to encourage me to proceed as fast as possible. De- spite his tremendous administrative load, K.A. was deeply and personally involved in educating young physicists. He taught quantum electrodynamics, always lecturing with great passion and enthusiasm. His lectures lasted for 4 or 5 hours so that by the end of the lecture my classmates and I sometimes felt completely and absolutely exhausted. When we were not active enough in class K.A. would interrupt his lectures to ask us if we had any questions. In these cases he used to say: “If you have no questions then you either understand everything or you understand nothing.” He did not continue until all of us became engaged once again. Moreover, when K.A. lectured until 6 p.m. or so he often organized tea/coffee breaks for us. He knew that our stipends were rather low and that some of us (including myself) could not afford to have lunch in the ITEP canteen. K.A. tried to ensure that every student who studied/worked in ITEP had some additional stipend from ITEP. All MIPT students were assigned to different ITEP laboratories. K.A. regularly asked the students he taught if they had a supplementary stipend from ITEP. Having found out that a student had no supplementary stipend he reacted immediately by calling directly the head of the corresponding ITEP laboratory and asking why this was the case. K.A. tried to help all MIPT students that he taught as much as he could. He was a truly remarkable teacher! I have never in my life met another teacher like K.A. Karen Avetovich did not just teach me quantum mechanics and quantum field theory, he also taught me many other things. In particular, he wanted students to be capable of defending their research results. I still remember what he said to me before my first seminar: “There can be a few people in the audience who may try to argue with you during your seminar. Remember, you are going to present your results which you know much better than anybody else.” After I graduated from MIPT cum laude I joined the ITEP graduate school. During my Ph.D. studies I communicated a lot with April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6f˙Nevzorov-Karen

Memories of Karen Avetovich 215

K.A., he became my second scientific adviser. (My main scientific adviser was Mikhail Iosifovich Vysotsky.) In 1997 I got involved in assisting K.A. with his course of lectures on quantum electrodynamics. At a certain point he realized that his administrative duties prevented him from active involvement in research. Because of this he made the decision to pass the leadership role associated with the new MIPT specialization to Yurii Mikhailovich Zaitsev and then, later, to Mikhail Vladimirovich Danilov. Almost simultaneously he organized a new laboratory in the ITEP Theory Department and became a head of this laboratory. Although K.A. stepped down as a formal leader of the MIPT groupinITEP,whichhehimselfhadcreated,hecontinuedtobe an informal leader generating new ideas, and sometimes acted as a “driving force” for new initiatives. His communication skills were amazing. Every time a problem emerged K.A. called either ITEP or MIPT officials (i.e. the Dean, Vice-Rector, etc.) and always managed to sort the problem out. He simply did not accept no for an answer from such people. The ITEP and MIPT officials tended to respect Karen Avetovich, while he, in turn, used his influence to help MIPT students who studied at ITEP and to promote the new MIPT specialization that he had created. The list of his initiatives and good deeds is pretty long. Here I would like to mention only some of them. For example, K.A. knew that a few Ph.D. students including myself worked at ITEP till very late at night almost every day. To make our lives easier, he convinced the ITEP administration to organize a small hostel inside a huge fence that surrounded the ITEP territory, where the ITEP and MIPT Ph.D. students could stay. At some point K.A. realized that it was rather problematic for young scholars in ITEP to make short (15 minutes) presentations at conferences. He then managed to move some parallel sessions of the Young Scien- tist Conferences from MIPT to ITEP. K.A. and other leading ITEP physicists participated in these parallel sessions on many occasions. K.A. and I worked together – this was the most cherished part of my interaction with him. The subject of our mutual interest was supersymmetry. In particular, K.A. and I investigated the Higgs April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6f˙Nevzorov-Karen

216 R. Nevzorov

sector within the simplest supersymmetric extensions of the Stan- dard Model: minimal and next-to-minimal supersymmetric standard models. Both K.A. and I believed that the Higgs mechanism was responsible for the electroweak symmetry breaking. The supersymmetric models that we considered led to a relatively light Higgs that could have been discovered at LEP, generally speaking. In fact, the presence of the SM-like Higgs boson with mass below 130 or 135 GeV is a robust prediction of these models. When I explained this to K.A. he burst with enthusiasm because he realized that these models could be ruled out in the nearest future. K.A. wanted all his students to work on something that could be measured/tested in experiment. He had a wide range of interests and enjoyed discussing formal aspects of quantum field theory including supergravity, supersymmetry-breaking mechanisms, superstring-inspired models, etc. At that time, he himself worked mostly on QCD, heavy quark physics, neutrino physics, supersymmetry, and Grand Unifica- tion. Discussing all these topics with K.A. was a stimulating experience, indeed. Usually, after he became interested in some question, his enthusiasm would grow to a level at which his passion and energy were spilled upon other people involved in the discussion. Because of this many theorists and experimentalists from ITEP and other institutions from Russia and abroad enjoyed to discuss with K.A. their research results. He was also one of the most interested participants of all ITEP seminars and had never hesitated to debate with the seminar speakers. K.A. always welcomed new ideas that he could understand and appreciate. I recall that in 2003 I told him: “You know, Karen Avetovich, my collaborators and I are trying to estimate the value of the cosmological constant in the supergravity models....” This was enough to draw his attention. He replied: “We must find some time this week, Roman, to converse about your ideas.” If K.A. got interested, like in the case of our project mentioned above, he could spend many hours discussing the new idea. On the April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6f˙Nevzorov-Karen

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other hand, if he did not like the idea he would usually assert as much quite straightforwardly. He taught all his students and collaborators to get to the bottom of the problem at hand. This was another reason why conversations and physics discussions with K.A. were so valuable. Traditionally the majority of the ITEP Theory Group members worked on different aspects of the Standard Model, namely, QCD, CP violation, heavy quark and neutrino physics, etc. They were extremely skeptical with regards to its various extensions. K.A. was an expert in the above areas of theoretical particle physics. At the same time, he was invariably interested in new ideas related to physics beyond the Standard Model. Once I asked him why he considered all these new and sometimes rather speculative ideas so seriously. He told me: “You know, Roman, one of the biggest regrets in my life is that we did not take QCD seriously immediately after the original idea was published.” One can naively think that K.A. strongly exaggerated. However, I am sure that he really meant what he said. K.A. could not live without thinking about theoretical particle physics. His research was a part of his life. Theoretical physics was not just his metier, it was his lifestyle. When I worked in the UK in 2004 and 2005 I phoned K.A. a few times. He was already rather sick but his physics imagination was still vivid; until his very last days Karen Avetovich was deeply involved in research and full of new ideas. I joined the ITEP group in a very difficult time. This was the post- Soviet-Union era when the science budget was dramatically reduced and a lot of scientists were almost at the verge of starvation. In these circumstances many people asked K.A. for help. K.A. could find words of support and/or good advice for everyone. He and his wife, Bella Artemievna, also never hesitated to directly help his colleagues and friends. I witnessed at least a few cases when they in essence rescued other people. As I have already mentioned, K.A. made every effort to support students and young physicists who worked on the problems that he was interested in. He personally organized several grant applica- April 5, 2013 15:4 WSPC/Trim Size: 9in x 6in for Proceedings 6f˙Nevzorov-Karen

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tions, to INTAS, CRDF and RFBR (Russian Foundation for Basic Research), which were successful. Financial support provided by these funding agencies allowed quite a few ITEP and MIPT students to successfully complete Ph.D. studies. A few years after K.A. passed away I met another distinguished particle theorist, James Bjorken (B.J.). He visited the University of Hawaii in the beginning of 2012 when I worked there. B.J. gave a number of talks and I had several discussions with him. He talked about particle physics with a passion and enthusiasm similar to that of Karen Avetovich. In conversations with B.J. I realized that I was thinking about K.A. all the time. This helped me to recognize that KarenAvetovichTer-Martirosyan,aremarkablepersonandagreat theoretical physicist, will always be with me. I am absolutely sure that he will remain in the hearts and minds of many other people as well. April 5, 2013 15:5 WSPC/Trim Size: 9in x 6in for Proceedings 6g˙Naya-Karen

AFEWLINESABOUTKAREN∗

NOEMI SMORODINSKAYA Institute for Theoretical and Experimental Physics Moscow, Russia [email protected]

Karen had tons of amazing students, and it’s unfortunate that they could not contribute to this collection. They would have a lot of marvelous stories to tell, since they spent so many days and nights at Karen’s house, enjoying Bella Artemievna’sa hospitality and kindness. Karen was a diﬃcult person, with many eccentricities, but at the same time he was very kind and forgiving. When people he knew had troubles, he always did whatever he could to help them. I should add, however, that due to the many tragedies he had experienced in his family life, Karen’s threshold for what counted as troubles was unusually high, and what others perceived as major problems struck him as the minor complications of everyday life. I remember how Karen was worried that Roman Nevzorov, his last student, might have to leave to work in a bank. Roman’s salary at ITEP was so meager that he was always penniless. “Wow”, Karen told me, “it’s good that Roman doesn’t know how much money people are paid in banks.” I am sorry that I didn’t interact with Karen enough over the years. Only toward the very end we started talking from heart to heart. Karen died because of the chaotic carelessness of our medical system.

∗Translated from Russian by A. Cherman. aBella Artemievna was Karen Ter-Martirosian’s wife.

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DAVID ABRAMOVICH KIRZHNITS∗

B. M. BOLOTOVSKY, YU. M. BRUK, V. L. GINZBURG, V. I. RITUS, and G. V. SHPATAKOVSKAYA P.N. Lebedev Physical Institute of the Russian Academy of Sciences Moscow 119991, Russia

A remarkable theoretical physicist, Russian Academy of Sciences corresponding member David Abramovich Kirzhnits (1926-1998) left us a multifaceted and brilliant scientific legacy. Basic to his scientific vision was an understanding of the unity of physics as a reflection of the unity of nature. “...This unity,” he said in his lectures for upper-level students at the Moscow State University department of physics, “emerges not only in the existence of general laws of nature, whose scope of action covers the widest range of scales – from 10−33 cm (the submicroscopic world) to 1028 cm (the Metagalaxy)... More- over, it turns out that Nature also successfully uses specific physical mechanisms concurrently in the most diverse types of phenomena ... such as the ‘superconductor’ mechanism for forming the masses of elementary particles.” Namely at the junction of field theory and the theory of superconductivity D. A. Kirzhnits together with his student A. D. Linde built a model of cosmological phase transition in the early universe. With recent advances in elementary particle theory and the unification of weak, electromagnetic and strong interactions, the delineation of phase transitions served as a source of inflationary cosmology, the theory of cosmic strings, etc., and became an essential element in our understanding of the Universe. For pioneering work in this area, D.A. Kirzhnits and A.D. Linde were awarded the Russian Academy

∗Published in Russian in D.A. Kirzhnits, Works on Theoretical Physics and Recollec- tions, (Fizmatlit, Moscow, 2001), p. 7. Translated from Russian by James Manteith.

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224 B. M. Bolotovsky et al.

of Sciences’ M.V. Lomonosov Prize for 1978. D. A. Kirzhnits’ first works were devoted to issues in field theory, but in his master’s thesis (1957) he improved the Thomas-Fermi model of multiparticle quantum theory, and in the future these two physics topics, seemingly remote from one another, often intertwined in his works. D.A. Kirzhnits’ 1963 book Field Methods of Multiparti- cle Theory reflected his own interests and became a tutorial by which several generations of physicists gained mastery of field methods. A cycle of works, spanning many years, on improving the Thomas- Fermi model with applications to nuclear physics and high-energy physics culminated in the award of the Russian Academy of Sciences’ 1998 I. E. Tamm Prize to him and his student G. V. Shpatakovskaya. In the late 1950s D. A. Kirzhnits was the first to point out that the substance of stars – white dwarfs – despite the tremendous “starry” temperatures in their cores, exist in a solid crystalline state. The perspective based on these concepts made it possible to explain the presence of several linear sequences in the Hertzsprung-Russell diagram and to determine the chemical composition of white dwarfs. Starting in the early 1960s, D. A. Kirzhnits worked to overcome the difficulties of field theory with nonlocal interaction. As a result, he provided a selfconsistent formulation of this theory. These results comprised his doctoral dissertation (1966). In the quantum problem of three or more bodies, Kirzhnits’ method is widely used in reference to atomic physics and low-energy nuclear physics. In the mid-1970s, engaged with the problem of high-temperature superconductivity long before this phenomenon’s discovery, David Abramovich showed that the widely held view on the mandatory positive sign of the static dielectric constant was incorrect. Indeed, later discoveries revealed a wide class of substances with a negative sign of this quantity, which happens to be necessary for a material to be a high-temperature superconductor. In the 1980s, D.A. Kirzhnits produced a theory of deceleration of fast particles (charges, neutrinos, magnetic monopoles) in media, having obtained a number of important universal relations. In this same period, he pointed out the important role of the effects of nonadiabatic interaction of light particles with a coupled system of heavy April 5, 2013 15:12 WSPC/Trim Size: 9in x 6in for Proceedings 7b˙Kirzhnits-Intro-Man

David Abramovich Kirzhnits 225

particles and developed a corresponding theory. In his final years, D. A. Kirzhnits published a series of works that contributed significantly to refining perspectives on superfluidity in neutron stars and how the general theory of relativity’s effects impact the rotation of superfluid nucleon systems. April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

MEMOIRS∗

DAVID KIRZHNITS

A little about my parents My mother, Liubov Solomonovna Kirzhnits, was born in Rogachev in Belarus in 1897. When L. S. was a little girl, grandfather and his family escaped from the Palea and moved to Irkutsk. He held an oﬃcial position as a public rabbi, which had nothing to do with religion but in the Jewish community corresponded to the functions of today’s civil registrar. Grandfather was also an amateur ethnologist, a correspondence student of Academician Veselovsky and the author of many books. Grandmother taught foreign languages. Grandfa- ther’s house was one of pre-revolutionary Irkutsk’s cultural centers, a gathering place for intellectuals, exiles, local Sabbath observers who practiced Judaism; one frequent guest was a well-known Asia scholar, ethnographer G. N. Potanin.b After graduating from high school, L. S. entered the history department of Irkutsk University, but studied there only two years. The birth of a daughter – my older sister – and then the Civil War forced her to abandon her studies. With her daughter and husband, she emigrated during the Kolchak regime to Harbin, from which the family planned to leave for America (they had even bought ship’s

∗Published in Russian in D.A. Kirzhnits, Works on Theoretical Physics and Recollec- tions, (Fizmatlit, Moscow, 2001), p. 337. Translated from Russian by James Manteith. aThe Pale of Settlement was a region of Imperial Russia in which residency by Jews was allowed and beyond which Jewish permanent residency was prohibited. The Pale included much of present-day Lithuania, Belarus, Moldova, and Ukraine. bGrigory Nikolayaevich Potanin (1835-1920) was a famous Russian explorer of Inner Asia (six major expeditions during three decades, from 1863 till 1893). After 1865 Potanin was active in the Siberian separatist movement. In 1889 he formed a group of intellectuals that founded the ﬁrst university in Russian Asia, in Tomsk (currently, the Tomsk State University).

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Memoirs 227

passes). Instead, they went back to Irkutsk, then lived until 1924 in Novonikolayevsk (Novosibirsk) and later finally settled in Moscow. With an incomplete education, L. S. worked in journalism for a number of years, then served in Soviet institutions and just a few years before the war found a job that suited her skills and temperament: she became a cultural worker in psychiatric hospitals, and worked in this capacity (not counting the war) until retirement. The job was far from easy and required, apart from purely professional literary, artistic, musical and theatrical culture, also certain psychological and medical knowledge, intuition and quick reflexes, simple human courage (she sometimes had to work with violent patients). During the war she worked as a medical statistician and kept track of everything to do with wound patients (as the wounded were called then) in hospitals – first in Evacuation Hospital No. 3881 in Lower Kyshtym, then in Evacuation Hospital No. 3116 on Lake Uvildy. In the new year of 1942, in a strong snowstorm, she rallied several other mothers and they walked 25 km to Metlino from Kyshtym. L. S. was a person of firm moral principles, with a strong sense of duty and conscience. Right before the war, through a fateful mishap she unintentionally caused harm to a certain woman, and this tormented her incessantly, right up to the last days of her life. She combined a high level of culture and natural intelligence, and had a good knowledge of literature, history and music; she herself played the piano quite well. At the same time, she was completely free of snobbery toward so-called “ordinary people,” and more than once I witnessed how they bonded with her, grateful for the good they saw her do. After mother’s death, which came in 1977, three days before her eightieth birthday, a considerable number of people retained good memories of her. Father, a very busy man, gone from my life when I was just 11 years old, did little for my upbringing. This care fell almost entirely on the shoulders of my mother, to whom I’m obliged for everything good there was in me when I set out for independent life... My father, Abram Davidovich Kirzhnits, was born in 1887 in Bobruysk to the family of a craftsman. Although his official education comprised just four grades at the town school, he became a April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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highly educated person (for instance, speaking several European languages). A. D. owed this to self-education. When filling out forms, under “Education” he would write “prison” (in the 1920s and 1930s this was a commonly understood notion), as he’d spent considerable terms in jail and exile before the revolution; at that time prison was a genuine hotbed of culture. Also, though, in the late 1930s in his Bu- tyrka jail cell, through which engineers, teachers, military personnel, doctors and scientists passed, father organized a lecture hall, where each person shared his specialized knowledge with his cellmates. For a blackboard, they used the back of a hunched-over listener in a dark jacket; for chalk, they contrived to break off a chunk of plaster. By the way, the physicist Landau, also imprisoned at Butyrka then, never thought of this and suffered greatly from the lack of a pencil and paper (I know this from his words). By profession father was a historian of the revolutionary movement and revolutionary press, a bibliographer and journalist. He authored dozens of books and pamphlets, as well as many newspaper articles. Unfortunately, very little of his literary legacy survived, and he began writing his own bibliography when already hospitalized, shortly before his death, and only had time to start it. To my shame, I, his son, had little idea of the scale of the mark he left in the historiography of early twentieth century Russia. I was still more surprised when, twenty years ago, the young historian A. B. Ratner found me, and when approached ten years later at a meeting of the Academy of Sciences by corresponding member R. Sh. Ganelin, from Leningrad. They were both interested in father’s archives. Still more surprising was a phone call from Minsk from the office of the Belarus Encyclopedia with a request to send an article on father. Long before the revolution, father became an active member of the Bund,c which is known for fighting for the national and cultural autonomy of Jews in Russia. No wonder that in the late 1920s, when territory on the Amur was set aside for development by our own and

cThe Jewish Socialist political movement founded in Vilnius in 1897 by a small group of workers and intellectuals from the Jewish Pale of tsarist Russia. The Bund called for secular Jewish nationalism and cultural autonomy. April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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foreign Jews,d father became one of the leaders of the accompanying resettlement organization,e OZET. He traveled there more than once: first to the Tikhonkaya station with the first group of settlers, who cleared brush in the taiga in bitter frost, and then in the city of Birobidzhan which sprang up in this place. Not so long ago, during a conference on the Amur, I found traces of my father’s work in the archives there. In early 1938 father was arrested and detained for two years at Butyrka. A large trial was being prepared, “On the Sale of the Far East to the Japanese,” where a large group of OZET employees figured among the accused. In the end, the investigation (which took on an “active” character) dragged on until Beria came to power; the case was dismissed, and father himself was freed in January 1940. We were waiting for him, as both the arrest and the release of OZET workers took place in alphabetical order. In April of the same year, father died, his health undermined... At his funeral, mother led me up to a group of men in hats, said, “This is A. D.’s son,” and they held out their hands to me and introduced themselves by name: Peretz Markish, David Bergelson, Samuel Galkin, Leib Kvitko. Mother said, “Son, remember this moment: you’ve met the flowers of Jewish literature.” After the war, they were all tried in the Jewish Anti-Fascist Committee case and were shot (except Galkin) in 1952. I don’t know what common points father shared with these people. Unfortunately, this scene surfaced in my memory too late, when I was writing an article on the 100th anniversary of father’s birth and there was no longer anyone to ask...

dA bizarre attempt by Stalin at national engineering, designed as an alternative to the Zionist movement, the Jewish Autonomous Region, with the capital in Birobidzhan, was established in 1934 as the national homeland of all Jews. World Jewry, very sensibly, declined to emigrate to their “homeland,” which today has a Jewish population of under 6%. eRussian acronym for Society for Settling Toiling Jews on the Land which existed in the Soviet Union from 1925 till 1938. In 1937 the leadership of OZET and ranks were decimated in the Great Purge. In May 1938 the agency was liquidated by special order of the Central Committee of the CPSU as a “corner of various counter-revolutionary Bundist elements, turncoats and spies.” April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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Where the city of Chelyabinsk-40 will rise On July 8, 1941, two weeks after the start of the war, a special train left the platform of the Savyolovsky station, carrying Moscow medics’ children who were being evacuated to the Urals, where a children’s boarding school camp was being made for them. Upon arrival at the location – the city of Kyshtym in the Chelyabinsk region – the school was temporarily housed in a Young Pioneer camp at the foot of Mount Egoza, then at the beginning of the school year was relocated to winter quarters. These quarters were based in a vacant holiday home opposite the village of Metlino on the Techa River, 25 km from Kyshtym. Namely there later stood the closed city of Chelyabinsk- 40, where a 1957 explosion, hidden from the world, raised many tons of radioactive waste into the air... From the autumn of 1941 to the summer of 1942, I commanded the boarding school’s radio, and the stories in the following recollections relate directly or indirectly to this experience.

Extension school There was only a seven-year school in Metlino, so the older guys – about10to15people–weresentbacktoKyshtym,whichhada ten-year school. I went with them, having completed seven years of school before the war. Kyshtym, a small dusty industrial town, held little of interest, and I was enticed by my friend’s suggestion that we study the school’s program by extension. As a result, with oﬃcial permission, we returned to Metlino, where I stayed for a year, while my tempter soon went to join his mother (a doctor at a hospital on the shore of Lake Uvildy, where my mother, sister, then I later started working). I had serious ambitions to get through the program for two grades – eighth and ninth – in a single school year. This was wholly realistic: the boarding school, thank God, helped me with textbooks, I had a knack for working independently with a book, nothing distracted me from work, it was relatively warm and there was no great shortage of food. There were no problems at all with physics and chemistry, and I’d gotten through much of the ten-year school math program April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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even before the war; the humanities posed the greatest difficulties, especially foreign languages. But somehow in the late winter and early summer of 1942 I made my two trips to Kyshtym to take the exams for both grades. The teachers treated me very warmly and even maternally (there were no men among them), and I still have fond memories of school principal Berlinskaya, and especially head teacher Nina Vasilyevna. I also well recall the French teacher Olga Lvovna Dolgopolova, an evacuee from Moscow, who, I later learned, was one of the country’s leading specialists in Romance languages and had written several dictionaries. I’m unfortunately unable to recall the name of the astronomy teacher (a professor evacuated from Leningrad’s Herzen Pedagogical Institute), who constantly exclaimed while testing me, “Ah! I keep forgetting you’re in school, not university...” On the whole, all this was difficult but interesting. After a year at the same school, having gotten through the tenth- grade program in correspondence-based high school, I took the final exams as well. As a result, in the summer of 1943 I found myself holding a certificate of secondary school completion. With this certificate I went to the regional military recruitment office in Chelyabinsk in- tending to apply for military academy – and was kicked out with the words, “Take a hike until you’re drafted!” With this same certificate I returned to Moscow in the late summer and entered the Moscow Aviation Institute.

The “Collective Farmer” radio So, in the fall of 1941, I wound up in the Metlino boarding school, where I turned out to have seniority (just shy of 15). At the time, as an exception, the boarding school received permission to have a radio, and we soon found ourselves with a three-tube battery-powered superheterodyne “Collective Farmer” – the poor relative of our pre- war receivers SI-235, EChS-3 and EKL-34. It was placed along with the batteries in a special lockable chest. It should be clariﬁed that early in the war there was an order to hand in all radios (apparently due to fear of information sources outside government control). To illustrate, I’ll add that a year later, already living at the hospital and working in the school there, I found April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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a galena crystal in the waste heaps of an old mine, then wound a var- iometer coil, while my colleague, a teacher, had a condenser left over from “pre-war.” From all this we assembled a simple detector radio that barely picked up the Chelyabinsk station (90 km away). By the way, namely this receiver told us of our troops’ shift to the offensive at Stalingrad, and in our joy we roused the entire household. But in the morning the hospital’s political officer complained, confiscated the receiver and ordered an inquiry to Chelyabinsk as to whether detector receivers were allowed. The regional radio committee stated in reply, “Reproducers only”... The duty of working with the “Collective Farmer” and keeping the key to the chest was entrusted to me: I had seniority and was also considered a radio buff. Indeed, before the war for several years I belonged to a radio club, first at a House of Pioneers, then at a children’s technical station. Through this I learned about the start of the war earlier than others. It so happened that in the late evening of June 21, 1941, my friend and I, done mounting a three-tube regen- erative receiver at his summer cottage, lay down to sleep. Returning from an early morning swim, we heard from my friend’s pale and shaken father (upon waking, he’d started twisting the knobs of the receiver) that the whole world was already screaming about the Ger- man assault on Russia. Meanwhile, until noon – until Molotov’s speech – our standard radios broadcast non-stop marches... As master of the “Collective Farmer,” my duty was to listen to Soviet Information Bureau reports twice daily and post them for the general public. For this, of course, I had to adjust the antenna and ground, monitor the state of the tubes and batteries, not leave the chest unlocked and generally keep the receiver in order. All this I dutifully performed until the summer of 1942, when the batteries finally ran out, with no hope of getting new ones. Soon afterward, I left the boarding school and went to join relatives at the Uvildy hospital.

German radio I also did something “dishonest,” and want to repent. Imagine Oc- tober 1941, the German assault on Moscow, the city in a state of April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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siege, the panic of October 16 (although we learned of this later). My mother is in Moscow, and there’s been no news from her (I later learned she had tried to evacuate, returned to Moscow and then evacuated a second time). Not surprisingly, I felt very anxious about her. There was tremendous anxiety about Moscow itself. Every morning, hearing the call sign and the words, “Attention! This is Moscow...” we breathed a sigh of relief (although it’s clear now that the same words would have been said even if the Germans had reached Kuiby- shev). However, information about events on the front was clearly scarce, and what came gave no way to understand the catastrophic pace of our autumn retreat (only much later was there word of the Vyazma and Bryansk pockets, which essentially determined the situation near Moscow at the time). So, in search of more information, my friend and I decided one night, after considerable hesitation, to try picking up foreign radio. Of course, this was a gamble, if anything because we knew no foreign languages. Fortunately for us, the broadcast happened to be of Hitler’s command before the start of another oﬀensive (by the way, it was a copy of Napoleon’s orders: “Soldier, thus and such many capitals of Europe have bowed before you. Now you are at the gates of the last capital: Moscow. Warm winter quarters await you, etc.”). This was read in all the languages of conquered Europe, including Polish, Slovak and Serbian, so its meaning was clear. What we heard – ﬁghting 100 km from Moscow in the vicinity of Mozhaisk, Maloyaroslavets, etc. – coincided with our data and somewhat reassured us. But the story of that listening by night had a dramatic continuation. Soon I was summoned by our head teacher Rebecca Borisovna Slavina (whom I take this opportunity to salute for all she did for all of us, and sincerely wish her good health). She introduced the unfamiliar young man in a blazer and tie as an employee of the district Komsomol committee. Then from him I heard that they were aware of regular listening to German radio taking place at the boarding school by night, and that he expected me to explain this matter. What a shock this sent through me! I immediately realized that April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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this was no Komsomol member but an NKVD oﬃcer;f Iknewfrom mother’s repeated calls for caution that full criminal accountability begins at 12 years old, and I felt clearly that my conduct over the next few minutes would decide my fate. Usually I control myself poorly at serious moments, turn red, mumble, but here realizing the critical natureofthesituationledtoanincreaseinbothpresenceofmind and composure. As R.B. later told me, my facial expression stayed unaltered as I told him I didn’t know where he had gotten such information, that my duty, which I performed, was to receive and post reports from Moscow, that on rare occasions, when requested, I arranged for us to listen to music, but that I hadn’t picked up German radio and had no plans to do so. Apparently these words had considerable weight, and the Chekist, after a pause, muttered, “Well, all right, you can go now.” Luckily everything ended there and the incident had no consequences, not counting how long it took me to recover to a normal relaxed state (true fear only came a day later). Later I found out – I don’t remember how – we’d been informed on by the teacher on night duty who happened to be not very far from the receiver. What prompted her to expose teenagers to a fourteen-year sentence under Article 58? Apparently this was one of the terrible consequences of the era of 1937: survivors’ infection with spy mania, fear of the enemy, Pavlik Morozovg fever...

Conversations by the radio Another of my “dishonest” acts connected with the radio involved conversations with our boarding school’s accountant, whose last

f The Soviet acronym for the name of the secret police at that time. The Soviet secret police has changed acronyms like a chameleon. It started out as the Cheka, and then became the GPU, the OGPU, the NKVD, the NKGB, the MGB, and ﬁnally the KGB. Even today, however, people often simply refer to the secret police as “the Cheka” and the secret agents as “the Chekists.” gPavlik Morozov was a Soviet youth praised by the Soviet press as a martyr. According to the oﬃcial version, in 1932 Pavlik (who was 13 years old at that time) denounced his father to the authorities and was in turn killed by his family. This story was a subject of reading, songs, plays, a symphonic poem, a full-length opera and six biographies. According to modern research, the story is most likely false, although Pavlik was a real child who was killed. April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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name was Obradovich (as far as I can remember, his given name was Sergei Dmitrievich). He was a typical “rough-cut” intellectual: short in stature, graying, in pince-nez, with a modest brush mustache and old-fashioned pronunciation. The situation on the front brought us together. It was July 1942, the Germans were at Rostov and rushing toward Stalingrad and the Caucasus. S.D. was tormented by such events, knowing Russia’s fate was being decided. He thus regularly sat beside me as I received reports. Of course, we didn’t keep silent, and often, especially when unaccompanied by outsiders, spoke on very diverse topics. Above all, these were commentaries on events at the front (I gathered that S.D. had some kind of tie to the army during the First World War). I remember, for instance, that there was no direct mention of the fall of Rostov in the reports, but that its name suddenly vanished from the reports, while fighting appeared in the vicinity of Bataysk (a city past the Don south of Rostov). I suggested that perhaps the Germans had bypassed Ros- tov, but S.D. interrupted me, saying, “Don’t be a fool, don’t you see the army’s on the run...” He also asked me a lot about my parents; he had a good laugh upon learning that my grandfather in Irkutsk had hidden three escaped convicts – a Menshevik, a Bolshevik and a Bundist – then married off his three daughters to them; and he asked me many questions about my life before the war. S.D. told me a little about himself. I no longer remember exactly, but I have an impression that he and his family were subjected to some form of repression. Apparently he had a lot of pent-up feelings in his heart and was in dire need of someone to talk to. Strange as it might seem, he more than once far overstepped the bounds of caution and prudence in our conversations, essentially entrusting his fate to a 15-year-old who could have betrayed him through simple inexperience or carelessness, if nothing else. Thus, replying to my question about the reasons for our defeats in the first two years of the war, S.D. said the repression of Tukhachevsky, Yakir and othersh had been followed by

hThe Case of Trotskyist Anti-Soviet Military Organization (or the “Tukhachevsky Case”) was a 1937 secret trial of the high command of the Red Army, a part of the Great Purge. April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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that of many thousands of senior and mid-ranking commanders. He gave me to understand that although he was praying for our victory (as I understood it, S.D. was a deeply religious person), he saw the German invasion as a just – in a certain higher sense – retribution on the country’s leaders for the sacrifices (human and spiritual) the country endured in the pre-war years, and on the population for having tolerated such leaders. Concurrently he talked a lot about the totalitarian apparatus of the German Reich, the leading role of the Nazi Partyi (its cells were formed not by workplace, like ours, but by place of residence), etc. In general, S.D. led me to think that there was no significant difference between Germany and the Soviet Union and that, terrible to say, our regime was not very different from the Hitler one. The same refrain kept sounding: “Ill-fated Russia!” – meaning, as I understood it, not only 1942 but also the preceding quarter century. These conversations by the radio reinforced my critical views (these are discussed below), although of course they brought no added happiness – it became still harder to live with this burden. Why then did S.D. show significantly less caution in talking with me than the era’s harsh laws might have suggested? I’ll try to answer this question next.

The Thirties It seems to me that S.D. simply considered me trustworthy. Above all, he saw at once that I was an introvert, that I held my thoughts and emotions inside and that it took an eﬀort to bring them out. So it was unlikely that I’d simply blurt out something loosely. Most importantly, S.D. felt that in my development I stood notably nearer to him than to my peers. I realize that saying this is more likely to raise disbelief and will be seen as projecting a current mindset onto that time. Still, attempting to persuade the reader, I’ll have to step back from boarding school themes and return to pre-war times. My parents, I think, understood quite a bit – father was an old revolutionary, a Bund member who had stayed non-Party when that party merged with the Russian Communists, and mother held uni-

iThe National Socialist German Workers’ Party headed by Hitler. April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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versal human values most precious of all – but they said nothing bad about the regime in my presence. (Yet during the Great Ter- ror, when certain rare guests were constantly heard to say, “Maybe Stalin doesn’t know...” my father smirked so openly that even I, a young man, noticed it. However, I had an uncle (the fugitive Menshe- vik who had hidden at grandfather’s, see above), an intelligent and brave enough person who didn’t mince words. “We’re being ruled by a gang of bandits!” was his changeless cry, sounded when the family gathered at the table and he unfolded the newspaper, in the early 1930s. A snot-nosed six or seven year old, I of course couldn’t grasp this cry’s meaning, but it left a kind of mark in my soul. Later this mark gradually deepened. 1932 and 1933 were years of the doorbell constantly ringing, peasants with children asking for a crust of bread, the starving lying on benches along the boulevard on the way to school, you can’t tell if they’re alive, and soldiers (peasant children themselves!) rounding them up with boots and riﬂe butts. In 1932 (or thereabouts) I’m six years old; we, always hungry charges of a children’s group on Yauzsky Boulevard, stand around a boy and watch him eat dazzlingly white bread with some kind of red ﬁsh I’ve never seen before. But we do well to have a slice of brown bread with jam. “My papa is a Chekist,” the boy says proudly. 1934, December, dark outside, I’m coming back from school and stop near a news stand. “Kirov Killed” – and behind me a voice, “Well, now things will really get started, just hang on tight... Cui prodest.j” 1936 and 1937, a mass bacchanalia, family friends vanishing one by one, old convicts and exiles, heroes of the Civil War and the underground, my idols since early childhood; questioning my parents (“Could Uncle Vasya, who has a sword with a medal, really be an enemy of the people?”) and their unintelligible explanations. 1937, the Pyatokov-Radek trial, nationwide rallies demanding their execution, I’m surrounded by housewives and pensioners at the ZhAKT (currently ZhEKk), frantic faces – try saying something

jCui prodest (literally “as a beneﬁt to whom?”) is a Latin adage that is used to suggest that the person or people guilty of committing a crime may be found among those who have something to gain from the crime. My mother explained this to me. – D.K. kHousing maintenance oﬃce, a subsidiary of the regional State Housing Authority. April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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wrong, they’ll tear you to shreds. February 1938 – father’s arrest, a search of the home, a Red Army soldier rummages in my bed, Lieutenant Ogurtsov phones for a car, father is driven away.... March of the same year, the end of the Bukharin trial – during long recess at school, I’m with my friend Volodya Shumyatsky (the son of an executed Siberian Bolshevik), playing under the stairs as a janitress wipes the floor a flight above, and the radio spits out: “sentenced to capital punishment – by firing squad: Bukharin, Nikolai Ivanovich; Rykov, Alexei Ivanovich; Krestinsky, Nikolai Nikolayevich...” and the janitress mutters under her breath, “Ooh, cannibal, you haven’t drunk enough blood yet, it’s never enough for you, little tyrant!” and we hear this and exchange glances. January 1940 – father is acquitted and returns home, his health shattered after two years of investigation at Butyrka; I eaves- drop on his bare-bones stories on the nature of an “active” investigation: at the investigation’s start (for those who will go on to trial), a medical commission seeks to identify the body’s weak spots, which the investigator can then exploit; father, plagued all his life by, to put it delicately, itching, is seated on a chair with a rusty nail sticking out; he managed to make a noose, but wasn’t allowed to end his life (he died in freedom three months after his return). Early in 1941, instead of literature classes we’re taken to the Gorky Museum at his home on Spiridonyevka. The Ryabushinsky- Shechtel mansion, luxurious apartments, a marvelous staircase, a rare collection of Japanese belt decorations – “netsuke” – on which the Stormy Petrel probably spent no less than Ryabushinsky on his homes and yachts. Oh my god, great proletarian writer...! And yet another tragic event, whose horror unfolded before me gradually... The aforementioned Uncle Vasya (Vasily Sergeyevich Anuchin) had a daughter, Lyalya, my childhood friend; our mothers were girlfriends in high-school days. In 1937 her father, the com- mander of the squadron that had liberated Irkutsk from the White Guards in the Civil War, at the same time winning the young student’s heart, was arrested and soon shot (his ashes rest in Mass Grave No. 1 at the Donskoy Cemetery). A short time later, her mother was also taken away, and Lyalya, about two years older than me, was April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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taken in by distant relatives. After this she vanished and no longer appeared at our home. When I asked about her, my mother looked away in a strange manner. Later I accidentally overheard her talking with someone and learned that Lyalya, unable to bear missing her parents, bullying at school and the bitter life of an orphan staying with relatives, had shot herself with a hunting riﬂe, 15 years after her birth... All these events slowly but surely warped my mind, undermining the kinds of stereotypical attitudes and behavior mastered by my friends. Their delight in Young Pioneer symbols, in feats of Timu- ritel altruism, paper and metal recycling, conﬁdence in their happy childhood as a gift from great Stalin in the most free country in the world, convictions that the country is swarming with spies and saboteurs – I began responding to all this with a smile (and later with irritation). Although this was of course a long way from a real understanding of what had transpired with our ill-fated country in the twentieth century, what I already knew was enough to cause the loss of that uncomplicated perception of the world which a normal childhood and adolescence demands. Still, many children and teenagers separated from their parents and abandoned in children’s shelters, special children’s orphanages and even in camps had it a hundred times worse... Hopefully this excursion into the accursed pre-war years not only explains where a still completely green youth could have come up with critical views, and the nature of my older friend’s trust in me. I hope this account will convince my friends from boarding school that their senior comrade was often “sunk in thought” (as Rina Mezhebovskaya later wrote in her poem) not out of having a great mind, but rather the opposite: out of agonizing (after all, a deadly struggle against fascism was under way!) and mainly feeble attempts to answer a heap of burning questions, totally impossible

lThe Timurite movement was an ideological movement in the Soviet Union promoted via mass youth organizations of Little Octobrists and Young Pioneers. The idea of the movement was borrowed from the popular novel for youth Timur and His Squad by Arkady Gaidar. Later the Timurite movement was centralized and organized, with Central Staﬀ and Congresses. The book was an obligatory part of school curriculum in the Soviet Union. April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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to address directly and openly to those around me...

The East Ural Radioactive Trace In August 1949, the first Soviet nuclear test explosion was conducted, ending the American monopoly on nuclear weapons. The nuclear charge for this test was prepared at a top-secret plant, Mayak (also called Chelyabinsk-40, now Ozyorsk). The plant was situated east of Kyshtym (and south of Kasli, world-famous for its artistic iron casting) – the exact location of our boarding school at the beginning of the war. The plant’s construction began in 1946 – three years after the boarding school was shut down – and in 1948 it started to yield production. This was weapons-grade plutonium, built up in the first Soviet industrial nuclear reactor, which formed the heart of the plant. In addition, the plant included a number of radiochemical, chemical and metallurgy operations, where plutonium was separated from the uranium fuel rods extracted from the reactor, underwent stages of purification, metallization, etc. This technology was created in the country for the first time, under terribly rushed conditions imposed from above, and often was transferred straight from laboratory test tubes to factory shops without the necessary processing and error controls. It was of course far from perfect – foremost in terms of safety and especially ecological factors. The plant became the source of a huge amount of waste containing highly radioactive products of uranium fission: radionuclides. Radioactive waste water was dumped into Lake Karachai and the open river system of the Techa and Iset. As a result, even before the explosion, the area of these rivers’ basin (including the village of Metlino, to which the boarding school stood adjacent) became largely uninhabitable. Radiation contamination of soil, water, air and, as a result, food products, caused mass cases of radiation sickness with all its consequences – cancer, genetic mutations and other effects, impacting all sectors of the population, from the elderly to unborn babies. The plant’s more than 40 years of operation ultimately resulted in a vast area, including the Chelyabinsk, Sverdlovsk, Kurgan and Tyumen regions, becoming significantly contaminated with long- April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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lived radionuclides. The overall activity of waste from the plant is assessed at the gigantic figure of 1 billion Curie.m The environmental situation in the region deteriorated radically after September 16, 1957, when the thermal (not nuclear!) explosion of one of the storage tanks for highly active waste (long-lived radionuclides, mainly strontium 90Sr). Of the 80 tons of waste contained in the tanks, about 10% was raised in the air to a height of 1 km, with the rest scattered around the tank. As a result, a radioactive cloud took shape, moving north by northeast and forming the so-called East Ural Radioactive Trace (EURT) – a strip of territory contaminated with radiation. The total area contaminated is estimated at 1-15 thousand km2 with a population (rural) of 270 thousand at contamination density 0.1-2 Curie/km2. Although the accident at Mayak was considerably weaker than Chernobyl (the amount of radiation released was 25 times smaller, while the area of contaminated territory was 10 times smaller than in Chernobyl due to the fact that the EURT bypassed areas of urban settlement, etc.), it was a catastrophic disaster comparable in its effects to the natural cataclysms that shake humanity from time to time. Exacerbating matters, it came crashing down on the heads of a completely uninformed populace. Even the people (teachers, doctors) whose qualifications would have enabled them to grasp the nature of the incident had to subsist on random rumors. As with Chernobyl, a special and very serious psychological problem lay in radioactive danger not being “seen,” “heard,” “smelled,” etc. The illness and death of many people, genetic consequences, mass forced displacement with loss of homes, livestock, etc., the huge damage to agriculture (slaughter of livestock, withdrawal of vast territo- ries from economic circulation, etc.), the harm to organic and inor- ganic nature – this was the second blow, after collectivization, fate dealt the East Urals. The occurrence of the Chernobyl catastrophe 29 years later showed how little we’re capable of learning from the technological tragedies we ourselves cause. The state’s totalitarian

mThe Curie is a unit of radioactivity, named after Marie and Pierre Curie. One Curie is roughly the activity of 1 gram of the radium isotope 226Ra, corresponding to the emission of 1010 particles per second. April 5, 2013 15:13 WSPC/Trim Size: 9in x 6in for Proceedings 7c˙Kirzhnits-Memoir-Mant

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system and the atmosphere of absolute secrecy intensified the consequences many times over. ***** So what about the fate of the village of Metlino and its envi- rons, where the boarding school stood? The villagers began to suffer from radiation sickness and were resettled to other areas even before the accident in 1957. The accident led to the place’s catastrophic contamination, and the village was completely destroyed. Buildings were burned and buried, then the village area was flooded. The site where my boarding school friends and I spent the first two war years may now lie under rolling waves... April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

MEMORIES OF DAVID KIRZHNITS∗

B. M. BOLOTOVSKY Theory Division P.N. Lebedev Physical Institute of the Russian Academy of Sciences Leninskii prospekt, 53 Moscow 119991, Russia [email protected]

In the mid-1950s, a new staff member appeared at the Theory Di- vision of the Physical Institute of the Academy of Sciences (FIAN): David Abramovich Kirzhnits. A Moscow State University alumnus, after graduation he had been assigned to a large defense plant in the city of Gorky, where he had worked for several years as an engineer. He was “liberated” from there by Igor Evgenyevich Tamm, our department head, who managed to transfer him to FIAN. Igor Evgenyevich knew D. A. Kirzhnits – they had met in Moscow before Kirzhnits finished university. At that time Kirzhnits was performing thesis work with professor A. S. Kompaneyets as academic adviser. At his adviser’s suggestion, D. Kirzhnits consulted with I. E. Tamm on questions pertaining to the thesis topic. I. E. Tamm took a great liking for the diploma student, and he even wanted to recruit D.A. Kirzhnits for the Theory Division immediately after graduation. But at that time (1949) this proved impossible for several reasons. First, D. Kirzhnits was, as they say, an “invalid of the fifth group”a – a Jew – which during those years of violent struggle against cos-

∗Published in Russian in D.A. Kirzhnits, Works on Theoretical Physics and Recollec- tions, (Fizmatlit, Moscow, 2001), p. 348. Translated from Russian by James Manteith. aAn allusion to the so-called “entry number 5.” Soviet ID documents contained (in addition to the home address, marital status, etc.) information on ethnicity – referred to as “nationality” in the Soviet parlance – in entry number 5. “Entry number 5” became a euphemism for Jewish.

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mopolitanismb often proved an obstacle in looking for work. Second, during the years of mass repressions D. Kirzhnits’ father had been arrested on treason charges (according to the charges, he had wanted to sell the Far East to Japan). After intensive investigation his father was released, but he lived only a little longer. Reports of this also could have impeded his acceptance. Third, Igor Evgenyevich didn’t have enough weight in officials’ eyes at that time and so was unable to overcome “first” and “second.” During his spare time while in Gorky, Kirzhnits continued scientific research begun during his student days. Gorky University had a strong radiophysics department. D. Kirzhnits became acquainted with several physicists, including G. S. Gorelik, M. A. Miller and others. Some of these scientific contacts grew into friendships. This was particularly true in the case of Mikhail Adolfovich Miller, with whom D. Kirzhnits kept up a friendship for the rest of his life. In Gorky, he also met V.L. Ginzburg, who had come from Moscow to lecture at the radiophysics faculty. I don’t recall exactly, but in 1954 or 1955 D. Kirzhnits sent I. E. Tamm several of his works (on quantum electrodynamics, on the meson theory of nuclear forces – three manuscripts in all). I. E. Tamm relayed these works to his staff member Viktor Pavlovich Silin, a classmate of D. A. Kirzhnits, assigning him to talk about them at a Theory Division seminar. After V.P. Silin’s report and the ensuing discussion, it was decided to seek D.A. Kirzhnits’ transfer from the Gorky plant to the FIAN Theory Division. By then, Igor Evgenyevich had finally been elected a full member of the USSR Academy of Sciences, awarded the highest state honors (after the triumphant test of the hydrogen bomb), and he was treated with great respect by the big shots on whom D. Kirzhnits’ transfer depended. That’s how the new employee appeared at the Theory Division. When I encountered D. Kirzhnits at the Theory Division in the first days and months of his term there, I almost always noticed a certain confused expression on his face. He couldn’t believe his own luck. When you saw him, he smiled, and his smile was at once

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friendly and happy, and again somewhat confused. Like D. Kirzhnits, I had studied at the Moscow University Physics Faculty, one class younger than him. While studying there, I never had a chance to make his acquaintance, but I knew his face and heard a lot about him. He was exceptionally knowledgeable. Once in the wall bulletin I saw a humorous announcement: David Kirzhnits is offering consultations on quantum field theory for the professors and teaching faculty. Shortly after David Kirzhnits joined the Theory Division staff, we got acquainted, and this acquaintance and then our friendship and close contact over several decades occupied an important place in my life. His departure left a void that nothing can fill. Among my acquaintances from my youth, there have been many people I liked a lot at first; then with time I grew disappointed in them and my initial dispositiongavewaytoawishtokeepmydistancefromthem.This never happened in my relationship with David. Over the many years of our interaction, he never said or did anything to make me doubt him. This doesn’t mean I agreed with him about everything. We often argued bitterly about certain issues on which we took opposite sides. But as Nadezhda Yakovlevna Mandelshtam said, antipodes are points of a single space. We shared the same system of values. There are people I disagree with about many things, about many things very important for me. But nonetheless it would never occur to me to see them as antipodes. We inhabit different spaces. But my arguments with David, despite occasional sharpness, pursued a single goal – perhaps unattainable, but shared – discerning the truth. David introduced me to his wife, the beautiful and intelligent Rada Poloz. Rada’s father, Mikhail Poloz, like David’s father, had fallen under the grindstones of Stalinist repression. He was arrested and shot in 1937, and later Rada, as the daughter of an “enemy of the people,” was exiled to Kazakhstan and could return only under Nikita Khrushchev. Both David and Rada knew the actual state of things in our country much better than me; as the saying goes, they learned the state of things with their own skin. For many people, myself included, the fifties and sixties were a time of insights. Many components played a role in my insights: N. S. Krushchev’s speeches directed against Stalin’s cult of personality, the songs of April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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Galich, Okudzhava, Vysotsky and Kim,c the books of Solzhenitsyn and much more – not least of all, conversations with David. ***** In FIAN’s main building, the Theory Division was housed behind the stage of a conference hall. The rooms were on the third and fourth floors, directly above the library book archives. The space allotted to the Division wasn’t very big, and the staff was expanding, albeit slowly. Fairly soon the Division became crowded. There were several staff members sitting in each room. The only exception may have been V.L. Ginzburg’s “office” – but this was such a small room that a single person also felt crowded there. David was given a workspace which on the one hand was prestigious and on the other not quite permanent. He worked in Igor Evgenyevich Tamm’s office and sat at Igor Evgenyevich’s desk. Along with David, Vladimir Ivanovich Ritus also worked in this room. But they could only occupy their workspace in Igor Evgenyevich’s absence. When Tamm came, D. Kirzhnits and V. Ritus gathered their papers and vacated the premises – they went to the library or looked for free space in other Theory Division rooms. Often, though, Igor Evgenyevich came to discuss his findings and difficulties in the work process with David. Igor Evgenyevich Tamm occupied a very special place in David’s life. David treated no one else, except maybe his mother, with as much love and respect. It was thanks namely to Igor Evgenyevich that David had gotten the chance to do his favorite kind of work. I.E. Tamm had secured David’s transfer from his engineering job at a large Nizhny Novgorod factory to the FIAN Theory Division for work as a scientist. And after David was at the Division, Igor Evgenyevich put no pressure on him at all about choosing an area of study, granting him complete independence. Some time after appearing at the Theory Division, David decided to switch from field theory issues to problems of condensed matter physics and continue

cPopular poets, songwriters and singers, who had an immense eﬀect on the Soviet society in the 1970s and 80s. Largely ignored by the oﬃcial cultural establishment their work was not welcomed by the political authorities. April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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the work on refining the Thomas-Fermi model he had started while still in Gorky. Igor Evgenyevich’s research interests were remote from this area, but after learning of D. Kirzhnits’ plans, I.E. Tamm enthusiastically supported them. On more than one occasion, David said he regarded his move from the factory to the Theory Division as a miracle and thus revered Igor Evgenyevich as a miracle worker. In turn, Igor Evgenyevich greatly prized the depth of D. Kirzhnits’ knowledge, often discussing his own findings and research-related difficulties with him. Once, stopping by I.E. Tamm’s office, I saw a humorous note from Igor Evgenyevich to D. Kirzhnits on the desk (I quote from memory): “Kirzhnits, Kirzhnits, sweetie-pie, Kirzhnits, Kirzhnits, darling mine, Give this wretch the answer, please, I’m mixed up disgracefully!” The note meant Igor Evgenyevich needed to discuss some physics problem with D. Kirzhnits. I.E. Tamm expressed his gratitude to D. Kirzhnits at a meeting of the FIAN Academic Council on the day when David defended his doctoral dissertation. In his speech, Igor Evgenyevich praised David as a scientist, and added, “Over the last three years, I’ve been working on quantum space and time based on the hypothesis of curvature in the momentum space. During this work, I’ve received an extraordinary amount of help from David Abramovich – not only much valuable advice, but also key guidance, in the true sense of the word. I’d like to take this opportunity to thank him for this help.” D. Kirzhnits could have defended his doctoral dissertation several years earlier than he did. Strange as it seems, his passion for science interfered. After all, work on a dissertation usually amounts to sys- tematizing what had been done previously. On the one hand, such work is important and useful. In the work process, the author himself gains a better understanding of what’s already done and what still needs discerning, and besides this, he has a chance to give a clearer, more coherent account of the results he’s already obtained, and this is also very important. A scientist doesn’t write a dissertation for April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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himself; other people will read it. But there are scientists, although not many, who don’t want distractions from considering the constant stream of new interesting problems for the sake of returning to issues already explored, sitting down at a desk and writing a dissertation dedicated to things already done and understood. To some degree this dislike for distraction from new interesting problems for the sake of already answered questions was typical of David. In addition, he demanded a lot of himself. This is a common trait among many modest people. He knew his strength but subjected himself to very harsh demands. He demanded much of others, but this exactingness stemmed foremost from how much he demanded of himself. So he couldn’t decide that he’d already done enough to aspire to the academic degree of Doctor of Physical and Mathematical Sciences. If he hadn’t been under ever-growing pressure – from Igor Evgenyevich and really the whole Division staff – D. Kirzhnits would never have written his doctoral dissertation. In his day, K. S. Stanislavsky divided actors into two groups: some admire art in themselves, others admire themselves in art. A quite similar division exists among scientists: some admire science in themselves, others themselves in science. David was one of those who admire science in themselves. We also acted through his wife Rada, wanting to encourage David to write his doctoral dissertation as quickly as possible – why don’t you at least persuade him, we’d say – and until a certain time this didn’t help at all. But at last he started writing a dissertation and finished it quite quickly, based on his published works on the theory of extended particles. His defense went very well, unanimously. Igor Evgenyevich was among those at the defense. His presentation is described above. Then after the defense, at a festive banquet table which seated the entire Theory Division staff, David gave a short speech in which he basically said nothing new compared to what he had expressed before. He called his move from the factory to the Theory Division a miracle and proposed a toast to the health of this miracle’s worker – Igor Evgenyevich Tamm. Everyone joined in this toast with great pleasure, all the more so in that Igor Evgenyevich himself was sitting April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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at the table with us, rejoicing in David’s success. Igor Evgenyevich had such a cheerful smile that it was always nice to look at him, and it was especially nice this time around. FortheoccasionofDavid’sdefense,Iwroteasong–asoldier’s song, “How David Abramovich Wrote a Doctoral Dissertation.” We rehearsed this song ahead of time – Boris Leonidovich Voronov, a few other people and myself – and performed it at the banquet on the day of the defense, to the accompaniment of whistling and stamping. The banquet abounded in brilliant speeches, witty jokes, funny congratulations. Against this backdrop, the song didn’t stand out very much and was quickly forgotten. But Igor Evgenyevich turned out to have memorized several places in this song. Several years later, already seriously ill, he asked me on one of my visits, “About those song lyrics of yours, ‘Our job’s to calculate, not contemplate.’ What does that mean?” I haltingly began explaining that the song was written from the point of view of an obliging lackey. But on seeing I.E. Tamm’s merry smile, I quickly fell silent. All I was saying had been clear to him even before he asked his question.

*****

In 1960 my son was born. After giving birth, my wife didn’t work for a year, money was always running scarce, and we had to borrow. I recall with gratitude that David unfailingly lent me money and never refused. To my credit I’ll say that my debts were honestly repaid. Usually royalties for published articles and giving lectures went toward paying debts. In 1963 my wife died suddenly, leaving behind a two and a half year old son. For me this was a severe shock. I couldn’t work properly, I wasn’t thinking about work, indulging in the bleakest kind of thoughts. David and Rada did a lot then to get me out of this state. They took me with them on hikes in the countryside, and I was often a guest at their gracious home. Each meeting with them lifted my spirits. In 1964 I became a close neighbor of David and Rada. Our family – my parents, my son and I – settled on Obruchev Street, while David lived on Innovators Street. We began to see more of each April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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other. Usually I came by his home unannounced, when I turned out to have a free moment. David would put aside his work and get up from the desk where his typewriter stood, then we would go to the kitchen to drink tea. “Drinking tea” is only a figure of speech – in fact before tea, a bottle appeared on the table; David would withdraw a bottle from the fridge, Rada would put a snack on the table and sit down beside us, and the talking would begin. David was a master storyteller, a master of conversation. And he was always interesting to listen to. He talked a lot about people he knew, and he knew many interesting people. He would sometimes say: “I recently met a wonderful person!” And he’d start telling about this person and what he learned from his new acquaintance. This was always interesting and instructive. It also sometimes happened that David would meet a young physicist, John Doe, who had come for advice, to discuss his findings and hear D. Kirzhnits’ opinion of his work. David would speak with him about science, about life, and then would talk admiringly about what a wonderful person this was. A week or two after making the person’s acquaintance, David would read the dissertation the young person had left and like the dissertation less and less. In such cases, David didn’t feel disappointed about his new acquaintance and didn’t decline to offer critique, if he’d already promised. He would say: “This person is much better than his dissertation.”

*****

Once a few days straight went by without my having a chance to talk with David at work. We saw each other occasionally at the institute, said hello, and each of us ran along about our business. Seeing him, I got the impression that David was unusually silent, even gloomy. On the very ﬁrst day I was not busy, I visited him at home. At home, too, he was untalkative and behaved as if some great misfortune had befallen him. I quietly asked Rada what had happened. “Didn’t you know?” she asked. “He’s punishing himself for bad work.” And Rada told me that every few years, David would add up the balance, so to speak, of what he’d done in science in that period April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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of time. And almost every time he would severely criticize himself for not working hard enough and making little progress. In fact David worked very successfully and productively in many areas of theoretical physics. But he was so highly exacting toward himself that despite all the successes in his work, he considered his achievements insufficient. And this clearly spoiled his mood. Fortunately such fits of foul temper came rarely (once every few years) and didn’t last long. Work brought David great joy. When he talked about physics news, his face would brighten and glow with a smile of pleasure. The joy of work would chase off the bad mood. I once told him that his harsh periodic self-examination reminded me of the mental illness that goes by the name of circular psychosis. In this illness, the patient’s mental state passes through three stages with periodic repetitions: normal, manic and depressive. In the normal stage, the person behaves like all healthy people. In the manic stage, the patient takes on numerous hopeless tasks, but he himself doesn’t see his efforts’ hopelessness and is full of the rosiest plans. When all his plans suffer collapse, the patient falls into depression. He is seized by despair and indifference to his environment. Then the depression passes, the normal phase begins and everything is repeated. David heard me out and said with a smile: “That means I have circular psychosis, but without the normal stage.”

*****

In fall 1968, the Soviet Union and certain other Warsaw Pact countries invaded Czechoslovakia. The leaders of Czechoslovakia, supported by the whole society, intended to carry out a series of democratic reforms (as it was said then, “building socialism with a human face”). The troop deployment was intended to prevent such a development. The occupation of Czechoslovakia was accompanied by a loud propaganda campaign. In print, on the radio and in television broad- casts, it was said that forces hostile to peace and socialism had con- spired in Czechoslovakia to tear the country away from the socialist April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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community, that troops from the countries in the North Atlantic Treaty were ready to seize Czechoslovakia but that we had managed to outmaneuver them. Most people believed this, having no other sources of information. Still, a fair number of people didn’t believe the official propaganda and disapproved of this military action, which they thought would come to no good. However, these people kept their disapproval to themselves, fearing the inevitable persecution. A few brave people openly expressed their protest and for this were severely punished. In those days, a few representatives of the creative intelligentsia decided to appeal to the country’s leaders with a letter condemning the troop deployment in Czechoslovakia. Presumably the first to put his signature on the letter was to be Igor Evgenyevich Tamm. Igor Evgenyevich was then at his country house in Zhukovka near Moscow. He was seriously ill. The illness had led to a paralysis of the respiratory center, and after this Igor Evgenyevich had been hooked up to a breathing machine. Many people from the Theory Division staff, myself included, visited Igor Evgenyevich. I was asked to take him the letter for signing on one of my visits. The letter took up half a standard sheet of typewriter paper. The lower half was free and intended for signatures. Igor Evgenyevich immediately began to ask questions about the latest news. Everything interested him – events at the Theory Divi- sion, events in the country, events in the world. He was cut off from everyday life and eagerly inquired about everything. I told him I had brought the letter for signing. He said: “I’m signing this letter with a heavy heart. But all right, let’s play chess first, then I’ll sign it.” Igor Evgenyevich was an avid chess player. We played a few matches. I was afraid of tiring him, but after every match he proposed playing another. He would win, then I would win. The result was a draw. Finally, Igor Evgenyevich said: “All right, thank you! Now let’s have the letter.” He took the letter in his hands – his fingers obeying with difficulty – read it, paused a little and said: “You know, Boris Mikhailovich, I’ve written and signed a lot of April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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letters sharper than this one in my life, but in this case I’m not sure I should give my signature.” I asked him why, and he replied: “Because I don’t have enough information about what’s happening. Some approve of the troop deployment in Czechoslovakia, some condemn it, and I listen to them, trying to form my own opinion, and the picture still isn’t clear for me. Maybe you’ll tell me what you think?” I said that in any case, using violence is no way to solve conflicts between states. “But we’re not using any force there!” exclaimed Igor Evgenye- vich. “Our troops in Czechoslovakia haven’t fired a single shot!” I write “exclaimed,” but Igor Evgenyevich could no longer speak loudly. We spoke on exhales. Igor Evgenyevich was unable to breathe. A breathing machine did this for him. It pumped air into his lungs and then sucked it away. To be able to say anything, Igor Evgenyevich would use his fingers to pinch the tube from the breathing machine at the moment when the machine started to suck out air. While the air left his mouth, passing the vocal cords, Igor Evgenye- vich could speak. His speech was little more than a whisper. This was a painful sight. But the person talking with him soon no longer noticed all this, as Igor Evgenyevich completely preserved his charm and the liveliness of his reactions. After Igor Evgenyevich’s words about our not using force in Czechoslovakia, I didn’t know what to say in reply. After all, a troop deployment in itself already constitutes a use of force. Besides, I doubted that our troops in Czechoslovakia hadn’t fired a single shot. But I didn’t say any of this to Igor Evgenyevich. Before me lay a sick elderly man; he didn’t have the information about events to form his own opinion. So I said: “Igor Evgenyevich, if you have doubts, you don’t have to sign the letter.” “No,” said Igor Evgenyevich, “I promised. And I’ll sign.” He took a pen and signed the letter. On the way home, sitting in an empty car of the commuter train, I found myself caught up in grim reflections. I had to relay the letter April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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to the people who had given it to me. I admired these people then and admire them no less now. And I agreed with their opinion on the invasion of Czechoslovakia. But it kept troubling me that Igor Evgenyevich had signed the letter with no certainty that he was doing the right thing. So before handing over the letter, I went to David Kirzhnits for advice: what should I do? David heard me out, and we decided to return the letter to Igor Evgenyevich so he could make a final decision on whether to sign it or not. In the next few days I fell ill and was unable to visit Igor Evgenyevich. David brought him the letter. He told me later that Igor Evgenyevich had taken the letter in his hands and asked: “Will you despise me if I tear up this letter?” David assured him that he would view any decision with complete respect. Then with obvious relief Igor Evgenyevich tore up the letter. It seemed to me then, and I think the same now, that it was inappropriate to have a person in Igor Evgenyevich’s state take an action that demanded intense mental and physical efforts even from ahealthyperson. It is interesting to note one significant detail: after learning that Igor Evgenyevich hadn’t signed, all the other authors abandoned their intention to send the letter. They were ready to place their signatures on the letter under I. E. Tamm’s – so to speak, behind his back – but without Tamm they lacked the courage. Remember, all this happened in 1968, at the dawn of dissidence. People feared repercussions much more than today, and they had many reasons for this. Igor Evgenyevich lived another two and half years after this. Both David and I visited him many times and spoke with him about many things. But he never again mentioned the above incident.

*****

David appreciated jokes and generously made witty remarks himself. In 1971, I married a second time. During my nuptials David was in Uzbekistan, where he gave several lectures at Andijan Pedagogical Institute and then spent a month near Andijan at Chortak Resort, April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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a place where hot mineral waters emerge on the Earth’s surface. On the advice of our mutual friend Oganes Sergeyevich Mergelyan, David decided to rest and recuperate there, taking hot mineral baths. He congratulated me by phone from there and said he’d bring me a wedding present from Uzbekistan. David kept his promise: on arrival in Moscow, he presented me with a donkey bridle. There was no point in commentary. When I stopped by his oﬃce, he would say: “Sit down, there’s no truth in the legs.” But after I’d sit down, he would add: “But there’s no truth higher up either!” David loved jokes and enjoyed listening to them. If the joke was frivolous in content, he would also listen to the end and then ask whoever had told it: “So can you tell any jokes that aren’t about sex?” He would tell jokes himself. There were several he repeated on occasion. As a rule, these weren’t jokes so much as parables in the form of jokes. One of them was a take on the Biblical saying, “In the sweat of thy brow shalt thou eat thy bread.” David said that many people interpret this message as “Thou shalt eat thy bread until thou sweatest.” Here’s another joke I heard from him several times: “Mr. Wilson has a serious problem. He bought a new boomerang but just can’t throw away the old one.” In essence, this is a parable about how hard it is to break free of old habits.

*****

In 1969, Andrei Dmitrievich Sakharov returned to the Theory Division. In 1948, while a junior researcher at the FIAN Theory Division, he was sent to a secret site where work was done on creating a hydrogen bomb. He worked at this site for about 20 years, playing a decisive role in creating thermonuclear weapons. He came back an academician, three times a Hero of Socialist Labor and a world-famous person. He was known by then not only as the “father of the Soviet hydrogen bomb” but as the author of the remarkable work “Reﬂections on Progress, Peaceful Coexistence and Intellectual April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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Freedom.” In this work, dedicated to social issues, to the state of affairs in the Soviet Union and the world, Sakharov voiced a number of proposals aimed at ensuring the Soviet Union’s normal development while eliminating conflict between states with different social systems and shifting from confrontation to cooperation in the sphere of international relations. Many statements expressed by A.D. Sakharov in this article departed from the official Soviet ideology. For this reason, A.D. Sakharov was considered unreliable and lost his job at the secret site. Not without difficulty, Igor Evgenyevich Tamm, Sakharov’s teacher, secured a place for his unemployed student on the staff at the FIAN Theory Division. By then, A.D. Sakharov’s work “Reflections on Progress, Peace- ful Coexistence and Intellectual Freedom” had been translated into many languages and published in the West, with a total of about 20 million copies in circulation. Meanwhile, in our country it was banned. Nonetheless, typewritten copies of the article were passed around. One of these copies reached David, and he read it himself and gave it to me for a few days so I could familiarize myself with it. The article was typed on thin, almost transparent tissue paper as a carbon copy. The sheets were worn, and it had obviously passed through many readers’ hands before us. Certain places in the text were hard to decipher – we’d gotten far from the first copy. I remember that we were struck then by author’s independence: he thought the state could develop successfully and ensure its citizens decent lives only if it was built on foundations different from those it was built on for us. A.D. Sakharov wrote what he thought needed to be done for this. Many of A.D. Sakharov’s pronouncements have proved prophetic. But no one is a prophet in his own land. For me, much of what was written was new; I’d never thought about all this. David was a more mature person; the sparing comments he made in discussing what we’d read allowed me to better grasp this important work. We agreed with the article’s main content, but found the “best option” for humanity’s development proposed by A.D. Sakharov at the end to be utopian and unrealizable. And unfortunately we proved right. A. Sakharov’s and Kirzhnits’ research interests largely over- April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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lapped. Kirzhnits’ works on the equation of state of matter in extreme conditions – at high temperatures, densities and pressures – interested A.D. Sakharov, as they related to the mechanisms of a thermonuclear explosion, as well as to various scenarios of early stages of the Universe’s development. Quantum field theory, cosmology and the general theory of relativity were also in the sphere of their shared interests; both were active in these fields. So after Sakharov’s arrival at the Division his scientific communication with David became quite close. But there was also communication beyond the bounds of science. Andrei Dmitrievich was increasingly engaged in social activism. At that time (the first half of the 1970s) a person could be arrested because of a forbidden book found during a search. For this “crime” a person was then tried and sentenced to prison or a camp. The same punishment threatened those who openly expressed views counter to official morality. For such crimes, a normal person could be shut up in a psychiatric hospital. When Andrei Dmitrievich heard about such cases, he tried to ease the fate of prisoners of conscience however he could. He wrote letters in their defense to the country’s leaders, helped prisoners’ families, collaborated with their lawyers. During free minutes, Andrei Dmitrievich sometimes told the staff about certain instances of unjust persecution. One day he brought by a letter he’d written in defense of one of the prisoners and asked if anyone would care to sign the letter with him. “It’s a very proper letter; there’s nothing that could offend the leadership,” said A. D. The letter was indeed proper and moderate, pursuing only one goal – easing the predicament of a man arrested over being found with several banned books during a search. David and several others present signed the letter. After that – I don’t know how – it got onto the “voices” (the common term for Western radio stations broadcast in Russian). The letter was read aloud and the names of those who’d signed it were announced, including David. This turn of events could have had the worst consequences for David. Since the hostile “voices” had read a letter signed by him, this meant he had taken the side of our enemies. So he too should April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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be considered an enemy, with all the ensuing consequences. This was the perverse logic of the Soviet leaders. David waited with obvious tension to see what punishment would follow, and we were all worried for him. But that time he slipped by. At least when it came to outward appearances. Of course, David was put on notice by whomever and wherever was needed. Somewhat later, along with others on the Division staff, David refused to sign a letter condemning A.D. Sakharov’s social activism. That is, from the party leaders’ perspective, he behaved improperly: he signed letters that a conscious Soviet man shouldn’t have put his signature on, and refused to sign letters that absolutely had to be signed. Perhaps this explains the fact that David almost never traveled outside the USSR for science conferences. A.D. Sakharov attached great significance to his scientific contact with David. This became evident when these contacts were interrupted in connection with A.D. Sakharov’s exile from Moscow to Gorky.d When Division staff members were allowed to travel to exchange scientific information with the exiled academician, in several letters sent to Theory Division head V.L. Ginzburg and the Divi- sion’s senior researcher E.L. Feinberg, Andrei Dmitrievich requested that D. Kirzhnits be sent to him for the discussion, he wrote, of “earth-shaking” physics questions. However, at first David couldn’t get an “okay” to travel to Gorky. The situation was that every business trip to meet with A.D. Sakharov needed approval at a level higher than the directors of our Institute. I don’t know exactly what this level was, but most likely the trip candidates were affirmed by the KGB. Anyway, David initially wasn’t sent to Gorky; other staff met with A.D. Sakharov. Andrei Dmitrievich kept insisting on D. Kirzhnits visiting Gorky, and finally in one letter he announced that he refused scientific contacts if D. Kirzhnits wasn’t allowed to make this trip. He was writing these letters to the wrong address – it wasn’t up to the Division whether David could visit A.D. Sakharov. But apparently his letter had more readers than the recipients it ad-

dSakharov was arrested in 1980, following his public protests against the Soviet intervention in Afghanistan in 1979, and was sent to exile in the city of Gorky, now Nizhny Novgorod. He was allowed to return to Moscow in 1986. April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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dressed. D. Kirzhnits received permission for business trips to the city of Gorky. Over the years of A.D. Sakharov’s exile, David visited him three times. The trips to meet with A.D. Sakharov were a difficult experience for David. On the one hand it was a great honor and a rare opportunity to discuss relevant science problems with a scientist as outstanding as Andrei Dmitrievich Sakharov. And for Andrei Dmitrievich the scientific information brought by D. Kirzhnits was also important, since in exile he was in total isolation; the Gorky physicists weren’t let near him. On the other hand, it was unbearably hard to see the conditions the greatest man of our time was placed in, exiled without trial or examination, cut off from the outside world, placed under relentless degrading control by an unjust merciless authority. In the evening, after the discussions were over, David said goodbye to Andrei Dmitrievich and went to see the Gorky physicist M.A. Miller, with whom he had begun a friendship while still an engineer at the Gorky defense plant. On the way, he would buy a bottle of vodka. Misha Miller and his wife Svetlana loved David. Spending several hours with them brought him relief. Close to midnight, David would say goodbye to his friends and go to the station for the night train to Moscow. But nonetheless a joyful day arrived – thanks to Gorbachev – and Andrei Dmitrievich returned to Moscow. On the day of his return, he came to FIAN, and for all of us this was an occasion of great joy. In the first elections after A.D. Sakharov’s return from exile, David was chosen as a corresponding member of the USSR Academy of Sciences in the nuclear physics division. Andrei Dmitrievich actively contributed to this election. After returning to Moscow, Andrei Dmitrievich lived only a little while longer. But these few years were enough to dispel the fog of official lies and slander that had enfolded him for almost two decades. Those who saw and heard A.D. Sakharov could no longer believe any slander. On the evening of December 14, 1989, he died, and this was a great loss for a tremendous number of people. On the morning of the next day, David and I went to Chkalov Street to the place where Andrei Dmitrievich had lived. The courtyard entrance was April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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wide open, with flowers lying on the sidewalk along both sides of the entrance. We left our bouquets there, then took the elevator to the sixth floor. The landing in front of the entrance to A.D. Sakharov’s apartment was crowded with people. The door to the apartment was open. Andrei Dmitrievich’s body had just been taken away, but no one was leaving. Elena Georgievna passed by us, staring straight ahead with a blank gaze. Everyone made way for her. Not sure whether to approach her, we stood on the landing, then entered the apartment. There were also many people in the room from which the coffin had just been carried. We spent a few minutes in this room and left with a sense of sorrow over the tragic loss. David wrote several fine memorial articles on Sakharov, discussing both Andrei Dmitrievich’s scientific achievements and his human qualities. In addition, he was a member of the editorial board for the publication of A.D. Sakharov’s scientific works and in this capacity performed a huge amount of work despite already being seriously ill then. The collection was published in 1995.

*****

David worked intensely at home and at the institute. Whenever I visited him, I always saw him at work – in the early years holding a pen, and later at a typewriter, and still later at a computer. At home he was distracted from work when guests came to visit – he always welcomed guests. Often at work, though, on entering his oﬃce I would hear, “Excuse me, please, I’m busy,” or, if he wasn’t alone, “We’re busy.” But as busy as he was, he always found time to read the most interesting works of ﬁction – just-published books by Soviet and foreign writers, publications in literary journals and much more. If he praisedanewbook,Ialwaystriedtoreadit. “What, haven’t you read this book yet?” he would say. “Then I envy you. You still have a chance to read it.” When the novels of Kurt Vonnegut appeared, David read them with great interest, and after reading would praise them and often retell favorite parts. He very much liked Vladimov’s novel Three Minutes of Silence. But Dudintsev’s book Not by Bread Alone,which April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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I read with enthusiasm, left him indifferent. I remember that when A. Solzhenitsyn’s novel One Day in the Life of Ivan Denisovich, and then the stories “An Incident at Krechetovka Station,” “Matryona” and his little stories were published, David told me a new great writer had appeared. This wasn’t so clear to me then as it was to him. Then Solzhenitsyn was no longer published. His novels Cancer Ward and The First Circle went from hand to hand in typed samizdat copies. These copies reached me, and after reading them I understood and agreed with David that Russian literature had a new great writer, who mercilessly and with great artistic power condemned human beings’ degradation by inhuman power. Talking about Solzhenitsyn’s books, David and I vied in retelling each other the episodes we found we remembered best. Solzhenitsyn turned fifty while in Ryazan, his permanent place of residence at that time. His works were not published, and the criticism of him in newspapers was as harsh as it was unfair. David learned Solzhenitsyn’s Ryazan address, and we sent him a congratu- latory telegram. If my memory serves me correctly, we wrote, “Con- gratulations on your fiftieth birthday. Awaiting new works,” and signed. We didn’t expect an answer, understanding that many people were sending him their congratulations and he couldn’t answer everyone. At our institute’s library worked Tamara Konstantinovna Khachaturova, a remarkable woman in many respects. She knew Solzhenitsyn. David asked her to find out whether he needed material assistance. Tamara talked with Solzhenitsyn. He said he didn’t need money but that he wouldn’t refuse a few jars of instant coffee – this would help him work. In those years instant coffee was hard to buy. David tracked down a few jars and sent them to Solzhenitsyn through Tamara. In addition, Solzhenitsyn said that if we would collect money, he would give it to a typist to retype the novel The First Circle, and the typed copies would go to us. We each chipped in 120 rubles – there were five of us, including David and myself – and some time later each of us got three hefty volumes in cardboard covers. The novel took up so much space because it was typed on a typewriter with a rather large typeface, not meant for books, and on one side of each sheet. The copy I got was hardly the first, but it April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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was legible. This was a criminal offense; The First Circle was a banned book. If it was found during a search, its owner faced imprisonment. But, as they say, the devil is fearsome but God is merciful. We got away with it. Almost forty years have passed since then. Rada told me that the typewritten three volumes that went to David have survived to the present day. It’s essentially a museum piece, which speaks eloquently of the past. As for my three volumes, they almost immediate made new rounds and their tracks soon disappeared. I wasn’t upset; let people read them. ***** David’s father, the journalist Abram Kirzhnits, took an active part in the creation of the Jewish Autonomous Region (Birobidzhan) in the Far East.e In part, he was one of the founders of the newspaper Birobidzhaner Stern (The Birobidzhan Star), which was published in Yiddish. People in Birobidzhan remembered Abram Kirzhnits. Sometime in the early 1980s David was invited to Birobidzhan for a jubilee celebration of the autonomous region’s fiftieth anniversary. He was invited as the son of Abram Kirzhnits. David spent ten days in Birobidzhan. When he returned, he told me enthusiastically about the people he had met there, about his visit to the newspaper’s editorial office. He was glad that his father was remembered. David said that at the Birobidzhaner Stern offices he was struck by the typewriters: while they worked, they moved not right but left. The reason for this was that Yiddish writing goes from right to left. Later, for several years after his visit to Birobidzhan, if David happened to see a typewriter, he would often recall his impression of the typewriters set up to work in Yiddish. When he told about his trip to Birobidzhan, I asked him whether he’d encountered many Jews besides at the Birobidzhaner Stern offices. David said, “Here and there.”

eSee footnote, p. 225. April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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***** In the late 1980s and early 1990s, one of the country’s most widely read magazines was Ogonyok. One day I saw a report in the magazine about the creation of a fund that aimed to provide medical facilities with disposable syringes. At that time reusable syringes were used in our country, they were poorly sterilized, and the syringes spread infections. The fund was established, and one of the next issues of Ogonyok contained a list of those who had contributed money to the fund’s running account. The list included Kirzhnits. ***** In the years when Russia’s president was B.N. Yeltsin, freedom of speech bloomed in the country. I don’t know whether it was complete freedom of speech, but in any case, the situation in this respect was strikingly different from what it was in the pre-Gorbachev years with their comprehensive censorship. However, freedom of speech in the Yeltsin era had one characteristic feature. Typically, the authorities didn’t refute the numerous reports in the press and on television about different abuses by high-ranking officials and political figures, so there was every reason to believe the reports were accurate. On the other hand, the authorities took no action based on these media reports – no court cases were commenced, no indictments, no one was removed from the posts they held. In general, the authorities didn’t reckon with the press or television, and behaved as if the reports on abuses didn’t exist. It was as if glasnost (openness) and power existed in different dimensions. Once in a conversation with David we got to talking about this. It was still the early 1990s, in the first years of the Yeltsin presidency. David said: “The current glasnost can be defined like this: say what you want, write what you want, but I’ll do what I want.” ***** When E. Gaidar’s economic reforms began, David was full of enthusiasm and strongly supported all of Gaidar’s measures. I meanwhile quickly came to the conclusion that Gaidar’s action was pri- April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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marily destructive: it destroyed the foundations of the prior socialist economy along with everything bad and good it had contained. At the same time, Gaidar made no attempt to create any deﬁnite new system in place of the destroyed one. Such a course of action couldn’t lead to an economic upturn, and promised only chaos and destruction. In presenting my point of view here, I don’t at all insist that I’m correct, but what happened, happened – I thought that way then, and think the same now. Gaidar’s reforms were like what M.E. Saltykov-Shchedrinf spoke of: “The old temple will be destroyed, no new one will be erected, and, ﬁlled with litter, it will vanish in order to make room for another reformer who will also come, litter and leave.” David and I had long debates on this topic. David consistently spoke in support of E. Gaidar. Our mutual friend Moris Fiks was often present during these debates. He always took David’s side. In Duma elections, David voted every time for Gaidar’s faction Demo- cratic Choice of Russia. Having learned one day that I had voted not for Gaidar but for Yavlinsky, David condemned me, using several non-parliamentary terms in my address. He was devoted to Gaidar to the last days of his life. It’s not for me to judge which one of us was right. But there is a saying that reconciles everyone: vote for whomever you want, and you’ll still be sorry later.

*****

For the last few years of his life David was seriously ill. He suffered from painful asthma attacks. The asthma may have come about as a delayed consequence of his work at the Gorky plant. This plant’s production cycle included chemical reactions involving fluorine, an extremely active chemical element. From time to time it leaked. In fact, David explained that he had a thick head of hair because fluorine strengthens hair roots. However, it also apparently affects the respiratory tract. In addition, David was a smoker, and he smoked

f Mikhail Yevgrafovich Saltykov-Shchedrin (1826-1889) was a major Russian satirist of the 19th century. April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7d˙Bolotovsky-Kirzhnits

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like a chimney. He smoked not cigarettes but rolled tobacco of a single kind, Belomorkanal, until these stopped being made. After smoking one of these, he would light another a few minutes later. At seminars and scientiﬁc sessions he couldn’t sit through the allotted time without smoking; he would go back to the last rows and have a smoke, and after ﬁnishing would stick the butt in an empty match- box or a paper cone twisted up especially for this purpose, then put everything in his pocket – there were no ashtrays in the conference hall – and return to his seat. In time the asthma was joined by heart disease. David spent several months a year in the hospital. But in the hospital he also kept working intensely, as soon as the state of his health gave him the opportunity. During these years, he gave two completely new courses of lectures at the Moscow State University Physics Department – “Structure of Matter” (from Democritus to Quarks) and “At the Junction of Nuclear and Condensed Matter Physics.” He found it hard to prepare for lectures and deliver them, but took great satisfaction in lecturing these courses and in the interest shown by the audience of students and teachers. He spoke of this many times and praised the students. David had returned to teach where he had studied. In mid-April 1998, David was hospitalized. His condition was serious, and he was placed in intensive care. After a while he felt better and there were hopes for improvement. Yet these hopes were to prove unfounded. On May 4, 1998, David died. He is buried at the cemetery of the former crematorium near the Donskoy Monastery. April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7e˙Linde-Kirzhnits

DAVID ABRAMOVICH∗

A. D. LINDE Stanford Institute of Theoretical Physics and Department of Physics Stanford University Stanford, CA 94305, USA [email protected]

My parents recently found an old letter I had written them shortly before finishing the graduate program at the Physical Institute of the Academy of Sciences (FIAN) and which I myself had long since forgotten. My work was going well, but the future was unclear. I wrote that after graduate school maybe Zeldovich could offer me a job with him, but that “It’d be better if I went to the Food Institute but worked with Kirzhnits.” I admired Zeldovich; the Theoretical Division had no vacancies at the time, so this phrase appeared quite ridiculous from a practical perspective. I couldn’t know that a year later everything would take shape and I’d be hired to work on cosmology in the position opened at the Theoretical Division for the development of biophysics. But I knew I didn’t want to trade the happiness of working with David Abramovich for anything. I first heard about him in a lecture by Evgeny Lvovich Feinberg on modern physics at the Polytechnical Museum. Evgeny Lvovich was talking about how physicists were daring to encroach on the inner sanctum of modern science, the principle of causality. Basically, you’re not supposed to break the principle of causality, because then you might be able to kill your grandmother and because of this never be born. But as one poet said, if it’s forbidden, but you really want to, then it’s all right. You just have to do it at short distances and

∗Published in Russian in D.A. Kirzhnits, Works on Theoretical Physics and Recollec- tions, (Fizmatlit, Moscow, 2001), p. 387. Translated from Russian by James Manteith.

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very quickly, and make sure the consequences of this don’t ruin the properties of our macroscopic world. But how could this be? Who was working on this? It was then that I first heard about non-local theory, and heard the name of David Abramovich Kirzhnits. I heard it and immediately forgot it. But something stayed in my memory, like a smell, like a premonition of something unusual. I already knew what I wanted... A few years later, also on Evgeny Lvovich’s advice, I approached David Abramovich at the seminar and said I’d like to be his student. No, it wasn’t love at first sight, either from his side or mine. I’d never seen him before this. I’d expected to see a giant whose genius was overwhelmingly self-evident, but what I saw was a simple exceptional person, something the Theoretical Division obviously had many of. With a cigarette. He asked me what I wanted to work on. Having read all kinds of literature, which I understood only in part, I glibly said I’d like to work on either microcausality violation or the connection between cosmology theory and the theory of generalized functions. He squinted, looked at me for a long time and said, “Well, all right, to start with, calculate me the cross section of neutrino-electron scattering.” Where were my dreams?! And this was the great science for the sake of which I’d come to the seminar at the Theoretical Division every Tuesday with fear in my heart, fully aware of my nothingness but also fully aware that for me there was no going back? And instead of non-local theory and understanding the world’s structure – the cross section of neutrino-electron scattering?.. For two years I worked on this problem, and came to love it. There turned out to be much that was interesting about it. In first-order perturbation theory everything is simple, but then came renormalizations, which at that time no one knew how to do in the theory of weak interactions. And there were also double logarithmic asymptotics, the summation of soft photons... At first David Abramovich apparently hoped I’d grow tired and leave him alone; he told me he had fourteen students, that he had no time, but gradually things got more and more interesting, and he decided to apply his own invention to this problem, a method of charge differentiation which he’d used successfully in April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7e˙Linde-Kirzhnits

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his approach to non-local theories. “At last,” I thought, and set to work with new vigor. The calculations didn’t fit on usual sheets of paper. I used the backs of double-sized sheets of computer paper. The structure of the resulting expressions was too complicated, and it was necessary to come up with new graphical symbols to facilitate understanding. Then suddenly something happened that I had in no way expected: it turned out that one of the key assumptions made by David Abramovich didn’t hold in relation to this task. I was in a state of consternation. Kirzhnits couldn’t have been mistaken. And if he’d been mistaken, that would disprove the idea we’d been developing for several months. What should I do? How could I tell him about this? And what if I was wrong? God, how disappointed he’d be! All our work was leading to a dead end! I checked and double-checked, and finally decided to call David Abramovich. What awaited me came as a surprise. Understanding immediately, he said, overjoyed, “Fantastic! So situation is escalating!” There are events that can seem simple and insignificant, but which hold a hidden source of tremendous power. I was stunned. I could have expected anything, just not this. His theory was falling apart, and he said, “Fantastic! So the situation is escalating!” What else is there to say? What can a teacher tell a student about love of science, about honesty and distrust of authorities, including his own authority? There’s enough in this single phrase, which has stayed in my memory for my entire life. And the work continued – continued successfully in spite of it all. Then there was a thesis defense, it was declared the year’s best thesis at the Physics Department’s quantum theory division. I got into the FIAN graduate program and immediately after winter vacation went to see David Abramovich, proudly expecting that the time had come for me to publish my first scholarly paper. But I was again mistaken. The first phrase David Abramovich greeted me with was “Drop everything! There’s a new theory of weak and electromagnetic interactions, and we’re going to work on it!” “Drop everything!”... But what about the two years of my work, the huge sheets of paper covered with tiny writing, all my trips to see him on Innovators Street, when I’d be exhausted after several April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7e˙Linde-Kirzhnits

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grueling hours of discussions and then freeze at bus 108 stop? After all, it was good work. How could this be? “Drop everything!”? Oh, how right he was! It was the beginning of 1972, when ’t Hooft made the statement about the renormalizability of gauge theories with spontaneous symmetry breaking. It suddenly turned out these were the very theories that Fradkin, Tyutin and Kallosh were working on at the Theory Division.Nooneisaprophetinhisowncountry.Seeminglythey had been working on pure mathematics – some kind of Yang-Mills fields. But it turned out that these fields, combined with the scalar field enabling the violation of gauge invariance, are fundamental to the unified theory of weak and electromagnetic interactions. Events developed rapidly. The ’t Hooft work was only the first step, followed by the works of Fradkin and Tyutin, then Tyutin and Kallosh, ’t Hooft and Veltman. It became clear to everyone that a true revolution had taken place in science and there was no going back to the past. But a genuine understanding of the new theory did not come immediately. According to the theory, the difference between weak and electromagnetic interactions arises after a nonzero vacuum average φ appears in the scalar field. But according to quantum field theory, these averages should always exactly equal zero. Many people at the time said that the average value φ made no sense and that the spontaneous symmetry breaking mechanism should simply be understood as a heuristic trick, necessary only to guess special relations between masses and coupling constants of various fields for which the theory becomes renormalizable. At this point David Abramovich took a decisive step that provoked many people’s mistrust at the time. He pointed out the similarity between the new theories of elementary particles and the Ginzburg-Landau superconductivity theory, and said that the appearance of a non-zero vacuum average φ is comparable to the formation of a condensate of Cooper pairs. This could be taken as simply a poetic analogy, but Kirzhnits was always consistent. We know, he said, that when temperature increases, the condensate of Cooper pairs disappears and superconductivity breaks down. The same thing should occur in the theory of April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7e˙Linde-Kirzhnits

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electroweak interactions. In the early universe, when the temperature was very high, the average value of the scalar field φ must have vanished. This means that in the early universe there must have been no difference between weak and electromagnetic interactions. The difference arose only later, when the universe’s temperature became low enough. At this stage, a phase transition with the emergence of φ occurred, which as a result led to the appearance of the difference between weak and electromagnetic interactions. In the spring of 1972, David Abramovich wrote an article in JETP Letters with a description of the idea, then we sent a joint article to Physics Letters. For two years, these articles caused no reaction. People shrugged and asked where we saw temperature in the La- grangian. Here I got yet another life lesson from David Abramovich. As I said already, the first lesson was that a scientist should rejoice over a correct result, even if it conflicts with his prior convictions. Now I saw the reverse side of the same thing: a person shouldn’t bow to other people’s opinion, if he’s deeply convinced of being right. These two rules are easy to state but hard to put into practice. Where is the right line between uncritical trust in others’ opinions and ignoring what other people think? How can you learn to believe in yourself and still not become a fanatic? I saw how scrupulously and ruthlessly David Abramovich examined his own arguments, compared them with other scientists’ arguments, came to a conclusion he considered correct, and took the next step. This was the work of aMaster. My contribution to our work in 1972 was still very small; I was studying, learning the theory of phase transitions, the concept of effective potential, and Green’s function technique at a non-zero temperature. All of this finally paid off and led to the creation of the theory of high-temperature phase transitions in theories with spontaneous symmetry breaking. The corresponding formalism was developed in 1974 concurrently by Weinberg, Dolan and Jackiw, and by David Abramovich and myself. And after this – suddenly everyone believed. Another thing that helped in this was the important work by Zeldovich, Kobzarev and Okun on the occurrence of domain walls after cosmological phase April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7e˙Linde-Kirzhnits

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transitions. Seemingly the work was completely finished and it was time to move on to something else. But it turned out we were only halfway through. First, it turned out that in some cases we can’t truly speak of a phase transition and the full restoration of symmetry due to the pathological behavior of Yang-Mills fields at high temperatures. On the other hand, it appears that phase transitions can occur not only at high temperatures, but also at low temperatures, but at a high density, and also in the presence of external fields and currents. David Abramovich’s intuition, based on his knowledge of solid state physics, was simply invaluable in this. But the most unexpected result, published in our work in Annals of Physics in 1976, was the conclusion that in some cases, phase transitions are first-order transitions. They can occur as an abrupt leap from a supercooled state with unbroken symmetry, accompanied by strong energy release. We realized that the energy of the state with unbroken symmetry looks like vacuum energy, and referred to the process of energy release during first-order phase transitions as energy transfer from a vacuum into matter. At the time we didn’t know whether the theory of cosmological phase transitions would really be important for cosmology. Perhaps David Abramovich, with his characteristic honesty, would say that we don’t know this for certain even now. But it seems to me that at the moment when he first started talking about cosmological phase transitions, he must have had a premonition of the significance of his discovery. “Drop everything!” he said to me then. Now, almost thirty years later, it is possible to draw some preliminary conclusions. 1. A significant part of modern ideas about the early universe are associated with inflationary cosmology. At present this theory is the only explanation of why our universe is so large, flat, homogeneous and isotropic. Inflationary theory was proposed after the failure of all other attempts to solve the problem of relic monopoles. Monopoles arise due to cosmological phase transitions in all versions of the unified theory of weak, strong and electromagnetic interactions. 2. The first versions of inflationary theory were based on the mechanism of first-order cosmological phase transitions from a su- April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7e˙Linde-Kirzhnits

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percooled vacuum state. Means (found later) for obtaining an inflationary regime didn’t presuppose phase transitions at the initial stage of inflation, but then it turned out that similar phase transitions can occur at intermediate stages of inflation and even after it, without requiring, generally speaking, of thermodynamic equilibrium. 3. At present there are only two versions of the theory of the formation of the large-scale structure of the universe. The first option (currently the leading one) is associated with inflation. The second is associated with cosmic strings and textures formed after phase transitions in the early universe. 4. After inflation, the density of the particles, including baryons, proves exponentially small. This means we can no longer assume that the currently observable excess of baryons over antibaryons existed from the beginning. It must be assumed that baryons appeared after inflation through mechanisms based on the famous idea of Sakharov. But the study of this question by Kuzmin, Rubakov and Shaposh- nikov showed that nonperturbative processes occurring in the early universe before the phase transition, in the theory of electroweak interactions, usually lead to the erosion of baryon asymmetry, which was formed just after the end of inflation. One way to solve this problem is to consider the possible genesis of baryon asymmetry through non-equilibrium processes which could have taken place if the phase transition in the theory of electroweak interactions was strongly first order. The list could go on, but the conclusion is already clear. A significant part of modern theoretical cosmology, starting with inflationary theory and ending with the theory of the creation of matter in the universe, is somehow connected with Kirzhnits’ original idea. One could discuss the question of the role of personality in history, but judging by the attitude that his idea provoked in 1972, another few years could have gone by before its statement by anyone else. Everything described here conveys only a small part of the picture. Besides the theory of phase transitions, David Abramovich created many other things, which his other students will write about. He was interested in everything: the theory of elementary particles and cosmology, the theory of superconductivity, the crystallization of su- April 5, 2013 15:14 WSPC/Trim Size: 9in x 6in for Proceedings 7e˙Linde-Kirzhnits

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perdense matter in white dwarfs, many-body theory, the theory of chaotic processes, quark confinement, movement of monopoles in the environment, the theory of fractal dimensionality, and the connection between the violation of causality and instability. But it wasn’t just that his talent was multifaceted. There was something else which made many people relate to him with a certain special, anxious feeling. Which made his friends love to stop by his office to talk about important things and have a cup of coffee. Something not reducible to the sum of his scientific works. A certain pure note, a combination of emotional firmness and vulnerability, deep seriousness and delight in the beauty of science. I can say nothing about this better than the words of Boris Voronov: “He was a beautiful person. And he lived beautifully!” I remember my visits to his home. Rada Mikhailovna would set the table, David Abramovich would brew coffee and we would talk about different things, significant and insignificant. I remember how, returning from travel to distance places, I would feel happy that I could tell him about what was happening in the world in my field of science. I wanted to share beauty, and I knew he would appreciate this. Obviously there was something else in him which I can’t define, however much I try, and because of which I, a person generally not given to sentimentality, so love to look at his old black-and-white photograph, as if trying to continue our unfinished conversation... But I wouldn’t want to end my memories on a sad note. David Abramovich was with us, this was happiness, and we loved him. In 1986, for his sixtieth birthday, I wrote a comic song to the melody of Vysotsky’sa “That night I didn’t drink or eat,” and sang it in a hoarse and furious voice. Later that evening at his home David Abramovich asked me to sing it again. Versifying was never the strongest side of my talent, but this song evokes my memories of the joy it gave us to spend time with David Abramovich, of his home, his smile, and us, still relatively young guys then, warming ourselves by the fire of his soul.

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For a more technical review see pp. 488–523. April 5, 2013 15:21 WSPC/Trim Size: 9in x 6in for Proceedings 8c˙Gribov-Intro

VLADIMIR NAUMOVICH GRIBOV∗

Gribov was an outstanding theoretical physicist, a deep thinker. His profound insights and results, powerful theoretical constructions lie at the heart of theoretical description of soft particle collisions at high energies. They continue to be used all over the world, both by theorists and experimentalists. V. N. Gribov was born in Leningrad on March 25, 1930. In 1947 he enrolled at the Physics Department of the Leningrad State University. He graduated with honors in 1952, with specialization in theoretical physics. At first, until 1954, he had to work as a teacher at a vocational school, carrying out physics research only at spare time, at home, and attending Shmushkevich’s seminars at the Physico-Technical Institute of the Academy of Sciences of the USSR in Leningrad (PTI). In 1954 I. M. Shmushkevich and K. A. Ter- Martirosyan succeeded in getting him a job at the Theoretical De- partment of PTI, playing on a relative decline in state-sponsored anti-Semitism. Thus, he became a research assistant which allowed him to entirely focus on research. The first paper of V. N. Gribov, Interaction of Two Electrons,was published in 1953 in the journal Vestnik Leningradskogo Universiteta [Leningrad University Bulletin]. This work, on the theory of ionic dielectrics and hydrodynamics, was carried out in cooperation with L. E. Gurevich. Then Gribov’s scientific interests shifted, under the influence of L. A. Sliv, K. A. Ter-Martirosyan, and I. M. Shmushke- vich, to nuclear and elementary particle physics. His PhD dissertation on neutron excitation of the rotational levels of non-spherical nuclei was completed in 1956 under the supervision of K. A. Ter- Martirosyan.

∗This compilation is based on two articles: Ya. I. Azimov et al., Sov. Phys. Usp. 33, 872-873 (1990), and A.A. Anselm et al., Phys. Usp. 41, 407-408 (1998), and Yuri Dokshitzer, unpublished.

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In a number of papers published in 1957–1959 Gribov developed a phenomenological theory of near-threshold reactions that produce several particles. He worked out what later became a classic method of determining pion-pion scattering lengths. This work was followed by a large number of papers on analytic properties of the scattering amplitudes in quantum field theory. V. N. Gribov’s lectures on quantum field theory – a limited release of PTI – became the standard textbook for an entire generation of Soviet physicists. The decisive phase of Gribov’s scientific career started at the end of the 1950s, with regular journeys to Moscow, to attend the seminars run by L. D. Landau and I. Ya. Pomeranchuk and to discuss physics with them. Both held an extremely high opinion of Gribov’s talent. Landau treated him as his successor. Pomeranchuk’s interest in hadron collisions at asymptotically high energies can be traced back to Gribov’s influence. In 1962 Gribov became the Head of the PTI High Energy Theory Department. In the 1960s, V. N. Gribov, together with I. Ya. Pomeranchuk, was instrumental in the development of the theory of complex angular momentum, the so-called Regge theory. With remarkable virtu- osity, Gribov used the analyticity and unitarity of the S matrix and predicted that the diffraction cone in elastic hadron scattering must contract asymptotically with increasing energy; this corresponds to a logarithmic growth of the interaction radius. The American theorists Geoffrey Chew and Steven Frautschi came to similar conclusions almost simultaneously, and the French theorist Marcel Froissart derived the limit for the rate of the asymptotic growth for hadron cross sections (the so-called Froissart limit). In 1962, Gribov and Pomeranchuk, and independently the Amer- ican theorist M. Gell-Mann, showed that the Regge pole exchange leads to the so-called factorization, and established asymptotic relations between the cross sections of various processes. For example, the squared cross section of the pion-nucleon scattering must be equal to the product of the pion-pion and nucleon-nucleon cross sections. The Regge pole with the quantum numbers of the vacuum was called the Pomeranchuk pole or Pomeron. It led, in a natural way, to the Pomeranchuk theorem on the equality of the particle and April 5, 2013 15:21 WSPC/Trim Size: 9in x 6in for Proceedings 8c˙Gribov-Intro

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antiparticle cross sections for the scattering off a given target. Then a straightforward path led from the Pomeron to poles with other quantum numbers, such as those of the ω meson, ρ meson, nucleons, and so on. Research of the multiparticle unitarity constraints on complex momenta that began with Gribov’s seminal 1964 paper co-authored with I. Ya. Pomeranchuk and K. A. Ter-Martirosyan, culminated in 1967 with the development of the Gribov Reggeon field theory. Gri- bov’s analysis of scaling laws, carried out together with E. M. Levin and A. A. Migdal in the tight-binding version of the interacting Pomeron theory, played an important role in the evolution of modern theory of type II phase transitions. In 1972 V. A. Abramovskii, V. N. Gribov, and O. V. Kancheli published their famous AGK paper in which they derived the relation between multi-Pomeron contributions to the elastic scattering amplitude and the inclusive spectra in multiparticle production processes, the so-called AGK cutting rules, that underpin modern theory of the soft inclusive processes. For a long time Gribov’s papers on the Pomeron theory and inclusive processes topped the list of the most cited works by Soviet physicists. To understand what impact Gribov had on the Regge theory it suffices to list a number of classic results that bear Gribov’s name: The Froissart–Gribov partial wave decomposition; factorization theorem of Gribov and co-workers, the Gribov–McDowell symmetry of the fermion trajectories, the Gribov–Volkov conspiracy relations, the Gribov–Morrison selection rules in diffractive dissociation: the Gribov–Pomeranchuk–Ter-Martirosyan Reggeon unitarity conditions; the Gribov Reggeon field theory; the Abramovskii–Gribov– Kancheli cutting rules for the inclusive processes, etc. His studies of the Regge theory propelled V. N. Gribov into the leaders’ club of high-energy interaction theorists and brought him worldwide ac- claim. The 1965 paper by V. N. Gribov, B. L. loffe, and I. Ya. Pomer- anchuk deserves special mention. In this paper they were the first to discuss a possible increase of longitudinal distances relevant in strong interaction dynamics. This paper and Gribov’s subsequent 1973 lectures on the parton model and its connection with the Reggeon field April 5, 2013 15:21 WSPC/Trim Size: 9in x 6in for Proceedings 8c˙Gribov-Intro

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theory played a key role in the development of the current space-time picture of the inclusive processes. The idea of a relativistic increase of the secondary particle production domain is now a fundamental ingredient in theory of multiparticle production in nuclear collisions. Gribov also made significant contributions to the theory of interactions between nuclei and high-energy particles. In 1969 he developed a field theory for such processes, based on the theory of inelastic screening. Inelastic screening is of crucial importance in the estimate of the neutron cross-sections from data on interactions with deuterons. Also in 1969, Gribov formulated a model of generalized vector dominance that is now widely used in analyzing relations between photo-absorption and deep inelastic lepton scattering off nucleons and nuclei. In the late 1960s Gribov initiated an impactful program of studies of the Reggeization in quantum field theory (Quantum Electro- dynamics, QED). This is despite a general disbelief in field theory which descended on the Soviet theoretical community after Landau’s discovery of zero charge (i.e. infrared freedom of QED). In a number of groundbreaking papers written with V. G. Gor- shkov, L. N. Lipatov, and G. V. Frolov devoted to this topic Gribov and co-authors obtained a fundamental result: in QED the vacuum singularity – Pomeron – lies in the plane of the complex momenta with j>1 and corresponds to an increasing total cross-section. For the purpose of this investigation the authors basically invented a double logarithmic approximation, which became a standard tool in hard processes of this type. In 1972 V. N. Gribov and L. N. Lipatov constructed a consistent field formulation of the parton model and proposed a computational technique for evaluating deviations from scaling that occur in deep inelastic scattering and electron-positron annihilation into hadrons. In these papers, which preceded quantum chromodynamics, they were the first to derive equations for the evolution of parton distributions, which today are known as the DGLAP equations. With the advent of QCD the Gribov–Lipatov program was generalized to cover non- Abelian gauge theories. This opened a large field for theoretical activities. In 1977 Yuri Dokshitzer and independently Guido Altarelli April 5, 2013 15:21 WSPC/Trim Size: 9in x 6in for Proceedings 8c˙Gribov-Intro

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and Giorgio Parisi presented a generalization of the Gribov–Lipatov 1972-1974 results, the DGLAP equation. This was a beginning of an avalanche of papers. Of special interest is the kinematic region of soft partons which was thoroughly studied at the electron-proton collider HERA (DESY). This kinematic region was theoretically analyzed by Lenya Gribov, V. N. Gribov’s son, in his turn an exceptionally talented theoretical physicist. The death of their only child in 1984 in a mountaineering accident in the Pamir mountains was a tragic blow for his parents. The 1969 paper by V. N. Gribov and B. M. Pontecorvo on neutrino mixing anticipated many results of the wide-ranging debate on neutrino oscillations that started a decade later and culminated in the discovery of the neutrino oscillations. This was in 1969, long before the τ-lepton discovery. With the advent of QCD Gribov’s interests shifted again. He concentrated his efforts on non-Abelian field theories in the nonperturbative regime and, in particular, on the phenomenon of confinement. He was the first to point out that instantons correspond to tunneling transitions between different pre-vacua in Yang–Mills theories. Unfortunately, this paper remained unpublished. In fact, that was his habit, he never rushed to publish leaving his ideas up in the air. Another example of this type is as follows. Long before S. Hawking, Gribov insisted, in discussions with Ya. Zeldovich, that black holes must emit particles via quantum tunneling. Now this phenomenon is known as the Hawking radiation. In 1977 Gribov discovered a non-uniqueness in the quantization of the non-Abelian gauge fields, the so-called Gribov copies. The problem of the Gribov vacuum copies has not yet been completely solved till this date. In the last two decades of his life Gribov invested enormous efforts in understanding color confinement from a non-conventional standpoint. Fifteen-year long profound studies led him to the conclusion that QCD confinement in the real world is driven by the presence of practically massless quarks (u and d). In the early 1990s Gribov came up with the supercritical light-quark confinement scenario similar to a physical phenomenon known in QED under the name of April 5, 2013 15:21 WSPC/Trim Size: 9in x 6in for Proceedings 8c˙Gribov-Intro

282 M. Shifman

supercritical binding in ultra-heavy nuclei. Gribov generalized the supercritical binding problem occurring in the ﬁeld of an inﬁnitely heavy color source to the case of two massless fermions. He found that in this case the supercritical phenomenon develops much earlier. Namely, a pair of light fermions interacting in a Coulomb-like manner develops supercritical behavior if the coupling hits following critical value:a αcrit 2 = C−1 1 − 0.137. π F 3

After PTI’s split, when the Leningrad Institute of Nuclear Physics was created in 1971, Gribov became the Head of the Theoretical Sec- tion of this Institute. Now, the theoretical section of the Leningrad Institute of Nuclear Physics is staffed almost exclusively by two generations of his students. Gribov had many students in Moscow, Tbil- isi, and elsewhere. Gribov’s lectures and evening seminars at the annual Schools of Nuclear and Particle Physics held by the Leningrad Institute of Nuclear Physics always attracted an enormous audience. In 1980 Gribov moved to Moscow and became the Head of the Theoretical Physics Section at the L. D. Landau Institute of Theo- retical Physics of the USSR Academy of Sciences. The scientific achievements of V. N. Gribov brought him wide recognition. In 1971 he became the first recipient of the L. D. Landau Prize of the USSR Academy of Sciences. In 1972 he was elected as a Corresponding Member of the USSR Academy of Sciences and a Honorary Member of the American Academy of Arts and Sciences in Boston. In 1978 he was awarded the Badge of Honor.

aFurther details can be found in Yu.L. Dokshitzer and D.E. Kharzeev, The Gribov conception of quantum chromodynamics, Ann. Rev. Nucl. Part. Sci. 54, 487 (2004) [arXiv:hep-ph/0404216]. April 5, 2013 15:21 WSPC/Trim Size: 9in x 6in for Proceedings 8c˙Gribov-Intro

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Gribov’s books and monographs: • Vladimir Gribov, Strong Interactions of Hadrons at High Ener- gies, Prepared by Yu. Dokshitzer and J. Nyiri, (Cambridge Univer- sity Press, 2009); • V.N. Gribov, The Theory of Complex Angular Momenta: Gribov Lectures on Theoretical Physics, (Cambridge University Press, 2003); • V.N. Gribov, Gauge Theories and Quark Confinement,(Phasis, Moscow, 2002); • V.N. Gribov and J. Nyiri, Quantum Electrodynamics: Gribov Lectures on Theoretical Physics, with J. Nyiri, (Cambridge Univer- sity Press, 2001); • The Gribov Theory of Quark Confinement, Ed. J. Nyiri, (World Scientific, Singapore, 2001). May 10, 2013 11:57 WSPC/Trim Size: 9in x 6in for Proceedings 8d˙Frenkel-Gribov

VLADIMIR NAUMOVICH GRIBOV∗

A. FRENKEL Research Institute for Particle and Nuclear Physics Wigner Research Center for Physics, Budapest, Hungary [email protected]

V.N. Gribov was incapable of sparing himself. All his life he has acted as passionately, as intensely as he did in his youth when he worked with Landau and Pomeranchuk and led the Theoretical Physics Department of the Ioffe Institute, and later of the Nuclear Physics Institute in Leningrad. For him “leading” meant simply hiring the most talented students to join the institute and then engaging in merciless, endless but fruitful discussions with them on the problems they worked on. He did not care who was right, he cared only about the right answer. Incidentally, only in physics did he push tirelessly to reach a decision. In conversations about literature or politics as a rule he argued mildly and kindly. Not that he did not have thoughtful and firm opinions about many questions, but because he seemed to realize that in these matters different standpoints were arguable. In the beginning of the 1980s when in addition to his position at the Landau Institute in Moscow, he was appointed as a part-time scientific adviser at the Institute for Particle and Nuclear Physics in Budapest, Gribov was already known world-wide as one of the leading scientists in the theory of particle physics and in quantum field theory. Together with Bruno Pontecorvo, he had formulated the theory of neutrino oscillation; he provided basic theorems of the dispersion relations and of the non-Abelian gauge theory; he worked out the Gribov Regge calculus and made other far-reaching contri-

∗Adapted from the funeral commemoration in August 1997, published in the Hungarian Journal “Fizikai Szemle” (Review of Physics), 1997/9.

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butions to theoretical physics. In the capacity of a scientific adviser he could indeed choose to give only advices. Instead, he began then, at the age of fifty, to work on the solution of one of the most exciting problems of particle physics, namely the theory of quark confinement. He considered this to be the most important of the questions he had ever dealt with. Gribov belonged to those few who speak openly about their ma- turing ideas and about their unfinished work. This offered a glimpse into the workshop secrets of the Landau school. First a loose sketch is prepared, the ingredients of which may come from various fields of physics. In his theory of quark confinement Gribov relied on the theory of supercharged nuclei, on the theory of superconductivity and on a modified Dirac sea. Then came the mathematical elaboration, in the course of which the original sketch may undergo modifications. Gribov always tried to prove himself wrong, that the whole line of thought or some parts of it had to be changed, and indeed he did so several times. The work took almost twenty years and only near the end of his life did he feel that the time for summing up had come. He was still able to finish the first part, published under the title “QCD at short and large distances.” The second part, “The theory of quark confinement,” has been assembled by his wife Julia Nyiri and by Yuri Dokshitzer on the basis of Gribov’s notes. If the ideas exposed in these papers are right, Gribov will be among those who decoded the mystery of quark confinement. The fact that Gribov got a position at the Ioffe Institute only in 1954, two years after he finished his university studies, was probably related to the anti-Semitic course of the Soviet leadership at that time, which lasted until the death of Stalin in 1953. Later, the official promotions of Gribov were hampered by his refusal to make compro- mises he considered unacceptable. Although Landau proposed as early as in 1962 to elect the 26-years old Gribov a member of the Academy of Sciences of the Soviet Union already, he was admitted as a corresponding member only in 1972. In 1962 Gribov was permitted to participate in the International High Energy Physics Conference in Geneva, but after that he was not allowed to travel for the next 15 years, even to “socialist” countries. April 5, 2013 15:22 WSPC/Trim Size: 9in x 6in for Proceedings 8d˙Frenkel-Gribov

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In 1977 Livia Jenik, one of the organizers of the EPS Conference in Budapest, had the lucky idea to invite Gribov as a tourist. To our surprise he was able to come and he gave a talk that was not included into the program of the conference. Nor dared we to publish the talk in the proceedings fearing that then next time he would not be allowed to come even as a tourist. I got acquainted with Vladimir Naumovich during this conference. Above forty years of age friendships are rarely formed, but it happened to us. I got acquainted also with Lilya, Volodya’s ﬁrst wife and with their son Lyonya who lost his life in 1984 at the age of 27 in a tragic accident. I keep with piety the text of those songs of Vysotsky a I heard from them, written down for me by Lyonya. In the life of Volodya a much more important event happened during the conference. It was here and then that he and Julia Nyiri found each other and in 1980 they married. Theirs became a very happy marriage. It always seemed to me that they looked at each other with the same joy as in the beginning. With Pali, Julia’s son from her ﬁrst marriage, they formed a nice family. If Volodya would have known how to spare himself, perhaps he could have lived longer, but I do not think that he would have a happier and more complete life.

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V. N. GRIBOV 1930–1997∗

YURI DOKSHITZER LPTHE, University Paris VI and CNRS Paris, France [email protected]

This article is intended to make the physics world aware of the loss it suﬀered on August 13, 1997 when professor Vladimir Gribov passed away, all of a sudden, in Budapest where he was steadily recovering after a mild stroke.

***

He was Vladimir Naumovich for youngsters, Volodya for friends, BH (his Russian initials taken as Latin letters) for colleagues worldwide. His devotion to physics was so intense, his knowledge, shared with anyone willing and prepared to listen, was so deep, that I feel one can still seek his advice, discuss problems with him, try to probe new ideas from the incredible physical intuition of this man, to match them with his “picture.” I am sure that many physicists, from St. Pe- tersburg, Moscow and Novosibirsk, as well as those western theorists who knew him well, share such feelings.

***

Gribov graduated from Leningrad University in 1952, when for a young man with Jewish blood, there was not a slightest chance to get a decent job. After Stalin was gone, the paranoid anti-Semitic

∗A preliminary version of this article appeared in 1998 in [1]. A full version is ArXiv: physics/9801025.

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wave receded. With the help of Ilya Shmushkevich and Karen Ter- Martirosyan, Gribov, having served his term as a teacher at an evening school for adults, was able to start his scientific career in Russia’s first research institution — the Physical-Technical Institute (later, the Ioffe Physical-Technical Institute) in Leningrad. Soon he was recognized as an informal leader of the theory group created and cherished by Shmushkevich. This group, under Gribov’s lead, was to become one of the centers where world-class physics of the 1960’s–70’s was being developed, later to be known as the “Leningrad school.” In 1971, the theory group became a part of a new Nuclear Physics Institute (LNPI) in Gatchina, near Leningrad. In the late 1950’s, Gribov was brought to Moscow and introduced to Lev Landau. It did not take long for Dau to form a high opinion of Gribov. A special fund was created to allow a young physicist to commute from Leningrad (400 miles one way) to participate in the weekly Moscow Landau seminars. There Volodya was to meet Isaak Pomeranchuk who became his close friend and collaborator and made a great impact on Gribov the physicist. Gribov always referred to Pomeranchuk as his true Teacher. He admired Chuk’s intuition, style of doing research and his attitude to life and to physics. BH belonged to a generation of physicists, now almost extinct, for whom physics, in all its variety and complexity, was still felt as a single subject, who “had a picture,” in his words. “He has a picture,” was Gribov’s highest compliment, a universal formula ranging from appreciation to admiration. Gribov was always open to discussion. He never refused, as far as I know, to discuss a physical problem, be it of nuclear physics or elementary particle physics, cosmology or radiophysics, solid state physics or atomic physics. Not only did he know quantum physics as deeply as one can know it, he felt quantum mechanics, he thought quantum-mechanically. FSU physicists remember Yakov Zeldovich saying at the plenary session of the annual Academy meeting: “What a fool I was not to listen to what Volodya Gribov was telling me, long before Steven Hawking’s work, on why and how black holes should radiate via quantum tunneling.” Gribov was the first to interpret an May 10, 2013 11:59 WSPC/Trim Size: 9in x 6in for Proceedings 8e˙Dokshitzer-Gribov

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instanton — a classical solution of non-linear Yang–Mills equations, found by Polyakov and collaborators — as an under-the-barrier trajectory linking vacua with different topology of the non-Abelian field. This interpretation has become a common wisdom. He also came to the conclusion that classical fields (instantons, monopoles, etc.) are of little relevance for the long-standing problem of QCD color confinement (which wisdom still awaits acceptance by the community). “I am not smarter, – BH used to say, – I just think more”...

***

For decades he was not allowed to travel abroad: a free-minded person was not the KGB’s idea of a loyal citizen. One can only guess how much harm Gribov’s isolation has done to theoretical physics. Given an ever-red traffic-light on the road from LNPI to the West, many western physicists visited Leningrad in the 60’s-70’s to discuss new ideas with BH and his colleagues, to learn, and to go through the beneficial ordeal of a notorious “Gribov seminar.” This was a legendary seminar. It had no time limit and would go on as long as was necessary to establish the truth. Some visitors hated it and would never repeat that most dreadful experience of their lives; others loved it: finding the truth of the matter was at stake and the speaker would be the first to benefit. For a speaker, it was a test of self-confidence, of the depth of his or her knowledge of the subject. Equally, it was a challenge for the audience: to participate during seminars (“to work on seminars”) was one of the two unquestionable duties of the members of the Gribov theory department. (The second one being: “never refuse help to an experimentalist.”) To understand the spirit of the seminar you have to accept the notion of “aggressive friendliness.” No merits counted, no excuses were given: a newcomer and a renowned academician were treated equally, both amicably and aggressively. After 5 minutes of a smooth introduction, BH would jump to the blackboard and make his three points: what this guy is trying to tell us, why it is “all wrong” and how the problem had to be approached. This would trigger May 13, 2013 15:9 WSPC/Trim Size: 9in x 6in for Proceedings 8e˙Dokshitzer-Gribov

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a hot discussion involving all the audience (including the speaker; though, markedly, there were historical exceptions when a speaker would leave the seminar room). BH as a speaker would be given the same friendly treatment. That is, the story goes, how Lev Lipatov, now a world-known theoretician and an academician, became a co-author of the famous Gribov & Lipatov work of 1970–71 which laid the basis of a ﬁeld-theoretical description of deep inelastic scattering and e+e−-annihilation. Gri- bov was presenting his work, and the young man made a couple of “killing” comments. Gribov got stuck trying to answer Lipatov’s questions: “Lev, you are a co-author already, help me,” was the solution. Many a diﬃcult problem was cracked in this fashion, at the blackboard, in the noisy (and, in early days, smoky) atmosphere of PTI/LNPIa seminars.

***

Gribov was never an icon, and a rosy picture of this character would not be realistic, and therefore false. He had a strong personality, strong both in its rights and wrongs. It was not easy, to say the least, to argue with BH. In spite of his mind being fast, flexible and receptive, a prejudice of his could be stone solid. You would not dare to start arguing with him before making absolutely clear to yourself that the man was wrong. Such a dispute could eventually rise to a fight, sometimes reaching heights which any stratum of (physics and nonphysics) society with a minimal awareness of good manners would classify as absolutely unacceptable. To shout at your boss, though, was pretty safe: Gribov and his Leningrad colleagues always remembered the heritage of Ilya Shmushkevich: “a scientific argument cannot lead to administrative conclusions” (sounds much better in the original Soviet newspeak). Neither was Gribov always right in his vision. It took a good 10

aPTI is the acronym for the Physical-Technical Institute in Leningrad; a part of this institute later became LNPI, Leningrad Nuclear Physics Institute in Gatchina. April 5, 2013 15:22 WSPC/Trim Size: 9in x 6in for Proceedings 8e˙Dokshitzer-Gribov

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years for him to accept quarks as the true basis of hadron physics. He encouraged, though, his young students to play with a new hypothesis and discussed with them applications of the quark picture to hadron scattering. Hence, the famous Frankfurt–Levin ratio of the pion–proton and proton–proton cross sections of the early days of the quark model.

***

“When I was young I was happy to see the pieces of a lengthy calculation cancel and produce a zero result. This told me that I had been smart and had not make a mistake. Only later did I recognize that this was stupid: a good physicist should know apriorithat the answer will be zero.” This recollection of Gribov’s can tell you much about his research style, a very special way of attacking a difficult theoretical problem that he developed and used with brilliance. He had a profound knowledge and skill in using mathematical methods in physics. However, when describing his results, Gribov would not stress the mathematical difficulty, not even the mathematical beauty, of the solution he found. What mattered most was, once again, “a picture.” He would approach the problem from different angles, abstracting its essential features and illustrating them with the help of simplified models and analogues from different branches of physics, solid state physics being his favorite source of inspiration. You were led to see that the answer is correct because there is a clear physical picture behind its structure and its properties, not merely because it has emerged as a result of a derivation following the mathematical deduction rules. People unfamiliar with this style were often confused. After Gribov’s talk some felt they were being cheated: a couple of chalk drawings, a strain of hand-waving arguments, and — here you are: that’s the answer? Such listeners were not aware that they fell victim to the speaker’s generosity: for Gribov, it went without saying that the receiving party is capable of reproducing the necessary mathematical calculations and analysis, this being a default professional quality. He was talking physics. Even when a mathematical framework to envelop a foreseen physi- May 13, 2013 15:9 WSPC/Trim Size: 9in x 6in for Proceedings 8e˙Dokshitzer-Gribov

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cal answer was not developed, with the problem remaining unsolved, this would not stop him from sharing his ideas and arguments with anyone willing to listen. Physics was given top priority, ambitions put aside. “Physics goes first” was the motto. One inside story to illustrate the point — A project BH was pursuing with his student had run at some point into a rather difficult mathematical problem. The student was given a page of notes where the basic idea of how to approach the problem was briefly explained, followed by few lines of calculations. He was shocked to find out that the very first equation that the maˆıtre had written was wrong. Having done the job and having noticed that the other nine equations that followed were dead wrong as well, the student arrived at the answer. He compared it with what was written on the bottom of the Gribov note, and the answer there was the correct one. Weird though it might seem, it was neither a miracle nor an accident. Ac- cording to Alexei Anselm, for many years Gribov’s collaborator and friend, “Working with BH you had a strange feeling that numbers were his personal friends: all those factors of 2 and π simply knew their place in Gribov’s formulae.”

***

Gribov left Leningrad in 1980, on the eve of turning 50. It was a hard blow for the LNPI theory laboratory — the Gribov laboratory. It remained a group of top-class theorists but was never again the unique team that it had been. The loss for BH proved to be comparable, if not stronger. Having moved to Moscow for personal reasons, he found himself pretty much in isolation. The Landau Institute for Theoretical Physics in Chernogolovka, with which he formally became aﬃliated, had its established orderly way of things. It goes without saying that everyone respected Gribov, a “ring-bearer” of the Landau tradition. At the same time, the community as a whole was not ready to accommodate such a disturbing and virulent force: he did not ﬁt into the style of Chernogolovka seminars. Later, he lived permanently in Budapest with his new family and, in a wider world, was being warmly received in the US and Sweden, May 15, 2013 10:46 WSPC/Trim Size: 9in x 6in for Proceedings 8e˙Dokshitzer-Gribov

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France and Italy. Recently Gribov, as a Humboldt awardee, enjoyed the hospitality of the Nuclear Physics Institute in Bonn. However, no place was to be found in the West for a man about to turn 60, where he could start a new school and work in a team — a natural Gribov environment. Many a year went under the strain of personal tragedy. Lenya Gribov, the son of Volodya and his first wife Lilya Dubinskaya, per- ished in a mountaineering accident a few months after defending his Ph.D. in theoretical physics. Volodya cursed himself for having infected Lenya with his passion for mountains. Neither time nor the loving attention of wife Julia and step-son Palik could help to heal the wound. When asked by Julia what physics meant for him, Volodya said that he had realized quite early that if he made an effort he could find the truth. And therefore, he had decided, he must. He kept working, working on the most challenging problem, working with unmatched persistence and intensity which only doubled after the loss of his son. Being a perfectionist, BH would not write a paper before he had the final solution to the entire problem that he had set for himself. On August 13, 1997, Volodya Gribov concluded the process of writing up the work of his 20-year-long study of the problem of quark confinement in quantum chromodynamics.

***

Gribov’s contribution to physics deserves a special study. It suf- ﬁces to say that his name is attached to many a key notion of modern theoretical physics: Gribov–Froissart projection and the Gri- bov vacuum pole (Pomeron), factorization, Reggeon calculus, Gribov diﬀusion, the Abramovskii–Gribov–Kancheli (AGK) cutting rules,b the Gribov bremsstrahlung theorem, Gribov–Lipatov evolution equations, and many more. Gribov’s impact on modern physics is deeper than it is known to be.

bFor a technical review of Gribov’s contributions to the Regge theory, see p. 488. May 13, 2013 15:9 WSPC/Trim Size: 9in x 6in for Proceedings 8e˙Dokshitzer-Gribov

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One of his jewels “Interaction of photons and electrons with nuclei at high energies” where the space-time picture of particle interactions at high energies was established, found its way through the iron curtain. The key elements of this work were incorporated into the famous Feynman book which laid the foundation of the parton model, the Feynman–Gribov parton model. Gribov, with Alexander Migdal, developed an ingenious technique for analyzing dynamical systems with long-range fluctuations, which triggered a breakthrough in solid state physics. The physics of solids near the critical temperature proved to be similar to that of the so-called strong-coupling regime of high-energy hadron–hadron interactions. The subsequent works of the “two Sashas” — Polyakov and Migdal — and a contemporary more general AGK treatment suggested by L. Kadanoff and K. Wilson have established the scaling solution of the problem of the second order phase transitions. Gribov’s QCD studies produced a brilliant physical explanation of asymptotic freedom, based on an early observation of the antiscreening phenomenon made by Iosif Khriplovich in a prehistoric year 1969. In 1977, Gribov demonstrated the inconsistency of the standard field-theoretical treatment of gluon fields (Gribov copies, the Gribov horizon). Later he suggested the quark confinement scenario based on super-critical binding of light quarks by a quasi-Coulomb color interaction. His last works remain to be discovered, understood and developed.

***

Vladimir Gribov believed in the Truth in physics. Not that he was ana¨ıve man, but he could not (or rather did not want to) understand how some people calling themselves physicists would politely listen to and applaud “nonsense.” He thought that everyone shared his “physics goes ﬁrst” belief and was ready to put aside any political, mercantile considerations when a physical issue was at stake. In our pragmatic world such a scenario does not look very realistic. How- ever, since his commitment to physics was close to being religious, May 10, 2013 11:59 WSPC/Trim Size: 9in x 6in for Proceedings 8e˙Dokshitzer-Gribov

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we can consider it as Gribov’s prophecy for the physics world of the future.

Reference 1. Yuri Dokshitzer, V. N. Gribov, 1930-1997, in A. V. Smilga (Ed), Continuous Advances in QCD 1998, (World Scientiﬁc, Singapore, 1998) pp. xv-xxi. April 5, 2013 15:23 WSPC/Trim Size: 9in x 6in for Proceedings 8f˙Ioﬀe-Gribov-Mant

ON V. N. GRIBOV∗

B. L. IOFFE Institute of Theoretical and Experimental Physics B. Cheremushkinskaya 25, Moscow 117259, Russia ioﬀ[email protected]

No one is a prophet in his own land Vladimir Naumovich Gribov was undoubtedly the greatest theoretician of the postwar generation in the USSR. Even a short list of his major scientific achievements is impressive: the theory of threshold multiparticle reactions, Gribov–Froissart projection; shrinkage of the diffraction cone at high energies; Gribov–Pomeranchuk factorization of the contribution of Regge poles; Gribov–Morrison selection rules; Glauber–Gribov theory of diffraction scattering on nuclei; Gribov Reggeon diagram technique; Abramovskii–Gribov–Kancheli rules; the Bjorken–Gribov paradox and Gribov generalized vector dominance; Gribov-Pontecorvo neutrino oscillation; the theorem of bremsstrahlung at high energies; the Gribov–Lipatov evolution equations of structure functions; Gribov copies, and much else besides. In particle physics, he did more than anyone else in our country. But just as it’s held true for all ages and peoples that “No one is a prophet in his own land,” in the USSR (and abroad) during his lifetime, his achievements were valued much less than they deserved. Very belatedly, much later than a number of other theoretical physicists, he was elected a corresponding member of the Academy of Sci- ences, but for the rest of his life no place was found for him among

∗Published in Russian in B.L. Ioﬀe, Without Retouching. Portraits of Physicists in the Background of Epoch. (Moscow, Phasis, 2004). Translated from Russian by James Manteith.

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the Academy’s full members. Of all the awards, prizes, etc., possible in the Soviet Union and Russia, he received only one – the Landau Medal. True, he told me this was the only award he really wanted to receive. And only very rarely was Gribov invited to make prestigious rapporteur presentations at major international conferences (in the USSR only at the Dubna Conference in 1964). But there were people who immediately appreciated his talent: Pomeranchuk and Landau. In the late 1950s, N.N. Bogolyubov received a Lenin Prize nomination for the work on dispersion relations. Landau took part in reviewing the nomination materials. In his review, Landau wrote that the Lenin Prize for work on the given topic should go to Gribov, not Bogolyubov. A short time before this, Gri- bov did work on spectral representation of the vertex function in field theory, and Landau saw this achievement as much greater than Bogolyubov’s proof of dispersion relations. Note that this was at the dawn of Gribov’s career, before his famous works on Reggeistics (Regge theory) and all the rest! Of course, Landau’s review didn’t influence the Lenin Prize Committee: the prize went to Bogolyubov. It’s not hard to guess what consequences this review had for Gribov. He felt them for a very long time, perhaps even until the end of his life. Pomeranchuk was not only highly appreciative of Gribov; he just loved him. I remember the heroic time of starting work on Reggeis- tics, the joint works of Gribov and Pomeranchuk. (They collaborated on 14 papers.) For Pomeranchuk, and for all of us at ITEP, Gribov coming from Leningrad was always a cause to celebrate. Discussions began in the morning and continued into the late evening. A column of smoke would fill Pomeranchuk’s small office. Both of them, Gribov and Pomeranchuk, were desperate smokers. And after several days of work, out of chaos would come truth – those were real holidays for the heart! Pomeranchuk considered Gribov’s opinion extremely important, almost as much as Landau’s. A typical example was my joint work with Gribov and Pomeranchuk on the behavior of the annihilation cross-section of e+e− into hadrons at high energies, Pomeranchuk’s last work. This work is exceptional in his career. After the proof of April 5, 2013 15:23 WSPC/Trim Size: 9in x 6in for Proceedings 8f˙Ioffe-Gribov-Mant

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zero charge in quantum electrodynamics and meson theories, Pomer- anchuk believed, as did Landau, that “the Lagrangian is dead and should be buried with all due honors” (Landau’s words). For 10 years, Pomeranchuk developed phenomenological and analytically based methods in particle physics (the Pomeranchuk theorem, Regge theory, SU(3) symmetry, etc.). In the work in question, Pomer- anchuk returned to the methods of quantum field theory, that is, the Lagrangian. This return was difficult for him, and he wanted to be sure Gribov fully shared his views. Pomeranchuk was already seriously ill (cancer of the esophagus) and couldn’t swallow; he spoke through an amplifier. But he worked, wrote formulas! We carried on discussions. Sometimes Gribov came from Leningrad. And then, in one discussion – this was about two weeks before Pomeranchuk died – he and I (Gribov wasn’t in Moscow) concluded the work was done, the result obtained. “But,” Pomeranchuk said, “call Gribov, and if he agrees with everything, start writing the article.” I called Gribov, and he said he had doubts about the argument. I relayed this to Pomeranchuk. He responded that, although he, Pomeranchuk, had no doubts, as long as Gribov had at least a shadow of a doubt, there was no question of going forward. I called Gribov again and asked him to come immediately to Moscow. On his arrival, he and I took a couple of days to discuss our evidence and finally found a solution that settled all doubts. After this we went to see Pomeranchuk. It was Sunday, December 12, 1966. “Volodya,” Pomeranchuk asked, “do you have doubts?” “No,” Volodya said, and it seemed to me that I saw a trace of relief on Pomeranchuk’s face. But the conversation wasn’t a long one, Pomeranchuk didn’t feel well. He died on the night of Tuesday, December 14, 1966. The article had to be written without him. Scientific (and not only scientific) discussions with Gribov were always full of the intense heat of creativity, of its combustion. (I can’t find anything better than such hackneyed words.) At the same time, he was uncompromising in science. When his opinion was that a work was incorrect, it was impossible to convince him to accept or even keep quiet about it. But if as a result of discussions (often April 5, 2013 15:23 WSPC/Trim Size: 9in x 6in for Proceedings 8f˙Ioffe-Gribov-Mant

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very lengthy) Volodya agreed, you could be 100% sure the work was correct. Of course, this had its downside. Sometimes Volodya was mistaken and refused to accept a correct and sometimes even very good idea. And because his arguments were persuasive (but, as it sometimes turned out later on, incorrect) and his authority was great, people gradually relented to him. One example, very important (and distressing) for me. In the winter of 1972, after ’t Hooft proved the renormalizability of non-Abelian gauge theories, I realized the Landau–Pomeranchuk arguments about the internal contradictions of Yukawa theories (the unphysical pole of the effective charge at high energies) don’t apply to non-Abelian theories. This was the logic of my reasoning: the Landau–Pomeranchuk arguments were actually based on the Källen–Lehmann representation for the photon propagator in quantum electrodynamics (or the meson in meson theories). According to this representation, since the imaginary part of the propagator is positive, it should grow with the growth of energy, and then a pole’s appearance is inevitable. But in non-Abelian gauge theories, the gauge boson propagator is not gauge-invariant, and therefore it’s impossible to make such claims. However, I didn’t know the calculation technique for non-Abelian theories. Just then Vainshtein arrived from Novosibirsk; he knew the technique. I tried to convince him to do the relevant calculations, worked on convincing him for two days and on the third day convinced him. And here’s the catch: Gribov arrived from Leningrad and in a couple of hours made Vainshtein change his mind; Gribov argued with great confidence that non-Abelian theories will have the same pole (i.e., zero physical charge) as in quantum electrodynamics. To my embarrassment, I must confess that I overlooked Khriplovich’s earlier, published work where the calculations I needed were already performed, and Vainshtein, surprisingly, told me nothing about it. Studying the calculation technique for non-Abelian theories took time, which I didn’t have: I was due to leave for Czechoslovakia soon to start up a nuclear power plant. Gribov had a way of approaching a problem, a phenomenon, from a new, unexpected side, as a rule deeply physical, and the phe- April 5, 2013 15:23 WSPC/Trim Size: 9in x 6in for Proceedings 8f˙Ioffe-Gribov-Mant

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nomenon started to sparkle with new colors. Many examples can be cited: instantons (the idea that instantons in Minkowski space tunnel between vacuums with different topological multipliers belongs to Gribov), Gribov copies, etc. Or closer to home for me: the sum rule for γN and eN scattering (work done by Gribov, Shekhter and myself). Here Gribov managed to look at this problem from the viewpoint of Yang-Mills theory, and this made it much easier to understand. Another similar example is: Gribov’s work on the interaction of photons with nuclei and the connection of deep inelastic scattering with e+e− annihilation – the Gribov–Bjorken paradox. Finding and formulating a paradox, as Gribov was able to do, is the best way to achieve the advancement of science. At seminars, when Gribov made his presentations, he spoke while he thought (always without papers), as if inviting the participants to solve the problem along with him. In this respect he was like Pomer- anchuk, who also seemed to improvise when he lectured or spoke at seminars. (With Landau it was different: it was obvious that for him the problem was solved and that he was giving us, the ignorant, its outlines.) And seminars at ITEP, when Gribov spoke, and in the theory department at LNPI, as far as I know, almost always ran on until late in the evening. In mentioning the theory department of LNPI, I have to say that it was basically Gribov’s creation. Although I.M. Shmushkevich laid its groundwork, and this was a solid foundation, Gribov erected the whole building, and his traditions are still alive at LNPI (now PNPI). No major theoretical work, not only in particle physics, but also in other areas of theoretical physics, could leave the walls of LNPI without discussion with Gribov, and these discussions were always very productive for the authors. He also had a strong influence on experimental research at LNPI. The situation changed when Gribov moved to Moscow. I think this was (at least for the first few years after the move) a difficult, maybe even dramatic period in his life. Life in Moscow was completely different from that in Leningrad: here a greater role was played by various relationships peripheral to science and sometimes by even intrigues, the scientific hierarchy. One thing or the other was forbidden. Gribov wanted to stay free of this, but on the other hand, April 5, 2013 15:23 WSPC/Trim Size: 9in x 6in for Proceedings 8f˙Ioffe-Gribov-Mant

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a life that totally ignored all this was impossible. His tie with the school he’d established in Leningrad weakened, despite supportive efforts on both sides. On the other hand, his scientific contacts in Moscow, although established, weren’t as close as in Leningrad. Fi- nally, in Leningrad, Gribov belonged to the overall intellectual elite, not only in physics or science: he knew and met with many different people, and many knew him. In Moscow there was none of this. Here in general the notion of an intellectual elite is much less clearly defined – a lot depends on a person’s closeness at a given time to those in power. On top of all this there was the tragic, senseless death of his son Lenya in the Pamir Mountains: he fell, broke through into a crevasse on a peaceful glacier, and was already dead when they pulled him out. I feel my own share of the blame for this accident. For several decades I spent time in the mountains, and then my son started to do the same. We were friends of Lenya’s. Our example may have somehow influenced him, and he took this up as well, although physically his preparation was worse. And here I want to return to where I started. All of us, close friends and colleagues of Volodya Gribov, should feel a sense of guilt that in Russia he never had the esteem or recognition his achievements deserved. This lack of recognition, of course, affected his mood. And I would like what I’ve written here to have resonance as my belated words of repentance. April 5, 2013 15:24 WSPC/Trim Size: 9in x 6in for Proceedings 8g˙Gershtein-Gribov

IN MEMORY OF A FRIEND∗

S. S. GERSHTEIN Institute for High Energy Physics Protvino, 142281 Moscow Region Russia [email protected]

It is really hard to write about Volodya. There are no words that can express my admiration for his talent and the charm of his outstanding personality. Time cannot soothe the pain of his untimely death. The passage of time only makes it worse, especially for the scientific world. The achievements which make Gribov a remarkable person are very well described in the previous articles of Yu. Dokshitzer and others. So, I will instead dwell on our – Volodya’s and mine – personal interactions and impressions. The first time I saw Volodya in was 1957 or 1958 at a seminar hosted by Landau, who was my post graduate supervisor at the time. I remember a young man, whom I had not seen before, stand up during the talk and start firing questions at the speaker. And the latter found it difficult to satisfy the young man with his answers. Landau took the young man’s side and agreed with his objections to the speaker. This inquisitive young man was Volodya. I got to know him better when in 1958 after completing my doctorate degree I came to work at Leningrad Physical-Technical Institute (PTI).a The atmosphere at the Theoretical Department was really pleasant. The Head of the Theoretical Department Ilya Mironovich

∗First published in Gribov–80 Memorial Volume, Eds. Yu. Dokshitzer, P. Lévai and J. Ny´ıri, (World Scientific, Singapore, 2011), p. 6. aCurrently A.F. Ioffe Physical-Technical Institute of the Russian Academy of Sciences in St. Petersburg.

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Shmushkevich, the friend of I.A. Pomeranchuk, was sticking to Lan- dau’s school and followed its traditions. One of the important elements of the Theoretical Department was seminar activity. Shmushkevich tried to clarify every aspect of a given issue in depth, and therefore the seminars went on for hours and involved lots of argument. Gradually Gribov, took the leading role and was the one who could clearly define the problems, and on most occasions find solutions to them. Those attracted to the seminars were not limited to the Theoret- ical Department. Ludwig Faddeev was one such who would attend them, and used to give a comprehensive explanation to mathematical problems that arose. People in the Department worked in a very warm atmosphere of understanding. We were young and tied together by interest in science and close friendship. I remember our amicable feasts. Sometimes we were invited by Shmushkevich to his place. I still remember those friends who are alive and those who passed away. Besides Volodya there were V. Shekhter, A. Anselm, I. Dyatlov, S. Maleev, Yu. Petrov and others. We – Volodya and me – made friends at once. Neither of our scientific career was smooth. Upon graduation from the University we had a hard time finding a job in a scientific institution. Volodya started as a teacher at an evening school, and I became a teacher in a village school 100 km from Moscow. However, after Stalin’s death the situation gradually changed. L.D. Landau (who was the one to test me on his theoretical minimum) was able to take me to a graduate school, and K.A. Ter-Martirosyan demonstrated his strong willpower by ensuring the acceptance of Volodya by PTI.b Apart from our professional struggles we had a similar family situation: we both had young sons and enjoyed exchanging our fa- therhood experiences. Volodya had a very rare talent for evaluating new works. He showed interest in other topics, not always connected with his own work. He would go deeply into the matter, find good qualities of

bIn 1971 PTI’s High Energy Physics Department was reorganized. Currently it is known as Petersburg Nuclear Physics Institute in Gatchina. April 5, 2013 15:24 WSPC/Trim Size: 9in x 6in for Proceedings 8g˙Gershtein-Gribov

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the work (if there were any) in addition to its weak points. His remarks, if the author listened to them, often led to new turns in research. Kind-hearted, he was intolerant both towards scholasticism and unreasonable results. In this respect he took after Landau. A few years later, when Volodya started working with I.Ya. Pomeranchuk, the latter said: “You can hardly imagine the pleasure of working with Volodya. He very much reminds me of Landau.” Volodya himself set high standards for his works. He never wanted to publish them as fast as possible, instead taking his time searching for additional proofs of his findings. I remember 1958 when I arrived in Leningrad and met Volodya. He was discussing the representation that determined analytical properties of the scattering amplitude over two variables, i.e. energy and momentum transfer, and was looking for convincing arguments in favor of the one. What he told me (and it was not published) coincided in essence with the Mandelstam representation that appeared the same year. Hence Volodya was well-prepared to use it and obtained the results, considered nowadays classical, on the asymptotical behavior of hadron scattering amplitudes at high energies. Yu. Dokshitzer and L. Frank- furt wrote about this in the preface to the book Gauge Theories and Quark Confinement.c In 1960 I started to work in the Joint Institute for Nuclear Re- search in Dubna. Several experiments on weak interactions that were rather interesting to me were being prepared there. However, Volodya and I continued to keep in touch. He often visited Moscow and stayed there for long periods of time. The results obtained by Volodya greatly impressed Landau and Pomeranchuk. Landau thought that Volodya’s approach was a way out of the tight corner the quantum field theory found itself in after the discovery of the “zero-charge.” From his point of view unob- servable quantities should have been taken away from the theory. Among them were field operators ψ and, consequently, the Hamil- tonian, which could be constructed only from the field operators. Following Landau’s ideas, the theory should be based on scattering

cV.N. Gribov, Gauge Theories and Quark Conﬁnement, (Phasis, Moscow, 2002), p. xv. April 5, 2013 15:24 WSPC/Trim Size: 9in x 6in for Proceedings 8g˙Gershtein-Gribov

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amplitudes with their properties: analyticity (causality), unitarity and crossing symmetry (relativism). Volodya’s results quite obviously pointed to the fruitfulness of such an approach, and gave extremely interesting predictions (for example, one pointed to the shrinkage of the diffractive cone in hadron scattering, i.e. to the growth of the hadron interaction radius with energy). Landau highly appreciated Volodya’s talent, his command of and devotion to science. I remember him saying many times that he would continue writing his course on theoretical physics with Volodya. It happened when Landau regained consciousness in the hospital after the accident. Everyone who knew Volodya noted his terrific intuition. There are many examples: the physical interpretation of the instanton, his remarks that in non-Abelian theories antiscreening was quite possible, his space-time picture of interactions, which was the predecessor of the quark-parton model, etc. Not all such remarks were appreciated by Volodya’s colleagues at the time, however. In 1965 S. Alliluev, A. Logunov and I managed to explain the behavior of hadron scattering at large angles, which had been established by Jay Orear, with the help of the model of scattering on Gaussian potential. In this model perturbation theory approximations grow at first, but then decrease. Summing them up, we obtained the required law. When in Leningrad I asked Volodya if it was possible to obtain the required result in the -plane. “No problem” was the response. “These are branchings, they should be able to explain this phenomenon perfectly well.” Our conversation took place in a small room right before a theoretical seminar. There were a lot of people present, but Volodya’s remark did not seem to interest anybody. It was only a few years later, that A. Anselm addressed this question in his doctorate thesis and derived the Orear law by summing branchings in the -plane (he did not even remember Volodya’s remark). Volodya not only had an amazing intuition in physics, but also was able to create the necessary mathematical apparatus. In 1968 my ten year old son and I, together with Volodya, his April 5, 2013 15:24 WSPC/Trim Size: 9in x 6in for Proceedings 8g˙Gershtein-Gribov

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wife Lilya and their son, went to the Caucasus on a guided tour, to the Chegemskoe Clove not far from Nalchik. Volodya took a tiny wireless radio with him, and one night we heard over the radio the news about American astronauts landing on the Moon. We were so happy and proud of this achievement. However, that over-the-top news was soon followed by alarming news – clouds started to gather over the “Prague spring,” and people’s hope for the “socialism with a human face” began to fade. Our hike ended at the other end of Chegemskoe Clove at the foot of the main Caucasian range. I sent my son back to Moscow by plane, where my mother was to meet him. I started for a mountaineers’ camp near the Adyl-Su, a tributary of the Baksan River.d Between the two cloves – Chegemskoe and Adyl-Su – there is the famous Baksan neutrino observatory, where experiments on solar neutrino detection were later carried out. On my way back I dropped in the post oﬃce in Baksan and was given a cable. “We are in Mestia. Volodya has had a heart attack.” I was just shocked. The cable had been sent about a fortnight earlier. I decided to start for Mestia immediately. It would have taken too long to reach the place by any means of transport, which meant that I had to go by peripheral roads. I returned to our camp to collect my documents, and immediately left the camp to pass through the Adyl- Su passage. I did not have any mountaineer’s equipment, so I had to literally crawl over shabby ice bridges across clefts. Finally I passed the cleft, but had to walk along the big glacier known as Leksor. It was only late in the evening that I reached the path leading to Mestia. In the suburbs of Mestia (the capital of Svanetia, Georgian region) I met with Yura Petrov. It was quite unexpected. Upon learning from a mountaineers group who left the camp a few hours earlier that I was on my way to the town, he had decided to meet me. I would like to spend a few words regarding Yura Petrov. He was one of the most faithful Volodya’s friends. In the winter of 1941–1942

dAdyl-Su is the river in the Caucasus originating from Jankuat and Bashkara glaciers. Adyl-Su can be translated from Balkarian language as splendid, beautiful. The adjacent valley in the Main Caucasus Range carries the same name. April 5, 2013 15:24 WSPC/Trim Size: 9in x 6in for Proceedings 8g˙Gershtein-Gribov

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his parents starved to death during the Nazi Siege of Leningrad. Yura was twelve years old at that time. He was evacuated together with other children from the orphanage to the Caucasus. In the summer of 1942 the Caucasus was occupied by the Nazis. Yura ran away and became a homeless child. After the war he attended an industrial school, then a technical college, and finally a university. He was hired in memory of his father (also a physicist) by the Physical-Technical Institute, but the level of his knowledge was not sufficient. He was in charge of performing numeric calculations of a nuclear reactor under plans for construction. However, in a short time Yura brilliantly mastered the physics of reactors, and in the end became one of the most qualified specialists. In the 1970s he designed (along with Konoplev) the PIK reactor with a unique 1015cm−2sec−1 neutrino flux. Today this reactor is fully operational. Having learned of Volodya’s disease, Yura immediately took a plane from Leningrad. When I arrived, Volodya felt quite well. He was given a separate room in a tourist camp. People around him treated him very warmly. The doctor who treated him was an excellent specialist, and Volodya said that the pain in his heart ceased when she came. Svanetia used to be an isolated area behind a remote dale at that time, but when enlightenment reached it, many people were carried away with it. (For example, there was a worker in the camp whose name was Edison, and his brother’s name was Newton). Volodya and I continued discussing a recently published work by Veneziano, which we had begun to consider in Chegemskoe. We kept discussing politics too. It seemed that everything was looking better. But then there was the first warning bell... I returned to Moscow on the 21st of August and was shocked when I saw a newspaper that said the countries of the Warsaw Pact had moved troops into Czechoslovakia. In March 1980 I was headed to visit Leningrad to celebrate Volodya’s 50th anniversary when I heard that he was in Dubna. I came to Dubna and saw a completely happy and a bit embarrassed Volodya, and learned about the changes in his life – his new marriage. I was very glad about his happiness and the fact that he was able to win it. I had known Julia Niyri for a long time, having met April 5, 2013 15:24 WSPC/Trim Size: 9in x 6in for Proceedings 8g˙Gershtein-Gribov

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her in Hungary at the neutrino conferences and was glad about their union. On the 25th of March, Leva Okun, Arkady Migdal and his wife Tanya, Volodya’s sister Inna, Julia’s friend Livia, and I happily celebrated Volodya’s 50th birthday. I am sure that it was Julia who was able to save Volodya from the terrible shock connected with the death of his son, Lyonia. Volodya loved him very much, and Lyonia himself had been doing very well and had carried out a brilliant work in theoretical high energy physics shortly before his death. When Volodya and Julia settled in Moscow, I often visited them on my way back from the lectures at Moscow Physical-Technical In- stitute. Volodya’s head was filled with new ideas. We spoke a lot about his quark confinement model, the role of massless quarks, the importance of non-Abelian symmetry, and the nature of the chiral anomaly. I think it was easy for him to discuss these things with me because I never keep to any doctrine and always try to understand a given physical idea. Besides, Volodya knew about our work with Yakov Borisovich Zeldovich on supercritical nuclear charges, and made use of it. To explain the nature of the supercritical vacuum he developed an analogy with a remarkable effect known in condensed matter physics: the Andreev reflection. He did not hasten to report in writing the findings of (nearly) complete works, but rather took his time thoroughly thinking them over. He liked a phrase said, I think, by Ingmar Bergman: “My film is practically ready. All I have to do is to shoot it.” Unfortunately, Volodya did not have time “to shoot” a lot of things, and after his death Julia and Yu. Dokshitzer had to do a heroic work: to compose his articles according to his notes. I liked to visit Gribovs’ hospitable house, discuss different questions about life, and talk to growing Pal,e who was so loved by Volodya. I remember our meeting at the University of Minnesota, where Volodya came earlier than he had planned because he learned that I had to leave to return to Moscow in time. He had just recovered from

eGribov’s stepson. April 5, 2013 15:24 WSPC/Trim Size: 9in x 6in for Proceedings 8g˙Gershtein-Gribov

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his illness, but as usual he smoked a lot (lighter cigarettes, though). In the morning we went to a workshop where Volodya showed his typical features of character. He could not be indiﬀerent as far as science was concerned. He hated pseudo-science and was able to criticize a speaker severely. In this instance, the way the question was put and hence the result obtained, seemed absurd to him. He felt so nervous that he left the workshop. That is how I remember him: talented, full of passion, and wise. April 5, 2013 13:33 WSPC/Trim Size: 9in x 6in for Proceedings 9a_Chap8-divider

CHAPTER 8 May 10, 2013 11:12 WSPC/Trim Size: 9in x 6in for Proceedings 9a_Chap8-divider May 13, 2013 15:48 WSPC/Trim Size: 9in x 6in for Proceedings 13˙Index

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ANATOLY IVANOVICH LARKIN∗

Anatoly Ivanovich Larkin – Tolya to his friends and colleagues – was born on October 14, 1932, in the small town Kolomnaa in central Russia. Later Larkin’s family relocated to Novosibirsk and then to Moscow. At the age of 17, Tolya was admitted, as physics major, to Moscow Mechanical Institute which in 1953 became Moscow Engi- neering Physics Institute. He was a student of Igor Tamm, Mikhail Leontovich, Isaak Pomeranchuk, and Arkadii Migdal. After two years of research under Andrei Sakharov’s guidance,b he joined Migdal’s group at the Kurchatov Institute.c His ﬁrst research paper was written under A. D. Sakharov’s supervision. In the Kurchatov Institute, Larkin joined the group led by Migdal, which at the time included B. T. Geilikman, V. M. Galitsky, S. T. Belyaev, and V. G. Vaks. That was the time when theoretical physics had not yet split into many narrow branches; following the example of their teachers, young scientists worked successfully in various ﬁelds. In his early papers, Larkin applied the newly developed Matsubara diagrammatics to the calculation of the thermodynamics of plasmas and the energy losses of fast particles passing through them. In a series of joint publications with Migdal, Larkin used the Landau Fermi-liquid theory to describe the atomic nuclei properties. In the beginning of the

∗This compilation is based on K. B. Efetov et al., Phys. Today 59, 88 (2006), A. A. Abrikosov et al., Physics – Uspekhi 48, 969 (2005), and Alexander I. Larkin, unpublished. aKolomna is an old town situated at the conﬂuence of the Moskva and Oka Rivers, 114 kilometers southeast of Moscow. bAndrei Dmitrievich Sakharov, the recipient of the 1975 Nobel Peace Prize, an outstanding theoretical physicist, later a dissident and human rights activist, was one of the fathers of the Soviet hydrogen bomb. For recollections of this two-year period in Larkin’s life see pp. 74–77 and 329. cThe Kurchatov Institute is Russia’s leading research and development institution in the ﬁeld of nuclear energy.

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314 M. Shifman

1960s, his attention turned to the theory of superconductivity; it became his lifelong passion. In 1966, he moved to the newly organized L.D. Landau Institute for Theoretical Physics in Chernogolovka, near Moscow, which became his home for the next 25 years. In 1995, Larkin moved to the William I. Fine Theoretical Physics Institute at the University of Minnesota, where he was offered a Chair in theoretical condensed matter physics. His favorite summer pastime was intertwining physics and hiking either in Chernogolovka or Aspen, Colorado. The ties with the Landau Institute did not break after 1995, when Larkin assumed the professorial position at the Univer- sity of Minnesota. Following the development of the Bardeen–Cooper–Schrieffer (BCS) theory of superconductivity in 1957, Larkin began his studies of that subject, which was to become his lifelong passion. Although he made a significant contribution to particle and nuclear physics and to the theories of phase transitions, magnetism, and disorder, it was superconductivity to which he kept returning and in which his impact was truly outstanding. Among his greatest achievements are the prediction of the fluctuation-driven enhancement of conductivity above the critical temperature Tc, the theory of the Josephson effect in superconductor-normal metal-superconductor junctions and in superconducting point contacts, the prediction of pairing with finite momentum, a semiclassical theory of nonequilibrium phenomena including nonlinear flux flow, the theory of collective creep, and ther- mally activated flux dynamics in high-Tc materials. On many of the above problems Larkin worked with his students. In 1961, Valentin Vaks and Larkin suggested that the properties of soft pions could be explained by a BCS-like spontaneous breaking of the chiral symmetry. Practically at the same time and independently, Yoichiro Nambu, the 2008 recipient of the Nobel Prize, arrived at the same conclusion. Later this concept proved to be an important step toward the creation of the standard model of particle physics. Nambu’s achievement is widely known (see e.g. the collection [1]) and was recognized with the Nobel Prize, while Vaks and Larkin’s work, published in JETP [2], is known to very few. In 1964, Larkin and Yuri Ovchinnikov treated, for the first time April 5, 2013 15:36 WSPC/Trim Size: 9in x 6in for Proceedings 9b˙Larkin-Intro

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ever, the formation of the Cooper pairs with nonzero momentum; the importance of this result was to be properly appreciated only much later. In a 1969 paper, Larkin solved the problem of the singularity of thermodynamic functions at the type-II phase transition in uniaxial ferroelectrics. It was the first successful application of the renormalization group in condensed matter theory. The paper was crucial in the development of the theory of critical phenomena. Larkin also made a great impact on the physics of one-dimensional metals. His calculations of the Green’s functions of fermions and the correlation functions of density and spin density laid the foundations of the modern theory of the field. His further contributions included applying the theory of collective pinning to the dynamics of charge density waves, and developing the theory of the thermal activation of Frölich’s conductivity. In the theory of disordered conductors, Larkin and his collaborators initiated several new research directions: weak localization, mesoscopics, and quantum chaos. In the last two decades of his life, Larkin worked on the theory of high-temperature superconductivity (jointly with L. Ioffe), the theory of vortex states (jointly with J. Blatter, V. M. Vinokur, V. B. Geshkenbein, and M. Feigelman), the theory of fluctuations (jointly with A. A. Varlamov and V. M. Galitsky), the physics of nanos- tructures (jointly with L. I. Glazman and K. A. Matveev), and the theory of diffusion and chaos (jointly with I. L. Aleiner and S. Tuan). Larkin’s decade in Minnesota was prolific. During this time he published over 50 papers, some of them milestones in condensed matter physics. When one reads his latest publications, one feels awe not only of their depth and topicality, but also of the fact that his first publication appeared half a century ago. It is regretful that he wrote only a few review articles and only one monograph (jointly with Var- lamov). A three-volume collection of Larkin’s scientific works has been recently published in Moscow.d In Larkin’s life, his achievements in science were inseparable from

dBy Moscow Center for Continuous Mathematical Education, Volume I, 2009; Volume II, 2010; and Volume III, in print. April 5, 2013 15:36 WSPC/Trim Size: 9in x 6in for Proceedings 9b˙Larkin-Intro

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fostering young theorists. He never had a large flock of pupils at any one time but his talent as a teacher brought to theoretical physics many gifted persons of very different types of personality and talent. He supervised PhD work of many students who later became outstanding physicists on their own, such as Lev Aslamazov, Vladimir Filyov, Lev Ioffe, Vadim Geshkenbein, Victor Galitsky, Chushun Tian, Konstantin Efetov, David Khmelnitsky, Yuri Ovchinnikov and Paul B. Wiegmann. Yuri Dreyzin, Konstantin Matveev, and Valery Rupasov were his students as undergraduates. Working with Larkin created a unique feeling of joy, which attracted to him many collaborators. Larkin received multiple formal signs of recognition. He was elected as a full member of the Russian Academy of Sciences (1991), and was a recipient of numerous prizes, including the Fritz London Memorial Award (1990) and the Hewlett-Packard Europhysics Prize (1993). In 2002, A.I. Larkin was awarded the Lars Onsager Prize given by the American Physical Society. The purpose of the prize was to recognize outstanding research in theoretical statistical physics, including quantum fluids. His citation reads “For elucidating roles of fluctuations and randomness in collective phenomena, including critical behavior of uniaxial ferroelectrics, dependence of critical exponents in four dimensions on symmetry, and how impurity pinning of vortices in superconductors destroys lattice order and controls critical currents.” It is not accidental that Tolya himself viewed his early work with Aslamazov [3] on this topic as one of his best. In 2003, Larkin was recognized with the John Bardeen Prize for his work on the theory of vortex matter. Tolya was happy to participate in Larkin–Fests organized twice by his friends and colleagues: in 1997 at the University of Minnesota and in 2002 at the Max Planck Institute for Physics of Complex Systems, Dresden, Germany. Tolya was a merry man, easy to smile; his smile carried a touch of kindness, depth and wisdom. He died suddenly, in the middle of heated physics debates and mountain hikes, which he cherished so much, at a theoretical physics workshop in Aspen, Colorado, on August 4, 2005. The life and death of a trailblazer ... April 5, 2013 15:36 WSPC/Trim Size: 9in x 6in for Proceedings 9b˙Larkin-Intro

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References 1. Dynamical Gauge Symmetry Breaking, Eds. E. Farhi and R. Jackiw (World Scientiﬁc, Singapore, 1982), p. 24. 2. V.G. Vaks and A.I. Larkin, On the application of the methods of superconductivity theory to the problem of the masses of elementary particles, Sov. Phys. JETP 13, 192-193 (1961). [The Russian original was published in ZhETF 40, 1896-1898 (1961); it was recently reprinted in A.I. Larkin, Collected Works, (Moscow Center for Continuous Mathematical Education, 2009), Vol. 1, pp. 37-41.] 3. L.G. Aslamazov and A.I. Larkin, Phys. Lett. 26A, 238 (1968). April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9c˙Larkin-ALEKSANDER

MY BROTHER TOLYA∗

ALEXANDER I. LARKIN National Research Nuclear University MEPhI Kashirskoye shosse 31, Moscow 115409, Russia [email protected]

“My mission is accomplished. I raised a student who turned out to be stronger than me.” Arkady Migdal

The title above is from our cousin’s school essay. In a way it tells how Tolya was cherished in our loving family scattered over many cities: Ryazan, Moscow, Lvov, Novosibirsk. Now I see that Tolya’s mentality – not just healthy, but sturdy and well-intentioned – was rooted in love and appreciation that he was surrounded with since early childhood. Tolya’s famous sweet temper was nourished by our relatives in Kolomna. All children, and Tolya as the ﬁrst-born in our generation in particular, were growing up in the environment of love and kindness. Of course, there was a downside of that. Life taught us that the world around was not quite the same as home of our grandfather in Kolomna. Later we had tough time, life beat us black and blue, to the point of nearly dying during the war. Naturally, it is too diﬃcult for me - to be objective here. I will try to limit myself to facts and notes of his colleagues, students and friends with short comments of mine.

∗Translated from Russian by Vadim Matyushin.

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Tolya’s Parents and Teachers

Our parents’ trades were noble and worthy – building houses and teaching children. Thanks to our parents Tolya could fulﬁll his calling: he became the theoretical physicist. In hungry post-war years we often heard from our parents that “who is given much, will be asked much.” I couldn’t understand what they meant since we actually didn’t have much anyway. But, of course, they were talking about things other than food or clothes. All his life Tolya felt responsibility before his parents and ancestors thanks to whom he was “given much.” • Many years later I heard from my brother: “ I think I was able to handle the ancestors’ legacy very well.” • After discussion about the story of Mozart and Salieri Tolya said short and deep: “Talent aggravates.” • Migdal’s reaction to the news of arrival to the Moscow Engineering Physics Institute of a committee for the best student selection: “Didn’t you understand that Sakharov and Zeldovich came to recruit you to their super-closed organization in Arzamas where they make atomic bombs and from where there is virtually no way out? You should have pretended to be a complete idiot!” That’s how Larkin found himself in Sarov. • “In Sarov I met Tolya and we became close friends. Tolya was my age and has just came from Moscow to Sarov for practical training. Later Tolya, Anatoly Ivanovich Larkin, gained a world-wide recognition became famous scientist. His supervisor in Sarov was Andrei Sakharov.” Professor Roald Sagdeev, University of Maryland. • Only when A.D. Sakharov wrote a personal letter concerning Tolya’s diploma thesis to the Rector of the Moscow Engineering Physics Institute, Tolya’s return from Sarov to Moscow became possible, which, in turn, allowed Tolya to start working with Landau and Migdal. When Tolya was elected as a corresponding member of the USSR Academy of Science there was a banquet. Among other people Tolya invited Andrei Sakharov. That was the time when the persecution of Sakharov was at its peak, just before his exile to Gorky. Andrei Dmitrievich understood that he would be watched and followed by KGB, and decided not to cause extra trouble to us. April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9c˙Larkin-ALEKSANDER

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“Everybody knows Sakharov as a great scientist, inventor and human rights activist. But I remember him as very kind person.”

Tolya’s remarks and jokes

• Tolya’s funny comments and jokes, being quite rare, were never accidental. It was always the right time – an impromptu well prepared. Whatever the topic was, almost always it turned out that Tolya had already thought about it. • “Landau’s spirit: ‘Do everything you can. Do as needed.’ American approach: ‘Do what is needed. Do as you can’. • “The only exception to the rule ‘I owe to nobody, I am not a member of anything’ is as follows: I decided that my party is Migdal’s school, Landau’s school. • “Does the Hamiltonian have an explicit form?” Trying to stop an endless stream of generalities and trivial considerations. He couldn’t stand conversations that Landau used to characterize as “Long play” or “About the weather.” • “Science helps the nation’s cultural growth, and, consequently, its defense capabilities.” • “What should you do? You should do not just what you like, and even not what you are generously paid for, but whatever you can do well.” • “Any work, and creative work in particular, should cause positive emotions not just in the future but every day.” • “If such a person as Sherlock Holmes existed he would never waste his time for this nonsense.” • “Awfully tired.” After spending one month vacationing in Italy, without work. • “I try not to think about what can’t be corrected. I focus on what I need to do tomorrow.” • “Who knows, maybe I would have done the same thing if I were in his shoe... ” Instead of blaming a person absent in the room for something he had done earlier. April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9c˙Larkin-ALEKSANDER

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• – The belay is set up not where it’s hard but where it’s dangerous. – The hook should be fixed as high as possible. – The most difficult thing is to refuse climbing. Mountaineers’ rule often quoted by Tolya at home. • “If the solution can’t be found, someone has to make a decision.” • It’s proven experimentally that it’s possible to run the red light.” When our driver ran the red light on intersection. • I really want to keep our good relationship, that’s why I would like to stay away from you, as far as possible.” Replying to Director’s offer to become the vice-Director of the Institute. • Was there the beginning and will there be the end of the world?” Tolya’s flyer at the Odessa Conference on cosmology. • “Any power spoils every person.” • Why do we need a boss? The most important task of any boss is to protect his subordinates from the bosses that are above him.” • “I consider to be the best years of my life the first years in the Lan- dau Institute. That’s when I did my best works. I am convinced that it is the Landau Institute that will ignite a resurrection of physics in Russia.” • “You have to believe that your cause is most important, Then neither cold nor heat Will distract you from pleasant nonsense.” Tolya put this G. Oster’s rhyme in his office. He told me: “My American colleagues didn’t appreciate this humor.” • He also liked another rhyme “from unwritten by Robert Burns.” It was born after a conversation about what features are more valuable: those a person inherited genetically or achieved bending every effort in result of his own improvement. I am stupid by birth, IamuglyfromGod, But after a long and thorough work I made a great scoundrel out of myself. • “When my son heard that you are getting married he said: ‘now they will have children – they will be so lucky’. I wish you to have better children than mine.” April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9c˙Larkin-ALEKSANDER

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• “It looks like the end of the world is coming – children no longer listen to their parents and everyone wants to write a book.” This ‘ancient wisdom’ Tolya recalled when he started working on the book “Theory of ﬂuctuations in superconductors.” • “When Migdal joined the Landau Institute I was concerned that it would be hard for him to pass from the environment of respectful students he got used to previously to a very liberal environment of the Landau institute. I even used to note to my student Dima Khmelnitsky, when he was acting too freely during the seminars of my Teacher, that ‘eggs can’t teach hens, especially if these eggs are in fact ‘grandeggs’.”

Remarks of his students, friends, and colleagues • “In the science world some works are being absorbed just naturally. That’s a crucial point. At the time when there were just a few Russian scientists in the West, several names were still spelled out, time and again, at all conferences. One of those mentioned most often was A. Larkin. His results and ideas were perceived as classics, they were widely known, constantly quoted, and experimentalists carried out dedicated experiments to test them.” M. Ya. Azbel and M. I. Kaganov • “Let’s ﬁnd out what elegant Larkin has to say about it!” During seminars at the Kapitsa Institute at the time of a discussion hitting adeadlock. •“Larkin proved to be the best Teacher if you take the level achieved by his former students as a criterion.” • In the center of his CV Tolya placed the list of his best students:

List of Selected Former Students

– K.B. Efetov, Director – Max-Planck Institute of Solid State Physics, Stuttgart; – L.B. Ioﬀe, Associate Professor – Rutgers University; – D.E. Khmelnitsky, Professor – Cambridge University, Hewlett- Packard Europhysics Prize Recipient; April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9c˙Larkin-ALEKSANDER

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– Y.N. Ovchnnikov, Deputy Director – Landau Institute, Hum- boldt Award Recipient, 1994; – P.B. Wiegmann, Professor – University of Chicago, Blaise Pascal Laureat. • “You can work with Tolya for 12 hours straight and not be tired at all.” • “My wife and, especially, my mother in law couldn’t imagine that famous scientist would stay late just to explain something to his students.” • “I remember the first time I saw Tolya in Migdal’s office. He seemed to me big and solid and not just by complexion, but by his way of speaking, choosing words carefully and being very considerate to other people in his explanations.... Well, how can I explain this to YOU?...” One of Migdal’s young students • “I remember this scene: there are two people in a room: Anatoly Ivanovich snoring on the couch, and Lev Ioffe crouched in a chair. Lev turns to me, with anguish in his eyes: ‘Well, here it is, he sleeps, but he thinks, and me, when I sleep, I just sleep, and that’s all! ’.” • “Tolya’s answer is not about what you have just asked. It is about what you were really interested in.” • “I described to Tolya the solution of my problem. Next day he suggested to continue our discussion and then it turned out that he understood the meaning of my solution much deeper than the author himself.” • “When I was totally confused and in a deadend, I would go to Tolya and ask for help. He knew and understood all areas of physics and could see the heart of the problem. He would say: ‘Let’s remove unimportant stuff and trivialize the problem’.”

Our joint work began • Tolya was the only person with whom I could talk about anything and practically always get a nontrivial answer or helpful advice. The most important thing was not to be a trivial or superﬁcial ‘ques- April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9c˙Larkin-ALEKSANDER

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tioner.’ But even in that case I would hear no more than “do we need to examine it?” ... meaning, “have you thought deep enough before asking this?” • There are plenty of PhD’s like me, but just not so many scientists like Tolya. Of course, I do not know all graduates from our university but, among whom I know, Tolya is the strongest. I became a physicist only due to my brother. • For quite a while we – my brother and me – were entertaining an idea to write a joint work, without other co-authors, just A.I. Larkin & A.I. Larkin. But due to Tolya’s high standards we were never able to start. In 2005 we started a certain experiment in a submillimeter range for which I had both, experience and equipment. Tolya got an idea that in this work one could implement a novel intermediate state and a smooth transition from this state to two limiting cases, one of which would ﬁt classical description while another quantum- mechanical. And right then my brother had to leave for the United States. My last letter to him was concluded with “you left too early.” After a few days I got his reply concerning the work which we had just started: “Let’s introduce the notation.... I am interested in.... I will think.”

Larkin-Fest In 2002 Tolya turned 70. His former students, Konstantin Efetov (Ruhr University) and David (Dima) Khmelnitsky (University of Cambridge) organized a large physics conference “Progress in The- oretical Physics of Condensed State.” It was held in Dresden, Ger- many, from October 28 till November 1, 2002.

Anatoly Larkin’s talk at Larkin-Fest Dear colleagues and friends, First of all, I would like to thank Max-Planck Institute for this conference. I would like to thank Kostya Efetov, Dima Khmelnitsky, Peter Fulde and Mandy Stieger for good organization of this conference. I also would like to thank all of you for coming. I am glad to April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9c˙Larkin-ALEKSANDER

My Brother Tolya 325

see here so many of my friends that even two ‘oral’ session are not enough to accommodate all speakers, and a poster session became necessary. I am especially glad to see a lot of good works here. They are my best birthday presents. My toast is also to these who are not here today. According to a Russian tradition the ﬁrst toast on the birthday party is to my parents, Ivan and Nadezhda Larkins. I would also like to pay tribute to my teachers Andrei Sakharov and Arkady Migdal. Everybody knows Sakharov as a great scientist, inventor and human rights activist. But I remember him as very kind person. He wanted me to join his group after my undergraduate diploma. However, I begged him to let me go to fundamental science and he helped me to become a graduate student of Arkady Migdal. I should have written poetry about Arkady Migdal. Unfortu- nately I am not a poet but you can read a book of recollections about him, which was published this year. When parents and teachers are gone, it is sad but it is a natural process. It is unjust and unnatural to lose former students and friends. I lost my students Lev Aslamazov and Vladimir Filev and my friends Viktor Galitsky, Volodya Melnikov, Igor Kobzarev, Arkady Aronov, Volodya Gribov, Vadim Berizinsky, and Oleg Dorokhov. Recently Bill Fine passed away. He was not a physicist but a great Institute of Theoretical Physics at the University of Minneapolis was created thanks to his ﬁnancial and organizational support. I want especially to mention my good friend and collaborator Albert Schmid. Our friendship has a long history. This story is very important for me but I have no time now and, therefore, I will present it in my poster. I would like to propose this toast in memory of Albert.

Albert Schmid. Anatoly Larkin’s Poster. It was October 14th, 1941, and it was my 9-th birthday. I said my last “good bye” to my granny who loved me so much. I haven’t seen her ever since. An open truck drove our family away from the war which got so close to my native town, Kolomna. I was sitting in the open wooden truck body and gazed at empty ﬁelds, an empty road and a lone plane in the sky. I though: “Is it a German plane?” April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9c˙Larkin-ALEKSANDER

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Suddenly, the plane started moving down to our truck and I saw a bomb falling down. It struck the field close to us, the truck jumped and got thrown out from the road. Luckily nobody was hurt. This is why later, for many years, I still didn’t want to go to Germany, until I met Albert Schmid at a conference in Copenhagen. His soft smile, his kindness made a miracle with me: I fell in love with Germany. I visited Albert in Karlsruhe many times, and he visited me in Moscow. Now bombs often fall down on the heads of children in different countries. I don’t want to judge politics and generals. I indeed do not know if there are other methods to fight terrorists. But I am sure that many children in Yugoslavia, Chechnya and Afghanistan hate Americans, Russians or both. Now nothing can be done with this hatred. I wish these children to meet somebody like Albert Schmid who will be able to cure their hatred with his love when all wars are finally over.

Sources

1. N. Lopatina, An. Larkin, and A. Larkin, LARKIN, (Moscow– Chicago, 2005). 2. Physicists, Ed. A.I. Akhiezer, (Nauka, Moscow, 1971). 3. Andrei Sakharov, Memoirs, (Znamya, Moscow, 1990; English Edition: Random House Value Publishing, 1995). 4. Recollections on Academician Arkady Benediktovich Migdal, Eds. N. O. Agasyan et al., (Fizmatlit, Moscow, 2003). 5. M. Ya. Azbel and M.I. Kaganov, O Sudbakh Nauki, (Moscow, 1996). 6.Viktor Mikhaylovich Galitsky (Nauka, Moscow, 1983). 7. A.I. Larkin Memorial Conference, Minneapolis, 2006. 8. A.I. Larkin Memorial Conference, Chernogolovka, 2007. 9. Upravlyaemoe Dissipativnoye Tunnelirovanie, Antology in Memoriam A. Larkin, Ed. Anthony J. Leggett, (Fizmatlit, Moscow, 2011). 10. Recollections and stories due to Al. Lopatin, N. Lopatina, An. Lopatin, An. Larkin, S. Anisimov, A. Dyugaev, K. Efetov, April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9c˙Larkin-ALEKSANDER

My Brother Tolya 327

M. Feigelman, A. Finkelshtein, I.M. Khalatnikov, D. Khmelnitsky, V. Kravchenko, V. Lebedev, G. Novikov, V. Osadchyev, Yu. Ovchin- nikov,R.Sagdeev,M.Skvortsov,A.Tsvelik,V.Vaks,A.Varlamov, L. Vinnikov, and P. Wiegmann. April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9d˙Vaks-Larkin

GLIMPSES OF TOLYA LARKIN∗

V. G. VAKS Institute of General and Nuclear Physics Russian Research Center Kurchatov Institute 1, Akademika Kurchatova pl., Moscow 123182, Russia [email protected]

I write this note as a tribute to my good friend, Tolya Larkin, who left this life so suddenly and much too soon. Perhaps, some readers of this book would be interested in his personal traits and some of the events in his life that demonstrated his understanding of his place and mission in this world. I met Tolya in the fall of 1951 when, after the reorganization of MFTI,a I was placed in the same group with him. Since that time, we studied, worked and climbed mountains together, and maintained a close relationship between our families. The last day we spent together was at Tolya’s home in Chernogolovka where I brought my grandson and asked Tolya’s family to look after him. I want to mention some of Tolya’s most important personal traits. He felt responsible for everybody to whom he was related in one way or another. This circle included relatives, colleagues, students, and those with whom he interacted at work, in bringing up children or even doing some chores around the house. I want to tell you about three diﬀerent events that show how Tolya treated his teachers (and others who helped him), how kind he was to his friends, and how much he cared for his students (of which there were many). The ﬁrst event was the party Tolya threw after he had been elected

∗Translated from Russian by Vadim Matyushin. aRussian acronym for Moskovskiy Fiziko-Tekhnicheskiy Institut, the Moscow Institute of Physics and Technology.

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Glimpses of Tolya Larkin 329

to the USSR Academy of Science. Usually, this was just a routine event that a new member of the Academy had to go through. Tolya decided to break this formal style and make the party truly memorable by recounting his biography in documents from his early childhood through his university years. People who knew Tolya were aware of how hard public speaking was for him, and the many hours he had spent preparing for this. So, after covering his younger years in a humorous manner, he became very serious and said, “Now I want to read one of the most precious documents that affected the mostimportantturninmylife.”HethenreadaletterfromAn- drei Sakharov where Sakharov stated that young scientist Anatoly Ivanovich Larkin could leave the Arzamas-16 Research Institute because he was accepted in A. Migdal’s graduate course in Moscow. For those who are not aware of Tolya’s life in the 1950s, I hasten to add that before finishing at the Moscow Engineering and Physics Institute in 1955, Tolya, along with some other students, was sent to a top-secret research group in Arzamas-16, where he was supposed to complete his thesis and continue to work there afterwards. Arzamas- 16 was the main research center for developing nuclear weapons, and Andrei Sakharov was one of the chief administrators there. Sakharov was Tolya’s scientific adviser for his thesis and also wanted Tolya to stay, as he valued him very much. So when Tolya asked for permission to leave, Sakharov could easily have said no since, in addition to everything else, at that time he truly believed in the importance of developing nuclear weapons in the USSR. However, Sakharov let him leave and even assisted him in the process. Tolya stressed how important that letter was, and added that he was very grateful to Andrei Dmitrievich Sakharov for all he did for him. By the way, this party took place in a large banquet hall in 1979, by which time Sakharov’s name was officially associated with the “archenemy of the state.” Such an open respect and gratitude from Tolya was courageous, though I doubt if he ever looked at it in this way. The second event happened in the early 1960s when Tolya and I worked together in Migdal’s laboratory in Kurchatov’s Research Institute. One time we were invited, along with other scientists, April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9d˙Vaks-Larkin

330 V. G. Vaks

to an elementary particle conference in Uzhgorod that was held in the fall. The highlight of that trip was a tour of local wine cellars, along with a wine tasting. We were young and, to put it mildly, unspoiled by good food and wine at that time. The winery visit was the primary reason of going to Uzhgorod since, from a scientific viewpoint, the conference subject matter was rather boring. On the scheduled day everybody gathered at the town square to catch the tour bus. I was late for some reason and, when I got there, the only person who was waiting for me was Tolya. He didn’t want to leave me alone, so he stayed when all the others left. He didn’t even show disappointment that day. This was a typical example of how Tolya cared for everyone around him – family, students, and friends. I remember many times when he went the extra mile to help others. Many years later, during a trip to Minnesota I was informed that my mother died and had to fly back home immediately. Tolya and his family spared no effort in helping me purchase a ticket and get to the airport within a few hours. He also took care of my trip back to Minnesota after the funeral. These are just a few of the many examples of Tolya’s kindness and caring nature. Now I would like to mention Tolya’s pedagogical talent. Everyone who was acquainted with Tolya and theoretical physics in the last couple of decades knew what a wise and attentive teacher he was, and how many great students he had trained. He had a rare gift of not just answering the questions but explaining what the inquirer really needed to know. That is why it was always such a pleasure to work with him and it is no wonder he had over 200 joint works with his students and other theorists. And finally, a few words about relationships between Tolya and his students. They were naturally based on his sense of responsibility for those who relied on him. Tolya had a large number of students, and he cared for each one personally. He tried to help as much as he could in hard times. I am reminded of our meeting right before Tolya’s departure for Minnesota. We were having a long, friendly conversation. Tolya left suddenly, referring to an urgent matter. Later on, his wife explained that Tolya was trying to help the family of a student, Vladimir Filev, who had recently passed away. It was April 5, 2013 15:37 WSPC/Trim Size: 9in x 6in for Proceedings 9d˙Vaks-Larkin

Glimpses of Tolya Larkin 331

so natural for Tolya to behave in this way – “If not me, who will do it?” For all of us who knew and loved Tolya, his death was an unexpected and sorrowful event. But life goes on. He is survived by his family – wife, children, grandchildren and grand-grandchildren – all very diﬀerent but nevertheless talented and kind in heart. The memory of Tolya, who was a great scientist and wonderful person, will continue to shine through our lives. April 5, 2013 15:38 WSPC/Trim Size: 9in x 6in for Proceedings 9e˙Ovchinnikov-Larkin

A STUDENT’S MEMORIES

YURI OVCHINNIKOV L.D. Landau Institute for Theoretical Physics Acad. Semenov prosp., 1a 142432, Chernogolovka Moscow Region, Russia [email protected]

I first got the chance to study with A. I. Larkin in 1961, on the recommendation of V. B. Berestetsky. At this time Larkin worked under A. B. Migdal at the Institute of Atomic Energy and concurrently at the Moscow Institute of Physics and Technology’s department of theoretical physics, which V. B. Berestetsky headed then. At the time, Migdal’s sector was housed in the cafeteria building of the Institute of Atomic Energy. One could hardly call it spacious. This was the era when staff started leaving for Novosibirsk to join the newly created Siberian Center. V. M. Galitsky and S. T. Belyayev had already gone there. The people of Migdal’s sector worked not only on nuclear physics. In the early 1960s there was highly active research on second-order phase transitions. Earlier Onsager had obtained the precise solution of a two-dimensional Ising model with nearest neighbor interaction. This solution was then greatly simplified in work by Onsager and Kaufman – simplified to the point of readability. Zhora Ryazanov and N.V. Vdovichenko managed to make considerable headway in this task. They obtained a very compact solution, which greatly stimulated further research. At the time, Tolya Larkin mainly worked with V. G. Vaks. They discovered that in the Ising scheme it’s possible to devise and solve models where intersection of lines of interaction occurs only at lattice sites. One of these models was created in our joint work (Vaks, Larkin, Ovchinnikov). In this case, the phase diagram proved far

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A Student’s Memories 333

from trivial. This was the time of the start of studies in the field of superconductivity. Tolya’s work from this period became widely known, as did mine, “Heterogeneous Condition of Superconductors.” In 1965, Larkin was invited to work at the newly created Insti- tute of Theoretical Physics in Chernogolovka. At that time, the in- stitutehadveryfewstaffmembers:A.A.Abrikosov,L.P.Gorkov, I. E. Dzyaloshinsky, I. M. Khalatnikov, G. M. Eliashberg, M. Ya. Azbel, Yu. Bychkov, I. Privorotsky, V. Pokrovsky, E. I. Rashba, S. I. Anisimov and S. V. Iordansky. Additions in 1966 included M. Falkovsky, Yu. Ovchinnikov (that is, me), D. Chernikov, I. Fomin, and somewhat later V. Melnikov and A. Kazantsev. Larkin actually moved with his family to Chernogolovka in 1966, settling at first in a three-room apartment. A year later, the Insti- tute of Chemical Physics allocated our institute three cottages, and Larkin, Pokrovsky and Dzyaloshinksy moved into these. The site of the institute was initially on the ninth floor; Fri- day “coffee” seminars took place there as well. All employees were required to participate in the Landau seminar on Thursdays and present regular lectures on particularly interesting new works. The Institute had an established tradition of taking part in two annual events: in Bakuriani (usually in February) and in Odessa (usually in May). I first attended the Bakuriani symposium in 1965. Having learned of the symposium, I went to Larkin and asked him whether there was any way to get invited to it. Larkin said it would probably be simple enough, because B. T. Geilikman was well acquainted with Andronikashvili and would write him a letter request- ing an invitation. I got the invitation soon after. The Bakuriani event was open to participants from any Soviet republic, with V.Z. Kresin, E. Shapoval and other “superconducting” people among those who traveled there in that era. A downhill skiing club was born in Chernogolovka at this time, and Larkin became a member. Regular trips to Paramonovo got Larkin and his whole family downhill skiing. Subsequently he made many trips to Bakuriani and Chembulak (Medeo). Larkin loved swimming and could swim in any water (he took a dip in the Rhine April 5, 2013 15:38 WSPC/Trim Size: 9in x 6in for Proceedings 9e˙Ovchinnikov-Larkin

334 Y. Ovchinnikov

in March once, shocking Albert Schmid). This was partly why he participated in all the Odessa symposia. By 1965 Larkin and I started studying the Josephson effect. We solved the problem of the non-stationary Josephson effect at an arbitrary contact voltage, studied the question of emission line width, and examined the Josephson effect within the BCS model without using the tunnel Hamiltonian approximation. Around the same time, Larkin accepted M. Aslamazov for graduate studies. They jointly produced a work on the Josephson effect between conductors separated by a thin layer of normal metal. Active experimental and theoretical research of the Josephson effect was also carried out at the Institute of Low-Temperature Physics and Engineering (I. K. Yanson, I. M. Dmitrenko, I. O. Kulik, V. Svistunov). At the ILTPE’s initiative, the results of the experimental and theoretical works on the Josephson effect were nominated for the State Prize of the USSR. Back then, though, as at other times, the works’ high level, broad international recognition and unquestionable practical interest weren’t the decisive factors for this prize’s award. At the last stage, the work was deferred to the long-list shelf. At this point Larkin told me that we wouldn’t be wasting any more time on State Prize paperwork. Anatoly Larkin later received many international prizes and awards (the London Prize, the Bardeen Prize, the Hewlett Packard Prize, the Alexander-von-Humboldt Award, the Onsager Prize). But he received no prize or award from Russia. Near his cottage was a small plot of land, four or five hundred square meters. Larkin loved working there, and started a small garden. He had a table set up there, which we often worked at, and Tanya (his wife) always brought us tea. Impurity diagrammatic technique as usually presented is extremely cumbersome. Nonetheless, the fact that the theory of superconductivity has a large parameter (P0ξ 1, to be precise) raised hopes for significantly simplifying the equation, as in the case of semiclassical approximation in normal metal. We did a lot of work on semiclassical method in the theory of superconductivity, on Green functions (integrated over the energy variable), on accurate account- April 5, 2013 15:38 WSPC/Trim Size: 9in x 6in for Proceedings 9e˙Ovchinnikov-Larkin

A Student’s Memories 335

ing for scattering by impurities, on equations for the non-stationary case. Research on macroscopic quantum tunneling, heterogeneous superconductors and weak pinning had a special place in our work. Each of these problems actually makes up an entire field in low temperature physics. Normal (more or less) life continued until 1991. What began after this was less like life and more like survival. Borders opened; many left right away and essentially forever. There were also many who started off on a different path, as scientific “shuttle traders.” At first Larkin “shuttled.” But in 1995 he received a permanent position as a professor at the University of Minnesota, and moved to work there. Every summer he returned to Chernogolovka, but his summer sojourns in Chernogolovka became ever shorter. For his part, he hoped and constantly said he would come back to do more work in Chernogolovka. I didn’t much believe this, though. The loss of Larkin was irreparable for our Institute. Larkin had a tremendous sense of intuition and was evidently a top authority on diagram techniques in condensed matter physics. A single one of his works, done jointly with Aslamazov, “The Influence of Fluc- tuation Pairing of Electrons on the Conductivity of Normal Metal,” has spawned a huge wave of followers and research over the years. Even today, research remains undone in this area; works continue to appear. And many of Larkin’s results are included in textbooks on low temperature physics. Here is a list of Larkin’s students: Yu. N. Ovchinnikov, L. G. Aslamazov, D. E. Khmelnitsky, K. B. Efetov, P. Wiegmann, V. M. Filyov, L. B. Ioffe, V. B. Geshkenbein, K. A. Matveev, and I. Aleiner. April 5, 2013 15:39 WSPC/Trim Size: 9in x 6in for Proceedings 9f˙Pokrovsky-Larkin

HE LIVED AMONG US∗

V. L. POKROVSKY Department of Physics and Astronomy Texas A&M University College Station, TX 77843, USA [email protected]

I initially got acquainted with Anatoly Larkin at the ﬁrst Odessa theoretical school, probably in 1959. Amid the brilliant company gathered in Odessa (Abrikosov, Khalatnikov, Gorkov, Keldysh, Perel, Pitaevsky), he astonished me at the time with his fundamentality, the soundness of his judgment and the ease of his receptiveness to new ideas. Later in Novosibirsk, where I lived then, Roald Sagdeev told me A. B. Migdal, Tolya’s research supervisor for graduate work, had invited Tolya to move with him to Novosibirsk, to the Budker In- stitute of Nuclear Physics, with the promise of a fast-track academic career. Tolya refused, and then A.B., who held Tolya’s opinion and collaboration in high regard, also decided to stay in Moscow. By this time, jointly with V. G. Vaks [1] and concurrently with Nambu, Tolya had already authored a work on the mechanism of particle mass generation as a result of spontaneous symmetry breaking, which later became known as the Higgs mechanism, and, jointly with A. B. Migdal, works on the superﬂuidity of atomic nuclei [2]. It surprised everyone when Tolya decided to set aside this research and study the theory of phase transitions and superconductivity. Explaining what led to his decision, he said that experiments with macroscopic systems are incomparably more interesting and varied than experiments in nuclear physics and elementary particle physics, where all they can do is make particles have head-on collisions.

∗Translated from Russian by James Manteith.

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He Lived Among Us 337

In the 1960s, we were both heavily involved in researching the general theory of second-order phase transitions and critical phenomena. From time to time we met and discussed new results and prospects. I don’t know about Tolya, but I found these discussions very useful. Tolya contributed very significantly to the theory of phase transitions. Along with V. G. Vaks, in 1963 he proposed an idea of universality classes in the theory of phase transitions with strongly developed fluctuations [3], naturally generalizing Landau’s 1937 theory of phase transitions. In 1969, jointly with D. E. Khmel- nitsky, he developed a renormalization-group theory of phase transitions in 4-dimensional space [4] and found the logarithmic singularity of specific heat. From there it was a seemingly small step to the theory of phase transitions in 4 − ε dimensions, but this step was taken only three years later by Wilson and Fisher [5]. In K. Wilson’s 1982 Nobel Prize statement, the Nobel Committee mentioned the Larkin and Khmelnitsky work as the direct precursor to the Wilson-Fisher theory. Wilson himself gave it due acknowledgment in his Nobel speech and briefings. Very typically for Tolya, he found an application for this abstract theory in real systems, in uniaxial ferroelectrics in the real three-dimensional world. His predictions found brilliant confirmation in experiments with ferroelectrics [6]. In 1966, we transferred to the newly established Institute of Theo- retical Physics, later called the Landau Institute. Much has been said and written about the Institute’s special, stimulating atmosphere, in whose creation Tolya played a very important role. The original, profound fields he developed, such as paraconductivity, disordered system theory, mesoscopics and collective effects in tunneling, drew young and talented students and staff to him, attracted theorists and experimenters, and became part of the Institute’s international reputation. I well remember the seminars in a ninth-floor apartment in a Chernogolovka housing block,a with seven to ten people attending, and Tolya or someone else from his staff recounting something new every time. Equally important was his involvement in discussing others’ work.

aThis was one of three apartments reserved for the Landau Institute’s visitors. April 5, 2013 15:39 WSPC/Trim Size: 9in x 6in for Proceedings 9f˙Pokrovsky-Larkin

338 V. L. Pokrovsky

When in 1966 I appeared at the Institute a year and a half after publishing my joint work with Patashinsky on scaling in the theory of phase transitions [7] (a work which Tolya greatly appreciated), the first thing I heard from Tolya was the question, “I suppose you’re working on dynamic scaling now?” This unfortunately wasn’t the case. The year had been unproductive for me. I was sick, had been moving from Novosibirsk to Chernogolovka, and hadn’t been working much. Tolya’s advice was right on target, but a couple of months after our conversation, works on dynamic scaling started appearing one after the other, by Ferrell and his colleagues, Halperin and Ho- henberg, Kawasaki, Kadanoff. After that, there was no way to keep up with them. About three years later, Vadim Berezinsky visited us at the In- stitute to discuss his later famous work on the properties of two- dimensional systems with a continuous symmetry group. In the first work [8], which we discussed then, he showed that Goldstone mode fluctuations lead to the destruction of the long-range order, but conserve shear modulus (for example, the elasticity coefficients in a two-dimensional crystal or the superfluid density in a Bose liquid or gas), resulting in a power-like decay of correlation (algebraic order). After listening to him, Tolya remarked that not everything had been accounted for: there should be localized excitations, such as vortices. This remark grew into Berezinsky’s remarkable theory and the analogy with two-dimensional plasma [9]. A year later, the same ideas were independently developed by Kosterlitz and Thou- less [10], but they also found a remarkably simple universal relation for shear modulus at the transition point. At the Institute, our offices were side by side. Whenever I appeared, Tolya was already in his office and working with one person or several, mainly with his undergraduate and graduate students. And when I’d leave, he’d still be working. The Larkin school was rigorous. Students would work with him for many hours, sometimes to the point of exhaustion. From the Institute they would go to Tolya’s home and continue there. Tanya Larkin recalled often seeing Lev Aslamazov asleep at the table beside an energetic Tolya. Paul Wiegmann told me more than once how difficult he found these tests April 5, 2013 15:39 WSPC/Trim Size: 9in x 6in for Proceedings 9f˙Pokrovsky-Larkin

He Lived Among Us 339

of endurance. The tough school was amazingly effective. Tolya’s students were few in number, but each of them has made a significant contribution to theoretical physics. The names Aleiner, Galitsky, Geshkenbein, Efetov, Ioffe, Matveev, Ovchinnikov, Wiegmann are known and respected by physicists worldwide. An important role in Tolya’s work with undergraduates and graduate students was played by his wife Tanya, who was always ready to feed hungry co-authors. The circle of Tolya’s colleagues went beyond his undergraduates and graduate students. Many talented young theorists came into its orbit, among them Vladimir Melnikov, A. Finkelstein, M. Feigel- man, M. Skvortsov, A. Varlamov, V. Vinokur. Tolya also productively collaborated with theorists from his own generation, including Dzyaloshinsky, Gorkov and Aronov. Certain figures characterize Tolya’s tremendous labor and its ef- fectiveness. Among Tolya’s publications, 25 articles have more than 100 citations, 15 more than 200, 12 more than 300, 8 more than 400 and 7 more than 500. Tolya’s works are characterized by an amazing combination of fundamentality and refinement. In his pioneering work with Asla- mazov [11], which marked the beginning of a new branch of science, paraconductivity, i.e. fluctuation manifestations in a normal state, the primary result is expressed by a formula of a simplicity and beauty rare for the arsenal of theoretical physics. One of his most popular works is a Journal of Experimental and Theoret- ical Physics article [12] written jointly with Gorkov and Khmelnit- sky, with the first identification of the physical object subsequently known as the Cooperon, and thus marking the beginning of weak localization theory. Together with Hikami and Nagaoka [13], Tolya was the first to discover the important role of spin-orbit interaction in the mesoscopic: in changing the symmetry, the interaction puts the system in a different universality class. In the work with Ovchinnikov [14] on the coexistence of ferromagnetism and superconductivity, which generated an extensive literature, the main idea on the origin of Cooper pairs with nonzero momentum is formulated with a disarming simplicity and persuasiveness. In the literature, April 5, 2013 15:39 WSPC/Trim Size: 9in x 6in for Proceedings 9f˙Pokrovsky-Larkin

340 V. L. Pokrovsky

the two variants of the resulting periodic structure have come to be known as LOFF (Larkin-Ovchinnikov-Fulde-Ferrel) or FFLO. In the work [15] devoted to the behavior of an elastic body in a random Gaussian potential, Tolya found an important characteristic fluctuation length which became known as the Larkin length, and which also plays an important role in the problem of quantum particle localization in a random potential (independently but later, this length wasrediscoveredbyImryandMa[16]).Thetoprankingbynumber of citations belongs to a cycle of Tolya’s works on pinning and vortex creep [17,18] (and on elastic systems overall), a very important work for high-temperature superconductors. These works, like a number of others by Tolya, are distinguished by careful comparison of theory with experiment. This makes Tolya’s works much different than Landau’s and those of the Landau school’s first generation. I think this reflects a certain change in philosophy. Strange as it may seem, Dau, who scorned philosophy as a whole, was strongly influenced, in my opinion, by the German philosophy of science, nature-philosophy (Die Natürphilosophie), which he absorbed along with the works of Einstein. The Landau-Lifshitz course gives a clear sense of a conviction that all theoretical physics can be derived from first principles without any reference to experiment. Tolya, like his peers, felt the hypnotic effect of Einstein’s personality less strongly and was more open to the scientific influence of the English empiricist school of thought, with its preference for experiment over abstract speculations. I know next to nothing about Tolya’s childhood and school years, except the following episode. He finished school in Novosibirsk. As he told it, in eighth or ninth grade (I don’t remember exactly) he learned of the existence of mathematical analysis and wanted to know what it was. After tracking down a textbook on analysis for technical institutes, he began reading it, but understood nothing. Then he went to the Novosibirsk public library, and there he was given Newton’s Principia, translated into Russian by Academician Krylov, a mathematician and ship designer. This text proved completely comprehensible, so that for some time Tolya called derivatives fluxions and integrals fluents and only gradually learned the modern terminology. May 10, 2013 12:5 WSPC/Trim Size: 9in x 6in for Proceedings 9f˙Pokrovsky-Larkin

He Lived Among Us 341

For several years we shared a small cottage with four extremely cramped apartments, with tiny rooms connected by a narrow corridor and a still narrower staircase. For two people it would have been tolerable, but for a family with two children the space clearly wasn’t enough, especially when Tolya’s mother would arrive; besides that, Tolya’s colleagues also paid long visits. But the crowded and uncomfortable conditions didn’t seem to bother Tolya. In any case, he made no effort to trade this dwelling for anything more spacious. Tolya was bound to this cramped apartment by his extraordinary love of the land. He was a passionate gardener, growing vegetables and flowers. Every morning we saw Tolya leaning motionless on a shovel in the middle of his garden, deep in thought. But these long reflections didn’t interfere with his agricultural undertakings: his garden vegetables and flowers grew well, and unfortunately all this fell into disrepair when he died. Tolya came from a family of intellectuals, but had the traits of a peasant lineage. These surfaced in his extreme thriftiness, which he recognized, saying of himself, “I’m miserly, but not greedy.” Since almost no one could understand how these concepts differed, he explained that he found it hard to part with what belonged to him, but felt no regret whatsoever at another person’s gain. Tolya was thrifty when it came to his own wants but a real and self-effacing friend in need to others. In all the time of our acquaintance, I remember only one quarrel between us, and even then only because when I told him I wanted let him know everything I thought about his behavior in a certain situation, Tolya replied, “Valya, please, don’t say anything, let me think.” There are few people who can restrain their irritation and avoid casting a pall over their close relationships. Tolya’s reply taught me an important lesson, although after this there were also times when I said too much in the heat of the moment and came to regret this later on. After 1992 our encounters were rare but always warm, and we always discussed scientific and commonplace news. Each year during summer visits to Chernogolovka Tolya and I would meet. As before, he would spend ages sitting in his office and would work with his colleagues. In 2002 in Dresden, Tolya celebrated his seventieth birthday. May 10, 2013 12:5 WSPC/Trim Size: 9in x 6in for Proceedings 9f˙Pokrovsky-Larkin

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Tolya’s students organized an anniversary conference. The party was a success. Many people came, and the conference was interesting. Tolya’s old colleagues came, as did his students and many famous physicists. Before leaving, my wife and I went to say goodbye. It was already late in the evening. Tolya opened the door half-undressed. This didn’t shock us: we had once traveled together on the rivers and lakes of Lithuania and had seen each other in swimsuits. But my heart sank, because Tolya looked unhealthy; he’d gained weight, looked exhausted. Apparently he wasn’t taking much care of himself, and the constant excessive strain had undermined his naturally robust health. The last time we met was in Chernogolovka in the summer of 2005. Tolya and Tanya invited us over to their home along with Natasha Kirova and Sergei Brazovsky. We sat at the table in that same cramped apartment in the cottage and were glad to see each other. Tolya was animated and cheerful, looking much better than in Dresden. We toasted to health, to the younger generation, and to getting together more often. He died two months later in Aspen. Only then did I realize how important his presence had been in my life.

References 1. V.G. Vaks and A.I. Larkin, ZHETF 40, 1896 (1961). 2. A.I. Larkin and A.B. Migdal, ZHETF 45, 1036 (1963). 3. V.G. Vaks and A.I. Larkin, ZHETF 49, 975 (1965) [Sov. Phys. JETP 22, 678 (1966)]. 4. A.I. Larkin and D.E. Khmelnitsky, ZHETF 56, 2087 (1969) [Sov. Phys. JETP 29, 1123 (1969)]. 5. K.G. Wilson and M.E. Fisher, Phys. Rev. Lett. 28, 240 (1972). 6. R. Frowein and J. K¨otzler, Phys. Rev. B 25, 3292 (1982); J. Nikkel and B. Ellmann, Phys. Rev. B 64, 214420 (2001). 7. A.Z. Patashinsky and V.L. Pokrovsky, ZHETF 50, 439 (1966) [Sov. Phys. JETP 23, 292 (1966)]. 8. V.L. Berezinsky, ZHETF 59, 907 (1970) [Sov. Phys. JETP 32, 423 (1971)]. 9. V.L. Berezinsky, ZHETF 61, 1144 (19710 [Sov. Phys. JETP 34, 610 (1971)]. 10. J.M. Kosterlitz and D. Thouless, J. Phys. C 6, 1181 (1973). 11. L.G. Aslamazov and A.I. Larkin, Phys. Lett. A 26, 233 (1968). 12. L.P. Gorkov, A.I. Larkin, and D.E. Khmelnitsky, Sov. Phys. JETP Lett. 30, 288 (1979). 13. S. Hikami, A.I. Larkin, and Y. Nagaoka, Prog. Theor. Phys. 63, 707 (1980). April 5, 2013 15:39 WSPC/Trim Size: 9in x 6in for Proceedings 9f˙Pokrovsky-Larkin

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14. A.I. Larkin and Y.N. Ovchinnikov, ZHETF 47, 1136 (1964) [Sov. Phys. JETP 20, 762 (1964). 15. A.I. Larkin, ZHETF 58, 1466 (1970). 16. J. Imry and Ma, Phys. Rev. Lett. 35, 1399 (1975). 17. A.I. Larkin and Y.N. Ovchinnikov, J. Low Temp. Phys. 34, 409 (1979) (1156 citations). 18. M.V. Feigelman, V.B. Geshkenbein, A.I. Larkin, and V.M. Vinokur, Phys. Rev. Lett. 63, 2302 (1989) (888 citations); G. Blatter, M.V. Feigelman, V.B. Geshkenbein, A.I. Larkin, and V.M. Vinokur, Rev. Mod. Phys. 66, 112 (1994) (3694 citations). April 5, 2013 15:40 WSPC/Trim Size: 9in x 6in for Proceedings 9g˙Varlamov-Larkin

REMEMBERING LARKIN∗

ANDREI VARLAMOV INFMandIstitutoSPIN–CNR Via del Politecnico - 1, I - 00133 Rome, Italy [email protected]

Knowing Anatoly Ivanovich – Tolya for his friends and colleagues – for years I can’t recall him ever writing mathematical expressions on a sheet of paper as he was usually solving problems in his head. Tolya was Homo Sapiens in its true, literal sense of this word. A side observer would hardly notice his mastery and deep understanding of modern methods of theoretical physics and mathematics as there were no piles of paper speckled with math symbols on his desk. But there was a blackboard in his office, all covered with fragments of problems he was discussing with various coauthors. He was famous among his students and coauthors for “falling asleep” in the chair in his office and then writing the solution on the board immediately after awakening. He always treated formulas and math symbols carefully, even lov- ingly. I remember when we just started our booka and I wrote without hesitation the coefficient in the Ginzburg–Landau functional as

A = αTcε, (1)

Tolya immediately reacted and suggested that we shouldn’t use α as we may need it soon. He was right: pretty soon we ran out of Greek and Latin letters for new physical quantities. We decided

∗Translated from Russian by Vadim Matyushin. aA. Larkin and A. Varlamov, Theory of Fluctuations in Superconductors (Oxford Uni- versity Press, Oxford, 2005).

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to use different fonts – gothic for functionals, and calligraphic for operators. Tolya used to say, jokingly, that when the number of works in his CV reaches 200, he would stop working. But even with the number being 210, 220, ... he didn’t even think to slow down. When our book on superconductors was finished, it had 500 pages in it. He looked at it with surprise and said, “Did we really write all this?” Tolya was very friendly and I can’t even imagine him being hard on someone. His famous critical note of a speaker with lots of speculations without solid proofs was: “Is there any explicit form for the Hamiltonian?” Once in 2005 me and Alexei Kamenev asked him about his way of selecting students and choosing their first projects. “Well, students come on their own,” – he responded – “and I don’t accept all to have enough time for those whom I take. To check their understanding of physics I usually give them one and the same problem: A rope is thrown over a tree branch, and a weight is tied up to one end of it. What force has to be applied to the other end in order for the weight to be pulled up steadily?” Then he recalled that Yuri Ovchinnikov solved this problem for an arbitrary form of the branch cross section. “I try to find the first physics project that would fit my student, his abilities and interests. For a creative person I try to find a problem where a new approach is needed. For the one with strong computational skills I choose an appropriate problem where he can use these skills.” To those who barely knew Tolya he might look as totally devoted to science, as he spent all days long in his office. However, he was reading internet news, followed all world events and had his own clear and original vision of many of them. Once he shared with me some of his political observations which he made while working in Israel, and they really impressed me. I suggested to publish them but he never cared about it. I really wish I could find and publish them now. Last time I saw Tolya on July 14, 2005. I was visiting Larkin’s hos- April 5, 2013 15:40 WSPC/Trim Size: 9in x 6in for Proceedings 9g˙Varlamov-Larkin

346 A. Varlamov

pitable house in Chernogolovka.b We were working on the Russian edition of our book. Occasionally we would drift into a discussion of the exciting topic of quantum fluctuations in the Nernst effect. After lunch Tolya’s wife Tanya had to go somewhere. She left their great-grandson with Tolya. Tolya’s face shone with love, kindness, and unconditional happiness while he was playing with the little boy telling him something is his incomprehensible baby’s “language.” He enjoyed life in Chernogolovka and never missed a chance to come back there. When we were together in Minnesota in December of 2003 he found out that I was going to fly to Moscow for the New Year’s eve. He immediately decided to fly to Russia for Christmas holidays too. It looked like he just found an excuse to go home. He mentioned that he worked in America but would prefer to die in his homeland. Tolya died too early, and it was even more unexpected considering that he was a sturdy man, fond of long hikes and biking, even in harsh Minnesota winter. But still I think that he died being happy. He became a famous scientist while being very young, was widely respected for his wisdom, talent and diligence, and gained many scientific recognitions worldwide never really aiming at it. He died suddenly, surrounded by his relatives, after walking down the mountains that he loved so much. May he rest in peace with the righteous! For he barely had any time to sin.

bChernogolovka is a small town in the Moscow region, 60 km north-east of Moscow, where many institutions of the Russian Academy of Sciences are situated. April 5, 2013 15:41 WSPC/Trim Size: 9in x 6in for Proceedings 9h˙Shifman-Larkin

TOLYA LARKIN AT THE INSTITUTE

M. SHIFMAN William I. Fine Theoretical Physics Institute University of Minnesota Minneapolis, MN 55455, USA [email protected]

The Institute I’ve been a part of since 1990 is unusual even for the U.S., with its whirlpool of foreign postdocs and researchers from all over the world. Out of six permanent members, only one – Keith Olive – is a genuine American. The rest of the faculty came in the early 1990s from the former Soviet Union, toward the beginning of a Great Exodus of physicists and mathematicians from the collapsed Soviet Empire. Our high proportion of researchers with Soviet background came about as a matter of timing. The Institute officially came into existence in 1987, but its faculty search didn’t start in earnest until 1989, when Larry McLerran was appointed Director. Needless to say, we brought to cold Minnesota our scientific culture: 2 or 3 hours-long seminars, heated debates at the blackboard, with loud shouts in Russian, emotional handwaving and sometimes even direct accusations of impropriety. At first, observing such a debate, our secretaries thought the debate participants were mortal enemies fighting each other to the death. Only later did they understand the proceedings were no more than a friendly exchange of opinions. Since these opinions rarely coincided right away, adjust- ments were needed, and how best to find out who was right or wrong? Indeed, through passionate debate, a sort of a verbal fencing. For the few first years after our arrival to Minnesota, we used to come to the Institute even on weekends, a practice common in Russia (at least in my former institute, ITEP). Our Minnesota weekends, free of disturbances from the time-consuming university routine –

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teaching, committee meetings and the like – were reserved for urgent unfinished projects. To compensate for long weekend hours, usually during the work week we didn’t appear at the Institute until 11, leaving at around 7 or 8 in the evening. But gradually the inevitable happened: the Western pattern started to take over – first slowly, then ever faster. Seminars eventually shrank to a mere hour and a half (still with many inquisitive remarks along the way, though!); faculty started arriving at the In- stitute earlier, not leaving as late as they used to, and spending fewer hours at the Institute on weekends. Tolya Larkin joined us in 1995. For the next ten years his behavior never changed even a bit. He used to come at around nine and, as a rule, was the last to leave for home. Whenever for some reason I showed up outside regular work hours, or on Saturday or Sunday, I’d see Tolya in his office, usually sitting in his armchair and looking at the blackboard with one or two concise mathematical expressions on it. That’s how I will remember him forever. Tolya was always surrounded by students, postdocs or collaborators. Sometimes he reminded me a shepherd with a flock of sheep. The presence of students did not change the picture. Tolya would still be in his armchair looking at the blackboard, thinking and occasionally letting a few words fall. Students either occupied other chairs with a view of the blackboard, or sometimes tried to explain something to Tolya, adding their scribbles to those already on the blackboard. For many years we had neighboring offices, and whenever I passed, I would inevitably glance into Tolya’s office. Most of the time he seemed to be quite skeptical about what his students had to say. However, he never discouraged them, and there was never a shortage of those who dreamed of having Tolya as a teacher. I hasten to add that in many instances his students were exceptionally bright. Suffice to mention Igor Aleiner. Apparently to handle such a large number of students and collaborators Tolya had to pre-arrange a timetable. Not only students wanted to delve into physics with Tolya. He was a highly desirable collaborator for many outstanding researchers with established reputations. In the corridors of our Institute I often April 5, 2013 15:41 WSPC/Trim Size: 9in x 6in for Proceedings 9h˙Shifman-Larkin

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saw people who had come from as far away as Europe, Russia or Israel for the single purpose of exploring the mysteries of condensed matter with Larkin. The fact that Tolya attracted so many physicists of diverse backgrounds and with nontrivial ideas was his priceless gift to the Institute. It seems to me that Lyonya Glazman’s departure for Yale was a consequence of Larkin’s untimely death. Tolya and I never worked together: our scientific interests lay too remote from each other. However, once in a while I would ask him a physics question. He didn’t like to answer right away, preferring to think over the question thoroughly and answer only later and in a comprehensive way. Tolya sometimes took a little nap in his armchair in the office. It wasn’t that he planned such naps beforehand; they just used to happen. As Alexei Tsvelik recalls: “One of the younger generation’s greatest mentors was Anatoly Larkin... Anatoly might have seemed like a slowpoke. You would begin to discuss something with him and he would fall asleep. The thing to do was not to hesitate but to continue talking. At the end of the monologue Anatoly would wake up and give the answer, always correct.” An Israeli colleague of mine wrote in a letter: “Tolya Larkin lectured us ignoramuses on quantum mechanics. I still remember the bursts of his mid-word “k” sounds; he had a slight stutter. Many years later he came to the Chelom State Yeshiva (as I jokingly call the Weizmann Institute of Science). He was given an office with a window opening on the “Eastern Courtyard” – that is, a small pond surrounded by bamboo and papyrus, inhabited by frogs with extremely loud voices. Apparently in a contest with Larkin the frogs came out the winners: they interfered with Tolya’s “work with documents” after lunch. In 1991-1993, a Swiss philanthropist financed the launch of the program “Landau Institute - CSY,” through which almost the entire Landau Institute faculty spent time at CSY, some for a couple of weeks or a month, and some (like Volodya Lebedev) for up to a year, with more visits later on. Anatoly Ivanovich was among the first; April 5, 2013 15:41 WSPC/Trim Size: 9in x 6in for Proceedings 9h˙Shifman-Larkin

350 M. Shifman

he spent about a year at CSY, and immediately all kinds of legends started spreading about him. The tale of the frogs goes like this: everyone knew Tolya’s habit of napping after lunch, accompanied by his fantastically loud snoring. The sound had such resonance that sometimes it drowned out the concert of frogs from the “Eastern Pond” right under Tolya’s window. But often the frogs won and interfered with the Academi- cian’s “document work,” as this activity was called at the time in B.N. Yeltsin’s oﬃcial daily schedule.” Tolya lived with the family of his son Victor – including Tolya’s daughter in law and two grandchildren – in a modest apartment not farfromcampus.Heusedtobiketoworkinthemorningandthen return home in the evening. Rain or shine, summer or winter (winters in Minnesota can be cold and snowy), he kept to his routine. Sometimes when the weather wasn’t good enough to park the bicycle downstairs, we would take it to his oﬃce. Once I asked him: “Why don’t you buy a comfortable house in a suburb and a car to commute?” “I have no driver’s license, I can’t drive, and I don’t want to waste my time on such things. I feel very comfortable with Victor’s family and my bicycle. Besides, I have a house in Chernogolovka,” he replied. To outsiders Tolya could seem taciturn. Indeed, he himself rarely initiated conversations on non-physics issues. Once asked, though, he could show profound – almost professional – knowledge in various areas of human thought, such as history or politics. He never hesitated to express unconventional opinions. Shortly after Mikhail Khodorkovsky’s arrest and conviction, a conversation during a tea break accidentally drifted toward Russia. I should say that our Institute has its pessimists and optimists. One of the latter said: “Believe me, in a couple years Khodorkovsky will be released and eventually will become president of Russia.” Tolya listened carefully and didn’t immediately respond. Later, however, he said: “I don’t know whether Khodorkovsky will be released; probably not. But I’m absolutely sure he will never ever be president of Russia.” April 5, 2013 15:41 WSPC/Trim Size: 9in x 6in for Proceedings 9h˙Shifman-Larkin

Tolya Larkin at the Institute 351

“But why?” “He’s half-Jewish,” answered Tolya. For reasons I cannot comprehend, Tolya Larkin had a deep lack of faith in American medical doctors. Even though our University provides excellent medical insurance for all its employees, supposedly Tolya never paid a visit to a doctor in all his 10 years in the United States.a He loved long hikes, especially in the mountains. In fact, this was one of the reasons why he so cherished the physics programs held in Aspen every summer. This was his favorite pastime: long hikes intertwined with physics discussions and seminars. The last hike, the last seminar, the last discussion in Aspen ...

aAccording to my colleague Boris Shklovskii. April 5, 2013 13:34 WSPC/Trim Size: 9in x 6in for Proceedings 10a_Chap9-divider

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For more technical reviews see pp. 524 and 526. April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10c˙Diakonov-Anselm-Mant

ALEXEI ANDREEVICH ANSELM∗

D. I. DIAKONOV Petersburg Nuclear Physics Institute Gatchina 188000, St. Petersburg, Russia and Academic University, 195220, St. Petersburg, Russia

Alexei Andreevich was born on July 1, 1934. During the war, he was evacuated to Kazan. In 1951 he enrolled at the physics department of Leningrad University. He graduated with honors in 1956 and then enrolled at the Ioffe Physical-Technical Institute. Among the teachers who influenced him most, in his view, were K.A. Ter- Martirosyan, I.M. Shmushkevich, L.D. Landau (with whom he once entered into a scientific dispute – more on this below) and of course his older colleague V.N. Gribov, with whom he did many joint works. In the late 1950s, Landau and other renowned theorists tried to prove the inevitability of the “Moscow zero charge” in quantum field theory, including models with four-fermion interaction, regardless of the sign of the coupling constant. In the calculations, they used the rather complicated so-called double-limit technique. In 1959 Alexei Andreevich studied a two-dimensional model with four-fermion interaction and showed, first, that this technique leads to incorrect results, and, more importantly, that the model is not “zero-charge” but the reverse: the effective coupling constant decreases at small distances.a This was, in fact, the first discovery of a tremendously important phenomenon in quantum field theory, later called “asymptotic freedom.” Fifteen years later, Anselm’s model was rediscovered and become known as the Gross-Neveu model. Asymptotic freedom today is the cornerstone of the theory of strong interactions (quan-

∗Translated from Russian by James Manteith. aSee two articles in Chapter 11, pp. 524 and 526.

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356 D. I. Diakonov

tum chromodynamics) and the Standard Model in general. It’s funny to think that if Alexei Andreevich had been older than his 25 years, if Soviet physicists hadn’t been mostly cooking in their own juice for decades, the entire history of the theory of elementary particles could have taken a different course. In the early 60s, the prevailing view internationally was that the era’s quantum field theory couldn’t reflect reality and that a more adequate description of elementary particles and their interactions at high energies is the theory of complex angular momenta and an approach based on unitarity and analyticity of scattering amplitudes. Vladimir Naumovich Gribov was a main author and creator of this approach, and it’s not surprising that his closest colleagues, including Alexei Andreevich, enthusiastically took up its development. In this new field, together with Ya.I. Azimov, V.V. Anisovich, G.S. Danilov, I.T. Dyatlov and V.M. Shekhter, Alexei Andreevich achieved outstanding results which have received world recognition. Among these are the theory of the production of three particles near the threshold, the study of Regge poles in perturbation theory, the prediction of the interference minima in a cross section of elastic collisions at large angles, and much more. In those years, the theory department of the Leningrad Physical-Technical Institute (later the Leningrad/Petersburg Nuclear Physics Institute) became a Mecca for theorists working on high-energy physics worldwide. The quark model appeared, and Alexei Andreevich and his colleagues calculated the probability of electromagnetic decays of vector mesons; coincidence with the experiment was a serious argument in favor of the “materiality” of quarks. In a new stage of scientific development, field theory’s rights were restored, and Alexei Andreevich began to work with gauge theory, which soon became the Standard Model of strong, electromagnetic and weak interactions. He was particularly interested in issues related to spontaneous symmetry breaking in gauge theory. Together with his students (Diakonov, Johansen, Uraltsev) Alexei Andreevich explored many questions: whether the asymptotic freedom of gauge theory can be combined with the Higgs phase which prevents the infrared pole, an electron mass can be obtained in the form of a “ra- April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10c˙Diakonov-Anselm-Mant

Alexei Andreevich Anselm 357

diative correction” from a muon mass, whether there’s a contradiction between the CP-violation experiment and the Weinberg model where CP violation is achieved due to the complexity of the Higgs sector, and so on. Alexei Andreevich was a born teacher: nuanced, attentive and generous. He had a rare trait of understanding when another person didn’t understand, and patiently and skillfully explaining the crux of the matter not in general, but namely based on the needs of a given person or specific audience. Niels Bohr was once asked what is “complementary” to the notion of “truth.” After some thought, Bohr answered, “Clarity.” This dualism is familiar to any teacher, but not everyone can escape it without casualties. A.A. had an amazing talent for minimizing the inevitable casualties: his explanations were clear and didn’t compromise the truth. He treated his students scrupulously: if he felt he hadn’t gotten “hands on” enough in a joint work, he irrevocably refused co- authorship, even if he’d contributed his ideas and some of his own calculations. He didn’t think his suggestion of thesis topics for Balit- sky and Diakonov, or dissertation topics for Dokshitzer and Uraltsev, provided sufficient grounds for him to be named co-author of the corresponding publications. He once told someone, “I only take on graduate students and employees whom I consider stronger than myself.” This statement was of course far too self-critical, but very characteristic for him. It wasn’t in his nature to feel anything even re- motely like envy – on the contrary, he rejoiced exceedingly over his pupils’ and colleagues’ successes and openly called on others to do the same. After Gribov left for Moscow and Vladimir Mikhailovich Shekhter died soon after, the theory department went through a difficult period in its existence. In the end, the restoration of normal life came about namely thanks to the benevolence of Alexei Andreevich, appointed head of the department in 1983. In a sense, history repeated itself in 1992, when strong centrifu- gal tendencies emerged at the institute as part of the wave of general collapse and divisiveness. The two institute divisions with the largest headcounts – high-energy physics and neutron research – had April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10c˙Diakonov-Anselm-Mant

358 D. I. Diakonov

a “blocking minority,” and there was a real danger of the institute falling apart. In the end, all sides showed wise restraint and an almost ideal compromise was achieved: PNPI became a federation of autonomous Divisions, but with a single infrastructure, a common directorate and a Coordination Board where each Division has the right of veto. Alexei Andreevich, a theoretician, was elected PNPI director, and his election effectively solved many problems, as he showed empathy and insightfulness toward everyone and also well understood the essence of the changes taking place in the country. The institute wasn’t commercialized (a destructive shift for more than one scientific institution), the financial management remained transparent, there was no collapse, the institute as a whole obtained the status (and funding) of a State Research Center, and basic moral and scientific values were preserved. During the very difficult time of Alexei Andreevich’s directorship, the institute achieved a smooth and optimal transition to a new quality. Hearing about the night- mares taking place at certain scientific institutes in the country, each “PNPI-ist” could say with pride, “With us it’s different.” Skipping ahead, mention should be made of one of Alexei Andree- vich’s hardly trivial administrative policies. He was convinced that a person has a right to be “boss” only up to a certain age, which he defined as 65 years, regardless of merit. Incidentally, his parents stepped down from all administrative posts at this age, so there again he witnessed a good example. In the mid-90s he started calling for generational change among the sector heads at the Theoretical Physics Division. It certainly merits regard that V.V. Anisovich, I.T. Dyatlov, S.V. Maleyev and Yu.V. Petrov voluntarily resigned their powers; new sector heads were democratically chosen among representatives of the next generations. On the whole Alexei An- dreevich carefully and even somehow ceremoniously supported the Division’s democratic traditions, although as the Scientific Council’s director and chair he formally had extensive rights. Nonetheless, he would discuss any more or less serious administrative problem at length with the staff (and occasionally changed his original opinion), while issues ultimately went before the Scientific Council, where he didn’t so much speak as listened. Alexei Andreevich himself volun- April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10c˙Diakonov-Anselm-Mant

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tarily resigned as PNPI general director in 1994, having spent only two years in office, and in 1997 also resigned as director of the The- oretical Physics Division. Already terminally ill, he stepped down before the date he’d set for his retirement. Alexei Andreevich obtained many notable results in the 1980s and 90s. Most of his works from this period relate to electroweak theory. In particular, he sought a way to make a non-contradictory modification to the Standard Model. According to one familiar way of classifying theorists, he was more of an “inventor” of new ideas than a “calculator,” although he wasn’t afraid of laborious calculations and did them well and reliably. He proposed a new mechanism of spontaneous symmetry breaking in electroweak theory – due to strong “radiative” interaction of heavy quarks. He devised an ingenious composite model of quarks and leptons based on five components, which he called “quints.” Concurrently, independently from the better-known work of future Nobel Prize laureate G. ’t Hooft, he advanced the principle of the quantum anomaly cancellations at the level of constituent particles. Together with N.G. Uraltsev he proposed and studied in detail the possible existence of massless or very light Higgs particles. Our today’s knowledge does not contradict the existence of one or more massless Goldstone bosons, which A.A. called “arions.” Alexei Andreevich pointed out the analogy between arion and magnetic fields and proposed ways of experimentally verifying their existence. It’s difficult to predict how science will develop, but it is likely that Anselm’s works will prove prophetic. In the 1990s, Alexei Andreevich produced widely known works (part of which were done jointly with A.A. Johansen, L.N. Lipatov, M.G. Ryskin, and A.G. Shuvaev) devoted to the emergence of coherent pion fields in ultrarelativistic collisions of heavy ions. Under the influence of J. Bjorken, who greatly esteemed these works by Alexei Andreevich, coherent pion fields began to be called “disoriented chiral condensates.” These works by Alexei Andreevich have been cited hundreds of times; the possibility of “DCC” is discussed widely in connection with experiments at the Relativistic Heavy Ion Collider facility in Brookhaven. Alexei Andreevich was a world-class specialist on a very broad range of issues, and his more than 130 published April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10c˙Diakonov-Anselm-Mant

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works also cover very broad ground. He played an outstanding role in the establishment and formation of the Theoretical Physics Di- vision. Perhaps half of the TPD staff worked directly with Alexei Andreevich at one time or another, and many others also felt his influence in various ways. In 1992 the Russian Ministry of Science created science policy committees in various research areas, and Alexei Andreevich was appointed chairman of the committee on fundamental nuclear physics. The aim was to identify and materially support the most interesting and promising research projects in Russia. Alexei Andreevich contributed much work to this committee, along with his ideas about how such a committee should function. It must be said that these ideas differed from certain traditions of the Soviet era. In addition to leading Russian scientists, the committee included several major international experimental physicists, who showed a notably serious and sincere attitude toward their duties. For all projects under consideration, several parallel reviewers were appointed, who then reported their evaluations to the committee. After lengthy and detailed discussions chaired by Alexei Andreevich, a decision was pronounced. Unfortunately, at this time financial support for science was generally sharply reduced, but it’s safe to say that the limited funds available to the committee were put to optimal use. For many years, Alexei Andreevich was essentially the chief organizer of the annual PNPI Winter Schools. He loved this work, and his wonderful taste for true science, his friendship with leading physicists and his own talent as a lecturer ensured that every Winter School became a major event. When in the early 1990s the Theo- retical Physics Division was on the verge of financial collapse, Alexei Andreevich organized the International Winter Schools of Theoreti- cal Physics. The grants obtained for the schools’ organization helped the theory department endure this difficult time. Alexei Andreevich founded a scientific school not just in words but in deeds, and it’s not surprising that in 1997 the “Anselm School of Science,” one of very few schools at the institute, received formal recognition and support from the Russian Foundation for Basic Research. Alexei Andree- vich gave us all a final, stunning lesson with his departure from life. April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10c˙Diakonov-Anselm-Mant

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He underwent one serious operation after another, but never gave the slightest hint of knowing he was doomed. Despite the pain, and whatever took place in his heart, he stayed as calm, cheerful and good-natured as ever until the end. It was hard to imagine, at the Winter School in 1998, that his warm, perceptive words in memory of the prematurely departed Gribov would prove to be his farewell to the Institute as well. Alexei Andreevich believed that fundamental physics is very important, but is a part of broader human culture. Our task is not only to pursue our science on the highest international level, but also to find our place in the broader cultural process. He enjoyed friendships with many well-known writers, filmmakers, performers, artists, sculptors and representatives of other sciences, sometimes supporting them during difficult times. In this life he was interested in everything, and everything he did received the imprint of his intense personality – as a citizen of his country, as a physicist, as a human being and intellectual. April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10d˙Polyakov-Anselm-Mant

ALYOSHA AND I WERE CLOSE FRIENDS∗

A. M. POLYAKOV Department of Physics Princeton University Princeton, NJ 08544-0708, USA [email protected]

Alyosha and I kept up a friendship for a quarter of a century and were very close, although we lived in diﬀerent cities – he in St. Petersburg, and I in Moscow. When I moved to America, we didn’t see each other for years, but our closeness and understanding endured despite the distance. We met several times in America, at Princeton, and always started talking again as if in mid-word, as if our previous conversation had ended only the day before. While still very young, Alyosha did wonderful work,a which made his name, but for me to tell about this work, my story needs some perspective. The early 1950s saw the creation of a new science, quantum electrodynamics, which describes the interaction of electrons and photons. One remarkable prediction of quantum electrodynamics was that a vacuum is no vacuum at all, but a medium where certain combinations of elementary particles periodically ﬂare up and fade. So the electron we observe is not a basic electron but a kind of formation dressed up in a cloud made of virtual particles. In the 1950s, Landau, Abrikosov and Khalatnikov did work containing a prediction that this cloud of elementary particles in some sense must eliminate the electron from the spectrum: the charge of the electron plus the cloud must equal zero, since the virtual particles must screen the elec-

∗Translated from Russian by James Manteith. aSee two articles in Chapter 11, pp. 524 and 526.

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tron charge. And that no matter what charge we originally selected, it would be screened. This finding was experimentally inconsistent, and Landau and others concluded that quantum electrodynamics- type theory was indefensible. Landau wrote that the only correct equation in field theory is that zero equals zero. Landau and his colleagues found many other examples involving other particles and obtained the same result. They concluded that field theory contained internal contradictions and needed replacement by something radically different. This idea won over the masses, and no one seriously challenged it. Then Alyosha did work that contradicted Landau’s finding, but unfortunately it failed to receive the proper resonance. He considered an isolated model that made no claim to describe real phenomena but modeled one possible application of field theory. Alyosha discovered a phenomenon opposite to the findings of Landau and others, namely that the basic electron charge isn’t screened but anti-screened. The cloud gives it a supplementary charge. If you view this object at large distances you see a charged particle, but at short distances interaction is eliminated. As a result, interaction is apparently absent at short distances, but intensifies at large distances. Fifteen years later, this phenomenon was rediscovered in theory describing the real world. It was called “asymptotic freedom.” It’s one of the fundamental properties of nature, incorporated in the Standard Model. Alyosha’s work was published in Journal of Exper- imental and Theoretical Physics and naturally got a negative reaction from Landau and his colleagues. They decided the work was flawed, but checked the work as professionals and found it correct. It was brave for a young man to produce findings opposed to the ideas of the main school of theoretical physics. He did this and came out victorious. This made a name and reputation for him in the Landau school. He was now treated with respect and caution: no one knew what else he might think up. But unfortunately, his work concerned an isolated model, and the main group of physicists responded, “Yes, this is correct, an interesting example, but still isolated. And there can’t be examples that describe natural phenomena” – so field theory kept being seen as a pathological science despite this work. This April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10d˙Polyakov-Anselm-Mant

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viewpoint persisted right up until the 1973 discovery of an identical real phenomenon. This was revolutionary: field theory became a mainstream science again. Alyosha worked on many different things. He also had an interest in problems of interactions at very high energies. In Leningrad, where he worked, an entire school was established, led by Vladimir Gribov, for studying high-energy interactions. This school became a juggernaut, and no one in the field could compete with it. But the problem was that most of the school’s representatives considered their successes too absolute. Successful results naturally make people want to label the success as universal – that is, relevant beyond the limits where it was achieved. Many of this school’s representatives showed extreme intolerance of field theory. Alyosha, though, had common sense and intuition. Field theory, meanwhile, kept evolving. I remember that he made my life a lot easier, because at the time I happened to be studying field theory. The main representatives of this school of physics considered my studies pathological. Alyosha represented this school, but the breadth of his views, intuition and experience told him there was something to this [theory]. My works were published thanks to him. In this sense, he played a positive role in Soviet physics. At the right moment, Alyosha sensed that the area the Leningrad school had been working on had exhausted itself, that the time had come to look elsewhere, which he did. In the 1970s he came up with a lot of clever things, which I won’t dwell on here. I’ll only mention his last idea, related to the strong interaction of elementary particles. Collisions of elementary particles usually cause the birth of other particles. You smash protons, and other protons appear, π mesons, a whole particle stew. Alyosha’s idea was that in the collision something else might appear, not a particle but a coherent extended pion field. The thing is, there is a certain duality in quantum field theory: each particle is associated with a field, and we observe either the particle or the field. But conventional fields aren’t produced like particles; they are spilled all over the entire space. Alyosha found that in the case of π mesons, some objects occur which are, in fact, extended coherent clusters of pion fields, the so-called disoriented April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10d˙Polyakov-Anselm-Mant

Alyosha and I were Close Friends 365

chiral condensates. He predicted this completely new object. Alyosha’s main strength was his correct vision of the world, his common sense. Common sense means envisioning the world correctly; that is, intuition. He accurately predicted what might work. I think there’s a good chance his invention exists in nature. In physics, theoretical physicists have a whole range of specializations. Some are drawn to mathematics in the sense of being interested in certain mathematical structures; others, on the other end of the spectrum, work on processing experimental data. There are theorists who work on pure theory and devise general constructions. The criteria for these constructions is logical consistency and something more nebulous – the beauty of the construction. These theorists’ work has no specific connection with experiments. Other theorists work closely with experimentalists and devise temporary models, like scaffolding to explain the observed experiment. From the standpoint of eternity, their work has no relevance to theory. Alyosha worked in the middle; he understood both theorists and experimentalists and was a link between them. On the one hand Alyosha’s works satisfied the criteria of good theory, while on the other almost all his works contained predictions or an interpretation of known results. In his last years, he wrote several philosophical works and published them in the magazine Zvezda. This was probably his way of contributing to popular science. He wanted to give laypeople a sense of the mysteries of nature, to convey that many of these mysteries can be solved in completely unexpected ways, not primitively but somehow involving problems of the theory of relativity. He tried to show these concepts’ beauty and grandeur. I think he succeeded. He had a good literary style. In good part he was a person of the humanities, and I liked how he wrote. In these articles he also fought against ignorance. There are two issues here. One is social – how to protect society from falling into a fatal ignorance, which can influence the overall development of science. For example, senators shut down a supercollider, and they can shut down all science. All scientists agree on this issue. But there’s another problem, more subtle – science going in the wrong direction, which wins over broader scientific circles. These circles are remarkably intolerant of other directions April 5, 2013 15:54 WSPC/Trim Size: 9in x 6in for Proceedings 10d˙Polyakov-Anselm-Mant

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in science. This is particularly dangerous for young scientists. But Alyosha tried to reduce the level of general ignorance. This is a very useful endeavor. Alyosha was my closest friend at that time. His last days are hard for me to speak about. He bore everything wonderfully... It’s an irrevocable loss... April 5, 2013 15:55 WSPC/Trim Size: 9in x 6in for Proceedings 10e˙Mila-Anselm-mant

MEMOIRS∗

LUDMILA ANSELM [email protected]

“As long as you’re alive, I’ll also have life...” A. Anselm My story, you might say, reminds everyone of the well-known fairy tale about Cinderella: a provincial girl from Irkutsk winds up in Leningrad, where she meets... Alyosha and I studied together in the physics department at Leningrad University. We got to know each other in our third year there. I lived in the dormitory; we had a party. Suddenly Alyosha appeared, came up and asked me to dance. I think of this party as the start of our friendship. A new and exciting world opened before me. Alyosha, like me, felt drawn not only to science but to literature and art, and he talked and talked about all this... I found this fascinating and important... He helped me to get my bearings in an unfamiliar, wonderful city, to understand a lot of things... Then we married after graduation. By this time I was completely sure what I felt – it was love, great love... I moved in with Alyosha. His parents welcomed me very kindly. We lived together in an apartment with Alyosha’s parents for about twenty years. Alyosha’s parents belonged to the intelligentsia. They were educated people, with physics backgrounds. Alyosha’s mother Irina Viktorovna’s father worked as a doctor. He organized the Leningrad Pediatric Institute. At the start of the revolution, Leon Edmon- dovich Mochan,a Irina Viktorovna’s cousin, emigrated with his fam-

∗Translated from Russian by James Manteith. aIn France his name was spelled as L´eon Motchane.

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ily to France, where he founded the Institut des Hautes Etudes´ Sci- entiﬁquesb after the war, in the 1950s. Much later, at his invitation Alyosha spent a month working at this institute. Alyosha’s ancestors on his father’s side, the Anselms, were winemakers in Ger- many. After a crop failure due to a cold winter, frost killed the vine- yards, and in 1817 they moved to Russia to try their luck. Settling in the North Caucasus, they again took up winemaking, grew rich and began buying up land in Belarus. Alyosha’s grandfather Ivan Adamovich Anselm, a chemist-technologist, worked as director of a brewery in Odessa. After the revolution he was invited to Moscow, where he headed the Dorogomilovsky brewery and Mikoyan himself awarded him the Order of the Red Banner. When the Great Patriotic Warc started in 1941, Alyosha’s grandfather and grandmother, who had German roots, were sent to Kaza- khstan along with other Russian Germans. His grandmother died in Kazakhstan and his grandfather is buried in Elabuga, where he’d moved to be with Alyosha’s parents, who worked for Leningrad Uni- versity, which had been evacuated to Elabuga in wartime. Because of his German name, Alyosha’s father, Andrei Ivanovich Anselm, faced the threat of labor army conscription during the war. A close family friend, Anatoly Petrovich Alexandrov, came to his aid. He invited Andrei Ivanovich to Kazan, where the Leningrad Physical- Technical Institute was evacuated. A.I. Anselm defended his doctoral dissertation in Kazan. After the war, the Anselm family returned to Leningrad... Alyosha’s abilities made him a natural physicist. He studied mathematics seriously in school. And during Alyosha’s last years in high school, Andrei Ivanovich began giving him and his friends lectures on physics. Since Alyosha was half German, half Jewish, his parents worried, not without reason, that the physics department

bA famous French institute supporting advanced research in mathematics and theoretical physics, located in Bures-sur-Yvette, south of Paris, the French analog of the Institute for Advanced Studies in Princeton. L´eonMotchane enjoyed the support of Robert Oppenheimer and Jean Dieudonn´e. cThe term Great Patriotic War is used in Russia to describe the period from 22 June 1941 to 9 May 1945 of World War II. Germans invaded Soviet Union on 22 June 1941. April 5, 2013 15:55 WSPC/Trim Size: 9in x 6in for Proceedings 10e˙Mila-Anselm-mant

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wouldn’t accept him. Those were the times... And when Alyosha was due to file for a passport, there was the question of what nationality he ought to choose.d Irina Viktorovna insisted on his registry as a German. Alyosha won a silver medal. At the entrance interview he answered all the questions, but didn’t get accepted at the physics department. Instead, it was proposed that he try the geography department, where there was no contest to enroll. Later, after the departure of the commission that checked university ethnic quotas, Alyosha obtained a transfer to the physics department all the same. I also received a silver medal. At the entrance interview, I barely had to answer any questions, since I’m Russian and the physics department had run short of this nationality. In the years of our youth, physics was considered a fashionable major, and bright young people raced to be on the cutting edge of science. At that time, not only in our country but all around the world, many talented people dreamed of becoming physicists. To make it into the physics department meant happiness; those who succeeded felt like important intellectuals. It’s said that many are called but few are chosen – later on, everyone had their own destinies. At first acquaintance, I was struck by the unusual traits of Alyosha’s character. He was full of a positive energy, an ebullience and kindness that overstepped the usual boundaries, gushed past the edge. Introducing me to his friends, he tried to show their best sides, while he himself stayed in the shadows. At first this surprised me, but then I realized that he not only loved his friends but took pride in their friendship. Later he had similar relationships with his colleagues at work. There was usually a gathering of colleagues and students around his large desk. They worked all day and went home only late at night. He was happy and proud when someone in his department obtained interesting results, and he always saw himself

dIn Russian the word “nationality” is used to mean ethnic origin. What is known as nationality in the West is called citizenship. Each Soviet citizen, upon receiving a passport at the age of sixteen, had to indicate his “nationality.” If both parents had the same nationality this would be the one; if not, he/she could choose between the two nationalities of the parents. April 5, 2013 15:55 WSPC/Trim Size: 9in x 6in for Proceedings 10e˙Mila-Anselm-mant

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as surrounded by friends. But eventually it turned out he’d been wrong: some of the colleagues felt less friendly toward him than he had thought. Alyosha was deeply hurt by this discovery. Our house was always full of people. At first Alyosha’s friends were mainly physicists; then writers and poets appeared. He dreaded provincialism, seclusion in a narrow circle of professionals. Alyosha had an unusual gift of striking up friendships wherever in the world his work brought him. He was a “man of friendship.” In the 1960s, Professor Elliott Leader invited him to London to work at the physics department of Westfield College. There Alyosha made friends with several English physicists. After this trip, he wasn’t allowed abroad for fifteen years. He had no contact with his English friends: personal computers didn’t exist then, and exchanging letters was forbidden. But as soon as perestroika started, Alyosha immediately reestab- lished his old ties, and his friends from England with whom he was closer – John and Mary Taylors, Eliot Leader, Norman and Henri- etta Dombey, Volodya von Shlippe – were among our frequent guests. One of them, Volodya von Schlippe, after he retired in England, was hired by Alyosha to work at his institute. These ties with Alyosha’s friends, who became mine as well, have lasted to this day. I meet with them in Russia, in America; it’s delightful to get regular calls from England... Before perestroika, when non-party physicistse weren’t allowed abroad, scientists from the U.S., England and Germany would travel to visit the institute’s theory department, seeing it as their mission to communicate with Soviet scientists in order to keep up the scholarly contacts necessary for scientific development. Theoretical physics contains no military secrets – especially his research area, quantum field theory – and so this science is international. It can and should unite scientists. When serving as director of the Leningrad Nuclear Physics Institute, he did much to broaden international contacts at the institute in Gatchina. Spending time in Paris acquainted him with life in the West, and after this trip, right at the beginning of perestroika, he wrote the article “West is West, East is East,” empha-

eNon-members of the Communist Party. April 5, 2013 15:55 WSPC/Trim Size: 9in x 6in for Proceedings 10e˙Mila-Anselm-mant

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sizing that Russia is a country of European culture and should follow the West’s path. The article was published in the journal Neva. Alyosha was a good lecturer (he lectured on physics at Leningrad University) and could speak on various topics with no preparation. Once in my presence Yuri Kolker, who anchored a science program for the BBC, asked him to answer a rather difficult physics question. The initial discussion with Kolker took only a few minutes, after which Alyosha gave a smooth, confident and comprehensible account of the basic problem for fifteen minutes on the radio. Alyosha spoke on scientific issues for the BBC during several of his London trips. He saw physics as a modern philosophy and endlessly speculated on themes concerning this science’s ongoing development. He felt responsible for physics, although he didn’t consider himself an outstanding physicist and usually said that although he had a huge number of published works, not even one of them was fundamental. In fact, he did work on that level early in his career, but it clashed with the views then prevalent among physicists of the Landau school and unfortunately went without adequate recognition.f Alyosha always worked long and hard, so lost in his ruminations that he didn’t even hear when called to the table. Concentrating on his thoughts, he could become scatterbrained. I remember once after a flight from St. Petersburg to Boston, on the bus home (our granddaughter Anya and I didn’t shepherd him closely enough) he managed to forget his jacket – which was returned the next day, by the way. Then when he gave a lecture at a seminar, Anya and I went on a long search for the glasses and umbrella he’d also left behind somewhere. Despite his busy schedule, he found enough time for politics, literature and history. He had a talent for articulating ideas, synthesizing them, engagingly discussing different topics: life, aging, death... Here are some meditations from his diary. “...Old age creeps up quietly as a person peacefully chews the cud of life. For a long time you don’t notice anything, and then suddenly you realize what a long road you’ve traveled. It happens like this...

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Whatever excites you – new published work, a trip to a new city or assignment to a new post, and with it joy and vanity, the new post’s new material opportunities, a first, second and tenth trip abroad, and finally, new women – all this repeats itself over and over in endless circles... And then you notice that when you sit down on a train heading to Moscow, you no longer look eagerly out the window...” “...Amazingly, I know a way to escape the finitude of the time allowed for life. This way is creativity. Any kind. Whether science or art...” Here are excerpts from his letters to A. Kushner,g a close friend in Alyosha’s last years. Alyosha wrote him letters from the hospital. “...There can be no single substitute for life in all its facets: not language, not music, not art generally, not love, not death. Among this array, though, the sense of approaching death probably comes closest to reaching the same level as the whole of life, and yet death also bows to life. Life is bigger...” “...For me, life’s beauty lies in its irreducibility to any, even the most wonderful, of its sides. I’m amazed by the lack of conclusive statements about life. Life is not... one thing or another or something else; it’s one thing and another and something else. And each particular life situation always has many sides, like that joke: ‘You’re right, and you’re right...’ Over the years, this inconclusiveness has become almost a religion for me and keeps me from living decently. How can you size up a situation when you see so many aspects of a problem? It was worst of all for me in my directorship days; it’s very hard to make decisions like a dragonfly, staring in all directions at once...” “All that’s left is beauty. It’s somehow surprising how much this vast word manages to unite: art, and science, and love... and death? It sometimes even seems like just a synonym for life, accenting one of life’s most important sides... It’s been a long time since I felt such happiness as when I wrote my recent sketch “What is Time?” I completely forgot that the ideas weren’t mine but Einstein’s, and to tell you the truth, what’s the

gAlexander Kushner is a contemporary Russian poet. April 5, 2013 15:55 WSPC/Trim Size: 9in x 6in for Proceedings 10e˙Mila-Anselm-mant

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difference? If that’s what beauty is? It seems to me that we, very specifically, as theoretical physicists, and even then far from all of us, have a great happiness given us, seeing the universe’s beauty from a certain perspective foreign to others... Somehow I’ve started philosophizing. And it’s not hard to guess why. “It’s time, it’s time, it’s time to return the creator the ticket!” Not from any wish to, but because it’s time... And here again there’s a kind of salvation in sensing higher harmony and the world’s beauty. Einstein was once asked about his attitude toward death. He replied that an individual person’s death changes so little in the world’s structure that it doesn’t cause him much concern. I don’t doubt his sincerity; he was generally a very sincere person. And in this, I hope, there’s no fundamental difference between Einstein and myself: if you’re able to sense this beauty, it’s fine to ignore that you weren’t the one who discovered it. Beauty is higher than the question of authorship! And death is like a frame setting boundaries to life’s canvas. A frame plays a not insignificant role in viewing artwork, but it certainly ought to match the art itself. It seems to me the fear of death needs overcoming not by trying to forget death, but only through close scrutiny of it and life together...” Perhaps Alyosha’s main quality was his insurmountable love of life in all its forms: he loved holidays, loved making interesting acquaintances, gladly received visitors and paid others visits, and loved women, which of course at one time couldn’t help but cause jealousy, but strangely enough even this memory is pleasant now. He had a way of creating a joyful, euphoric mood around himself and passing this mood on to others. Yes, he loved life, but the romance was one-sided: he passed away too soon... During Alyosha’s illness, we moved to Boston hoping American medicine would help him. But it was too late... He courageously fought for his life, bore all the hardships he was destined to endure: three operations, endless chemotherapy sessions, tedious examinations. He never complained of feeling unwell; he worked until the last day of his life, wrote on physics for a popular audience. Af- ter his death, three of his articles appeared in the magazine Zvezda: April 5, 2013 15:55 WSPC/Trim Size: 9in x 6in for Proceedings 10e˙Mila-Anselm-mant

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“What is Time?”; “The Philosophy of Physics is the Philosophy of the Twentieth Century”; and “The Structure of this World.” In these popular articles he set himself the key task of helping everyone understand the wonder of scientific achievements, encouraging their appreciation and warning against cluttering the consciousness with mysticism, astrology and faith in psychics. Alyosha was very fond of St. Petersburg, the city where he was born and lived almost all his life. In Boston he constantly remembered his city, missed friends he’d left behind there. In St. Petersburg we had places where we especially loved to go walking. We would imagine ourselves repeating our walks through Petersburg: “Now we’re crossing Manege Square, then up Maple Alley to the Engi- neer’s Castle, then onto the Field of Mars, then across the Neva, up Kamennoostrovsky Prospekt... He often repeated Brodsky’s poem, “Let it not be my fate to die far from you...” It was his fate, unfortunately... In Boston we also took walks. Sometimes we stopped by American cemeteries and spent a long time looking over the fence at the head- stones. I realized that Alyosha wanted to know how things would be after his death... Our daughter Irina lives in Boston. She’s a pediatric neurologist. She passed all the examinations in medicine and now works at the best children’s hospital in the United States. Alyosha rejoiced at her successes and felt proud of her. She helped him receive free treatment at a hospital in Boston. Irina’s daughter, Alyosha’s and my granddaughter Anya, who was born back in Leningrad, now lives in New Hampshire. She’s a schoolteacher, a Spanish instructor at a school. Alyosha loved being with Anya when she was little. Every evening he would tell her a long, endless fairy tale involving the whole family and various characters from adventure novels. The main characters were Anya and himself. I don’t really remember what he concocted: different adventures in the jungle with tigers and monkeys, and on the sea with pirates. I only remember how once Alyosha told me, “Do you know what Anya’s grandmother, that is, you, hauled off and did? She left us and married Captain Nemo.” I don’t know how he guessed that April 5, 2013 15:55 WSPC/Trim Size: 9in x 6in for Proceedings 10e˙Mila-Anselm-mant

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Captain Nemo was one of my favorite childhood heroes. Irina gave birth to a son whom Alyosha never got to see. In honor of his grandfather he was named Alyosha. Now he’s in the sixth grade and enthusiastically involved in basketball and baseball. When he was little, he filled several notebooks with stories about a boy who feels good everywhere: in a cafe, at the pool, outdoors and even at home... I sometimes think his cheerful character resembles his grandfather’s... I’d like that, anyway... Three years after Alyosha’s death, while going through his papers, I unexpectedly found a letter he wrote me back in St. Peters- burg while undergoing treatment at the hospital. The letter actually turned up his birthday, the first of July... I’ll give some lines from this wonderful letter... “April 9, 1996. I don’t even know what I plan to write: a letter to you or something like notes from the house of mourning. Yesterday I was writing a farewell letter, of course, but today now that everything’s settled at last and I’m in the hospital, my mood is suddenly very different. During the day I even perked up and thought, here’s what seems like a most unfortunate turn of events: hospitalization in such a dismal place (the Central Scientific Research Institute of Roentgenology and Radiology – TsSRIRR, the abbreviation alone is spine-chilling!) could just be my only chance for at least a little relaxation. Everything depends on the illusion of doing something active, trying to stave off fate. It’s evening now, I’m by myself in the ward, feeling melancholy creep closer again. But I’ll still try to write you again about what I planned to write before I ran out of time. I want to write you about how much I love you. All the tortures I put you through seem so unfair to me now; such a pity, those ill-spent years, those years lived wrongly only by my own fault alone. But if you really do read this after my death, I ask you to forget all the bad things and remember how much was wonderful! Somehow only now I’ve realized that, in the end, for our first ten years harmony was a struggle, but for thirty years we lived as good friends. And what’s perhaps most surprising – this happens only rarely, I think – with the years, our closeness increased many times over, and perhaps our love did as well. It now April 5, 2013 15:55 WSPC/Trim Size: 9in x 6in for Proceedings 10e˙Mila-Anselm-mant

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seems to me that no one we know (husbands and wives among our peers, I mean) loves each other as much as we do. We have grown into a single person, and that’s why it hurts you so much to lose me and me to leave you. But for the same reason, as long as you’re alive, I’ll also have life. The only thing is that for some reason this brings me little comfort, although seemingly it ought to. And again, about death... It seems I’ve managed to make peace with the thought that soon I’ll be gone, that I’ll no longer be taking part in anything – in fact, this really isn’t a universal catastrophe, after all! But how is it possible to pass away without pain or fear? At least, without much fear. After all, you and I spoke of a life of sixty-odd years as not being so short. And in fact my life really fit in a lot of things: perhaps enough for eighty years (if not more) of a life of average intensity. So there’s no need to regret that I lived a brief life. First, it wasn’t all that brief, and second, from a somewhat more distant point of view (say, Anya’s grandchildren looking over their family tree), really, having been 62 years or 82 years old will appear almost the same. And then let’s also remember what you and I also spoke about: everything depends on scale of reference, everything happening with us is nothing compared with certain other peoples’ tragedies. So my death is no universal tragedy, but just the natural death of one elderly man: against the backdrop of things that happen in the world, a rather insignificant event. I keep writing about myself, but really you’re the one who con- sumes my thoughts. For you there will be an “afterward,” and I recognize how much you’ll have to endure. Still, though, the worst time for you will be the beginning, and then caring for Anka and Irka (and maybe Irka will have another child or you’ll live to see Anka’s children!) – caring for them ought to dull the pain of your loneliness. When you read this letter, you won’t believe it, but it’s true. April 10, 1996. My dear, you can’t imagine what sudden changes of mood I’ve been having. Today you came and started discussing the possibility of an operation in the future, and surprisingly enough I again fell into an abyss of despair. And it’s not at all that I’m so afraid of the operation; I’m terrified to think of following the preordained routine of a cancer patient right up until my death. April 5, 2013 15:55 WSPC/Trim Size: 9in x 6in for Proceedings 10e˙Mila-Anselm-mant

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Yet after all, at this moment I can’t make any real decisions. And apparently that means I shouldn’t think about this but about how to live for now. So I decided that if I feel better after chemotherapy and no new surprises come up, I’ll try going to Marseilles and then, if possible, to Italy, and then, if possible, to England (in the last two years of his life, Alyosha went to Marseilles, England and Italy)... I think it’s safe to say that one way or another this won’t work out, but clearly what’s needed for now is to live as if I still have another twenty years of life ahead. Lord, I know nothing can save me from my illness, there can be no such miracle, but maybe I can somehow control myself and still live – even if not very happily – some normal, peaceful months? Because it’s not right to live as I’m living now. April 11, 1996. Milush, my beloved! How strange that my latest letter to you has started evolving into some kind of spontaneous diary. I’ve even started to think these notes are addressed not only to you (forgive me for this as well, darling), but who needs them except you, Irka and maybe Anka when she grows up? Read this to them; they’ll remember me longer. You’ll remember me to the last regardless of these notes. And if you want, you can show parts of these letters to others...” I’d like to ﬁnish by saying that in my memoirs I like returning to the past, because I felt good when I was there... Our daughter Irina, as I already wrote above, gave birth to a boy twelve years ago and named him Alyosha; this year our granddaughter Anya gave birth to a girl and named her Olivia Anselm (her middle name) Helbling... Alyosha continues to live beside us in his grandchildren and great- grandchildren. April 5, 2013 13:34 WSPC/Trim Size: 9in x 6in for Proceedings 11a_Chap10-divider

CHAPTER 10 May 10, 2013 11:14 WSPC/Trim Size: 9in x 6in for Proceedings 11a_Chap10-divider May 13, 2013 15:48 WSPC/Trim Size: 9in x 6in for Proceedings 13˙Index

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SNAPSHOTS FROM THE 1950s∗

YURI F. ORLOV Laboratory of Nuclear Studies, Cornell University Ithaca, New York, 14853, USA [email protected]

It happened that our careers in physics – that of Boris Lazarevich Ioffe and mine – started almost simultaneously at the Institute of Theoretical and Experimental Physics (ITEP) in Moscow.a Half a century later, my memories of this time are still vivid. We met around 1951, when I was about to graduate from Moscow University. Before graduating, I had to complete my senior thesis at ITEP on the theory of positronium. A little bit later, Pomer- anchuk asked me to check some calculations of anomalous scattering of muons, which had been previously made by experimentalists. I was supposed to do this with Alexei Rudik who shared an office with Boris. I would often drop by their office to discuss various physics topics. I liked Boris from the moment I first saw him. The conversations we had often carried two levels of meaning: the literal and the unsaid. The first level consisted of our discussions of scientific problems. The second level was an extension beyond physics – into the meaning that could be guessed from a simple remark, a glance, a smile. Those were still Stalin’s times, after all (and those right after his death);

∗This essay, published in At the Frontier of Particle Physics,B.L.IoffeFestschrift,Ed. M. Shifman, (World Scientific, Singapore, 2001), p. 65, is based on excerpts from Yuri Orlov, Dangerous Thoughts, (William Morrow, New York, 1991; translated from Russian by Thomas Whitney). The essay was revised and expanded by the author for the Ioffe Festschrift. aTo be more exact, at that time ITEP was known as Teplotechnical Laboratory, TTL. The very existence of TTL was classified. – Yu.O.

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times, when a seemingly insignificant gesture could reveal our deeply hidden thoughts. A gesture or a glance could tell more than long conversations. I could sense that Boris was a politically like-minded person, and in some ways more informed than myself. I had read a lot of world literature and philosophy. However, the names banned by Glavlit b were excluded from my readings. In fact, at that time, I simply knew nothing about Glavlit’s existence, unlike Boris, who must’ve undoubtedly been aware of it. I knew about life in villages, in factories and in the army—everything from my own experience; but I knew nothing about the life or the repression of the Russian intelligentsia. Boris knew a lot more about that. Nevertheless, our thinking eventually brought us to similar conclusions. Thanks to people like Boris Ioffe, Vladimir Borisovich Berestetsky (with whom I shared an office), Lev Okun, and others, the years that I spent working at ITEP were undoubtedly the happiest years of my life. But let me begin from the beginning. People said that Stalin himself signed the order establishing the Physical Technical Department c of Moscow University after the war. It was really a pact between scientists and the devil. The department prepared specialists mainly for fundamental nuclear and rocket research. Scientists badly wanted that for the sake of advancing science itself, and Stalin for the sake of producing bombs and rockets. The students were party to the pact, too. Most were untroubled by the idea of doing military work someday; others, like myself, believed we could manage to avoid paying that price for our education. Our teachers included the best Soviet scientists, such as Kapitsa, Landau, and Landsberg. Leading nuclear experts and rocket scientists had shaped the department to fit their idea of scientific training,

bGlavlit was an agency implementing total censorship in the USSR. Every material intended for publication, including such insigniﬁcant stuﬀ as, say, the business cards and the like, had to be cleared through Glavlit. A huge variety of books were forbidden for publication (or restricted in publication) by Glavlit.Theclassofdisfavoredbooks included not only those with political connotations, but, in general, all books which were considered not helpful for the Soviet ideology. cFrom 1951, the Moscow Institute for Physics and Technology, in Dolgoprudny, about 12 miles north of Moscow. April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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and the result was an unheard-of autonomy and a wildly un-Soviet regime. We, the department’s very first students, took great pride in that. Only laboratory work, examinations, and problem-sets were obligatory. We did not have to attend seminars and lectures — not even the lectures on Marxism, although official doctrine still declared that without thorough study of Marxism it was impossible to understand science. We were exempt from military training. And instead of the usual school spirit of collectivism and support for the untal- ented and backward, we met respect for individual uniqueness and a spirit of competition. I liked the competition, but had yet to understand that there are exceptional individuals whose achievements cannot be approached by any group, however large. Still partially hypnotized by Marxism, I did not believe very much in the uniqueness and the irreplaceability even of geniuses. So when Pyotr Leonidovich Kapitsa declared at a general assembly of the students, “If just one of you becomes a Newton, we will be happy,” I was amazed. He doesn’t believe there are many future Newtons among us? I protested to myself. Why can’t I become a new Newton? Kapitsa, who had not yet won his Nobel Prize, gave us a lecture course in experimental physics. Professors also attended it. He was about fifty years old, and his sparse gray hair did not make him seem any younger, but his face had preserved the features of an inspired boy and his sky-blue eyes were the eyes of a child. They teared a little, as happens sometimes with very young babies. In his first lecture he remarked that he had wasted rather a lot of time in his own life. It was a tactful bit of advice to us — don’t waste time. Listen- ing to Kapitsa was rather difficult because he organized his course as a history of measurements and discoveries, and understanding it required from the very start a good knowledge of all of physics. Be- sides that, he would erase with his left hand what he had just written with his right. But these difficulties could be surmounted, and the lectures were fascinating. Kapitsa would tell us about people — their discoveries, their mistakes, their bright ideas, and sometimes their “accidental” success — so that we felt we were together with them in their laboratories. Kapitsa’s personality fascinated us, too. April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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Stories circulated about his unheard-of independence, about how, for example, when he inexplicably returned from England to his homeland, he stipulated that there should be no special personnel office in his institute, and the Politburo went along with it just because he was Kapitsa, the great physicist.d Lev Davidovich Landau, who had not won his prize yet either, gave a lecture course in general physics from a theoretical standpoint and was even more difficult to follow than Kapitsa. His elegant concluding formulas derived almost “from nothing,” from general physics ideas, astounded us. Tall and lean, with a naturally elegant manner and a face bright with intelligence, Landau was the supreme model for me. My fellow students even claimed I consciously imitated his hairstyle, but that was untrue. I was the first student in the department to take special “Landau examinations” at his home, which was next to Kapitsa’s off the courtyard of Kapitsa’s Institute of Physical Problems in Moscow. After the examination we would usually chat. On one occasion I asked him not quite tactfully how many hours a day he spent in bed. It seemed to me that if I knew how this great scientist lived and worked, it would help me achieve a success like his. “Nine,” he willingly replied. “Sometimes more. One must work only with a fresh mind.” Abram Isakovich Alikhanov, director of the Institute of Theoreti- cal and Experimental Physics, where my study group did its practical work, was not such a genius as Landau or Kapitsa. But he was a distinguished scientist and honest man who gathered in his institute the same kind of men, and transmitted to us students his awesomely high standards. Once, after learning that only one student in our group (myself) had passed a theoretical physics exam with flying colors, enraged Alikhanov summoned us to his office.

dWe had no idea that Kapitsa was virtually a prisoner. He had been working for years in England at the Cavendish Laboratory, and had refused several oﬃcial invitations to return home for a visit. Finally he accepted. Once he got to the Soviet Union, he was never again permitted to visit the West until he was an old man. Niels Bohr and Ernest Rutherford, director of the Cavendish Laboratory, tried in vain to get him released. Rutherford then shipped Kapitsa’s laboratory equipment to him. There was nothing else he could do to help. – Yu.O. April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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“You are shit,” he began without any preface. “Either you intend to be researchers or not. If you do, then please be so good as to study theoretical physics thoroughly — whether you intend to become theoreticians or experimentalists. If you do not, then we’ll bid you good-bye.” The students did very well on the next examination. During our last years in the Physical Technical Department, seven of us from the group had been temporarily given a two-room apartment near ITEP. This meant good conditions for studying. We lived as a friendly commune and took turns cooking soup and kasha,discussed physics, and even organized a choir for Russian songs in which everybody sang. I was its conductor. One year before completing the university, I married a very serious young woman with big, beautiful, dark brown eyes. Her name was Galina Papkevich and she was half Polish. That is how, in the summer of 1951, I came to move with my suitcase out of the student dormitory and into a room in the very center of Moscow, where Galya and her aunt were living. To honor this event, my student friends presented me with a suit — the ﬁrst I ever had. At the end of 1952 a lovely son was born. We named him Dmitry. Galya worked as a technician at the very same aircraft factory where my father had once worked. I was carrying out research under the supervision of Vladimir Borisovich Berestetsky. The summer we were married, the Physical Technical Department had been reorganized into an independent institution, and like many in our group I was transferred to the Physics Department of the university. However, under the pretext of the reorganization the Jewish students were not sent there but to provincial and minor institutes, depriving them of access to “secret” work. This meant exclusion from future jobs in serious scientiﬁc laboratories. They were my friends, and I felt guilty when we met, but we did not trust one another enough even to discuss the situation. I wanted to graduate, to do science, to be with my wife. And so I kept silent like everyone else. The following winter, shortly after my graduation and the birth of our son, the Chekists revealed the plot of the “poisoner doctors” — April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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virtually all of them Jewish — and threw them in KGB e prison; even if the doctors had not drunk the blood of our babies, they had poisoned the blood of our leaders. Ordinary and not so ordinary Soviet people were discovering new poisoners here and there — poisoners of our children and our minds. Soviet ladies writhed in hysterics in the waiting rooms of Jewish doctors. Jews were being openly abused. Because of my curly red hair, people jostled me on the street, spat, and cursed: “Jew!” I refused to say that I was not. But I said nothing; to do otherwise seemed pointless. After a two-month wait for security clearance following graduation, my scientific career began. I had been offered three good choices of where to work: ITEP with Berestetsky, Kurchatov’s institute, or Institute of Nuclear Research in Dubna. I had already collaborated with Berestetsky; he had entrusted me with checking the calculations in the chapter of his book where electrons scatter on electrons. He was an outstanding theoretician and a sympathetic, cultivated man. Apart from that, I simply liked ITEP. So I began to work with Berestetsky in ITEP’s theoretical division. Headed by Isaac Pomer- anchuk, the division was the patrimony of Landau and consisted entirely of his disciples. Landau himself worked there half-time and ran his own division in Kapitsa’s institute. My research went well from the start. I worked so hard that calculations whirled about in my head even in dreams. At first I investigated the passage of particles through matter, and Berestetsky advised me to publish the results. However, they struck me as too small-scale; my first publication had to be something unusual. I dreamed of solving the problem of superconductivity, and began studying mountains of books and articles about it night and day. My new colleagues were similarly fanatic. “Science,” lectured Pomeranchuk, his spectacles and eyes sparkling, “is the most jealous of mistresses!” He did not just work evenings, as we all did, but at lunchtime snacked on sandwiches in

eThe Soviet acronym for the name of the secret police at that time. The Soviet secret police has changed acronyms like a chameleon. It started out as the Cheka, and then became the GPU, the OGPU, the NKVD, the NKGB, the MGB, and ﬁnally the KGB. Even today, however, people often simply refer to the secret police as “the Cheka” and the secret agents as “the Chekists.” April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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his office rather than going to the institute’s canteen. Goading me on in my work was the opinion of Landau, which Volodya Sudakov had told me about when we were students. Orlov, he said to Volodya, is talented but lazy. It would have wounded me less at the time had he said that Orlov was diligent but dull, for I had grown up in a family where lack of diligence was something immoral, and I was certainly not lazy. Yet Landau had correctly seen that I was not burying all of myself in theoretical physics, which demands very great abstraction from life around you. The fact was that more than just physics interested me. Indeed, I had come to physics from something else. It was impossible not to think about philosophy, social problems, and Soviet politics. Especially, now, about Soviet politics in science. Not long before Stalin’s death a general attack on physics was being prepared — an assault on quantum mechanics and the theory of relativity. At a special session of the Academy of Sciences, scientists were going to be forced to condemn publicly and without reserva- tion the obscurantist and subjective, in a word, pseudo-scientific, concepts of Albert Einstein and Niels Bohr. The philosophers and the most progressive Communist physicists had already begun the assault. The Ministry of State Security was rolling up its sleeves. Budker, with whom I became friends during the last years of his life and of my freedom,f told me how the catastrophe had been prevented. Igor Vasilyevich Kurchatov, the head of the nuclear program, warned Stalin that even the slightest distraction of physicists by a “philosophical discussion” would wreck the production schedule for nuclear weapons. The entire nuclear program was based on quantum mechanics and the theory of relativity. Everything will plunge off the rails, Iosif Vissarionovich. Stalin grasped this. Leadership in nuclear and rocket weapons was the primary goal of the state. These were weapons for future world domination. To achieve this goal with the aid of Leninist “beatings over their little heads” was a pleasant idea,

f Yuri Orlov was arrested by KGB in 1977 and sentenced to 7 years in labor camp, with the subsequent exile to Siberia, for the establishment of the Moscow Helsinki Watch Group. In 1986 he was stripped of his citizenship and deported to the USA in exchange for a Soviet spy arrested in America. April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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but unfortunately premature. Stalin had learned Lenin’s dialectic: to get to heaven it is necessary to pass through hell, to get to absolute supremacy it is necessary to pass through relative relaxations. So he ordered that the physicists, with their pseudo-scientific but, for mysterious reasons, powerful science, were not to be touched for now. Given the scale of things at the time, this was a small but remarkable retreat. And so physics was saved with the help of the atomic bomb. Alas, it was the bomb, too, that had given us our freedoms in the Physical Technical Department and had saved our professors. Budker described to me how, at the entry checkpoint of Kurchatov’s institute, where he was permanently based, the security guard had blocked his way and said, “Budker? You don’t have a pass!” Bud- ker needed no explanation of what this meant and what the sequel could be. He immediately phoned Kurchatov, who immediately explained to the proper quarters that Budker was a participant in the atomic program. Budker’s pass was quickly given back to him. In the Physical Technical Department the only one of our professors to disappear was our super-independent Kapitsa; but the general retreat of the regime from physics saved him, too. He was merely dismissed from his Institute of Physical Problems and from all his other jobs for refusing to work on nuclear weapons, and set down in his dacha instead of the Lubyanka. After Stalin’s death they apologized to him. I should say that we, in the Physical Technical Department, hadn’t really smelled gunpowder. We hadn’t even had an arrestometer. I learned about this Leningrad University apparatus from Berestetsky. In the thirties they had a gallery of professors’ portraits that the students, among themselves, called “the arrestometer.” Por- traits began to vanish from the walls. A portrait disappeared — the professor disappeared. Another portrait disappeared — and that professor disappeared. Finally the apparatus indicator went off the scale: all the portraits had been taken down. In the spring of 1953, Comrade Stalin finally died. His death on March 5 made no impression on me whatsoever. I sat out those days of national mourning, glued as usual to my desk in Berestetsky’s of- April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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fice. He asked me what did I think would change? In which direction? I replied that in my opinion nothing could change. And suddenly I added, surprising myself, that so many people were already in prison, there was already nothing else you could scare ordinary people with. Of course, I was overestimating the possibilities of “ordinary people” and underestimating the probabilities of change from above. My remark simply reflected an instinctive desire for a people’s rebellion — a desire that I consciously and firmly suppressed after several years and then rejected entirely. Berestetsky looked thoughtfully at me. I do not know what he was thinking, but from that time on he became muchfrankerwithmethanbefore. Soon afterwards a conflict sprang up between myself and Director Alikhanov. After reviewing old experiments, his laboratory discovered an anomalous scattering of muons. This being a serious matter, Pomeranchuk asked me to check the calculations. I discovered a mistake: because of the antiquity of the measurements, they had confused definitions of what had been measured. Alikhanov had to be told. “We’ve worked for so many years!” Abram Isakovich shouted. “But you—!” “How many years is irrelevant,” I said ruthlessly. “You made mistakes in the calculations.” He walked out, slamming the door with a crash; I was left alone in the office. In a few minutes he came back, listened, and understood. After that he became extremely friendly and warm to me, and I began to love him with all my heart. A few years later ITEP decided to build a proton accelerator with an alternating gradient. When Budker pointed out an important physical effect that might cause it not to work, Pomeranchuk, remembering my muons, included me on the accelerator team. His plan was that I would check this effect and then go right back to my usual subjects. I interrupted my study of superconductivity and in two years constructed the necessary theory of nonlinear oscillations (the effect turned out to be harmless for us), became a coauthor of the accelerator proposal, sent articles off for publication, and on orders from Pomeranchuk wrote a dissertation. “Writing a dissertation has no relationship to science,” he explained, “but it does to having April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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bread. You urgently need an increase in pay.” Salaries depended on academic degrees. And by now a second child, Alexander, had made his appearance. We definitely needed more money. However, our life had already improved a great deal: ITEP hired Galya as a technician and at the end of 1955 gave us a self-contained apartment of two rooms in a new building near the institute. It was like living in a palace, after the single room for the five of us. That room had been inherited by Galya from her mother, who received it from the Soviet government for contributions made to the Revolution by her parents, Polish revolutionaries. With my dissertation finished, I could finally go back to my previous investigations. But in February 1956, Nikita Khrushchev de- livered his dramatic report at the Twentieth Party Congress and left me an accelerator specialist for the rest of my life. Khrushchev’s report on the atrocities of the Stalinist epoch was read at closed Party meetings and shattered even those who, like me, were already anti-Stalinists. For the first time I realized the fearful scale of the crimes. Gangsters had been in power, and could get there again because in principle the structure had not changed. What should I do? There came that moment for which I had, in effect, been preparing my whole life — a life of tensely scrutinizing this strange, murderous, self-devouring society. I must state openly everything I thought about it. By order of the Central Committee, all Party organizations had to carry out closed discussions of Khrushchev’s report. The discussion at ITEP would be led by our Party bureau, which I had now been a member of for two years. Although Director Alikhanov, his deputies, and his division heads were nearly all non-Party, they tried to influence the composition of the bureau, as well as the trade-union committee, in order to have good or at least harmless people there. It was like organizing an all-round defense. So I had not declined to be elected to the bureau, believing that I could be of additional benefit to science in this way. Given all the twists of Soviet politics, even unexpectedly favorable ones like the death of Stalin, scientists always had grounds for fear. In the event of a general or local assault against physics or particular physicists, the position of the Party bu- April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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reau could, I thought, prove decisive in their defense. The bureau met twice to plan our March meeting. We decided to set its tone by speaking first. The opening speaker was Robert Avalov, a Georgian and orthodox Leninist who had graduated with me from the Physical Technical Department. My speech followed Avalov’s. Despite my excitement I spoke loudly and distinctly. “The terror carried out by the government,” I began, “has affected not only the economy of the nation but also every aspect of Soviet life. It has changed us ourselves.” We all, I said, from an ordinary worker to a writer, had been taught to sense where the wind was blowing and to adapt our souls to the current policy of the government. Everyone had got used to raising his hand obediently “in favor” — the members of the Supreme Soviet, and the members of the Central Committee, and all of us. In the conference room sat members of the Party who, like myself, were neither careerists nor fanatics. Now many of them, some timidly, some boldly, were opening their eyes and thinking about how to avoid a recurrence of Stalinism (although that term still did not exist). They seemed to like what I was saying. Volodya Sudakov, a talented theoretician and the secretary of the Party bureau, did not come forward himself but quietly offered the platform to everybody who asked for time to speak. He gave it next to Vadim Nesterov, an experimentalist (whose father later hid a copy of my speech at home, for safekeeping). The last to speak was Shchedrin, a worker and member of our bureau. People excitedly applauded our speeches and wanted to make their own. Since it was already late in the evening, we voted to continue the following day. But we were not permitted to conduct the next meeting. It was conducted instead by the chief of the Political Directorate of the Ministry of Middle- Machine Building, Mezentsev himself,g an expe-

gITEP was formally, but secretly, a military unit. Therefore, ITEP was just like the army with respect to Party control at that time: not subordinate to the nearest district Party committee, but to a special political administration — in our case, Mezentsev’s. The political section of ITEP was appointed by Mezentsev and existed parallel to our elected Party bureau. – Yu.O. April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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rienced Chekist. People said that in 1944 he had been in charge of deporting the Tatars from the Crimea. “No one is permitted to criticize the Central Committee!” Mezentsev shouted, pounding his fist on the table. The audience was nervous. I came forward to speak against his thesis, people shouted things from their seats, and no one publicly backed up Mezentsev. “We must pass a resolution condemning the anti-Party speeches of Orlov and the others!” he demanded. His proposal got voted down. The meetings over, the institute was frozen in expectation of what would happen next. The affair was being examined at a high level, we still did not know which one. All the speakers were ordered to write explanations to the Central Committee. Transcripts of the speeches were going there, including the statements of Mezentsev. Mezentsev would dispatch to the Central Com- mittee a separate report of his own. A week later an order came from somewhere in the sky,h firing the four bureau members who had made speeches, “owing to the impossibility of any further employment.” Alikhanov called us in. We stood before him as he paced back and forth. “Listen, if you knew what you were doing and what could come out of it, then you are heroes. If you didn’t — fools!”

hWhen I say that the decision came from the sky, I mean it. After the demise of the Soviet Union, the archives of the Central Committee of the Communist Party became accessible, for a while. Boris Ioﬀe managed to obtain the minutes of a meeting from April 3, 1956, devoted to the TTL case. He kindly forwarded a copy to me. Our activities were scrutinized at the very top. To mention just a few names, Brezhnev, Gromyko, and Suslov were present at the meeting. Here is a small excerpt from these minutes: “Avalov, Orlov and others made slanderous malicious subversive statements revising the general line of the Communist Party and the decisions of its 20th Congress. They were aimed at discrediting the democratic nature of the Soviet power, praised false liberties of the capitalist countries, and suggested unleashing a propaganda campaign in favor of the bourgeois ideology hostile to our country.” This was the same type of the Stalinist rhetoric we had heard during our whole lives. In 1956, however, it produced an opposite eﬀect rather than the one desired by the Party. Instead of evoking public outrage it evoked sympathy. In 1996 Mikhail Gorbachev told me that 40 years later he could still remember the tempest that followed our 1956 “revolt” at TTL. – Yu.O. April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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We kept silent. Were we fools — or heroes? “I telephoned Khrushchev on your behalf, but he said that he was not the only member of the Politburo. Other members demanded your arrest. He told me, ‘They should be glad they got off with dismissals.’ Good-bye.” He firmly shook our hands. We went out into the street. “Well, so be it! We simply won’t work for as long as the Party orders,” I joked. It was strange, but I felt only liberation — from a moral burden and from the incessant racing about at work. Buried in my science, I had forgotten the color of the sky and not noticed the change of the seasons. Now I discovered that out-of-doors it was spring. On April 5, 1956, Pravda ran a big editorial on problems of ideological purity. It mentioned the four of us. Several days later the four of us were driven from ITEP to Mezent- sev’s ministry, where we were formally expelled from the Party. They also took away the Party cards from the other members in ITEP, but returned them to whoever declared in writing that they condemned our anti-Party speeches and profoundly regretted that they had not opposed them at the meeting. Nearly everyone did exactly that. Yevgeny Tretyakov, a war veteran who had been in our student group at the university, refused and was expelled from the Party. Fortunately he was not fired. On a beta-spectrometer of his own design he went on to carry out a great many first-class experiments. Yet he would never do a dissertation, regarding the dissertation business as degrading and outside of science. They should have conferred a doctorate on him anyway, because of his work. But how could that be? After all—expelled from the Party, an unstable citizen! They warned me that I would not be permitted to defend my own dissertation, which had already been published. The articles I had sent to Soviet journals were blocked. Fortunately the European journal Nuovo Cimento managed to publish the first part of one article; it was impossible, now, to transmit the second part. My name on the title page of the accelerator proposal was painted over with black Indian ink and omitted from the lists of coauthors of several reports sent to an international conference at CERN. But they misfired with April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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one report. When they proposed to Yevgeny Kuprianovich Tarasov, my sole coauthor, that he drop my name from it, he preferred to drop the whole report. Although he was a well-known specialist on accelerators, he thereby lost any chance of travel abroad. During our visit to the ministry I had inquired why my name was being removed from all scientific publications. “It is very simple,” they replied. “Your name is a discredit to Soviet Science.” Alikhanov was pressured to fire Galya, a highly respected technician, but he swept aside the attempt. Everything was all right, then, with our apartment. While Galya was working, we had for the five of us her twelve hundred rubles a month, minus something to help my mother, plus the small pension of Galya’s aunt. This was not enough for meat. But bread cost only one ruble a kilo, so the situation was not catastrophic, and thanks to the solidarity of scientists we soon had almost the equivalent of my salary. Because of the Pravda article and a letter that the Central Com- mittee had sent to all Party organizations, the names of the four rebels from ITEP became known everywhere. Scientists came to our aid, distributing to each of us one thousand rubles every month. At the Lenin library metro station, future Academician Boris Chirikov twice secretly passed me funds gathered in the Siberian Institute of Nuclear Physics. One month someone presented me with funds gathered in Moscow at ITEP and the Lebedev Physics Institute, and the next month, funds from the Leningrad Physical Technical Institute. This was perhaps the first time that scientists in the Soviet Union had taken collective action to help their repressed colleagues. Under Stalin it would have been absolutely impossible. I decided to work on theoretical physics at home as if nothing had happened. Although it was dispiriting to live off the support of my friends, the formal end of my scientific career, which had begun so well, did not concern me overmuch — I believed in my ability to get good scientific results under any conditions. Galya, however, felt deeply disturbed. “You have to choose,” she said. “Either science or politics.” The uncertainty about my future worried her, not my political opinions. Had I decisively chosen the dangerous path of April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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politics, with its almost inevitable prospect of arrest, I am sure that she would have supported me. One day in June when I was lounging on the bed and feeling a little sorry for myself, Lev Okun, the theoretical physicist, dropped in and asked why I was lying there belly-up. “What can I do?” “Earn some money!” “But how?” “Give lessons to students preparing for entrance examinations. It pays well. I’ll give you one telephone number, and you can take it from there yourself.” Among the Moscow intelligentsia this was a well-known way to make a living in hard times. But I still wasn’t very close to the intelligentsia, and by myself would probably never have guessed that well-to-do bureaucrats paid well—fantastically well, on my mone- tary scale—for preparing their children to enter institutes. Okun’s advice changed the whole situation. Soon I had a multitude of private lessons. I worked all summer from 6:00 a.m. to midnight, seven days a week, and could stop accepting money from my friends. For the ﬁrst time in my life I purchased a refrigerator, a radio, a good suit. I sent my mother and Galya to stay in vacation homes, and even began saving money so that I could devote the coming winter entirely to theoretical physics. Despite running around all over Moscow to my pupils, I rarely missed seminars and conferences that did not require special permission to attend. Most of the scientists I encountered there tried to keep my spirits up. “Why are you hanging your head?” asked Bud- ker, although I wasn’t letting my head hang. “Remember that you are a hero.” But Lev Davidovich Landau was, as usual, dissatisﬁed with me: “One can help a person who knows what he wants. But if he doesn’t know what he wants, it’s impossible to help him.” “Lev Davidovich,” I objected, very much stung by his remark, “you used to tell how in prison where they stuck you in 1938 everyone thought, I’m not guilty of anything but the others must be guilty; it’s impossible that they’ve been imprisoned for nothing. And now you consider that I was dismissed for cause?” April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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“You’ve missed the point,” Landau calmly replied to my unjust charge. “In those years it was impossible to calculate anything. Peo- ple would ﬁnd themselves being punished as a matter of chance. Now things are diﬀerent. You could have calculated the consequences but did not want to. You consciously took a risk, then did not want to set things straight, and you gave up a good institute—for what? Do you really need physics?” The reaction of Bruno Pontecorvo was purely ideological. While traveling from one private lesson to another, I encountered the mysterious “professor” in the center of Moscow. The Italian physicist and Communist, who for some reason had moved from the West to the USSR, was gradually being “revealed”; a mere two years before, it had not been permissible even to utter his name. I had last seen him in Dubna, strolling along the shore of Volga, his bodyguard twenty paces behind. Dubna, with its nonsecret synchrophasotron, had been at the time reliably protected against spies and saboteurs by barbed wire and a zone of plowed earth around its perimeter, just like a good concentration camp. Surrounded by swamps, Dubna was in fact built with concentration-camp labor. It rested on their bones. The physicists were well aware of this, but absolutely none of them ever seemed disturbed. Pontecorvo greeted me and asked in his pleasant Italo-Russian accent: “What was the essence of your demands at the meeting?” “We called for the merging of socialism and democracy.” “Under socialism, bourgeois freedoms are impossible,” he objected. The next month, in late August, Alikhanov’s brother summoned me to his home in Moscow. He was director of the Yerevan Physics Institute of the Armenian Academy of Sciences. “My brother has advised me to hire you for work in Yerevan,” said Artemii Isakovich Alikhanyan. “We’re going to build a large electron accelerator. Will you come?” I discussed it with Galya. I did not want to go far from Moscow because Galya and children were here, and my friends, and the best physics centers. My work as a tutor was paying well. I could privately April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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discuss any scientific problem at all: none of the leading scientists denied me that; these were not Stalinist times. Nevertheless, the future hung by a thread. Today the authorities would put up with this, tomorrow—who knew? I had children. Anyway, they were not going to let me do scientific work in Moscow. But to leave our Moscow apartment for a distant province, with two small children and Galya’s elderly aunt, and no key in my pocket for at least one single room—only a lunatic would do that. And then there were our residence permits for Moscow. We could not have kept them, which meant losing forever the right to live in Moscow and the opportunity of a Moscow education for the children. We decided that I should accept the job, but would live in Yerevan alone. I spent in Armenia sixteen years, in a kind of exile. I had fallen in love with the mountains covered with sun-burned grass, the lichen- painted stones, the terraces with children running up and down them, the old courtyards and narrow side streets, the benevolent, peaceful, hardworking people. Iworkedhardtoo—Iwasinchargeofthetheoreticalsideofthe design of the electron accelerator. All my numerical calculations for the accelerator had to be surrendered to the “special section” after work, whereupon they immediately became “secret” and I no longer had the right to take them back, even one hour later, since I had no security clearance. I therefore always kept copies of my “secret” papers in my open desk; otherwise it would have been impossible to do any calculations. Although I now had my own group of physicists to lead, and a lectureship in Yerevan University, I could often find time in the evening to walk down into the gorge of the Razdan River, through the thickets of wild fruit trees alongside the rushing waters, and then up to the garden of my former dormitory. The old dormitory guard would put his copper coffeepot into a pan of hot sand on his stove and begin our usual conversation: I listening, he speaking. Years before, he had been a partisan struggling against Turkey and then against the Red Army invasion in Armenia. In its ten years of slow construction the Yerevan electron accel- April 5, 2013 16:0 WSPC/Trim Size: 9in x 6in for Proceedings 11b˙Orlov

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erator had become obsolete. After all, an accelerator is not a candy factory. We were nevertheless supposed to start it up in Novem- ber 1967 for the fiftieth anniversary of the October Revolution. On this special anniversary, decorations, promotions, big prizes were expected, and for that it was very useful to present big achievements. In view of my anti-Party attitude, no awards awaited me (although the academic council of the institute had proposed me for the Order of Lenin). But, keyed-up over the launch of the machine, I did not care. Once the accelerator was assembled, we swiftly got it going. I was satisfied and finally free of my moral obligations to Alikhanyan. Then the goodies were handed out. The order of Lenin—the highest award—went to the deputy director, Sergei Yesin, a very intelligent engineer and an orthodox Leninist to the point of stupidity. “The order of Lenin is a sacred honor for me!” he declared. “I could not go on living if it were proven to me that Leninism was incorrect.” The secretary of the Central Committee of the Communist Party of Armenia approached me. “If you submit an application to the Party right now,” he said, “we will arrange with Moscow not only to re-admit you but even to restore your Party seniority for the entire twelve-year period since 1956. Don’t lose a minute!” That was my prize. Curious as to what people thought of this ludicrous honor, I sur- veyed public opinion on the question: “Should I accept the offer to join the Party again?” Everyone answered, “Yes.” In Moscow I put the same question to Alikhanov, who was by now no longer director of ITEP. “What do you need that for?” he asked. “I certainly don’t need it. Of course, people say I could have permission to go on scientific trips abroad.” “I wouldn’t crawl into that bucket of shit even for the sake of trips abroad!” Alikhanov snapped. This was what I expected to hear from Abram Isakovich. I did not crawl into the bucket. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

BRUNO PONTECORVO: RECOLLECTIONS AND REFLECTIONS

S. S. GERSHTEIN Institute for High Energy Physics Protvino, 142281 Moscow Region Russia [email protected]

Now, when I am writing down these recollections, I can clearly see Bruno Maximovich arising in front of me, quite alive, with his invariable smile, humor, interest in people, craving for knowledge, his tact and profound democratism, owing to which he could speak equally freely to people of the highest positions and workers in a workshop, with his intolerance of any falsity and, especially, of ignorance in science, his readiness to give all support to new interesting experimental explorations. Bruno Maximovich belonged to that remarkable stratum of physicists whose works happened to form the foundation of modern nuclear physics, nuclear energy research and technology, and elementary particle physics. It is well known that the experiments carried out by young Pontecorvo together with Amaldi in Fermi’s group served as a stimulus for the discovery of the slowing down of neutrons – the eﬀect which underlies the operation of modern nuclear reactors, the production of many important isotopes, and which had played (and still plays) an important role in physics research. It was Pontecorvo who, in 1946, when the ﬁrst information on the relatively long lifetime of muons in matter was obtained, put forward the hypothesis of the universal character of weak interactions, of a new force in Nature, the only manifestation of which was hitherto represented by radioactive β decay. Bruno happened to be the father of experimental neutrino physics, having raised in 1946 the issue

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of possible detection of neutrino from nuclear reactors and having elaborated for this purpose the radiochemical (in particular, the so- called chlorine-argon) method for detecting nuclear reactions induced by neutrinos. In his famous report of the Chalk River laboratory in Canada, Bruno prophetically touched upon other aspects of neutrino physics by mentioning the Sun and accelerators as possible sources of neutrinos. I believe these ideas of Bruno reflected his human qualities – his incredible scientific courage and broad views. At that time, nobody actually thought it possible to implement such experiments. Even E. Fermi, as Bruno recalled, treated the idea of neutrino registration with considerable skepticism, and was much more interested in the technology of proportional counters, developed by Pontecorvo and applied by him in a number of studies (“Don Quixote was not Fermi’s hero,” Bruno noted, in this connection). Bruno’s ideas and calculations served as an impetus for experi- mentation. When the technique of large scintillators (which did not exist in 1946) had been developed, straightforward detection of neutrinos turned out to be possible, and was realized by Reines and Cowan in 1953–56. The chlorine-argon method was subsequently developed by Davis. This method allowed one to establish, for the first time ever, that reactor antineutrinos differ from the neutrinos. Solar neutrinos were detected, too. At the time when Bruno put forward his proposal for the detection of neutrinos, it was not known that the chain of thermo-nuclear reactions taking part in the Sun could (although with a small probability) result in production of 7Be and 8B nuclei, which are sources of neutrinos of quite significant energies capable of inducing the chlorine- argon reaction: ν +37 Cl →37Ar + e−. Such neutrinos were precisely detected by Davis who used the chlorine-argon method developed by Bruno. As to the main flux of solar neutrinos originating from the fusion of two protons into deuterium accompanied by the emission of a positron and neutrino, Bruno did not envisage in 1964 the possibility of their detection, owing to their energy being too small. It turned out, however, that the radiochemical method proposed by him was suitable for this purpose, too. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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At present, experiments aimed at detecting solar neutrinos attract the attention of physicists from all over the world. This is due to yet another brilliant idea of Pontecorvo. In 1957, he anticipated the possibility of one sort of neutrino undergoing, in vacuum, transformation into another, i.e. the so-called neutrino oscillations. It turned out that such a possibility is closely related to the Grand Unification of various interactions at super-high energies. Searches for neutrino oscillations have already been under way for many years in various laboratories throughout the world at reactors, accelerators, and meson factories, thus forming a significant focus of research programs. However, as indicated by Pontecorvo, only solar neutrinos (owing to the enormous distance from the source, as compared to Earth scales), provide the possibility of extending investigations to the region of small neutrino masses totally out of the reach of experiments on the Earth. Such precise neutrino masses are to be expected on the basis of Grand Unification models. Therefore, when the first experiments in which solar neutrinos were detected yielded a 2-3-fold decrease of their flux, as compared with calculations, Pontecorvo was the first to voice the idea that this fact might be related precisely to neutrino oscillations transforming electron neutrinos into other, “sterile,” states not capable of inducing nuclear reactions. The remarkable work of S. Mikheev and A. Smirnov demonstrated the coherent scattering of neutrinos in matter (considered by L. Wolfenstein) to significantly enhance neutrino oscillations. The Mikheev–Smirnov effect is operative in the case of small differences between the neutrino masses and small mixing (and can even result in all neutrinos passing into “sterile” states). After Mikheev and Smirnov’s work, B.M. Pontecorvo’s idea produced the most plausible explanation of the results of gallium, chlorine-argon and electronic (Kamiokande) experiments for detecting solar neutrinos. The gigantic experiments under preparation in several laboratories around the world will permit reliable testing of this possibility in the near future.a

aSince the time of writing of this article, a great deal of evidence for neutrino oscillation has been collected from many sources, over a wide range of neutrino energies and with many diﬀerent detector technologies. In 2002, KamLAND observed neutrino oscillations April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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Thus, Bruno’s ideas paved the way to the physics of the 21st century, making it possible to obtain information on the Grand Unifica- tion of the forces of Nature. However, this is not the only example of how the ideas and experiments of Bruno served as the starting point for experiments carried out for decades with ever-increasing accuracy. Such, for instance, are the searches for the μ → eγ decay and the determination of the electron neutrino mass from the spectrum of β-decay of tritium, initiated by Pontecorvo nearly half a century ago. I shall not mention other brilliant investigations carried out by Pontecorvo; I only wish to stress the importance of the work done by Pontecorvo for physics in the 20th and 21st centuries. Bruno arrived in the Soviet Union in 1950, when he was 36 years old and in the prime of his life. During his time in the USSR, he performed a series of brilliant investigations, including high-precision experiments on the scattering of pions off nucleons, parity nonconservation in the μ-decay, the muon capture in 3He, tests of the hypothesis of pair production of strange particles in nucleon–nucleon collisions, which he, incidentally, put forward before the appearance of Gell-Mann–Nishijima scheme, and many others. Then he formulated his famous hypothesis on neutrino oscillations and the role of solar neutrinos in the search of oscillations. Last but not least, Pontecorvo pointed out the possibility of performing accelerator neutrino studies (for instance, to answer the question whether or not νµ is identical to νe). Pontecorvo had a strong impact on the level of studies in elementary particle physics in the USSR, having established very high criteria, which had to be satisfied in some way or another. He educated a school of experimental physicists and stimulated many theoretical explorations. Many important new experiments were carried out owing only to the active support of Pontecorvo. Bruno Maximovich participated actively in establishing the Institute of High Energy Physics in Protvino and setting up its research goals. For many years he was the Chairman of the Neutrino Council at the USSR Academy of

consistent with the solar neutrino puzzle; in 2004 KamLAND observed neutrino energy spectral distortion as well as neutrino deﬁcit using reactor antineutrinos. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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Sciences. In later years, he was especially enthusiastic about the research program in neutrino astrophysics being implemented by A.E. Chudakov and G.T. Zatsepin. Together with A.M. Markov he did everything to support it at all levels. Regretfully, Bruno could not realize his own bold ideas: • detecting antineutrinos from reactors (which was done by F. Reines and K. Cowan in 1953–56 and for which Reines received the Nobel Prize in 1995); • demonstrating the muon and electron neutrinos to be not the same (for which L. Lederman, J. Steinberger and M. Schwartz received the Nobel Prize in 1988). Why that happened is quite evident. The answer lies fully in the conditions of life and scientific work in the Soviet Union during those times. As to the problem of two neutrinos, it could not be resolved in the USSR because of the absence of an appropriate accelerator, while the issue of making Pontecorvo’s proposal the basis of some international experiment at CERN or in the USA, involving his participation, could not even be thought of, given the conditions of those times (considering that even two decades later Bruno was not granted permission to go outside the “Socialist Camp” under the false pretext of his safety). The situation with the reactor antineutrino detection was even more offensive. I learned about it just by chance. In 1956, when I was a graduate student of L.D. Landau at the Institute of Physics Problems (IPP), one of the leading experimentalists of the institute – V.P. Peshkov – instructed Medvedev, one of his graduate students, to think about how to implement an experiment for detecting reactor antineutrinos. V.P. Peshkov himself was a refined experimental physicist in the field of low temperatures (thus, for example, he was the first to reveal the second sound in superfluid helium), and, in addition, he was a big shot in the State Committee for Science and Technology, thus having access to operating reactors. Knowing that I was interested in weak interactions, Medvedev contacted me and we started thinking about the experiment together. By that time, the presence of Pontecorvo in the USSR had already been made public, so when Bruno came to IPP we asked him to April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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take part in a discussion of the feasibility of such an experiment. He readily agreed. From the discussions with him we came to understand how naive we were to think it was possible to carry out such an experiment with the investment of relatively little effort. Bruno gave some useful advice, especially concerning backgrounds. I remember that he recommended putting the detector under a reactor, which would thus serve as a certain protection against cosmic rays. At the end of our conversation, we asked him why he himself didn’t conduct this experiment. First, Bruno avoided answering. But when, during the discussion, we once more asked him the same question, he reluctantly (with embarrassment, it seems to me) answered that he was not granted access to any reactor. I was astonished. Without a doubt, if investigations had started in 1950, when many industrial reactors were already operational and new ones were under construction, Pontecorvo, with his knowledge and skills, could have been the first to successfully detect neutrinos (given that new detection methods had appeared, which were unknown in 1946). This high fence set up by the authorities could not even be overcome by I.V. Kurchatov, who was very interested in the work of Pontecorvo. Thus, for example, he provided Bruno with a sufficient amount of 3He for an experimental study of μ capture, and V.P.Peshkov helped Bruno to thoroughly clean the sample 3He from tritium, the presence of which made it impossible to perform the experiment with a diffusion cloud chamber. The origin of this sample of 3He was evident. It was “waste” from tritium production (the material for the hydrogen bomb), so the amount of helium used was declared a secret and it was forbidden to make it public, when the results were published, although a competent physicist could easily calculate it knowing the experimental device and the conditions of the experiment. To everybody who knew Bruno it was obvious that he could have achieved much more working in the West and could have realized his own ideas himself. In this context, many people asked the question: “Why (or for what reason) had he come to the USSR?” Some were of the opinion that it was because of the naive belief of many foreigners, faithful to the idea of communism, that the USSR, April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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being the country of victorious socialism, was building a communist society. When it became more or less safe to discuss such issues, some people cynically called it “stupidity.” Others, especially malevolent to Bruno (there were such people, even though a small number), adhered to the version adopted then in America: he was a Soviet spy who fled when the danger arose of him being unmasked. Although we were friends with Bruno for many years, I personally never asked him this question, since I understood that it might be quite painful for him to discuss. But numerous conversations we had with Bruno allowed me to form a certain opinion in connection with this issue. I shall give some examples. Once at the JINR Scientific Council I happened to sit together with Bruno on the back benches. A talk was presented by Klaus Fuchs,b a well-known former Soviet spy, who, after having served his term in prison in England, had gone to GDRc and worked in Dresden. His talk did not seem very interesting to me (something about the Young tableau). Bruno, however, was very excited. One could see that this encounter made a strong impression on him seemingly somehow connected with his own life. “You know,” Bruno whispered to me, “Fermi was very tough in evaluating scientists. But he considered Klaus Fuchs a star of the first order.” I thought Bruno would like to speak to Klaus Fuchs at the end of the session, but he didn’t do so, and we left the Scientist’s Club together. Bruno was agitated. Most likely, he was recalling past years, just before he came (or, one can say, defected) to the USSR. “I would be very interested in reading the memoirs of Klaus Fuchs, if he wrote any,” said Bruno. “The point is that when Klaus Fuchs was arrested, we were all sure it was a police provocation against communists, since we knew that Klaus Fuchs was a communist. We had no idea Klaus Fuchs was a spy, and we thought it was a provocation in the spirit of McCarthyism, which had overflowed America and had extended to England.”

bSee footnotes, pp. 148 and 149. cGerman Democratic Republic, currently the eastern part of Germany. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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From these words of Bruno it became clear what he, a communist since 1936, could fear in England after the arrest of Fuchs and why he decided to change his life so drastically. It could also be possible that the prospect of working in Dubna at what was then the largest accelerator in the world played a significant part in his making the decision to go to the USSR. The construction of this accelerator was a secret at the time, but the secret KGB agents who organized Pontecorvo’s defection to the USSR, could have told him about it, or at least hinted about its existence. Bruno told me he joined the underground Italian communist party in 1936, at the time of war in Spain. Being a democrat and an intelligent young person living in a fascist country, he hated the fascist regime. The war in Spain threatened to spread – communists then were perceived by many as the most decisive Nazi opponents. And this fact pushed many very worthy people all over the world to em- brace them – both in Europe and in America. After he joined the communist party, Bruno took the communist ideology for a true science and faithfully followed it until his life in the USSR gradually destroyed his illusions one by one. It was a very painful spiritual process for him. Already after the perestroika, I don’t remember exactly when, in 1991 or 1992, at a general session of the Academy of Sciences, Bruno sat down beside me and said: “I am writing my autobiography for an Italian publisher. I have done a lot of thinking. Nearly all my life I considered communism to be a science, but I now see it is not science, but a religion. I thought of Sakharov as a very good person but naive, and now I see that it was me who was naive.” Bruno’s definition of communism as a religion was a very good point. It explains much in the behavior and fate of many faithful communists in the USSR and abroad. Most faithful western communists, who were the most ardent believers, loyal to the USSR, were undoubtedly advocates of communism “with a human face” and thought they were struggling for the happiness of the whole mankind. But since the basic dogma of a “scientific” communism, unlike “Utopian” communism, was that this goal could be achieved only through the dictatorship of the proletariat, they were compelled April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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to justify (to other people and to themselves) the suppression of freedom in the USSR by assuming it to be a temporary phenomenon related to the transition period. They did not (or did not want to) comprehend the scale of the atrocities and crimes that had occurred, not understanding that it was not a dictatorship of the proletariat that existed in the USSR, but rather a dictatorship of the criminal clique of party bosses (religion permits no doubt). I remember how at the time of the XXII CPSU Congress, when a (far from complete) unveiling of Stalin’s cult took place, one physicist from Dubna, who was not content with this, cruelly asked Bruno the question: “Was it possible for the foreign communists to know nothing about all this before?” “Yes,” answered Bruno. “In the 1930s all bourgeois newspapers wrote about it constantly, but we thought it to be lies. And those communists who believed the newspapers ﬁnished badly – they went over to the fascists.” At the time when agitated discussions of Stalin’s cult took place, Bruno tried not to give way to the general mood and to retain his objectivity. Thus he justiﬁed the conclusion of the Soviet-German pact of 1939 (we could only guess as to its secret Appendices, devoted to the division of Poland and the annexation of the Baltic states that happened immediately). “You didn’t live abroad and don’t realize,” said Bruno, “how all the bourgeois newspapers wrote that it was necessary to incite Hitler and Stalin to hostilities between each other, so they would destroy each other.” When, after an argument, we remained alone with Bruno, he added: “Truly, Stalin shouldn’t have sent a telegram of congratulation to Hitler after the division of Poland. That telegram surprised us communists very much and sowed doubt in our minds.” Bruno also thought that the repressions of 1937 resulted from internal political struggle within the party. I had to tell him much about various facts of our history: about the horrors of collectivization, the famine in Ukraine (I had heard about it from witnesses), the Leningrad process, doctors’ case, the tragic fate of the Alliluyev April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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family, and of my own, and about many, many other things. Bruno trusted my stories. Probably because being born into a family that experienced repressions and not being a party member, for a short time I, nevertheless, shared, like many others, the illusion that the so-called “Lenin norms of life,” if restored, would create socialism with a human face. At that time I did not understand that Stalin was actually a natural product of Lenin’s doctrine. The beginning of the end of these illusions was the defeat of the local party organization in ITEP in 1956 (immediately after the 20th CPSU Congress) and the fate of Yuri Orlov, who always was, and still remains, one of the most intelligent, honest, and courageous people I have ever met in my life. We also discussed this matter with Bruno, but a clear comprehension of what was happening came only later. When I first visited Italy in 1989, I met a young physicist from University of Rome who told me that when he was a student he believed in communism and worshiped the USSR. “Luckily,” he said, “my father, who was a pharmacist, prescribed me a good medicine. He bought me a tourist ticket to the USSR, and so I was cured. In my case,” he added, “the healing started already at the Moscow airport.” Regretfully, neither Bruno nor thousands of other believers had the opportunity to take such a medicine. In this context, I want to tell the story of an outstanding person, an Italian communist, whose name is known to just a few in our country (with the exception of old aviation experts) and whose fate, even more tragic than Bruno’s, made Bruno suffer significantly. This is Roberto Oros di Bartini. In 1962, N.N. Bogolyubov, then the LTP director, summoned me and asked me to study an article rejected by JETP that contained a review with very offensive comments. “This work,” said N.N., “was given to me by M.V. Keldysh, who knows the author well from their joint work in the aviation and cosmic industries. He asked me to see whether it could somehow be published upon introduction of some corrections. The author experienced a difficult life. As a young man he had come to the Soviet Union, achieved numerous merits in aviation, and was sent to prison in the 1930s, but at present he actively works again. Please, look at this article. Maybe it can be corrected and can somehow be published April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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in the newly founded journal Yadernaya Fizika (Nuclear Physics). If difficulties arise, I shall personally present it for publication in Dok- lady AN.” I started reading the article, full of concern for the author. The article began as follows: “Consider a total, and therefore unique, specimen A...” Only after considerable efforts was I able to understand that the author assumed the specimen A to be the entire Universe. Indeed, it is unique. Furthermore, the author assumed it possible for the specimen A to be realized in space-time of several dimensions (not necessarily four); he also assumed a nonvanishing probability that a transition occurs from one number of dimensions to another. At present, after the genuine Renaissance of theories of the Kaluza– Klein type and the advent of spaces of a large number of dimensions, with compactifications, such a hypothesis could well be accepted. But everything happened in the beginning of the 1960s, and it certainly seemed absolutely weird to all referees at that time. Nevertheless, I thought the author was entitled to put forward this hypothesis as a starting point (I was influenced by my sympathy for him). Further developing his hypothesis, the author arrived at the conclusion that the most probable space for the Universe should have 6 dimensions. On the basis of “geometrical” arguments, he derived a number close to the fine-structure constant 1/137. Then, slightly correcting this number to comply with experimental data, and taking the Bohr radius as an input, the author calculated the Compton length and the classical electron radius to be in “astonishing” agreement with the experiment. Naturally, this was just nonsense, since the Compton length and the classical radius reduce to the Bohr radius multiplied by α and α2, respectively. The article contained a certain expression for the gravitational constant, which could be considered empirical. It was quite clear to me that no physical journal would accept this article, both because of its physics content and because of the language in which it was written. I decided to change the text by rewriting it so as to render the author’s assertion comprehensible and to drop the “agreement” with experimental data, which was based April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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on the deﬁnitions of the quantities under consideration. Upon having prepared an “abbreviated” text, I called the author to discuss it with him. Bartini invited me to his apartment on Kutuzovsky Prospekt. When I arrived, I saw a charming, handsome person with surprisingly courteous and pleasant manners (Bruno told me afterward that Bartini came from a distinguished aristocratic family. He broke with his family when he became a member of the communist party, even though his father – a baron and a former governor of Fiume – was devoted to him, loved him, and had quite broad and democratic views.) From the very beginning I understood that I was dealing with a person unusually gifted in all respects. There were remarkable paint- ings on the walls of the apartment, small sculptures were scattered here and there, together with models of some fantastic airplanes. Everything, as I learned, was made by my host. Bartini very gently expressed his disappointment with my text. He thought I had cut out too many of his important ideas, and (despite my arguments that no journal would accept the article in such a form) fought for each word, literally. In doing so, he based his ideas on appropriate arguments from the book by Eddington and other similar books. I was not able to convince him that they would not be accepted as reasonable arguments by the editors. Our debate often went beyond the article per se, towards philosophical issues (I was astonished by author’s knowledge of ancient, classical, and Marxist philosophy). Thus, we spent several evenings hard at work. As I understood, Bartini worked in Podlipki, for a (well known to experts) classiﬁed aviation design bureau. But at that time he focused on the work we discussed considering it to be the main cause of his life. He was in despair because he could not get it published. “My ‘trade’ (he thus called his work in the design bureau) is quite successful, but the main thing is the work we are now discussing,” he said. During breaks in our discussion, when we had tea that was served right on the desk, I tried to direct our conversation toward Bartini’s work in prison. I had heard something about it from Yu.B. Rumer. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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Bartini spoke quite willingly: “We had three departments: Tupolev’s,d mine, and Rumer’s. Rumer dealt with dynamics, i.e. ﬂutter, and we were friends (so that’s where Bartini’s interest in multidimensional Universe came from, I thought). There were many people working in my department, who later became famous, such as, for instance, Korolyov. The future Director of TsAGIe worked under me as a draughtsman.” I don’t remember now whether it was Bartini who told me about an interesting episode in his life, or if I heard it from Bruno. The point was that Beriaf himself used to visit Bartini’s “sharashka.”g Upon arrival, he used to summon the department heads to discuss work progress and to hand out new assignments. This was all done informally, during tea-breaks. Once, seeing Beria’s good mood, prisoner Bartini addressed him: “You know, Lavrentii Pavlovich, that I am totally innocent.” “Of course I do,” answered Beria with a heavy Georgian accent, “if you were guilty you would have been executed. Okay, now you’ll make an airplane, receive the highest Stalin Prize and we will set you free.” Bartini, who in spite of everything did not lose his na¨ıvet´e, was perplexed: he couldn’t understand the relationship between an airplane and the horrible accusations of espionage and other sins for which he had been convicted. Had he been free, he would have worked faster and better on the construction of this machine. When a more or less abbreviated text of the article was agreed upon and sent to Yadernaya Fizika, I asked Ya.A. Smorodinsky to send it to me for refereeing. I wrote an objective review, pointing out the admissibility of Bartini’s hypotheses (their unorthodox nature

dAndrei Nikolayevich Tupolev was the founder and the head of an aviation and defense enterprise and design bureau. eThe Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI) was founded on December 1, 1918 under the initiative and leadership of N.E. Zhukovsky. It was the largest scientiﬁc research center for Soviet aviation, and later for spacecrafts. f Lavrentii Pavlovich Beria was the chief of the Soviet secret police (NKVD, later KGB) under Joseph Stalin. gSharashka was an informal name for secret research and development laboratories in the Soviet Gulag labor camp system, staﬀed by highly educated political prisoners. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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notwithstanding) and recommending publication. At the same time I asked Ya.A. to let me know the Editor’s decision, in case the article was rejected, because I was afraid Bartini might not recover from the rejection of his article, and I remembered N.N. Bogolyubov’s promise to present the article for publication. When, in spite of my review, the Editorial board of Yadernaya Fizika rejected Bartini’s paper, I took it to Nikolai Nikolaevich. He reflected for a moment. “You see,” he said, “if I present this article to Doklady, there may be a scandal, since I am a theoretician. It would be better if this were done by an experimentalist, who may later say he was not an expert. For instance, Bruno Maximovich has just been elected as a member of the Academy. He now has the right to present himself the paper for publication in Doklady.” I went to Bruno. “I wouldn’t like this article to be the first one I present, really,” he said, “but there’s nothing to do about it. Bartini has to be saved. Otherwise he’ll lose his mind.” So Bruno presented the article to Doklady,inasomewhatcor- rected form. (When it was published, Bruno was surprised that Bar- tini signed it with his full name, retaining the prefix “di”). Bruno was extremely concerned about Bartini’s fate. “He came to the Soviet Union as a very young man. In Italy, even in the communist party, nobody knows him; most likely only a few old people remember, such as Senator Terracini.” When the article was published, Bruno did experience some unpleasant moments. First, he immediately received letters from several “crazy” correspondents who accused him of presenting ideas stolen from them. Second, he received a telephone call from the Department of Science of the CPSU Central Committee inquiring as to whether or not the article was a joke. Such a complaint was sent to the Department of Science by certain mathematicians, who considered it to be a personal insult: after all, how could they publish their outstandingly brilliant papers in a journal that opens its pages to jokes? (They had no doubt that the article, starting from the very first phrase presented above, was a joke. They thought the April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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unusual name of the author to be a fabrication, which seemed to be an incomprehensible part of the joke). While speaking with a big shot from the Central Committee, Bruno (as he usually did when stopped by a policeman for a traﬃc violation) began speaking in very broken Russian, and indignantly repudiated the very suggestion of “Robert Oros di Bartini” being an imaginary person. “Go to the Defense Department of the Central Committee,” he said, “they should know him there. It’s very strange you have not yet done this.” The debate stopped there. Later on, I saw Bartini’s work in a collection on gravity published by K.P. Stanyukovich. Sometime in the middle of the 1960s, I saw an article about Bartini in the weekly Nedelya. There I read that when presenting Bartini to the Council for Science and Technology, S.P. Korolyovh called him his teacher, and that the Italian communist party awarded Bartini with a memorial medal. In the Soviet Union, Bartini was awarded with the Order of Lenin. The pupils and close collaborators of Bartini, supported by the Minister of the Aviation Industry, had a plan to organize Bartini’s museum. Accidentally, I happened to see a booklet by I. Chutko titled “Beautiful airplanes,” in which people who knew and loved Bartini told the story of his life and work. I would like to quote the words of Academician O.K. Antonovi from the preface to this book: “Roberto Bartini was a person of unbending beliefs, a person of crystal-clear soul, a passionate internationalist. ... His ﬁrm belief of a communist in the happy future of the mankind was the guiding star throughout his life.” Regretfully, in a rather good book by Ya. Golovanov about S.P. Korolyov, only a few words are said about Bartini, although Sergei Korolyov worked in his Department in the “sharashka” and subsequently considered Bartini to be his teacher. Evidently, the long-time habit of writing half-truths had some in-

hSergei Pavlovich Korolyov was the lead Soviet rocket engineer and spacecraft designer, the head of the Soviet space program. iOleg Konstantinovich Antonov was a Soviet aircraft designer, the founder of the Antonov ASTC, a famous aircraft enterprise in Ukraine. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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fluence here, too. It is quite clear that the image of S.P. Korolyov would not have tarnished, but, on the contrary, would have only been enhanced, had the real position of Bartini in the “sharashka” been revealed, as well as the obvious feeling of gratitude to Bartini that Sergei Pavlovich carried throughout his life. I would like to apologize to the readers for devoting in my recollections of Pontecorvo so much time to the story of R. Bartini. I did so being quite sure that Bruno would have approved. It must be said that Bruno sincerely loved physics, and rejoiced to hear of new achievements, no matter to whom they belonged. He could speak enthusiastically about the experiments of other people, admiring novel methods or ingenious realizations of experiments. I remember how much he appreciated the experiments performed by Yu.D. Prokoshkin, P.E. Spivak, F.L. Shapiro, V.M. Lobashov, and many others. He spoke with fascination about his collaborators, with whom he carried out experimental work, noted their creativity and contribution to successful completion of measurements, and spoke very warmly about his joint work with theorists L.B. Okun, V.N. Gribov, and others. I noticed that Bruno particularly liked talented and independent- minded people, who were known to be “unmanageable” and difficult to communicate with. He greatly appreciated original thinking (for example, he emphasized the originality of B.S. Neganov’s reasoning). I cannot say that he ignored small defects and weaknesses; on the contrary, he saw them quite clearly and liked to make jokes about them. But at the same time, Bruno was absolutely irreconcilable in his criticism, when he saw flaws in experiments, the absence of test measurements, a “frivolous” attitude towards data processing, and, in particular, cheating. In such cases he was categorical and had no mercy for cheaters, paying no attention to their positions. Such a stand of Bruno sometimes created new ill-wishers and even enemies. In this connection, a quarrel between Bruno and G.N. Flerovj was especially painful to me. In the past, Bruno had

jGeorgy Nikolayevich Flerov was a prominent Soviet nuclear physicist. Flerov’s letter written in 1941 convinced Stalin to pursue an atomic bomb. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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supported S.M. Polikanov in his dispute with G.N. Flerov concerning the insufficient proof of a newly discovered element; then he had helped S.M. Polikanov in his transfer to the Laboratory of Nuclear Problems. For this, Bruno incurred G.N. Flerov’s enmity. Regret- fully, in the spirit of time, G.N. used not only scientific, but rather political, arguments. Bruno indignantly showed to me the minutes of the meeting devoted to S.M. Polikanov, who emigrated from the USSR. Bruno himself was out of town at the time of the meeting, and thus couldn’t attend. The attacks by G.N. against Bruno were phrased in the spirit of the 1937 speeches. I regretted these hostilities very much, since, despite the many known drawbacks and absolutely unworthy behavior of G.N. at that meeting (I told him about that), I liked Flerov for his unusual character, his talent and firmness in pursuing scientific goals. It is true, though, that my attitude to Flerov could be biased by his good attitude towards me. I tried somehow to heal the existing hostilities, but to no avail. Objectivity of valuation was a rigorous rule for Bruno. Being in the midst of various competing groups and schools, Bruno never, as far as I know, violated this rule, irrespective of his scientific or personal sympathies. This also caused dissatisfaction among various parties. I remember how Bruno once complained to me that at a meeting devoted to certain organizational issues, K.A. Ter- Martirosyan called him a “compromiser.” “He called me, a member of a clandestine communist party since 1936, a collaborationist,” exclaimed Bruno. I understood how this obsolete word, which by that time had already vanished from the political lexicon, could affect such a communist. In 1936, the main task of European communist parties was established to be the all-out struggle against “compromisers.” This story, however, had no effect on the good relations between Bruno and Karen Avetovich, whom Bruno valued highly as a physicist and a very kind and straightforward man, ready to fight anything unjust. “He is a noble Don Quixote, sometimes even capable of attacking wind-mills,” Bruno used to say. Owing to his aspiration for objectivity, Bruno experienced particularly difficult times during the elections to the Academy of Sciences. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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He often sought advice and discussed the scientific merits of different candidates. At the time, I was quite far from the academic kitchen, so I was surprised when just before one of the elections he said: “I would very much like X to be elected to the Academy, he is my favorite candidate, but I cannot vote against Y, because Y is an excellent and original physicist.” I answered that that seemed quite natural to me. “Yes,” said Bruno, “but when some people adhere to objective valuation, while others vote only for “their” buddies, you are bound to lose. Nevertheless, I cannot behave otherwise.” Therefore, Bruno always tried to achieve a compromise. One of the means for doing so was the academic “game,” an unofficial straw vote held within the Department, which permitted identifying the most acceptable candidates to the majority of the Department members and then, on this basis, inciting an agreement between various groups on how they would vote. This strategy opened the way to electing favorable candidates during the official voting (since no votes were wasted). The official voting procedure was limited to three rounds, and if none was elected in three rounds the positions allocated to the Department were lost. Naturally, this method could be successful only if the participants of the straw votes did not change their minds during the official voting. Thus, to make a long story short, the “game” had to be “gentlemanly.” Once, Bruno quoted to me the words of I.M. Frank: “What a respectable Department we have! Everybody voted just as was agreed.” I was surprised by these words, not understanding how it could be otherwise. Later, however, it turned out to be quite possible. And Bruno was so shocked that he seriously thought of transfer- ring from the Department of Nuclear Physics to the Department of General Physics (and even started negotiations). Luckily, he was persuaded not to do so. The position of Bruno during the election was as follows: he thought that if a certain group absolutely wanted to elect their candidate by blocking the election of other candidates, who were more worthy in Bruno’s opinion, it was necessary to reach an agreement that would let the most worthy candidates be among April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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those elected. However, bearing in mind the results of the preceding “game” that had shocked him, he once demanded, in a critical situation, that the vote be actually open rather than secret. This showed that Bruno was no longer so naive as before. There were people who blamed him for this. But life proved Pontecorvo to be right. I remember Bruno for his exceptionally versatile interests. One of his hobbies was sport. As soon as he arrived in Dubna he started actively playing tennis (which was not yet in fashion at that time). He would speak passionately of tennis tournaments of his youth and would be surprised that I had heard nothing of the tennis stars of those times. It seems he was the first in our country to start underwater swimming and scuba diving, with A.B. Migdal and his friends. (A.B. was one of his closest friends, but Bruno also liked his companions. With particular warmth he spoke of Suetin – a brilliant engineer, inventor, and a talented person.) Once, Bruno nearly caused a state of emergency in the Black Sea Navy when he came out of the water in a hydro-costume and mask (unheard of in our country at that time), speaking with a foreign accent. He was misidentified by the border guards as a spy set ashore by a submarine. Bruno was an excellent cyclist. Once, he demonstrated to me his fast riding skills with his back to the steering handle. He continued biking even when he was ill. In 1990, he fell from his bicycle and broke his thigh bone. Luckily, G. Piragino, Scientific Counselor of the Italian Embassy in Moscow, helped to transport Bruno to Italy for a surgery, where there was a doctor familiar with Bruno’s illness and who knew which anesthetics could be applied in his case. It so happened that I went to Italy one week later and had the opportunity to visit Bruno in a hospital in Rome after the surgery. He was already feeling better and was happy not to have his unhealthy tremor. I think Bruno adored risk and adventure, both in science and in everyday life. But, while in science, his risk was always based on scientific arguments, in sport and in travel the risk often threatened his health and his very life. When once we were skiing down the slopes of Mt. Aragats in Armenia, Bruno noted: “I used to do this much faster without thinking of possible precipices beyond the bend of the hill. But after I broke my legs April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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several times I became more careful.” Once, a boat on which Bruno was aboard, along with Dolgoshein and others, (I think it happened near the Kuril Islands) capsized several kilometers from the shore, and everybody had to swim back. Misfortunes sometimes seemed to happen to Bruno for no reason at all. Once he decided to go for a walk along the frozen Volga river together with Marianne, whom he treated with touching attention and care, and fell through the ice so deeply that only his head and shoulders were above the water level. He managed to get out onto the ice. Later, when he was already ill, a man – obviously a maniac – hit him, so that Bruno fell and hurt himself quite badly. This happened in the center of Moscow. Such events always caused us concern. Bruno was keen on cinema. To a great extent, this was thanks to his brother Gillo Pontecorvo, whom he tenderly loved. After each Moscow Film Festival, Bruno was overwhelmed with impressions. He would tell us not only about the films he saw, but also about various funny situations. For instance, a very well-known Italian star asked Yuri Gagarin, who was invited to the festival, with an obvious hint: “What do you think, is it possible for a man like you to reach a star?” “No,” answered Gagarin, “modern technology won’t permit it.” “Think a bit more, might it not be actually possible?” “No,” stubbornly answered Gagarin, who, apparently, understood the hint. Bruno was very happy when Gillo Pontecorvo succeeded in producing a remarkable film entitled “Capo.” He told us of the problems that arose when the film was to be purchased and shown in the So- viet Union. Furtsevak seemed to have approved buying it, but some of the big shots in cinema were against it on the pretext that one of themaincharacters–aRussiansoldier–hadacoarseface. “It doesn’t at all seem coarse to me,” said Bruno when retelling the content of the film, “through this seeming coarseness one can clearly notice strength and intelligence.”

kYekaterina Alexeyevna Furtseva was the Minister of Culture of the USSR from 1960 till 1974. Full Member of the Politburo of the Central Committee of the Communist Party in 1957–1961. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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Bruno himself liked such people. Naturally, all such objections were just a pretext. The film was not bought nor shown in the USSR. Pontecorvo, naturally, felt homesick for Italy. But this nostal- gia was hidden very deep and could only rarely be noticed in some insignificant manifestations. For example, when we were passing together through Tbilisi on our way to a conference in Yerevan, he said: “Let’s go to the market. There, one can buy homemade cheese, which is so similar to the Italian cheeses.” Bruno liked the Caucasus – Armenia and especially Georgia. Something in the behavior of the local people reminded him of Italy. He had friends among the highest levels of the Georgian intelligentsia. Bruno learned to cook spaghetti and related sauces in accordance with all subtleties of Italian cuisine. I remember he once invited me, A. Logunov, and A. Tavkhelidze to supper, and we learned how well he could do it. It was very tasty (especially if one sips Tuscany’s Chianti with the food). The first time Bruno was permitted to go to Italy was in 1979, it seems, after persistent pressure from the Italy–USSR society. At that time I was no longer in Dubna, and I found out from friends what enormous difficulties had to be overcome in “pushing” this trip through the authorities. First one, then another bureaucrat would cross out Bruno from the list of the delegation. Ultimately, higher instances allowed Bruno to go, in apprehension of an imminent scandal. Why Bruno was not allowed to go abroad was quite clear: for the same reason that P.L. Kapitsa, L.D. Landau, and many others were not allowed to leave the country. An acquaintance of mine was accidentally present during a conversation between two party officers. One of them was explaining to the other why P.L. Kapitsa should notbeallowedtogooutofthecountry. “In England he has a house and a bank account. Think it over. Would you come back, if you had a house abroad and an account in a bank?” These people, who publicly preached communist ideals and April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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strictly followed the communist (religious) ritual, no longer believed in it – they just played believers. They snatched at their positions and privileges, fearing to lose them, would anything happen. They were not capable of understanding that their conversation was about a great scientist and a Russian patriot, that such people as P.L. Kapitsa, L.D. Landau, or B.M. Pontecorvo could not leave their pupils and the schools they had created. These bureaucrats had caused enormous damage to our science by isolating the most outstanding scientists from possible contacts with scholars of their own level abroad. One can only marvel that, despite the prohibitive efforts of such bureaucrats, Soviet physics had achieved remarkable success. But this success could have been much more pronounced, if not hindered by these chameleons. The essence of many of them was revealed during perestroika, when some individuals, who were in the highest echelons of power, in the Politburo of the Central Committee of the Communist Party, at the very top of KGB, etc. and who were always ready to worship the current “General Secretary,” enthusiastic lickspittles, – the very same people all of a sudden started examining their family trees in search of relatives persecuted by communists, relating how they had suffered under the Soviet regime and how they long had lost belief in the communist doctrine. How, in any way, could these cynical non- believing “priests” of the communist religion understand that among the prominent scientists “eccentrics” with firm principles could still be found? Therefore, in spite of apparent signs of respect, they never trusted Pontecorvo. Moreover, they had awful suspicions: “Couldn’t Pontecorvo happen to be a Jew?” When Bruno learned of such a supposition, he said: “I am from a Catholic family,” stressing that in Italy (unlike the country of “real” socialism, the USSR) people are distinguished only by their religion, not by racial or ethnic differences. As a result, Pontecorvo was allowed to travel to “socialist” countries. One could not escape from there. But before even going there, please, listen to instructions on how to behave abroad. We – Bruno and I – were fed with these instructions at the State April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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Committee for Atomic Energy before our visit to Hungary. A KGB officer (rumor had it that he was in the rank of the KGB general), with an intellectual appearance, from the State Committee for Atomic Energy, wearing gold-rimmed glasses began teaching us: “You can take with you two bottles of vodka. No more! There had been a case in our Committee. A respectable Academician – call him Ivan Ivanovich – wanted to take a box of vodka with him at any cost, saying that he just couldn’t do without it, abroad. No, we said, dear Ivan Ivanovich, you shouldn’t do that. And he obeyed.” Andwehadtolistentosuchtrashforanhour!Thenwehad to go to the State Committee for Science and Technology and there, too, swallow such instructions. I could feel Bruno boiling over with rage, but he restrained himself and even calmed me down saying that it was even worse before: “For instance, at a general instruction session before the Rochester conference held in Kiev in 1959, a Dubna officer of the Regime Departmentl pronounced literally the following: “Regretfully, it will not be possible to avoid contacts.” The audience laughed. Someone started explaining that conferences are held precisely for contacts. Today he keeps saying to everybody that he is “in favor of contacts.” “I think,” added Bruno, “that international visits can no longer be banned.” (This was at a time of an elevated international tension, and restrictions were imposed on “contacts”). “Just look at the huge staff of civil servants profiting from them that was created. They wouldn’t deprive themselves of this lucrative work.” Several times Bruno visited Hungary to take part in excellent conferences on weak interactions and neutrinos organized by G. Marx.m In particular, I remember the conference held in 1972. It was attended by R. Feynman, C.N. Yang, T.D. Lee, V. Weisskopf, and

lJoint Institute for Nuclear Research in Dubna was formally an international organization. Officially one was supposed to use the wording “Security Office” in regard to the Regime Department. However, with respect to all Soviet employees and visitors it played the role of a standard Regime Department, a KGB-related unit mandatory for all large research institutions. mGyörgy Marx (1927–2002) was an outstanding Hungarian nuclear and particle theorist. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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many other outstanding physicists. Bruno and Feynman, as honorary participants, each planted a tree. At the conferences held in Hungary, I could see the reverence and love Italian physicists felt for Bruno. He also spoke about many of them with admiration, often remembering his friends who participated in the joint work with Fermi, concerned for their success and saddened by failures. Of the new generation, he particularly liked Carlo Rubbia, whom he valued for his talent and for being an exceptionally bold physicist; he even liked the bravado of Carlo. Bruno himself liked jokes too. When he was awarded the Eötvös Medal for work in neutrino physics, a female journalist asked him: “Is there hope that people will benefit from neutrinos some day?” Bruno answered: “Why ‘will’? It is already benefitting some, right now.” We were glad for Bruno when he finally got the opportunity to freely visit Italy and meet with his relatives, friends, and colleagues. He was extremely touched that the Ferrara University (one of the oldest in Italy) elected him as Professor Honoris Causa. Bruno prepared his inauguration lecture very thoroughly. Having spent some time in Russia, Pontecorvo grew to like its expanses and its people. He liked Russian cuisine (he used to say it was better for him than French). Bruno liked the openness, the broad-mindedness and kindness of the Russian character. Bruno’s own personality, his charm and democratism, attracted extremely diverse people: medical doctors in hospitals liked him, technicians in laboratories, waitresses at the canteen of the Academy of Sciences and in the restaurant of the Scientists’ Club. He was surrounded by people, who felt sincere love and respect for him. When once we – Bruno and I – were passing by the Kamenny Most,n he said, looking from the bridge at the Kremlin ensemble: “I have been to many cities in the world, but, believe me, this view is the most beautiful I have ever seen.” Being a polyglot, Bruno admired Russian language and spoke and

nBolshoy Kamenny Most is a steel arch bridge spanning Moskva River at the western end of the Moscow Kremlin. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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understood it extremely well (although he spoke in Russian with an accent). He recalled the help in mastering the language rendered to him by Irina Grigorievna, who typed and corrected his articles. He always felt gratitude and much respect toward her. It is interesting that for a long time Bruno could not understand double negation existing in Russian language. And he was quite amazed when Migdal gave him an example of a triple negation: “It’s impossible not to remember without a smile” (literal translation). For a long time I tried to explain this phrase to him, and finally, when he got it, he was fascinated by this expression. Bruno often recalled with piety his teacher Enrico Fermi and the entire Rome group. He spoke of E. Majorana, whom Fermi himself considered a genius in physics, about his unpublished comments and his mysterious fate. He prepared an edition of a collection of Fermi’s works in Russian with extreme thoroughness. Much of what Bruno told me about Fermi was reflected in the comments he made about Fermi’s articles in this excellent collection, as well as in the book on Fermi written by Bruno. Therefore, I shall only present two comments here. Once, when I came to Bruno to discuss my calculations related to the diffusion of hydrogen mesoatoms, he exclaimed: “Look, this is Fermi’s theory of aging! Do you know why is it called in this way?” I thought it was related to the neutron life after its production. “Not at all! There exists a well-known Italian joke: a three-chimney ship leaves port such and such, with a cargo weight of such and such and a certain number of passengers. The question is, what is the captain’s age? That’s where the name comes from.” Then Bruno told me the following: “Fermi applied the ‘aging theory’ in creating the theory of nuclear reactors. At the same time, E. Wigner was writing integro- differential equations for the same purpose. Among his colleagues and friends, Fermi laughed over this: ‘Poor guy, how he suffers in solving them.’ A simple physical approach allowed Fermi to guess the result in a transparent manner and with sufficient precision.” “This does not mean that E. Fermi had not mastered appropri- April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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ate mathematical apparatus,” added Bruno, “he knew it extremely well and had published papers in pure mathematics. But he just considered that in dealing with a concrete problem in physics one must apply mathematics adequate to the problem at hand and not complicate it with look-like-high-science ‘rigor’.” Von Neumann was a person whom Fermi admired. A close friend of Fermi in America (an engineer rather than a physicist) told Bruno that Fermi answered a question concerning von Neumann as follows: “What do you think of me? Well, you must know that he is smarter than me, as I am smarter than you.” Bruno added that this statement did not offend the story-teller, since they were friends with Fermi, and that the difference between them was quite clear to both of them. Another interesting episode relates to Bruno himself. His work in Fermi’s laboratory started with studies in classical spectroscopy, although he naturally aspired to work in nuclear physics. “Once, I asked Fermi,” Bruno told me, “whether it would be possible to try to observe resonance scattering of γ -quanta in nuclear transitions?” Fermi reflected a moment, then went to another room and, upon coming back after approximately ten minutes, said it was impossible, owing to the recoil of the nucleus. Ithenjoked: “Too bad Fermi stayed in the other room for such a short time. The point is that he had studied molecules and crystals before this and had even written a monograph on this subject. Had he reflected a bit longer, he might have thought up the Mössbauer effect, and there would have been another of his work worthy of the Nobel prize.” Several times we discussed with Bruno how many works of E. Fermi might have been worthy of Nobel prizes, and we counted five or six. In connection with this Bruno story I would like to tell another similar one. In 1962, I.Ya. Pomeranchuk, speaking at the Rochester conference held in Geneva (I.Ya. Pomeranchuk went abroad for the May 10, 2013 12:9 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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first and last time), recalled that Houtermanso came up to him. “Well, and what did he tell you?” we asked. He said: “Chuk, we were idiots. We missed the Mössbauer effect.” The point was that, in Kharkov, Houtermans together with Pomeranchuk considered neutron scattering in crystals and knew of the possible existence of a non-shifted line due to scattering on the entire crystalline lattice. When I told Bruno this story, he said that he knew Houtermans to be an active German communist: “Like Georgii Dimitrov, he was exchanged in 1933 for some Ger- man agents.” I was very surprised to hear this, because we had always read in textbooks that Nazis were compelled to let Dimitrov go after his acquittal at the Leipzig process. “What, didn’t you know anything of this?” asked Bruno, “well, then, consider I haven’t told you anything.” Most likely, this was a well-known “secret” of Comintern,p which Bruno nevertheless considered himself not to be at liberty to disclose. Bruno’s illness caused much sorrow to us – those who loved and revered him. His medical condition deteriorated with time. Each

oFriedrich Georg “Fritz” Houtermans (1903–1966) made important contributions to geo- chemistry and cosmochemistry. Houtermans was a member of the German Communist Party since the 1920s. After Adolf Hitler came to power in 1933, his wife Charlotte insisted that they leave Germany. They emigrated to the Soviet Union in 1933. Houter- mans worked at the Kharkov Physico-Technical Institute but was arrested by NKVD in 1937. He was tortured and confessed to being a Trotskyist plotter and German spy. In 1939, after the Molotov-Ribbentrop pact, he was turned over to Gestapo and imprisoned in Berlin. Nazis let him go, however, after a petition signed by German physicists, in particular, Max von Laue. He ended up at Forschungslaboratoriums für Elektronen- physik, a private laboratory of Manfred Baron von Ardenne. Houtermans was the first to show that transuranic isotopes, such as neptunium and plutonium, could be used as fissionable fuels in substitution for uranium. Fortunately, the German authorities did not take this seriously because of Houterman’s disloyalty. Houtermans sent a telegram from Switzerland to Eugene Wigner warning people in the Manhattan Project of German work on fission: “Hurry up. We are on track.” After the defeat of Germany, Houtermans settled in Switzerland. See the book V.Ya. Frenkel, Professor Houtermans, Works, Life, Fate, (Academy of Sciences, St. Petersburg, 1997). pThe Communist International, abbreviated as Comintern, also known as the Third International (1919–1943), was an international communist organization initiated in Moscow. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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time I went to Dubna, I would visit Bruno to speak about physics and life. Once I saw him upset. At a conference, a speaker had attributed the idea of neutrino oscillations to somebody else, not Pontecorvo, and such references had already appeared in a few papers. I laughed and said that his priority was known to everybody, but that the best and most constructive answer to such insinuations would be a review, for instance in the Uspekhi, on the development of neutrino physics. Bruno answered that he would think of it, and he indeed wrote a very interesting and useful article. When he said good-bye, he added: “You know, I never cared about priorities. It’s just that I’m sick and therefore nervous.” Bruno was kind of ashamed of his illness, of his “trembling” as he called it. When he was nervous the tremor was especially bad. “What a misfortune that this illness (the Parkinson disease) clung to such a handsome and harmonious person as Bruno,” I heard from many people. Migdal organized several appointments for him with the famous Junaq and Bruno, being somewhat embarrassed, said he felt an improvement after sessions with her. Naturally, he didn’t believe in any magic but he actually noted her psychological inﬂuence and massage. She was but wrong in telling him she had ﬁngers that could feel neutrinos – that disillusioned Bruno. The last time I spoke with Bruno by phone was at the very end of July 1993, one day before he left Rome for Moscow. He told me about the European conference on Particle Physics and about the talk given by L.B. Okun, which he liked very much. “Lev Borisovich is quite right. The demise of SSCr is a blow not only to physics, but also to science as a whole, to culture, and to the entirety of civilization.”

qJuna (Eugenia Yuvashevna Davitashvili) is a healer, astrologer, artist, poet, composer and the President of the “International Academy of Alternative Sciences.” She is of Assyrian descent, since 1980, has lived in Moscow, and claims to have power to cure cancer and extend human life span beyond 100 years. rThe Superconducting Super Collider was a particle accelerator complex under construction in the vicinity of Waxahachie, Texas, that was set to be world’s largest and most energetic, surpassing the current record held by the Large Hadron Collider. Its planned energy was 20 TeV per proton. The project was canceled in 1993 by the US Congress. April 5, 2013 16:12 WSPC/Trim Size: 9in x 6in for Proceedings 11c˙Gershtein-Ponteco

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Three weeks later, it was Bruno’s 80th birthday, and his friends (myself included) thought about how to celebrate it. I didn’t know whether Bruno intended to stay in Italy or return to Dubna, but he said he was ﬂying to Moscow the next day. “To be honest, I have caught a little cold and feel quite bad, but I have decided not to cancel my journey,” he added. Just before his birthday I learned from my Dubna friends that Bruno was categorically against the organization of any jubilee party and had asked none to come. I obeyed, since it was Bruno’s wish, but subsequently I regretted it very much: his friends gathered anyway. Soon after, Bruno was no more. I consider it Providence, that I had the opportunity to meet with and to be a long-time friend of this extraordinary, great individual. April 5, 2013 16:1 WSPC/Trim Size: 9in x 6in for Proceedings 11d˙Shifman-ITEP

ITEP THEORY DEPARTMENT: GLIMPSES∗

M. SHIFMAN William I. Fine Theoretical Physics Institute University of Minnesota Minneapolis, MN 55455, USA [email protected]

My career in theoretical high energy physics began in the early 1970s. I was lucky – its beginning coincided with a very exciting time in this field, when a major breakthrough in our understanding of nature took place. The standard model of fundamental interactions was born, and quantum chromodynamics (QCD) gradually emerged as the theory of hadronic matter. Unlike many other theories created later, whose relevance to nature is still a big question mark, these two will definitely stay with us forever. And, fortunately, I happened to be in the right place at the right time so that I could appreciate these discoveries early on. The infancy of any true theory creates great opportunities for young researchers who suddenly find themselves pioneers in terra incognita, with so many interesting, important, and challenging problems around. For about twenty years I was a member of the ITEP theory group.a These years shaped my scientific career and my destiny. Admiration for physics was a part of the natural environment of ITEP’s Theory Department. This feeling became a part of me, a part of my personality. Blurry visions of great minds wandering in ITEP’s corridors follow me wherever I go. I owe them everything: all basic elements of theoretical knowledge, attitude to physical prob-

∗This is an abbreviated version of Foreword to ITEP Lectures on Particle Physics and Field Theory, (World Scientiﬁc, Singapore, 1999). aFor those who do not know: ITEP is an acronym for the Institute of Theoretical and Experimental Physics in Moscow.

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lems and their selection, folklore tricks in their solution... How many ideas I learned from my formal and informal teachers at ITEP? How well did they teach me to navigate the sea of knowledge? People say that theoretical physics is like the Olympic ﬂame – you get it only from hand to hand. Well ... I got it in the old Menshikov mansion on B. Cheremushkinskaya, the headquarters of the ITEP theory group. Since the ITEP theory group of the 1970s and 80s was quite an endemic phenomenon, it seems worthwhile to introduce it to the reader.

Glimpses of ITEP ITEP was more than an institute. It was our refuge where the in- sanity of the surrounding reality was, if not eliminated, reduced to a bearable level. Doing physics there was something which gave meaning to our lives, making it interesting and even happy. Our theory group was like a large family. As in any family, of course, this did not mean that everybody loved everybody else, but we knew that we had to stay together and to rely on each other, no matter what, in order to survive and to be able to continue doing physics. This was considered by our teachers to be the most important thing, and this message was always being conveyed, in more than one way, to young people joining the group. We had a wonderful feeling of stability in our small brotherhood, feeling so rare in the Western laboratories where whirlpools of postdocs, visitors, sabbatical years come and go, there are a lot of new faces, and a lot of people whom you do not care so much about.

Seminars The rules of survival were quite strict. Seminars (now known worldwide as the Russian-style seminars) were vital. The primary goal of the seminar speaker was to explain to the audience his or her results, not merely to advertise them. And if the results were nontrivial or questionable, or unclear points surfaced in the course of the seminar, the standard two hours were not enough to wind up. Then the seminar could last for three or even four hours, until either everything was clear or complete exhaustion set in, whichever came April 5, 2013 16:1 WSPC/Trim Size: 9in x 6in for Proceedings 11d˙Shifman-ITEP

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first. I remember one seminar in Leningrad in 1979, when Gribov was still there, that started at eleven in the morning. A lunch break was announced from two to three, and then it continued from three till seven in the evening. At ITEP we had at least three theoretical seminars a week, a formal one on Mondays and an informal coffee seminar which at first took place every Friday at 5 o’clock, when the official work day was over, but later was shifted to Thursdays at the same time. Usually, these were by far the most exciting events of the week. The leaders and the secretaries of the seminars were supposed to find exciting topics, either by recruiting ITEP or other “domestic” authors, or quite often by picking up a paper or a preprint from the outside world and asking somebody to learn and report the work to the general audience. This duty was considered to be a moral obligation. The tradition dated back to the times when Pomeranchuk was the head of the theory group, and its isolation had been even more severe than in my times. As a matter of fact, in those days there were no preprints, and finding fresh issues of Physical Review or Nu- clear Physics was in no way taken for granted. When I joined the group as a student – this was a few years after Pomeranchuk’s death – I was taken with pride to the Pomeranchuk memorial library, his former office where a collection of his books and journals was kept. Every paper in every issue was marked by Chuk’s hand (that’s how his students and colleagues would refer to him), either with a minus or a plus sign. If there was plus, there was a name of one of his students who had been asked to dig into the paper and give a talk for everyone’s benefit. This was not the end of the story, however. Before the scheduled day of the seminar Pomeranchuk would summon the speaker-to-be to his office to give a pre-talk, to him alone, so that he could judge whether the subject had been worked out with sufficient depth and that the speaker was ripe enough to face the general audience and its bloodthirsty questions. In my times, the secretaries of the seminars were less inclined to sacrifice themselves to that extent, but, still, it was not uncommon that a pre-talk would be arranged for an unknown, young, or inexperienced speaker. April 5, 2013 16:1 WSPC/Trim Size: 9in x 6in for Proceedings 11d˙Shifman-ITEP

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Ambassadors Scientific reports from the few chosen to travel abroad for a conference or just to collaborate for a while with Western physicists were an unquestionable element of the seminar routine. Attending an international conference by A or B by no means was considered as a personal matter of A and B. Rather, these rare lucky guys were believed to be our ambassadors, and were supposed to represent the whole group. In practical terms, this meant that once you made your way to a conference you could be asked to present important results of other members of the group. Moreover, while abroad you were expected to attend as many talks as physically possible, including those which did not exactly belong to your field, make extensive notes, and then, after returning, deliver an exhaustive report of all of the new developments discussed, all interesting questions raised, rumors, etc. Scientific rumors, as well as non-scientific impressions, were like an exotic dessert, usually served after nine. I remember that, after his first visit to the Netherlands, Simonov mentioned that he was very surprised to see a lot of people on the streets just smiling. He said he could not understand why they looked so relaxed. And then he added that he finally figured out why: “... because they were not concerned with building communism...” This remark almost immediately became known to “Big Brother” who was obviously watching us that evening, as usual, and it cost Simonov a few years of sudden “unexplainable allergy” to any Western exposure. His health condition, of course, would not allow him to accept any invitation to travel there. I cannot help but mention another curious episode with “Big Brother.” Coffee, which we used to have during the coffee seminars, was prepared in turn by all members of the group. Once, when it was Ioffe’s turn, he brought a small bottle of cognac and added a droplet or two in every cup. I do not remember why, perhaps it was his birthday or something like that. This was Friday evening, and very early next Monday morning he was summoned to the corresponding ITEP branch office to give explanations concerning his “obviously subversive activities.” The coffee seminars typically lasted till nine, but sometimes much later, for instance, in the stormy days of the November revolution in April 5, 2013 16:1 WSPC/Trim Size: 9in x 6in for Proceedings 11d˙Shifman-ITEP

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1974. The few months following the discovery of J/ψ were the star days of QCD and, probably, the highest emotional peak of the ITEP theory group. Never were the mysteries of physics brought so close to our hearts as during that time. There was a spontaneously arranged team of enthusiasts working practically in a non-stop regime. A limit to our discussions was set only by the schedule of the Moscow metro – those who needed to catch the last train had to leave before 1 a.m.

Students The ITEP seminars were certainly one of the key elements in shaping the principles and ideals of our small community, though by no means the only one. The process of selecting students who could eventually grow into particle theorists played a crucial role and was probably as elaborate as the process of becoming a knight of the British crown. Every year we had about 20 new students at the level roughly corresponding to that of the graduate students in American universities. Mostly, they came from the Moscow Institute for Physics and Tech- nology, a small elite institution near the city, a counterpart of MIT in the States. Some students were from the Moscow Engineering and Physics Institute, and a few from the Moscow State University. They were oﬀered (actually, obliged to take) such a spectrum of courses in special disciplines which I have never heard of anywhere else in the world: everything from radiophysics and accelerator physics; several levels of topics in quantum mechanics, including intricacies of theory of scattering; radiation theory and nuclear physics; mathematical physics (consisting of several separate parts); not less than three courses in particle phenomenology (weak, electromagnetic and strong interactions); quantum electrodynamics, numerous problem- solving sessions, etc. And yet, only those who successfully passed additional examinations, covering the famous course of theoretical physics by Landau and Lifshitz, were allowed, after showing broad erudition and ingenuity in solving all sorts of tricky problems, to join the theory group. Others were supposed to end up as experimentalists or engineers. Needless to say, the process of passing these examinations could take months, and even years, and was notoriously exhausting, but there was never a lack of volunteers willing to try April 5, 2013 16:1 WSPC/Trim Size: 9in x 6in for Proceedings 11d˙Shifman-ITEP

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their luck. They could always be seen surrounding Ter-Martirosyan and Okun, who were sort of responsible for the program. It should be added that the set of values to be passed from the elders to the young generations included the idea that high energy physics is an experimental science that must be very closely related to phenomena taking place in nature. Only those theoretical ideas which, at the end of the day, could produce a number which could be confronted with phenomenology were cherished. Too abstract and speculative constructions and theoretical phantoms were not encouraged, to put it mildly. The atmosphere was strongly polarized against what is now sometimes called “theoretical theory.” Students who were extremely bright but too mathematically oriented, like, say, Vadim Knizhnik, would have difficulty passing these examinations. Vadim, by the way, never made it to the end: he got upset and left ITEP. Nothing is perfect in this world, and I do not want to make an impression that the examination routine in the ITEP theory group was without flaws. The ITEP theory group was large – about 50 theorists – as well as diverse. Moreover, it was a natural center of attraction for the whole Moscow particle physics community. Living in the capital of the last world empire had its advantages. There is no question, it was an evil empire, but what was good, as usually happens with any empire, was that all of the intellectual forces tended to cluster in the capital. So we had a very dynamic group where virtually every direction was represented by at least several theorists, experts in the given field. If you needed to learn something new, there was an easy way to do it, much faster and more efficiently than through reading journals or textbooks: you just needed to talk to the right person. Educating others, sharing your knowledge and expertise with everybody who might be interested, was another rule of survival in our isolated community. In such an environment, different discussion groups and large collaborations were naturally emerging all the time, creating a strong and positive coherent effect. The brain-storming sessions used to produce, among other results, a lot of noise, so once you were inside the old mansion occupied by the theorists, it was very easy to figure out which task force was where – just step out in the corridor and listen. And, certainly, all these sessions were open to everybody. April 5, 2013 16:1 WSPC/Trim Size: 9in x 6in for Proceedings 11d˙Shifman-ITEP

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“Making physics” Now I would like to mention one more aspect which concerns me at present, a very strong pressure existing in our community, to stay in the “mainstream,” to work only on fashionable directions and problems which, currently, are under investigation in dozens of other laboratories. This pressure is especially damaging for young people who have little alternative. Of course, a certain amount of cohe- sion is needed, but the scale of the phenomenon we are witnessing now is unhealthy, beyond any doubt. The isolation of the ITEP theory group had a positive side effect – everybody, including the youngest members, could afford to work on problems that did not belong to the fashion of the day without publishing a single line for a year or two. Who cared about what we were doing there anyway? This was okay. On the other hand, it was considered indecent to publish results of dubious novelty, incomplete results (of the status report type), or just papers with too many words per given number of formulae. Producing dense papers was a norm. This style, which was probably perceived by the outside readers as a chain of riddles, is partly explained by tradition, presumably dating back to the Landau times. It was also due to specific Soviet conditions, where everything was regulated, including the maximum number of pages a given paper could contain. Compressing derivations and arguments to the level considered acceptable was an art which had its grandmasters. Arkady Vainshtein was especially good at inventing all sorts of tricks allowing him to squeeze in extra formulae with very few explanatory remarks. I remember that in 1976, when we were working on the large JETP paper on penguins [1] in weak decays,b wehadtomake 30 pages out of the original 60-page preprint version, and he managed to do that losing no equations and even inserting a few extra! This left a strong impression on me.

bBy “we” I mean Zakharov, Vainshtein, and myself. Arkady Vainshtein had a permanent position at the Budker Institute of Nuclear Physics in Novosibirsk. He commuted between Moscow and Novosibirsk for many years. April 5, 2013 16:1 WSPC/Trim Size: 9in x 6in for Proceedings 11d˙Shifman-ITEP

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Penguins By the way, about penguins. From time to time students ask about how this word could possibly penetrate high energy physics. This is a funny story, indeed. The ﬁrst paper where the graphs that are now called penguins were considered in the weak decays [2] appeared in JETP Letters in 1975, and there they did not look like penguins at all. However, later on they were made to look like penguins,

and called so by John Ellis. Here is the story as he recollects it himself:

“Mary K. [Gaillard], Dimitri [Nanopoulos] and I ﬁrst got interested in what are now called penguin diagrams while we were studying CP violation in the Standard Model in 1976... The penguin name came in 1977, as follows. In the spring of 1977, Mike Chanowitz, Mary K. and I wrote a paper on GUTs predicting the b quark mass before it was found. When it was found a few weeks later, Mary K., Dimitri, Serge Rudaz, and I immediately started working on its phenomenology. That summer, there was a student at CERN, Melissa Franklin, who is now an experimentalist at Harvard. One evening, she, Serge, and I went to a pub, and she and I started a game of darts. We made a bet that if I lost I had to put the word penguin into my next paper. She actually left the darts game before the end, and was replaced by Serge, who beat me. Nevertheless, I felt obligated to carry out the conditions of the bet. For some time, it was not clear to me how to get the word into this b quark paper that we were writing at the time. Then one evening after working at CERN, I stopped on my way back to my apartment April 5, 2013 16:1 WSPC/Trim Size: 9in x 6in for Proceedings 11d˙Shifman-ITEP

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to visit some friends living in Meyrin where I smoked some illegal substance. Later, when I got back to my apartment and continued working on our paper, I had a sudden ﬂash that the famous diagrams look like penguins. So we put the name into our paper, and the rest, as they say, is history.”

References 1. M. A. Shifman, A. I. Vainshtein, and V. I. Zakharov, Nonleptonic decays of K mesons and hyperons, Sov. Phys. JETP 45, 670 (1977). 2. M. A. Shifman, A. I. Vainshtein, and V. I. Zakharov, A possible mechanism for the ΔT =1/2 rule in nonleptonic decays of strange particles, JETP Lett. 22, 55 (1975). April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

LIVING IN TRUTH: V. N. GRIBOV AND THE POST-WAR GENERATION OF SOVIET PHYSICS∗

PAL´ NY´IRIa and JOANA BREIDENBACHb aVrije Universiteit, Amsterdam, the Netherlands bBetterplace Lab, Berlin, Germany [email protected]

What does it mean to live in truth? Putting it negatively is easy enough: it means not lying, not hiding, and not dissimulating. – Milan Kundera [1] Vladimir Gribov (1930–1997) was one of the leading figures in post-World War II Soviet theoretical physics. He and his colleagues worked at the cutting edge of quantum field theory, plasma physics, nuclear and elementary particle research at a time when mediocrity or decay (by international standards) ruled in many other fields of science, art, and industry. Yet, physics was in a special position: it offered both a tolerable living and an officially sanctioned exemption from ideological make-believe. Theoretical physicists like Gribov neither lived in ivory towers nor were willing accomplices in the state’s nuclear project. Instead they carved out a niche for themselves in which lifestyle and values were substantially influenced by their belief in physical truth.

Window to Freedom The fate of theoretical physicists of Gribov’s immediate postwar generation was shaped by a totalitarian state that needed them in order

∗This is an abbreviated version of Living in truth: Physics as a way of life, Anthropology of East Europe Rev. 20(2), pp. 43-54 (2002).

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to modernize and assert itself but was deeply suspicious of and hostile to their intellect – a state that offered them optimal working conditions, and at the same time wiretapped and killed them. When Gribov’s generation entered university, the Cold War had just started, and physicists were in urgent need. Their salaries were increased fourfold, and ample research funding made available [2]. More physicists were inducted into the Academy of Sciences, which meant faster access to a bearable flat or a dacha and special food deliveries. Yet salaries stagnated under Khrushchev, and an average physicist in the seventies earned less than the bus driver that took him to his institute. Families of physicists, like everyone else, spent considerable energy in order to satisfy their basic needs, not to mention obtaining luxuries. Nevertheless, it was not just the euphoria for science and privileges that made young people study physics after World War II; it was also the restrictive intellectual climate of the Soviet Union. The post-Stalinist generation of physicists who had come of age in the last war years lived in a society that denied them opportunities to express the horrors they had experienced under Stalin. To critically minded people physics offered a rare ideology-free niche in which one was officially allowed, even compelled, to search for the truth. In the 1930s and 40s, physics had faced attempts of ideological cleansing. Relativity and quantum mechanics had to be defended from philosophers’ accusations that they were bourgeois and ideal- istic theories. Many of the key physicists in Leningrad, Moscow, and Kharkov were arrested in the purges of 1938–39. In 1948, the threat of a massive attack on physics arose again, as plans were made for a congress at which leading physicists were to be denounced for ideological mistakes. If the congress had taken place, the fate of So- viet physics may well have mirrored that of Soviet genetics: Stalin’s protégé, the agricultural “scientist” Trofim Lysenko had just succeeded in having genetics banned in the Soviet Union (see [2], pp. 162-163). Two days before the physics congress was due to begin, however, it was canceled. Lavrentii Beria, the chief of the secret service, had learned just in time that work on the bomb was based on the bourgeois theories that were heading for damnation. According April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

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to an anecdote recorded by Gorelik, Stalin responded with the words, “Let them go. We can always shoot them later.” Landau called this the first case of nuclear deterrence in history [2]. Despite such threats, ideology had little impact on physics. Al- though textbook passages about the Heisenberg uncertainty principle proclaimed that the principle’s interpretation should follow Lenin’s thought, only a score of opportunists and mediocre scientists were actually impressed with the attacks on “idealism.” Boris Altshuler, today a professor of theoretical physics at Prince- ton, recalls his decision to study physics in the 1960s: “Career choices in the Soviet Union were obviously limited. Many careers either didn’t exist or offered no intellectual freedom. The natural sciences were the only profession that secured relative independence both in intellectual and economic terms.” Consequently, many of those who had actually wanted to pursue other professions also ended up in physics. When Lev Okun, who today divides his time between the Institute of Theoretical and Ex- perimental Physics (ITEP) in Moscow and CERN in Geneva, finished secondary school in 1947, he wanted to study literature: “My friend and I went to Moscow University, to the Department of Philology...and we wanted to talk to the dean. But before that, a professor [appeared] in this position [bent forward], and he opened the door as if a god was there, and he was very frightened and hu- miliated.... And my friend and I looked at each other, and we turned back and never entered this building again.... I never saw anybody [in physics] who behaved like this.” The desire for freedom played a role in prompting many of the most talented students to specialize in theoretical physics in their senior years of study. Experimentalists were vulnerable to material conditions, whereas the only thing theoreticians needed to work was their brains. In the country in which they lived, this was a big advantage: Landau performed the calculations for his theory of the shock wave in prison; later, physicists who did not find jobs in science could work at home. Not until the 1970s was the Soviet Union’s lag in computerization felt in theoretical physics. While work on projects related to bombs and nuclear power April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

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stations was expected, outside that obligation physicists enjoyed wide-ranging freedoms and little pressure to achieve quick results. Boris Altshuler describes the informal work style of theoreticians at the Leningrad Institute for Nuclear Physics in Gatchina, where he worked between 1978 and 1989, in this way: “We had no particular obligations. We didn’t have to teach, and we were basically free to decide what we wanted to work on. People in the U.S. can’t imagine that kind of freedom. Here, you spend a lot of your time writing applications for grants that you may or may not get. In Leningrad, if you wanted to switch from solid-state to particle physics, no problem: all you had to do is perhaps move to another group.” From the beginning, Soviet ideology had supported a close relationship between research and industry. Science was to serve the people, not be conﬁned to ivory towers. Yet in practice, the economy was unsuited to make use of most scientiﬁc innovations. Nonetheless, arguing that advances in physics are often based on unexpected discoveries, physicists at that time, i.e. before the late 1970s, succeeded in convincing the leadership to let them conduct the research they wanted.

Gribov’s Circle After the war, the exhausted Soviet people experienced a few years that were free from the campaigns and nightly arrests of the 1930s. Soon, however, the respite was over, particularly for Jews. In the twenties and early thirties, Jews, along with the rest of the disen- franchised populations of Russia – peasants and workers – gained access to education and upward mobility. Some of Landau’s students, including Isaak Pomeranchuk and Leonid Piatigorskii, came from shtetls. In 1937, however, Stalin’s nationalities policy made a clean break with pluralism. Later, war propaganda used Russian nationalism to raise morale, and after the victory, it took on a new life as a tool of oppression. The campaign against “deference to Western bourgeois science” [3] launched in 1947, was linked to the massive anti-Semitic campaigns of Stalin’s last years. Most of Gribov’s university friends April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

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were convinced atheists, but according to their identity documents, they were Jews. Gerasim Eliashberg, who belonged to the circle, notes: “[I]n 1950–52, the cruelties of the late 1930 appeared to repeat themselves. Those who were older had already developed a system of survival ... and were very closed to outsiders. But it took us fresh- men a while to realize that we had to be, too ... Our little group enabled us to survive and to stay human. [A]s a Jew I wouldn’t get the permission to specialize in nuclear physics. So in my second year at the university I made a cynical decision. I went to the Komso- mol leader. After the guy had understood what it was about, he said: ‘There is this Tito clique at the university. Write an article unmasking them for the wall newspaper.’ And I did. But then Volodia Gribov and his friend Lionia Alt- shuler came along ... and said: ‘Do something like this one more time and we won’t say hello to you again.’” Tania Altshuler, Lionia’s later wife, was one of the friends. “We had a toast,” she recalls. “We used to say: ‘To it!’ And that stood for ‘To (Stalin’s) kicking the bucket.’” Gribov graduated from the university in 1953. The Ministry of Middle Machine-Building – Soviet-speak for the Ministry of Nuclear Energy – assigned him to teach at a school in the town of Rzhev, Kalinin Province. But, in a textbook case of bureaucratic absurdity, he succeeded in exchanging that post for one at an evening school for workers in the Rzhevka neighborhood of Leningrad’s Kalinin District. During the day, Gribov went to seminars at the Physico-Technical In- stitute. “Volodia was very good,” recalled Karen Ter-Martirossyan, “and I encouraged him to sit for Landau’s theoretical minimum,” a unique examination that only 43 candidates passed. Landau, Gribov’s teacher, was not just a top physicist who got the 1962 Nobel Prize for his theory of superconductivity and whose nine-volume course of theoretical physics remains a standard text worldwide; he was also an electrifying personality whose impulsive habitus stood in contrast with the conformism of Soviet society. At the seminars, he was always ready for battle, initiating wild brain- April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

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storming sessions during which everyone interrupted and chased everyone else from the blackboard. Often offensive and brusque, he demanded the kind of uncompromising search for truth from his students that drove his own quest. He preferred to work at home, on the couch in his study. Lying there, he received fellow physicists, and when he tired of them he simply turned to the wall (see [4]). In the 1960s, Gribov’s seminars became to the physicists of the “new” Leningrad school what Landau’s had been to his own generation. Volodia Anisovich, a physicist at LNPI, recalls his first meeting with Gribov towards the end of his student years: “There are some ten people and someone is talking, and I even understand what he is saying. Suddenly a man with black hair and a sharp narrow face jumps up and says something, and I see that I understand nothing. I am even a bit irritated: everything has been fine, why did he have to jump up! Suddenly a second man...jumps up, a bit older and starts arguing...Volodia [Gribov] and Karen [Ter- Martirossyan]. After this a total mess sets in. The presenter disappears, Volodia and Karen shout at each other, pick up pieces of chalk, write something. At the end, Volodia is left alone at the blackboard, explaining something.... I have understood nothing of the whole thing ... so I go home.” Landau and Gribov were alike in another way. Both “felt” physics as a unity. Yuri Dokshitzer, today a professor at the UniversitéParis VI, describes [5] Gribov’s approach to physics in this way: “He had a profound knowledge and skill in using mathematical methods in physics. However...what mattered most was...a picture. He would approach the problem from different angles, abstracting its essential features and illustrating them with the help of simplified models and analogues from different branches of physics. People unfamiliar with his style were often confused ... some felt they were being cheated: a couple of chalk drawings, a strain of hand-waving arguments, and – here you are: that’s the answer? Such listeners were not aware that ... for Gribov it went without saying that the receiving party is capable of reproducing the necessary mathematical calculations. ‘I am not smarter, I just think more,’ Gribov once said.” April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

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Physics and the Struggle for Truth The Leningrad physicists around Gribov and the “Moscow Lenigra- dians” at the Landau Institute and ITEP shared more than a style of thinking and working: they also comprised communities of lifestyle and values. Physics was for them far more than a profession: it was a vocation and a way of life. When they were not at the institute, the theoreticians worked at home, thinking, smoking, and talking: “making physics,” as Gribov’s second wife Julia Nyiri, herself a physicist, called it. Summer and winter schools of theoretical physics were orgies of undiluted physics-making. Events of the Leningrad Physico-Technical Institute (later the LNPI) took place in the countryside holiday homes of the Academy of Sciences. Yuri Dokshitzer, whose father had made him suffer through a rigorous musical education, played songs by Okudzhava, Vysotskii, and Galich on his guitar.a Alexei Kaidalov from ITEP sang. The lifestyle of physics-making was punctuated by mountaineering and kayak trips and flavored by samizdat copies of poetry by Mandelshtam, Solzhen- itsyn’s prose, or Agatha Christie and Irving Stone novels bought during trips to the West. Physicists’ flats housed readings by actors and concerts by bards Bulat Okudzhava and Vladimir Vysotskii, members of an emerging alternative to the totalitarian uniformity of culture. Intellectual exchanges were of a particular intensity. Otherwise a mild man, Gribov could be harsh when he felt that someone was not honestly trying to get an answer. Intense curiosity and belief in the meaningfulness of one’s work, enjoyment of the creative process foritsownsake,andasensualpleasureinbeingabletoexpressa piece of physical reality in a clear form – all these may be particularly characteristic of theoretical physicists anywhere. But Western physicists too found the intellectual intensity of the exchanges that went on in the Leningrad school fascinating. Partly, the explanation lay in the oppressive nature of Soviet society, which gave any niche culture a particular intensity. Whereas any questioning of an official statement to the outside was dangerous,

aSee footnote, p. 246. April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

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discussions in the “inner circle” were endless and passionate. “How could brains seized by fear and ideological pressure at the same time think independently and creatively in their professional ﬁelds? Ap- parently the matter is that work was salvation, a sort of internal emigration,” writes Evgeny Feinberg [6]. In addition, there were simply fewer material distractions. As Vitaly Ginzburg put it [7], “Work andsciencewaseverythingtous:aperfumeandevenanarcotic.” Moreover, the search for truth in physics carried a broader meaning. It was the defense of a moral stand against falsehood that could not be publicly displayed in other domains of Soviet life. Indepen- dently of each other, both Evgeny Feinberg and Gerasim Eliashberg said the same sentence: “Physics was the only way to maintain one’s human integrity.” A third physicist, Yuri Petrov, a close friend of Gribov’s, emphasized: “Numbers cannot lie.” The rationality and objectivity of “pure science” oﬀered natural scientists a way out of irrationality and ideological license.

Physicists and the State The mistrust that characterized the relations between the power holders and the scientists they needed but whose work they could hardly control remained unchanged until the perestroika. Ella Ryn- dina, an experimental physicist and Landau’s niece, always had a pillow on the telephone to muffle the sounds picked up by the bug. Everyone knew to speak openly only during outdoors walks. One physicist who was giving an enthusiastic account of his trip to the West, added, for the ears of the spies: “But to think of it that they have to live under capitalism!” As division head in Gatchina, Gribov should actually have been a Party member. But he was reluctant to join, and among the 70 physicists on his staff there were just four or five members. This was unusual, even taking into account that physicists generally had very low Party membership rates, that rates among theoreticians were even lower than among experimentalists, and that ITEP in Moscow and LNPI in Leningrad had lower rates than other research institutes. Only some 10% of around 2,000 scientists in Gatchina were in the Party. So low were these rates that some of the leaders themselves April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

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grew concerned. Lev Okun recalls that Pomeranchuk, who was not a Party member, repeatedly tried to persuade him to join. “He said, ‘Look, there are no party members in our department, that’s bad, and for the benefit of others could you do this?’ And I would tell him, ‘Please go ahead, and I will follow you.’” Within the division, there was an intuitive understanding. Ioffe recalls: “Pomeranchuk used to come to my room and ask, ‘Have you read this morning’s Pravda?’ ‘Yes,’ I would say. ‘Aha! And did you notice anything in particular?’ ‘The article about the meeting of the Party committee in this and this province.’ ‘Aha! What about it?’ ‘The order in which the members of the Politburo were listed.’ ‘Aha!’ And that was the end of the conversation. Both of us understood that the order of the names pointed to some shift in the power configuration in the Party leadership.” Few Soviet physicists became open dissidents like Andrei Sakharov or Yuri Orlov. “Most of us were dissidents at heart and in the kitchen, but public resistance was more infrequent than with the biologists, who were being hindered in their work,” says Ilya Roizen, a student of Vitaly Ginzburg. Very few physicists were directly confronted with the choice between professional renown and human integrity that every artist or academic in the humanities had to face. They admired Sakharov’s courage but saw that political en- gagement barred one from the practice of really good science. Even theoreticians, who continued thinking under arrest and in camps, could not produce consequential work under persecution. “I understood that I had to choose between doing science and fighting with the KGB and the government.... I thought that my first obligation is to do physics as well as I can,” says Okun. There were subtle ways to resist. Every now and then physicists would be requested to sign a state-sponsored letter of solidarity or protest. Those who did not want to often disappeared for a few days. When the President of the Academy of Sciences, the physicist A. P. Aleksandrov, was asked to criticize Sakharov in an official letter, he had supposedly gone on an extended drinking binge and was “unfortunately” unavailable. April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

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Contacts with the West Soviet physicists suffered from the limits on contacts with their West- ern colleagues. Until the mid-thirties, they had regularly published in foreign journals, but then contacts became sparser and broke down almost completely during World War II, a state that lasted until the mid-fifties. With the exception of that period, Soviet physicists did have access to the main periodicals such as Physical Review, but even the short delay with which they arrived could be frustrating. In the early 1950s we used to calculate how much we are delayed by because of being separated from world science, says Yuri Novozhilov at LNPI. Contacts resumed in 1959, the first time a Rochester Conference, a major physics meeting, took place in the USSR. Soviet physicists were gradually allowed to go abroad again. But some remained “nevyiezdnye,” a term that could roughly be rendered as “unabroad- able.” Gribov, for example, was not allowed to go abroad for a long time despite the fact that several conferences in the West were devoted to the Gribov copies in the 1970s. “In 1968, I wanted to invite Alexei Anselm from Gribov’s team to London,” recalls the British physicist Elliot Leader. “The usual reply to invitations was: ‘Thank you very much for inviting Professor X. Unfortunately, he is unable to go, but we will send Professor Y.’ That was someone politically correct.” The first time everyone invited to a major conference in the West was actually allowed to attend was in 1988. But, says Lev Okun, “Maybe the lack of communication with the West was in a certain sense a blessing, because it gave originality to what we did. Many serious things were first done in Russia, like Regge calculus by Volodia [Gribov], CP violation by ITEP people and Landau. These were trend-setting for the West.” Three Soviet physics journals were translated into English in the United States; but by the time the scientific community was convinced of the cor- rectness of an idea and all officials had approved it, the same idea may already have appeared in the West. With the collapse of the Soviet Union, the symbiosis of theoretical physicists and totalitarian regime ended. Military budgets shrank; in the Academy’s institutes, cables fall from ceilings and paint from April 5, 2013 16:2 WSPC/Trim Size: 9in x 6in for Proceedings 11e˙Pale-Gribov-and-Time

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the walls. One can no longer live on an institute salary; there is no money for periodicals; and under President Putin, publishing is once again regulated. In the unlit corridors of ITEP, and on the wooded alleys of Chernogolovka and Gatchina, one still encounters physicists of the old guard, but most of them are visitors from abroad. Gribov, too, spent most of the time before his death in 1997 in such places as Princeton and Bonn.

References 1. Milan Kundera, The Unbearable Lightness of Being. Translated by Michael Henry Heim, (London, Faber and Faber, 1985), p. 109. 2. Gennadii Gorelik, Andrei Sakharov: Nauka i Svoboda [Science and freedom]. (Moscow and Izhevsk, RKhD, 2000). 3. G. E. Gorelik and A. B. Kozhevnikov, Chto spaslo sovetskuiu ﬁziku ot lysenkovaniia [What saved Soviet physics from Lysenkoisation?] http://www.nature.ru:8609/db/msg.html?mid=1178346&uri=i ndex.html , 1999. 4. Kora Landau-Drobantseva, Akademik Landau: Kak my zhili [Academician Landau: The way we lived], (Moscow, Zakharov-AST, 1999). 5. Yuri Dokshitzer, V. N. Gribov, 1930–1997, inEd.A.V.Smilga,Continuous Advances in QCD 1998, (World Scientiﬁc, Singapore, 1998) pp. xv-xxi. 6. E. L. Feinberg, Epokha i Lichnost’. Fiziki, [Time and personality. Physicists] (Moscow, Nauka, 1999). 7. Vladimir Shapiro, Neogranichennaya otvetstvennost, [Unlimited liability], Okna (Israel), 12 April 2001, pp. 14-15. April 5, 2013 13:35 WSPC/Trim Size: 9in x 6in for Proceedings 12a_PartII+Chap11-divider

PART II

CHAPTER 11 May 10, 2013 11:14 WSPC/Trim Size: 9in x 6in for Proceedings 12a_PartII+Chap11-divider May 13, 2013 15:48 WSPC/Trim Size: 9in x 6in for Proceedings 13˙Index

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GREAT UNIVERSALIST OF THE 20TH CENTURY∗

S. S. GERSHTEIN Institute for High Energy Physics Protvino, 142281 Moscow Region Russia [email protected]

One of the most prominent physicists of the 20th century, Lev Davidovich Landau, was at the same time a great universalist who made fundamental contributions in diverse areas of physics: quantum mechanics, solid state physics, theory of magnetism, phase transition theory, nuclear and particle physics, quantum electrodynamics (QED), low-temperature physics, ﬂuid dynamics, atomic collision theory, theory of chemical reactions, and other disciplines.

Fundamental Contribution to Theoretical Physics The ability to cover all physics disciplines and grasp them in their entirety is a typical feature of Landau’s genius. It manifested itself in an outstanding course of theoretical physics a created by L.D. Lan- dau in collaboration with E.M. Lifshitz, the last volumes of which were completed by his students, E.M. Lifshitz, L.P. Pitaevsky, and V.B. Berestetsky. Nothing similar exists in the world literature. Its comprehensive nature combined with accuracy and originality, a universal approach to problems, and extensive cross-referencing between all volumes made this course a reference book for many generations of physicists from various countries, for students and professors. Trans- lated in many languages, the course widely inﬂuenced the level of

∗This is the ﬁrst part of the paper published in Priroda, 2008, Issue 1, p. 15. Translated from Russian by Petr Kravchuk. For the second part, see p. 30. aSee Karl Hall’s review in Pedagogy and the Practice of Science: Historical and Con- temporary Perspectives, Ed. David Kaiser, (MIT Press, 2005), p. 253.

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theoretical physics all around the world. Undoubtedly, it will maintain its importance for future researchers as well. Minor additions concerning recent results can be included in the subsequent editions. It is impossible to describe all Landau’s results in a single article. I will discuss only a few of them. The pioneering works of Heisenberg and Schrödinger on quantum mechanics excited Landau and his friends, George Gamow, Dmitri Ivanenko, and Matvei Bronshtein,b then students of the Leningrad State University. Almost immediately, eighteen-year-old Landau introduced the density matrix description for subsystems of closed systems. This concept became central in quantum statistics. All his life Landau studied applications of quantum mechanics to real physical processes. In 1932, he showed that the transition probabilities in atomic collisions are determined by the intersections of molecular terms. He derived the corresponding expressions for transition and pre-dissociation probabilities (the Landau-Zener-Stueckelberg rule). In 1944, he (in collaboration with Ya.A. Smorodinsky) developed the “effective radius” theory which provided a model-independent way to describe scattering of slow particles by short-range nuclear forces. Landau made fundamental contributions to the theory of magnetic phenomena. In 1930, he showed that according to quantum mechanics, free electrons in metals obtain a quasi-discrete energy spectrum in the presence of a magnetic field, thus leading to diamagnetic susceptibility (connected with the orbital motion) of electrons in metals.c It constitutes one third of the diamagnetic susceptibility induced by intrinsic angular momentum of electrons (spin). At the same time, he noted that in real crystal lattices this ratio can be shifted in favor of the electron diamagnetism while in strong magnetic fields and at low temperatures a peculiar effect should be observed – the oscillation of magnetic susceptibility. In a few years this effect was found experimentally. It became known as the de Haas-van Alphen effect. The electron energy levels in the magnetic field are

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now referred to as the Landau levels. Determination of these levels at different orientations of the magnetic field allows one to find the Fermi surface (the iso-energetic surface in a quasi-momentum space corresponding to the Fermi energy) of electrons in metals and semiconductors. A general theory for these purposes was developed by Landau’s student I.M. Lifshitz and his school. Thus Landau’s study of the electron diamagnetism laid the foundations for all modern work on the electron energy spectra in metals and semiconductors. Let us note that the existence of the Landau levels was a crucial point in the interpretation of the quantum Hall effect (the discovery and explanation of which were recognized by the Nobel Prizes in 1985 and 1998). In 1933 Landau introduced the notion of antiferromagnetism as a special phase of matter. Not long before, the French physicist Louis Néel assumed that there can be substances that at low temperatures are composed of two sublattices spontaneously magnetized in the opposite directions. Landau showed that the transition into this state had to be discontinuous, similar to a phase transition at a certain temperature resulting in a change of certain symmetry rather than density. These ideas were successfully used by Landau’s student I.E. Dzyaloshinsky in conjecturing new types of magnetic structures, weak ferromagnetic and piesomagnetic materials, and pointing out their lattice symmetry types. In 1935, Landau (in collaboration with E.M. Lifshitz) developed the domain structure theory in ferromagnetic materials. He was the first to determine the domain shapes and sizes, to describe the behavior of magnetic susceptibility in varying magnetic fields, and, in particular, the ferromagnetic resonance phenomenon. The general theory of phase transitions of the second type developed by Landau in 1937 is of a major importance for a wide range of physical phenomena. Landau generalized the approach used for antiferromagnetism: any phase transition is accompanied by a change of symmetry, and hence, the phase transitions must occur not gradually, but rather as a jump with symmetry change at a certain point. If the density and specific entropy do not change, the phase transition does not exhibit hidden heat release. At the same time, the heat capacity May 10, 2013 12:14 WSPC/Trim Size: 9in x 6in for Proceedings 12b˙Gersh-Priroda˙Land˙TWO

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and the compressibility change abruptly. Transitions of this kind are now called the second type phase transitions. Transitions into ferromagnetic and antiferromagnetic phases, into ferroelectric phase, structure transitions in crystals, and transition to superconductivity in metals in the absence of the magnetic field are all of this kind. Landau has demonstrated that all these transitions can be described by the introduction of an order parameter which does not vanish in the ordered phase below the transition point and is zero above it. In the paper “On the theory of superconductivity” written in 1950 by V.L. Ginzburg and L.D. Landau, a function Ψ playing the role of an “effective” wave function of superconducting electrons was chosen as the order parameter characterizing the superconductor. The resulting phenomenological theory provided a way of calculating the energy of the contact surface between the normal and superconducting phases and proved to be consistent with the experiment. On the basis of this theory, A.A. Abrikosov introduced the notion of two types of superconductivity: type-I exhibiting positive surface energy and type-II exhibiting negative surface energy. The majority of al- loys turned out to be of type-II. Abrikosov showed that the magnetic field penetration in the type-II superconductors occurs through peculiar quantum vortices and thus the transition in the normal phase is deferred to considerably higher values of the magnetic field. Such superconductors have many applications in science and technology. After the completion of the macroscopic theory of superconductivity, L.P. Gorkov demonstrated that the Ginzburg–Landau equations can be derived from the microscopic theory and determined the meaning of the relevant phenomenological constants. This general theory of superconductivity is now known as GLAG – Ginzburg–Landau– Abrikosov–Gorkov. In 2004, it was recognized by the Nobel Prize awarded to Ginzburg and Abrikosov. One of the most outstanding Landau results is his theory of superfluidity which explained the helium-4 superfluidity discovered by P.L. Kapitsa. According to Landau, strongly coupled atoms of the liquid helium at low temperatures form a special kind of a quantum liquid. Excitations of such a liquid are sound waves which correspond to quasiparticles called phonons. The phonon energy represents the April 5, 2013 16:19 WSPC/Trim Size: 9in x 6in for Proceedings 12b˙Gersh-Priroda˙Land˙TWO

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energy not of an individual atom but that of the liquid collective excitation and is proportional to phonons’ momentum p, (p)=cp where c is the speed of sound. At temperatures close to absolute zero these excitations cannot arise in a subsonic flow, and, consequently, the liquid does not exhibit viscosity. As Landau thought up in 1941, in addition, there can be a rotational flow. The spectrum of the rotational excitations p2 r =Δ+ 2μ has a gap Δ. Here μ is an effective mass of the quasiparticle corresponding to the rotational excitation, the so-called “roton.” This term – roton – Lev Davidovich introduced following I.E. Tamm’s suggestion. Using the quasiparticle spectrum, he found the temperature dependence of the liquid helium specific heat and obtained hydrodynamic equations for it. He demonstrated that in some cases the motion of helium is equivalent to two separate motions – one of the normal (viscous) phase and the other of the superfluid phase (ideal). Moreover, the density of the latter becomes zero above the phase transition point and can be used as the order parameter of the corresponding type-II phase transition. A beautiful consequence of this theory was Landau’s prediction of the existence of unusual oscillations in liquid helium – ordinary and superfluid phases oscillate in counter-phase. This phenomenon was called “second sound.” Landau predicted its speed. The discovery of the second sound in remarkable experiments conducted by V.P. Peshkov was an impressive confirmation of the theory. However, Landau was concerned with a slight difference in the experimental and theoretical data for the speed of sound. After a careful analysis he concluded in 1947 that instead of two branches of the spectrum – phonon and roton – there should exist a unified formula. According to Landau the excitation energy should grow linearly at low momenta and have a local minimum near some momentum value p0, where it can be approximated as

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In this case, as Lev Davidovich emphasized, all conclusions concerning superfluidity and macroscopic hydrodynamics of helium-2 remain valid. In a follow-up work in 1948, Landau used an additional argument referring to N.N. Bogolyubov’s result obtained in 1947. Bogolyubov invented a trick that enabled him to calculate the spectrum of excitations of weakly interacting Bose gas, which exhibited a linear dependence for small momenta. It could be that this particular work, combined with Peshkov’s results, inspired Lan- dau to formulate the idea of the unified excitation curve. Landau’s theory of superfluidity was brilliantly confirmed in beautiful experiments by V.P. Peshkov, E.L. Andronikashvili, and others, and was further developed in joint works by Landau and I.M. Khalatnikov. Landau’s excitation spectrum was directly confirmed in X-ray and neutron scattering experiments (this possibility was pointed out by R.P. Feynman). In 1956–1957, Landau developed a theory of Fermi liquids (the Fermi liquids are quantum liquids in which the elementary excitations posses half-integer spin and, correspondingly, are described by the Fermi–Dirac statistics), applicable to a wide range of objects (electrons in metals, liquid helium-3, nucleons in atomic nuclei). From this standpoint, a microscopic theory of superconductivity predicting new phenomena could be naturally derived. Novel perspectives of using quantum field theory in condensed matter were discovered. Further development of the Fermi liquid theory by L.P. Pitaevsky enabled him to predict the superfluidity of helium-3 at sufficiently low temperatures. An exceptionally beautiful and nontrivial effect of the electron reflection from superconductor-normal metal contact surface was predicted by A.F. Andreev, the last student to be accepted by Landau to his group. This effect was called the “Andreev reflection” in the world literature. It is gaining a wide range of applications nowadays. From the very beginning of his scientific activities, Lev Davidovich was interested in problems of quantum field theory and relativistic quantum mechanics. The derivation of the formulas for the relativistic electron scattering off the Coulomb field of atomic nuclei accounting for retardation of the interaction (the so-called Møller scattering), April 5, 2013 16:19 WSPC/Trim Size: 9in x 6in for Proceedings 12b˙Gersh-Priroda˙Land˙TWO

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according to Møller himself, was suggested to him by Landau. In the paper with E.M. Lifshitz (1934), Lev Davidovich examined electron- positron production in charged particle collisions. Generalizations of these results eventually led to an important direction of experimental research – two-photon physics on electron-positron colliders. In the paper written in collaboration with V.B. Berestetsky (1949), Lev Davidovich Landau drew attention to the importance of the so-called exchange interaction in a system of particles and their antiparticles. The Landau theorem (proved independently by T.D. Lee and C.N. Yang), stating the impossibility of spin-1 particle decay into two free photons (valid also for gluons) plays an important role in modern elementary particle physics. It allows one to explain the J/Ψ small decay width, which had caused some perplexity in the beginning. A number of results of major importance for particle physics were obtained by Lev Davidovich with his students A.A. Abrikosov, I.M. Khalatinkov, and I.Ya. Pomeranchuk. The main difficulty in quantum electrodynamics (as well as in quantum theory of other fields) at that time was the issue of infinities in theoretical calculations of some physical quantities (e.g. the electron mass). In the late 1940s, a prescription for eliminating these infinities from observable quantities was found (R.P. Feynman and others). Landau was not satisfied with this prescription. He formulated an objective to develop a theory in which only finite quantities would arise at every stage. According to Landau, to meet these requirements, the local QED interaction should be considered as a limit of a nonlocal “smeared” interaction with a finite (but small) radius a. Corre- spondingly, the would-be infinite integrals in the momentum space are naturally cut off at Λ 1/a. The bare electron charge e1 becomes a function of the smearing radius a, i.e. e1 → e1(a). Then the“physical”electronchargee observed at large distances (small frequencies) is expressed in terms of the bare charge e1(a)as e2 e2 = 1 , (1) νe2 2 1 Λ 1+ 3π ln m2 where ν is the number of fermions contributing to the vacuum po- April 5, 2013 16:19 WSPC/Trim Size: 9in x 6in for Proceedings 12b˙Gersh-Priroda˙Land˙TWO

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larization, m is the electron mass, and the charges e and e1 are dimensionless quantities expressed in units of the speed of light c and the Planck constant , q2 e2 α / . = = c 1 137 The expression for the bare electron charge following from (1) is e2 e2 = . (2) 1 − νe2 Λ2 1 3π ln m2 It is interesting that before the calculation was carried out, Landau had thought that the bare charge e1(a)felloffwitha decreasing and tended to zero when the radius a → 0, thus leading to a self- e2 < consistent theory (the above calculation was valid assuming 1 1). Landau even developed a general philosophy corresponding to the modern principle of “asymptotic freedom” in quantum chromodynamics. Preliminary calculations seemingly confirmed this point of view. However, the preliminary calculation contained a disappointing sign error in Eq. (1) and hence in (2). (With the wrong sign in (2) it −1 is indeed the case that e1 → 0whenΛ=a →∞.) When the error was found, Lev Davidovich managed to withdraw their paper from the editorial office and fixed the error. The philosophy of “asymptotic freedom” disappeared from the paper along with the error. It was very unfortunate. If Yu.B. Khriplovich (a Novosibirsk theorist from the Budker Institute of Nuclear Physics) knew about it when he observed the fall off of the color charge in quantum chromodynamics with the decrease of distance, he could possibly develop a general theory of asymptotic freedom before Gross, Wilczek, and Politzer (D. Gross, H.D. Politzer, and F. Wilczek received the 2004 Nobel Prize for the discovery of this phenomenon). He did not know, however. In QED the effective electron charge falls off with distance. Collider experiments showed that the effective charge at distances ∼ 2·10−16cm is about ∼ 1/128 (compared to 1/137 at larger scales). The growth of the effective charge at short distances led Landau and April 5, 2013 16:19 WSPC/Trim Size: 9in x 6in for Proceedings 12b˙Gersh-Priroda˙Land˙TWO

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Pomeranchuk to the conclusion of fundamental importance: if the second term in the denominator of (1) is much larger than unity, then the physical charge e reduces to 1 e2 = (3) ν Λ2 3π ln m2

independently of the value of e1, and vanishes when Λ →∞or a ∼ 1/Λ → 0. Although there is no rigorous proof for this formula (the theory is valid only if e1 < 1), Pomeranchuk found some com- pelling arguments in favor of the validity of (3) regardless of the value of e1. This conclusion (if valid) means that the existing theory is inconsistent: it leads to the vanishing value of the observable electron charge in the limit of local interactions. Landau noted that the “crisis” of QED arises at such values of a at which the gravitational interaction becomes significant, that is, at distances ∼ 10−33cm (or energies ∼ 1019GeV). In other words, there was a hope that a unified theory containing gravity and incor- porating a fundamental length of the order of 10−33cm could solve the problem. This line of thought is inherent to a number of today’s theoretical constructions. The notion of combined CP-parity introduced by Lev Davidovich in 1956 is of great importance to modern physics. The issue of spatial parity and violation in weak processes arose in 1956 in connection with the so-called θ-τ problem. At first Landau’s attitude was critical: he did not want to consider this option. “I can’t understand how left and right can be unequal in our isotropic space,” he said. Since the so-called CPT theorem states that a local theory must be invariant under three simultaneous symmetry transformations: spatial reflection (P ), time reversal (T ) and charge conjugation (C) (i.e. interchange of particles and antiparticles), the spatial parity (P ) violation inevitably leads to violation of some other symmetries. Pomeranchuk’s collaborators B.L. Ioffe and A.P. Rudik assumed in the beginning that the violated symmetry was T because the C-parity conservation, according to M. Gell-Mann and A. Pais, explained the existence of long- and short-living neutral kaons. However, L.B. Okun noted that it can be explained by the conservation of T -parity April 5, 2013 16:19 WSPC/Trim Size: 9in x 6in for Proceedings 12b˙Gersh-Priroda˙Land˙TWO

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as well. As a result of conversations Landau had with Pomeranchuk’s students,d he came to the conclusion that the mirror symmetry violation was connected with the difference between particles and antiparticles. Landau’s idea was: “The processes with antiparticles must look as a mirror image of the same processes with particles.” He compared this situation with the existence of asymmetric “left-” and “right-handed” crystals – modifications of each other – related by spatial reflections. This was the reason that compelled Landau to introduce the notion of the combined CP parity. The subsequent experiments seemingly brilliantly confirmed its conservation. However, in 1964 a “milliweak” CP violation (at the level of ∼ 10−3 of the weak interaction) was discovered in decays of the long-living neutral kaons. The CP violation studies opened a novel area of active theoretical and experimental research. Nowadays, CP violation is well understood at the quark level. In addition to kaon decays, it was observed in some b-quark processes. Accord- ing to A.D. Sakharov’s hypothesis, the CP-symmetry violation combined with a (small) baryon number nonconservation can explaine the baryon asymmetry of our Universe (the observed absence of an- timatter). In parallel with the concept of CP violation, Landau proposed the idea of chiral (two-component) neutrinos, with the spin parallel or antiparallel to its momentum (independently of A. Salam, T.D. Lee, and C.N. Yang.) This corresponds to the maximal violation of P and C while CP is conserved. In this picture, there are right- handed antineutrinos and left-handed neutrinos, and no left-handed antineutrinos at all. Relying on this hypothesis Lev Davidovich predicted that in the β-decay processes all electrons should be polarized antiparallel to their momenta (in the case of the left-handed neutrinos). He predicted the two light neutral particles emitted in the μ-decay (μ− → e− + νν) to be two different neutrinos. (Today we know that one is the muon neutrino, ν = νμ and the other is the electron antineutrino, ν =˜νe.) The chiral neutrino concept attracted

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Landau also because the chiral neutrinos had to be massless. This seemed to be consistent with the fact that exceedingly more precise experiments yielded exceedingly stronger upper bounds on the neu- trinomass.ThechiralneutrinoideahelpedFeynmanandGell-Mann to suggest a hypothesis that all other (massive) particles participate in the weak interaction only through their left-handed chiral components. By that time, it had been already established that neutrinos were indeed left-handed. This hypothesis led Feynman and Gell- Mann as well as R. Marshak and E.S.G. Sudarshan to the discovery of the fundamental (V −A) law of the weak interaction which pointed out the analogy between weak and electromagnetic interactions and stimulated the discovery of the uniﬁed electroweak theory. Landau always reacted promptly to discoveries of new unknown phenomena and their theoretical interpretation. Already in 1937, he and Yu.B. Rumer invoked the physical idea of the cascade nature of the electromagnetic showers observed in cosmic rays (it was suggested by H. Bhabha and W. Heitler; J. Carlson, and J.R. Oppenheimer) to develop an elegant theory of this complicated phenomenon. Us- ing eﬀective cross-sections for bremsstrahlung of hard γ quanta by electrons and the electron-positron production cross-sections by γ quanta known from QED, Landau and Rumer obtained equations determining the shower dynamics. By solving these equations they found the dependence of the number of particles produced in the given shower and their energy distribution on the atmosphere penetration depth. In subsequent works (1940–1941) Lev Davidovich determined the width and the angle distribution of the shower particles. He also showed that the showers observed underground can be caused by heavier penetrating particles (the “hard” component of the cosmic rays that turned out to consist of muons). The methods and results of these papers laid the foundation for experimental and theoretical research that ensued. Today they are important for high energy physics research in two aspects. On the one hand, the theory of electromagnetic showers is important for determination of the type and energy of the primary cosmic rays particles, especially at very high energies ∼ 1019-1020eV. On the other hand, this theory is the basis for the electromagnetic calorimeters which became April 5, 2013 16:19 WSPC/Trim Size: 9in x 6in for Proceedings 12b˙Gersh-Priroda˙Land˙TWO

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one of the most common devices in the modern high-energy colliders. Landau’s determination of the number of particles in showers as well as his outstandingly elegant work on the ionization energy loss fluctuations of fast particles (1944) are particularly important for modern high-energy experiments. Lev Davidovich returned to the electron shower processes in his works with Pomeranchuk in 1953. In these works it was shown that the formation length in the γ-quantum bremsstrahlung by fast electrons is proportional to the electron energy squared, l ∼ λ(E/mc2)2.(Hereλ is the γ-quantum wavelength.) Therefore, in matter l can become larger than the effective length of the multiple electron scattering implying a decrease in the probability of the long wave length radiation emission (the Landau–Pomeranchuk effect). A number of works by Lev Davidovich is devoted to astrophysics. In 1932 he, independently of S. Chandrasekhar, determined the upper limit for the mass of white dwarfs – the stars consisting of degenerate relativistic electron Fermi gas. He noted that at masses larger than this limit (∼ 1.5 MSun), stars should exhibit a catastrophic collapse – the phenomenon which eventually became the basis for the idea of existence of black holes. In order to avoid such an “absurd” (Landau’s word!) tendency, he was ready to accept a violation of quantum mechanics laws in the relativistic domain. In 1937, Landau showed that in the process of a considerable star compression during its evolution, it becomes energetically favorable for the protons to capture electrons, thus forming a neutron star. He even thought that it could be the energy source of the stars. This paper became widely known as the prediction of inevitability of the neutron star formation as a result of evolution of sufficiently massive stars (the very idea of possible existence of the neutron stars was proposed by astrophysicists W. Baade and F. Zwicky soon after Chadwick’s discovery of neutron). An important part of Landau’s research is his work on hydrodynamics and physical kinetics. In addition to explorations in liquid helium, the latter topic contains Landau’s works on the kinetic equation for the Coulomb-interacting particles (1936) and the widely known classical work on the electron plasma oscillations (1946). In April 5, 2013 16:19 WSPC/Trim Size: 9in x 6in for Proceedings 12b˙Gersh-Priroda˙Land˙TWO

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this work, using the equation derived by A.A. Vlasov, Lev Davi- dovich showed that free oscillations in plasma died out even when the particle collisions could be neglected. (Vlasov had studied another problem – the stationary plasma oscillations.) Landau determined the dependence of the oscillation decay decrement on the wave vector, and studied penetration of a periodic external field in plasma. The term “Landau damping” has since become widely used in the world literature. In classical hydrodynamics, Lev Davidovich found a rarely encountered case when the Navier–Stokes equations can be solved exactly, namely the problem of a submerged jet. Considering the occurrence of turbulence, he proposed a new approach to this problem. A number of his papers were devoted to the shock wave investigations. In particular, he found that supersonic motion creates two shock waves at large distances from the source. A number of problems on shock waves solved by Lev Davidovich when he was actively involved in the Soviet nuclear project (some in collaboration with S. Diakov) have not yet been published. In 1945, Landau studied (with K.P. Staniukovich) the problem of detonation of condensed explosives and calculated the velocity of their product emission. This question became especially important in 1949 due to the preparations for the first Soviet nuclear bomb test. The velocity of products of normal explosives was of crucial importance for reaching the critical mass of plutonium by compressing it with these products. The measurement of this velocity was conducted in the beginning of 1949 by two different laboratories in Arzamas-16. In one of the laboratories, a mistake was made which ledtoaresultthatwasmuchlowerthanthevaluesnecessaryforthe successful plutonium compression. One can imagine how much anxiety it caused among the participants of the nuclear project. However, after the error was fixed, it turned out that the measured product velocity is sufficient and very close to the value predicted by Landau and Staniukovich. Knowing Lev Davidovich as the top level theorist with a broad range of interests, who could handle nuclear physics as perfectly as gas dynamics and physical kinetics, I.V. Kurchatov insisted on his April 5, 2013 16:19 WSPC/Trim Size: 9in x 6in for Proceedings 12b˙Gersh-Priroda˙Land˙TWO

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participation in the nuclear project from the very beginning. The value of Landau’s work for this project can be assessed from the words of its prominent participant Academician L.P. Feoktistov: “...The first formulas for the power of nuclear explosion were derived by the Landau group. We called them Landau’s formulas, and they were pretty well done, especially for that time. We predicted all further results using them. In the beginning, the errors did not exceed twenty percent. We had no calculators, instead, we used slide rules; it was only later when girls arrived to do computations using “mercedeses.”f No electronics, no partial differential equations. All formulas were derived from general nuclear-hydrodynamical considerations, and used some parameters that had to be fit. Hence the assistance of the Landau group was especially valuable.” It is worth mentioning that “Nuclear burning in a rapidly changing geometric background” (that’s how the report of the Landau group was entitled, according to Academician V.N. Mikhailov) was an exceptionally complicated problem because it required taking into account a wide range of factors: transition of matter, neutrons, radiation, etc. I think that only Landau could find the solution of such problems. The process of deriving “workable” approximations and expressions was captivating for him. This was totally different from the situation in the early 1950s when Landau had to work, out of self-preservation, on some problems imposed on him by the nuclear project management. How- ever, even in this case – even experiencing aversion to this work – he performed it with characteristic mastery and developed efficient numerical methods. It is hard to elaborate on many other important works of Lev Davidovich in such a short note: on crystallography, burning, physical chemistry, statistical theory of nuclei, multiple particle production, etc. However, all what I described above is sufficient for understanding that Landau was a genius physicist, one of the greatest universalists in the history of science.

f A slang name for electric arythmometers. May 10, 2013 12:16 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

LANDAU AND MODERN PHYSICS∗

V. L. POKROVSKY Department of Physics and Astronomy Texas A&M University College Station, TX 77843, USA [email protected]

1. Introduction The fate of Landau’s scientific legacy has been amazingly fortunate. It has been 46 years since he stopped doing science, but the number of citations per year of his papers is only increasing, rather than decreasing. It is rather difficult to give a quantitative estimate since, in many cases, when mentioning the Landau theory of phase transitions, the Ginzburg–Landau equation, the Landau–Lifshitz equation, Landau levels, the Landau criterion of superfluidity, the Landau theory of a Fermi liquid, etc., no citation to his original articles is given. Nevertheless, according to the science bibliography website Scirus, the number of formal and informal citations of Landau’s papers on phase transitions exceeds 30,000, on the Fermi liquid is about 45,000, on Landau levels is 75,500, on the Landau–Lifshitz equation is 23,000, on Landau damping in plasma is 12,000. In the year 2000, at the anniversary session of the American Physical Society, there were six stands demonstrating the development of physics in the 20th century. At four of them, the name of Landau was mentioned.

∗This article is partially based on the text of my presentation given at the scientiﬁc- memorial session devoted to the 100th anniversary of the birth of L. D. Landau (1908– 1968), held on 19–20 June 2008 at the Central House of Scientists, RAS, Moscow. The text of this article was created as a comment to the anniversary edition of the collected papers of L. D. Landau in 2008, but was not included in it for reasons independent of the author. Published in Phys.-Usp. 52(11), 1169–1176 (2009). – V.P.

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The goal of these notes is to follow the development of Landau’s ideas and their most important applications up to the present day. The breadth of Landau’s contributions makes this task practically impossible for a single person. Originally, this article was planned as a review written by several authors, but, unfortunately, this idea did not work out. That is why the part of this review published here is not complete. Certainly, many wonderful papers by Landau are not mentioned here, such as those on astrophysics, with predictions of neutron stars and a criterion of collapse, on elementary particles and field theory, on the theory of superfluidity, on the Fermi liquid theory, and many others. The material collected in these notes is related to three important and extremely popular articles by Landau: on phase transitions, on Landau levels, and on the Landau–Zener theory. Their further development and numerous applications clearly demonstrate that Landau’s papers are an important part of modern physics and are at the center of its interests. It is amazing how much one person was able to accomplish in slightly more than thirty years given to him by Providence for scientific work! The fact that for a short while I knew Landau personally had a strong impact on my life. These notes are my grateful tribute to his blessed memory.

2. Phase transitions 2.1. Spontaneous symmetry breaking, the mesoscopic description, universality In two articles [1, 2] published in the ominous year of 1937, Landau built a foundation for the general theory of phase transitions with a change in symmetry. This theory turned out to be most fruitful in terms of its inﬂuence on the subsequent development of physics. The number of publications devoted to its development and experimental evidences amounts to the tens of thousands. Landau’s theory of phase transitions is applied in crystallography, biology, high-energy physics and ﬁeld theory, astrophysics and cosmology, not to mention statistical physics and many branches of condensed matter physics. Four Nobel Prizes have been awarded for papers devoted to the de- April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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velopment of the ideas of this theory. Landau was the first to introduce a concept of spontaneous symmetry breaking, which has spread widely in statistical physics and field theory. Often those who deal with vacua with the spontaneous symmetry breaking think that this idea is a folklore, but this is incorrect: this concept has a clearly defined authorship. Landau introduced it many years before it started to be used in field theory and high-energy physics, noting that symmetry breaking is equivalent to the emergence of a long-range order in many-particle systems. Another important idea was first formulated in Landau’s theory of phase transitions: the idea of a mesoscopic description of ordering media. Landau realized that when a system approaches a continuous phase transition or critical point, the correlation length grows and microscopic details of the system are no longer important. Only the initial symmetry and how it changes as a result of the transition are important. All significant events occur on the scale between the inter- particle distance and the size of the whole system. The theory happens to be universal: phase transitions of a different nature, which have the same initial and final symmetries, are isomorphic. Landau suggested considering the amplitude of emerging (at the transition) irreducible representation of the initial symmetry group as a measure of symmetry breaking (an order parameter). Quantitatively, Landau’s theory was based on the self-consistent field approximation. Fluctuations were assumed to be negligibly small. Based on this approximation, Landau formulated group- theoretic rules allowing the classification of possible second-order phase transitions, under which the order parameter in the ordered phase continuously grows starting from zero, and the criterion for the transition to be always accompanied by jumps of some physical quantities (first-order phase transition). In the second of the cited papers, Landau showed that one-dimensional crystal order in two- dimensional and three-dimensional media is broken by fluctuations. A congenial statement was formulated by Peierls [3]: a long-range order in two-dimensional systems with spontaneously broken continuous symmetry is broken by fluctuations. April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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2.2. Classification of phase transitions; order parameters The development of Landau’s ideas took place in several directions. One of them was the concrete implementation of Landau’s general scheme for systems of the highest interest in physics. The first group- theoretic calculation of the phase transition between different crystal phases was performed by E. M. Lifshitz [4]. The literature on the reconstruction of crystals is widespread and partially connected with general crystallographic research. The conclusions of this work up to the middle of the 1990s were summarized in books by Izyumov and Syromyatnikov [5] and Tolédano and Dmitriev [6]. A review of phase transitions in crystals with initial colored (Shubnikov) group symmetry [7], which is physically interpreted as a magnetic crystallographic structure with discrete magnetic symmetry, is given in paper [8] based on Landau’s theory. Andreev and Marchenko [9] have built a full classification of magnetic crystallographic structures with an initial magnetic symmetry group of rotation SO(3), which is typical for exchange interactions. The phenomenon of weak ferromagnetism in crystals was predicted by Dzyaloshinsky [10] based on investigations of group invariants using Landau’s method, and was experimentally discovered by Borovik- Romanov [11]. A microscopic interpretation of weak ferromagnetism was given by Moriya [12]. Phase transitions in ferroelectrics were interpreted based on the Landau–Ginzburg–Devonshire theory [13], which had multiple experimental confirmations and technological applications [14]. In their famous study of 1950, Ginzburg and Landau gave a symmetry description of superconductivity near the transition point [15]. They introduced a complex wave function of superconducting condensate as the order parameter. This work had a deep influence not only on the theory of superconductivity but also on many other areas of physics and mathematics. An analogous theory for superfluids was constructed by Ginzburg and Pitaevsky [16]. Gross [17] and Pitaevsky [18] have proposed a nonlinear theory of a weakly nonideal superfluid Bose gas, which is applicable at low temperatures and perfectly describes modern experiments with laser-cooled gases April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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of alkali metal atoms. The Ginzburg–Landau theory and its application to the description of the vortex state in superconductors was the reason for awarding Abrikosov, Ginzburg, and Leggett the Nobel Prize in Physics 2003. Based on the principles of Landau’s theory, P-G. de Gennes built his theory of phase transitions from an isotropic liquid to a nematic liquid crystal, and from a nematic to a smectic liquid crystal (the so-called Landau–de Gennes theory) [19,20]. This theory represents a significant part of a cycle of works on ‘soft matter’, for which de Gennes was awarded the Nobel Prize in Physics 1991. The universal use of liquid crystals in displays, monitors, and televisions has converted Landau’s theory into an applied science. Many first-order phase transitions, in particular, all transitions of liquid crystals from the isotropic to nematic phase, are close to second-order transitions: the jumps in volume and the specific heats of transition are small. The theory of weak melting-crystallization based on Landau’s free energy was elaborated by Brazovskii [21]. Later on, it was used for the description of blue phases in liquid crystals.

2.3. Fluctuation theory In the middle of the 1940s, there was a crisis in the theory of phase transitions, related to the great achievement of L. Onsager – the exact solution of the two-dimensional Ising model [22]. This solution uncovered singularities of thermodynamic quantities, which were completely different from the predictions of Landau’s theory. Precise measurements of the specific heat of liquid helium near the transition to the superfluid state (Buckingham and Fairbank [23]) and of argon near its critical point (Voronel et al. [24]) have revealed a singular behavior which was not accounted for by the mean-field theory. This contradiction was explained by Levanyuk [25] and Ginzburg [26], who showed that the fluctuations in the order parameter and entropy, even if they are weak when far away from the transition point, become strong in its vicinity. The range of temperatures within which the fluctuations are weak and the self-consistent field approximation is valid does not exist by far in every system susceptible to a phase April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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transition [27]. In particular, it does not exist in the Ising model. However, there are reasons to believe that the behavior of systems in the region of strong fluctuations is universal in the above sense, and that it depends only on the initial symmetry and the method of its breaking. The hypothesis for universality in the fluctuation region was introduced by Vaks and Larkin [28] and was later proven by Kadanoff and Wegner [29]. Another hypothesis formulated in the mid-1960s (by Patashinskii and Pokrovsky [30, 31], Kadanoff [32], and, in a narrow sense, only for the equation of state, by Widom [33] and Domb and Hunter [34]) was the scale invariance of critical fluctuations. According to this hypothesis, when varying the linear scale the picture of fluctuations should not change if the units of measurement of the fluctuating fields were altered appropriately. Every fluctuating quantity, for example, an order parameter, entropy, temperature, etc. are characterized by their scaling dimensions (critical exponents). The hypothesis for scale invariance together with simple thermodynamic equations allowed finding a number of relations between the scaling dimensions, and therefore it reduced the number of independent dimensions, but did not solve the problem completely. In 1959, M. E. Fisher was one of the first who pointed out the significance of calculating the critical exponents, and introduced the index of anomalous dimension [35]. Powerful numerical methods of finding critical exponents using the first several series terms of the high-temperature perturbation theory allowed Domb et al. to find critical exponents of the three-dimensional Ising model with a precision of several percent [36]. However, a real theory did not yet exist. In the late 1950s, Landau formulated the problem of the fluctuating theory of phase transitions as one of evaluating a partition function of the system whose Hamiltonian coincides with the free energy of the self-consistent field of the order parameter, which he introduced in 1937. Exactly in this way, K. G. Wilson found in 1972 a constructive solution to the problem of a phase transition [37–39], for which he was awarded the Nobel Prize in Physics 1982. To calculate a partition function, Wilson developed a new version of the method of renormalization group which was first introduced in April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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quantum field theory by Gell-Mann and Low [40] and Stückelberg and Green [41]. An attempt to use the field-theory renormalization group in the theory of phase transitions was made by Di Castro and Jona-Lasinio [42], but it did not lead to quantitative results. In Wil- son’s method, the renormalization means a consecutive elimination of short-wave fluctuations, starting from the shortest waves and following to longer ones, and the calculation of the effective energy of the remaining long-wave fluctuations. This idea was put forward earlier by Kadanoff [32] but was accomplished only by Wilson. An- other important idea of Wilson and Fisher [38], which allowed finding critical exponents analytically, is the expansion in the powers of a small parameter ε equal to a deviation of space dimensionality from the critical value 4, at which the critical exponents have the same values as in Landau’s theory. The interaction between fluctuations leads only to logarithmic singularities which were found earlier in the work of Larkin and Khmelnitsky [43], although in the real world this parameter is not small (ε = 1) and to prove this procedure in a strictly mathematical sense is difficult. Nevertheless, the calculation of critical exponents [44] employing the method of series summation in ε with the use of the asymptotic behavior of the high-order terms (found by L. N. Lipatov [45]) leads to results close to the best numerical calculations and to the data of the most precise experiments.

2.4. Dynamics of critical fluctuations As the characteristic size of fluctuations grows, their motion gets slower. This is a so-called critical slowdown. The first quantitative theory of the critical slowdown was established by Landau and Kha- latnikov [46] in 1954. It was based on a phenomenological assumption that the critical dynamics is of a purely relaxational character: the time derivative of the order parameter is proportional to the self- consistent field – that is, the derivative of thermodynamic potential with respect to the order parameter. The kinetic coefficient Γ relating these quantities was assumed to be independent of the distance from a transition point. Hence, it followed that the relaxation time of the order parameter is proportional to the square of the correlation length. As in the static case, the fluctuations were considered to be April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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negligibly small in comparison with the average values. A new effect on anomalous absorption of sound because of the excitation of critical fluctuations at a frequency on the order of the inverse relaxation time was predicted. This phenomenon was examined experimentally [47]. The Landau–Khalatnikov theory has been generalized in various aspects. One of them is the transition to the region of large fluctuations. The simplest generalization was introduced by Pokrovsky and Khalatnikov [48], who assumed that the kinetic coefficient Γ remains a constant but the correlation radius and other physical quantities follow the laws of static scaling. A more detailed generalization was suggested by Ferrell et al. [49], and in a more general and physically transparent form by Halperin and Hohenberg [50] (so-called dynamical scaling). They have noticed that in systems with a continuous order parameter, the dynamics of the ordered state is determined by the conservation laws which follow from the remaining continuous symmetry, and therefore, in general, is nondissipative. The long-wave excitations are propagating waves. Their velocity is determined by thermodynamics, e.g., by the Laplace equation for the speed of sound. Thus, the frequency of the wave in the critical region is determined by static scaling. The dynamics have a purely relaxational character above the critical point at any wavelength λ and below the critical point at wavelengths shorter than the correlation radius ξ (e.g., fluctuational thermal conductivity near the transition to the superfluid state). The hydrodynamic and relaxation frequencies coincide to an order of magnitude at λ ∼ ξ. This relationship allows finding dynamic critical exponent z which determines the scaling dimension of frequency o.Forλ ξ,wehaveω ∼ λ−z and we can find the critical behavior of kinetic coefficients. This theory has found excellent agreement with experimentsa [51]. The renormalization-group theory of dynamic critical phenomena has been developed in papers by Halperin, Hohenberg, Ma, and Siggia (see review [52]).

aA detailed description of experiments on dynamic scaling and their comparison to the theory was done in review [52]. May 10, 2013 12:16 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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3. Landau levels 3.1. Landau levels and the diamagnetism of metals This is the commonly used name for the energy levels of a charged particle in a constant uniform magnetic field. The solution to this very important question, which was as important in quantum mechanics as the question of the spectrum of the hydrogen atom and the quantum harmonic oscillator, was found by Landau [53] in 1930. Landau found that particle’s motion in the plane perpendicular to the magnetic field is quantized.b The energy levels are strongly degenerate in the quantum number corresponding to the center of the Larmor circle in classical mechanics. The number of states per unit area, belonging to a given Landau level, is equal to the ratio B/Φ0 of a magnetic field induction to the magnetic flux quantum Φ0 = h/2e. In other words, each state carries one magnetic flux quantum. The energy of transverse motion of an electron on the nth Landau level equals

ε n 1 ω, n = + 2

where ω = eB/mc is the cyclotron frequency. The solution of this relatively simple problem led Landau to the important conclusion that the quantization of the transverse motion is the reason for the diamagnetism of electrons in metals, which could not be explained from the classical point of view, as was shown by Bohr [57] and van Leeuwen [58]. This was a remarkable ﬁnding.

bIt should be noted that Landau had predecessors: in 1928, I. I. Rabi solved the problem of Dirac’s electron in an external magnetic field [54], and in the same year V. A. Fock solved the harmonic oscillator problem in magnetic field [55]. In 1930, independently of Landau, the solution of the Schródinger equation for a nonrelativistic charged particle in a magnetic field was found by Frenkel’ and Bronshtein [56]. However, in none of these papers, the number of states on a magnetic level was found, and no linkage between quantization and diamagnetism and oscillations was established. This seemingly was the reason why the levels got Landau’s name. – V.P. May 10, 2013 12:16 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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3.2. Magnetic oscillations: Shubnikov–de Haas and de Haas–van Alphen effects At the end of his article [53] Landau noted that the quantization of energy levels leads to oscillations of diamagnetic susceptibility in a changing field. However, he believed that examining these oscillations experimentally would be hard because of the nonuniformity of the magnetic field. Most probably he did not know about the Shubnikov–de Haas [59] experiment, which was also performed in 1930. In 1937, Landau learned from D. Shoenberg about the de Haas–van Alphen effect [60]: oscillations of magnetic susceptibility vs. magnetic field. Landau immediately made a preliminary calculation of the oscillations and handed it to Shoenberg, but was not able to publish it because of his arrest. In 1939, Shoenberg published this calculation [61], obviously under Landau’sc name, as complementary material to his experimental work [63]. Landau made the calculation in an extremely simplified model of free electron gas. A more realistic approach, which accounted for the band structure of the energy spectrum and the anisotropy of metals, was introduced independently by I. M. Lifshitz [64] and Onsager [65]. They showed that quasiclassical orbits of electrons in momentum space are the cross-sections of the isoenergetic surface by planes perpendicular to the magnetic field. The orbits of electrons in the configuration space differ from orbits in momentum space by a rotation and scale factor, which is chosen in such a way that a magnetic flux through the orbit is equal to an integer number of magnetic flux quanta. Using this, Lifshitz and Ko- sevich [66] elaborated the theory of the de Haas–van Alphen effect for an arbitrary dispersion of electrons. Lifshitz and Pogorelov [67] found a solution to the inverse problem on reconstruction of a Fermi surface using experimental data on the de Haas–van Alphen effect. Numerous measurements of this effect, as well as of the Shubnikov–de Haas effect, allowed creating an atlas of Fermi surfaces [68].

cA friend and coauthor of Landau, Rudolf Peierls, participated in writing this Appendix (see Shoenberg’s book [61] and the historical review by M. I. Kaganov [62]). – V.P. April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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3.3. Quantum Hall effect With the creation of two-dimensional electron systems, inversion layers in silicon, and GaAs–AlGaAs heterojunctions, objects appeared for which the theory of magnetic Landau levels became fully applicable. In 1980, a completely unexpected effect was discovered in these systems, which is known as the quantum Hall effect (QHE) [69]. It turned out that at a relatively low temperature and a high mobility of carriers the Hall conductivity σH , i.e., the ratio of the current flowing in the direction perpendicular to the electric and magnetic fields to the magnitude of the magnetic field is quantized. In addition, the Hall conductivity quantum is equal to e2/h with a very high precision of ∼ 10−7. More precisely, this means that when a magnetic field B varies then σH , which is on average proportional to 1/B, becomes a step function of 1/B with the values of νe2/h on its steps (ν is an integer number). Klaus von Klitzing was awarded the 1985 Nobel Prize in Physics for the discovery of the integer Hall effect. The reason for the stepwise dependence of σH on 1/B is the localization of all states of a given Landau level by impurities, with the exception of a single edge state which corresponds to the drift of an electron along the boundary of the sample in the direction given by the magnetic field and the force holding the electron inside the sample. When all remaining states on the Landau level are occupied, the scattering on impurities for the edge state is not effective, since it is impossible to change the direction of rotation, and unoc- cupied states on the next Landau level are separated by an energy gap. The drift of the edge state gives the same effect as the motion of all Larmor circles (electrons) of the filled Landau level. Indeed, 2 integer values of σH in units of e /h correspond to the drift of all electrons with the flux density νB/Φ0 per unit area with the typical drift velocity cE/B. In 1983, Tsui, Störmer and Gossard [70] discovered the fractional quantum Hall effect: the Hall conductivity is quantized in fractions with an odd denominator, for example, 1/3, 2/3, 4/3, 2/5, 3/5 in the same units. This constitutes a more complicated phenomenon based on the interaction between Landau electrons. Laughlin [71] has explained this phenomenon using as an example the filling factor 1/3, April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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when there are 3 magnetic flux quanta per electron. In this case, electrons can more successfully avoid each other at small distances than at fractional concentrations with large denominators, and thus the Coulomb repulsion energy is reduced. This is the reason for theappearanceofagapinthespectrum,buttherestissimilarto the integer QHE. The excitations in this strongly interacting incompressible electron liquid carry as before only one flux quantum, and therefore they have a fractional charge of 1/3. For the discovery and explanation of the fractional quantum Hall effect Tsui, Störmer, and Laughlin were awarded the Nobel Prize in Physics 1998. Recently, K. S. Novoselov and A. K. Geim with colleagues have learned how to produce isolated crystalline sheets of graphite called graphene [72]. This material has opened new horizons in the study and use of Landau levels. Graphene is an ideal semimetal whose Fermi level resides at the boundary between two bands touching each other. Near the intersection point, the electron dispersion possesses an ultrarelativistic form: ε = vp with the velocity v ∼ 108 cm s−1, which plays the role of the speed of light. The Landau energy levels of the ultrarelativistic electrons are equal to √ εn = v 2nmω.

For small n, these levels are on the order of the geometric mean of the atomic and cyclotron frequencies. For fields of several Tesla, this energy falls in the range of several hundred kelvins. This means that the QHE and oscillatory effects can be observed at room temperature, whereas in usual metals these effects are observed only at helium temperatures. Indeed, the QHE at room temperature has been examined experimentally [73].

4. Landau–Zener transitions 4.1. History and formulation of the results In 1932, Landau formulated and solved one of the most important dynamic problems of quantum mechanics [74]. Independently from him in the same year, although a bit later, this problem was also solved by three outstanding theorists: C. Zener [75], E. G. G. St¨uckelberg [76], April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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and E. Majorana [77]. In the literature it is known as the Landau– Zener problem. Below we formulate the problem and its solution in modern terms and definitions. The problem is as follows. The Hamiltonian of a system H depends on the number of parameters R. The discrete energy levels En(R) and vectors of the state (wave functions) |Ψn(R) corresponding to them continuously depend on these parameters. If the parameters R vary with time t, the energy is not conserved and also depends on time. However, if the parameters vary slowly, the vector of state is equal to |Ψn(R(t)) in the leading approximation, i.e., the system follows the continuous change of parameters with time without making a transition to other states. This is the so-called adiabatic approximation. It is not valid if some of the levels cross. Near the crossing point of the levels there are intensive transitions between the corresponding states. In the Landau–Zener theory it is assumed that only two levels cross, and all other levels are far away. In this approximation, the problem reduces to finding 1 the states of a two-level system, i.e., to the problem of spin-2 motion in a time-dependent magnetic field. Using the fact that the time interval for the transitions is narrow, one can assume the time dependence of the distance between the approaching levels to be linear. Therefore, one can represent the transition frequency Ω as a linear function of time: Ω(t)=Ω˙ t. The matrix element Δ of the transition between the two initial (so-called diabatic) states is considered to be independent of time. In this approximation, the spin Hamiltonian takes the simple form

H = Ω˙ tσz +Δσx ,

where σx and σz are the Pauli matrices. The time-dependent Schr¨odinger equation is reduced to an exactly solvable equation for a parabolic cylinder. This is exactly how Zener solved this problem. Instead of this, Landau went around the crossing point in the complex time plane, which allowed him to avoid using the functions of the parabolic cylinder. The transition matrix calculated by Landau and Zener has the diagonal matrix element (amplitude of survival)

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and the oﬀ-diagonal element √ √ β − π − πγ iπ γ −iγ −1 = 2 exp 2 + 4 [ Γ( )] (calculated by Zener), where γ =Δ2/(2|Ω˙ |) is the dimensionless Landau–Zener parameter. The large values of γ correspond to the adiabatic regime when the system resides on one of the two adiabatic levels which are separated by the energy gap Δ, and performs the transition from one diabatic level to the other. The small values of γ correspond to the fast (anti-adiabatic) regime and to small transition probabilities. The Landau–Zener formula gives values of transition amplitudes beyond the limits of applicability of perturbation theory. The transition takes time tLZ =Δ/(|Ω˙ |) (the Landau–Zener time).

4.2. Applications The generality of the formulation has allowed applying the Landau– Zener theory to a wide variety of phenomena. Landau had in mind the description of a certain class of molecular reactions called predis- sociation. Later on, the Landau–Zener theory was applied widely in chemistry, chemical physics, and biochemistry. In particular, it is applied for the description of such an important process as the transfer of charge along with its energy [78]. Landau–Zener transitions play a significant role in photosynthesis [79]. The Landau–Zener theory has also found multiple and important applications in physics. At the earlier stage it was applied to the theory of atomic and molecular collisions accompanied by transitions between electron levels, in particular, charge-exchange collisions. The theory of these processes and their role in plasma physics was introduced by B. M. Smirnov, E. E. Nikitin, and others and described in detail in books by Smirnov [80], where one can also find experimental data. An alternative approach to this problem was described in the review by Solovyev [81]. A. P. Kazantsev and colleagues showed [82,83] that the Landau– Zener transitions of atoms in a standing light field lead to the appearance of a band structure in a spectrum of atoms which interact resonantly with this field. If a slow field amplitude depends periodically on time, the atomic states are described by Floquet–Bloch April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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wave functions and quasienergy [84]. Similar phenomena also occur in highly excited (Rydberg) atoms under the influence of a strong microwave field [85]. It is interesting to note that the number of citations of Landau’s above-mentioned paper has increased significantly in the last few years. This is related to the appearance of new experimental objects whose dynamics is determined by the Landau–Zener processes. Here, one should first mention qubits, which are the elementary units of a quantum computer. They operate with quantum states instead of binary numbers. Qubits have already been created experimentally. One type of qubit consists of two small superconductors connected via a Josephson junction [86]. Here, the role of diabatic states is played by the states of a Cooper pair in one of the two superconductors. Another realization of the qubit [87] is a so-called quantum dot, a tiny (several nanometers in size) piece of a semiconductor from which, with the use of a gate, almost all but a few electrons are pushed out. The diabatic states in this system are the spin states of an electron in an external magnetic field. In these and other qubits, the controlled superpositions of two quantum states are obtained by means of the Landau–Zener process. In the last 10–15 years, molecular magnets have been studied intensively. This is a family of molecules containing 100–200 atoms in which a ferromagnetic core (atoms of iron, cobalt, or manganese) is held together by organic bridges. The most popular are the molecules abbreviated as Mn12 and Fe8 . The former was investigated by an experimental group at the City College of New York under the guidance of M. Sarachik, while the latter was studied by the collaboration of French experimentalists from Grenoble and Italian experimentalists from Florence (B. Barbara, W. Wernsdorfer, D. Gatteshi, R. Ses- soli). Theoretical papers by E. Chudnovsky, A. Garg, N. Prokofiev, and J. Villain played an important role. The results of this research are presented in the book [88]. Both Mn12 and Fe8 molecules have spin S = 10 and really represent nanometer-sized magnets. Experi- mentalists deal with molecular single crystals but the ferromagnetic cores of their molecules are so far away from each other that their interaction is negligibly small. Therefore, the magnetic properties of April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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these systems are those of a single molecule. When measuring magne- tization as a function of the magnetic field, the hysteresis curves were obtained in both substances, which testified to a new phenomenon called molecular hysteresis. At a temperature below 0.5 K, the hysteresis curves stop changing, which proves the quantum character of the hysteresis. In the hysteresis curves one can see steps at particular values of the magnetic field. These steps were attributed to Landau– Zener transitions appearing at the crossing of terms with large spins, which are initially split by the anisotropy of the molecular field and are controlled by a time-dependent magnetic field. Thus, Landau– Zener transitions are the real reason for the quantum hysteresis. Several years ago, experimentalists working with alkali metal atoms cooled by a laser light to temperatures on the order of 10−8– 10−7 K learned how to obtain diatomic molecules at the so-called Feshbach resonance [89]. The atoms were placed in an external magnetic field, and by changing it they passed that magnitude at which the Zeeman energy of a pair of atoms becomes equal to the binding energy of a molecule. This is accompanied by the Landau–Zener process, and the atoms turn into molecules. In many theoretical papers, authors have attempted to apply directly the Landau–Zener theory to this problem [90]. However, the experiments were performed with degenerate Bose or Fermi gases. The identification of pairs of atoms in this gas is impossible because identical particles are quantum- mechanically indistinguishable. This problem should be solved by the methods of many-particle theory (see the next section).

4.3. Development of the theory A. M. Dykhne has proposed a modiﬁcation of the theory for the case where the crossing of the diabatic electron terms takes place not on the real axis but somewhere else in the complex plane of time [91]. This result was discussed with Landau and was approved by him. It is known in the literature as the Dykhne–Landau formula.d

dI participated in a discussion where Landau found a mistake in Dykhne’s initial solution. The same day Dykhne and Landau independently found the correct method. Landau refused to be a coauthor of the study. Later on, Landau’s approach was published in a May 10, 2013 12:16 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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At the crossing of electron terms of a molecule one has to deal not with a single level but with the bands consisting of vibrational and rotational sublevels. The problem of the crossing of a band of parallel levels with a single level was solved by Demkov and Osherov [92]. Some particular cases of crossings of many levels have been found by Demkov and Ostrovsky [93]. The transition probabilities in all these solutions are given by a product of the probabilities of the consecutive Landau–Zener transitions. Carroll and Hioe [94] have found a solution to the problem of the motion of an arbitrary spin in a magnetic field, when one of its components (z) depends linearly on time, and another one (x) is a constant. In this case, 2S+1 diabatic levels cross simultaneously. The exact solution is possible due to SO(3) symmetry and is given by the matrix of the Landau–Zener transition in terms of Jacobi polynomials. The most general construction, which allows finding a solution to a wide class of problems with the crossing of many diabatic levels, was introduced by N. A. Sinitsyn [95]. All exact solutions found earlier have entered into this class as particular cases. As for the general case of the crossing of many diabatic levels in different but sufficiently close points at different angles, only the amplitude of survival at the level with maximal or minimal slope is known. It is equal to the product of the Landau–Zener amplitudes of survival for the points of consecutive crossing with other levels. This result was initially formulated as a hypothesis by Brundobler and Elser [96], and later was proven analytically by Shytov [97], who generalized Landau’s method, and algebraically by Volkov and Os- trovsky [98] and Dobrescu and Sinitsyn [99]. The application of the Landau–Zener theory to qubits and molecular magnets has raised the question of the role of noise. Noise is responsible for the decoherence and errors in quantum calculations. The thermal noise in molecular magnets leads to a significant nar- rowing of the molecular hysteresis loop even at temperatures ∼ 1K.

new edition of Quantum Mechanics: Non-Relativistic Theory (Moscow: Nauka, 1963) which was proofread by Landau himself but was released after the ill-fated car accident, without citing Dykhne. According to Pitaevsky’s recollection, Landau told him that there was a mistake in Dykhne’s formula. However, by checking this formula one can show that the results of both authors coincide apart from notations. – V.P. April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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The longitudinal noise distorts adiabatic levels but does not lead to transitions, while the transverse noise causes spontaneous transitions. Purely longitudinal noise has been studied in a number of papers. The most detailed analysis was given by Ao and Rammer [100], who considered a number of limiting cases (in this article one can find a rather extensive bibliography). Unfortunately, we cannot describe the results obtained in Ref. [100] using simple physical patterns. The situation is reversed in the case of transverse noise. The pioneering work on fast transverse noise was introduced by Kayanuma [101], but this paper is not transparent in terms of physics, and a spectral composition of noise in it is taken rather artificially. A significant simplification was reached in the paper by Pokrovsky and Sinitsyn [102]. They showed that noise-induced transitions accumu- late during a time which is much longer than the Landau–Zener time. Noise transitions and Landau–Zener transitions turn out to be separated in time, which allows solving this problem exactly. The noise transitions, at a given instant of time, are caused by the spectral component of the noise which is at resonance with the current frequency of the two-level system. This allows using this frequency as the noise analyzer. A strong classical transverse noise leads to the equal occupation of two levels for any value of γ. This conclusion becomes invalid in the case of fast quantum noise, which was analyzed in paper [103]. Strong quantum noise brings a two-level system into equilibrium with noise or to a steady state if the noise is not thermal. The interaction of transverse and longitudinal noise leads to a change in the transition matrix element Δ. If the noise is due to phonons, this renormalization results in the isotopic effect. The Landau–Zener transitions in degenerate atomic Fermi gas with the creation of diatomic molecules have been described in papers [104–106]. In the first of them, a perturbation theory for the calculation of the number of created molecules has been developed up to the second order in the parameter δ = g2n/(2|Ω˙ |)(g denotes the atom-molecule coupling constant, and n is the gas density). It was shown that Fermi repulsion reduces the probability of molecule production in comparison with the same process in a gas of independent atomic pairs. The consideration in paper [105] is given beyond April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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the perturbation theory at the expense of a significant simplification of the model. A more general analysis [106] confirms the reduction of molecule production due to Fermi repulsion beyond the perturbation theory.

Acknowledgments The author is thankful to M. I. Kaganov and L. P. Pitaevsky for their fruitful discussions and useful comments. This work was supported by the US Department of Energy (DOE) under Grant DE-FG02- 06ER46278.

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71. Laughlin R B “Anomalous quantum Hall effect: an incompressible quantum fluid with fractionally charged excitations” Phys. Rev. Lett. 50 1395 (1983) . 72. Novoselov K. S. et al. “Electric field effect in atomically thin carbon films” Science 306 666 (2004); Geim A. K., Novoselov K. S. “The rise of graphene” Nature Mater. 6 183 (2007); Morozov S. V., Novoselov K. S., Geim A. K. Usp. Fiz. Nauk 178 776 (2008); [Phys. Usp. 51 744 (2008)] . 73. Novoselov K. S. et al. “Two-dimensional gas of massless Dirac fermions in graphene” Nature 438 197 (2005) . 74. Landau L. Phys.Z.Sowjetunion2 46 (1932) . 75. Zener C. Proc. R. Soc. London A 137 696 (1932) . 76. Stückelberg E. C. G. Helv. Phys. Acta 5 369 (1932) . 77. Majorana E. Nuovo Cimento 9 43 (1932) . 78. Nakamura H. “Nonadiabatic transitions and chemical dynamics,” Current Developments in Atomic, Molecular, and Chemical Physics with Applica- tions (Ed. M Mohan) (New York: Kluwer Acad./Plenum Publ., 2002) p. 71; Kuznetsov A. M. Charge Transfer in Physics, Chemistry, and Biology (Lux- embourg: Gordon and Breach, 1995); May V., Kühn O. Charge and Energy Transfer Dynamics in Molecular Sys- tems 2nd ed. (Weinheim: Wiley-VCH, 2004) . 79. Warshel A. “Role of the chlorophyll dimer in bacterial photosynthesis” Proc. Natl. Acad. Sci. USA 77 3105 (1980) . 80. Smirnov B. M. Atomnye Stolknoveniya i Elementarnye Protsessy v Plazme (Atomic Collisions and Elementary Processes in Plasmas) (Moscow: Atom- izdat, 1968); Physics of Atoms and Ions (New York: Springer, 2003) . 81. Solov’ev E. A. Usp. Fiz. Nauk 157 437 (1989) [Sov. Phys. Usp. 32 228 (1989)] . 82. Grinchuk V. A. et al. J. Opt. Soc. Am. B 2 1805 (1985); Kazantsev A. P., Surdutovich G. I., Yakovlev V. P. Mechanical Action of Light on Atoms (Singapore: World Scientific, 1990) . 83. Metcalf H. J., van der Straten P. Laser Cooling and Trapping (New York: Springer, 1999) . 84. Corwin K. L. “A circularly-polarized optical dipole trap and other developments in laser trapping of atoms,” Ph.D. Thesis (Boulder, CO: Univ. of Colorado, 1999) 85. Breuer H. P., Dietz K., Holthaus M. “Highly excited hydrogen atoms in strong microwave fields” Z. Phys. D 18 239 (1991) . 86. Pashkin Yu. A. et al. Nature 421 823 (2003) . 87. Shaji N. et al. “Few Electron Quantum Dots in Si/SiGe,” APS March Meeting, March 5–9, 2007, Abstract S33.007 (2007) 88. Gatteschi D., Sessoli R., Villain J. Molecular Nanomagnets (Oxford: Oxford Univ. Press, 2006) . 89. Jochim S. et al. Science 302 2101 (2003); Zwierlein M. W. et al. Phys. Rev. Lett. 91 250401 (2003); Bourdel T. et al. Phys. Rev. Lett. 93 050401 (2004); Donley E. A. et al. Nature 417 529 (2002); Strecker K. E. et al. Nature 417 150 (2002) . April 5, 2013 16:20 WSPC/Trim Size: 9in x 6in for Proceedings 12c˙Pokrovsky-Landau˙Mod˙Phys

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STRONG INTERACTIONS AT HIGH ENERGIES IN THE REGGEON APPROACH∗

K. G. BORESKOV, A. B. KAIDALOV, and O. V. KANCHELI Institute of Theoretical and Experimental Physics B. Cheremushkinskaya ul. 25, Moscow, 117218, Russia [email protected]

To the memory of Karen Ave- tovich Ter-Martirosyan, who did so much for the development of strong interaction physics at the Insti- tute of Theoretical and Experimental Physics

Introduction In this review we present the most important results obtained since the late 1950s in the theory of strong interactions at high energies. Many of them were contributed by theorists of the Institute of The- oretical and Experimental Physics (ITEP) in Moscow.a Up to now the method of complex angular momenta (the Regge theory) has been the basic theoretical approach in such topics. For a long time, problems in the theory of complex angular momenta have been the focus of attention for ITEP theorists and experimentalists and they were intensely discussed at ITEP seminars and schools in physics (see [1–7]). This line of work was developed at ITEP against the background of investigations of these problems all over the world.

∗Published in Russian in Yadernaya Fizika, 69, 1802, (2006). Translated from Russian by J. Nyiri and A. Isaakyan. aLet us be reminded that the term “hadron” for strongly interacting particles was suggested by L. B. Okun at ITEP.

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It should be emphasized here that not only were Soviet physicists at the front line of these investigations, but they also played a key role in obtaining many fundamental results. V. N. Gribov, who worked in close contact with I. Ya. Pomeranchuk, K. A. Ter-Martirosyan, and other ITEP theorists, was considered to be, without doubt, the leader in this field. In our review, a special attention is given to studies performed at ITEP. As to investigations carried out at other places, we mention predominantly those which contained key results and determined the direction of the further development of the theory. Of course, we do not claim to give an exhaustive review on the subject and are fully aware that our choice inevitably reflects our personal tastes and feelings. In Section 1, we discuss the fundamental results which were obtained in the late fifties and the early sixties; these are the Pomer- anchuk theorem and the basis of the theory of complex angular momenta. In Sections 2 and 3, we give a brief survey of works aimed at verifying this theory by describing two-particle processes and multiparticle production processes. It is noteworthy that not only an analysis of fundamental qualitative consequences of the theory was carried out at ITEP, but also the problem of a self-consistent quantitative description of all the experimental data available at that time was solved. A set of parameters that describe contributions of Regge poles and branch-points to elastic scattering and charge exchange processes in pion, kaon, and nucleon beams, including the case of backward scattering, was obtained. A quantitative model of the pion cloud of the nucleon was constructed at ITEP. This model made it possible to systematize and describe quantitatively a lot of information about exclusive and inclusive processes in a broad energy region. In Section 4, we describe problems that arise in attempting to relate the Reggeon approach to QCD. Since the Reggeon approach is intended predominantly for describing soft processes, the concepts used in this approach are associated with dynamics of long distances, where perturbative QCD is inapplicable. Nevertheless, the idea of quarks and gluons proved to be essential also in this region. The April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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model of quark-gluon strings, which was developed at ITEP, made it possible to employ information about the contributions of various cuts of Reggeon amplitudes and about the structure of Regge asymptotic behavior in various kinematical regions to describe quantitatively multiparticle processes up to the highest accessible energies. The developed models were widely used in planning new experiments and in estimating experimental backgrounds. As to the model of quark-gluon strings, it became one of the basic models for the numerical simulation of accelerator experiments and processes in cosmic ray physics. In Section 5, we present brieﬂy the results obtained in the framework of the Reggeon ﬁeld theory, taking into account the Pomeron– Pomeron interactions. This problem became especially relevant in connection with experiments in the region of ultrahigh-energy hadron physics and of interactions of relativistic heavy nuclei.

1. The Basis of the Theory After the discouraging results concerning zero charge in quantum ﬁeld theory, in the late ﬁfties hopes for constructing a self-consistent particle theory became connected with the use of general principles, such as relativistic covariance, probability conservation (unitarity), and microcausality (analyticity). The approach based on the Heisen- berg concept of the S matrix (scattering matrix) possessing the required properties of unitarity and analyticity seemed promising. By assumption, the observed particles were associated with the poles of the S matrix on the physical sheet. As to other singularities, there was a hope to obtain them from the unitarity requirement (see, for example, [8]). The method of dispersion relations and the Mandel- stam representation (double dispersion relations) served as a tool for employing the analyticity properties in physics. This method proved to be rather useful at high energies.

1.1. The Pomeranchuk theorem Pomeranchuk’s famous theorem [9] was one of the ﬁrst fundamental results obtained at ITEP for strong interactions at high energies. At May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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low energies, the total cross-sections for the interaction of particles and antiparticles with any target are usually very diﬀerent, and it seemed that there were no reasons to assume that this would not be so at ultrahigh energies. Nevertheless, Pomeranchuk showed in 1958 on the basis of rather general principles of ﬁeld theory that the total cross-sections for the interaction of a particle and an antiparticle with a target must coincide: σab(s)=σab¯ (s)ats →∞. Later, this nontrivial result served as a basis for introducing a special particle-like object, the Pomeron,b that has the quantum numbers of the vacuum, which therefore does not discriminate between particles and antiparticles, and which is responsible for the asymptotic equality of the cross-sections. The result of Pomeranchuk was based on the dispersion relations for the crossing-antisymmetric amplitude of forward scattering under the following additional assumptions. Assumption i: The amplitudes do not oscillate for s →∞; Assumption ii:

1 | Re T (s,0)| → 0fors →∞. ln s Im T (s,0)

The role of these assumptions was later discussed and refined in a number of studies [11]. In the Reggeon theory, Pomeranchuk’s theorem is satisfied automatically if the leading singularity (Pomeron) has vacuum quantum numbers. In this case, the differences of the cross-sections for particle and antiparticle interactions, Δσa, are related to the contribution of secondary Regge singularities and decrease according to a power law

bFor the first time, the leading Regge singularity was associated with the name of Pomer- anchuk in [10]. Throughout the years that followed, the Pomeron has been the main ingredient of an asymptotic description of hadron processes at high energies, both elastic and inelastic ones. Also, it naturally arises in perturbative QCD, first in the form of a two-gluon exchange and then in the leading-logarithm approximation in the form of ladder gluon diagrams (see Section 4). Work aimed at developing its dynamical nonperturbative realization in QCD (from first principles) has been continued up to now and is still far from completion. – K.B. May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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(see below). The existing data on Δσa do not indicate the violation of the Pomeranchuk theorem.c

1.2. Regge poles In the early 1960s it was understood that the behavior of scattering amplitudes at high energies is determined by the singularities of partial-wave amplitudes for the crossed channel in the complex plane of angular momentum j [12–14]. This approach, which is based on the rather general requirements of analyticity and unitarity, proved to be highly constructive and fruitful. It immediately attracted the attention of ITEP theorists, but only a few of them could follow the speed of Gribov and Pomeranchuk. Within a short period of time, they performed a series of fundamental works that resulted in establishing a number of important properties of the theory. Poles are the simplest singularities in the complex j plane (Regge polesd). The exchange of a Regge pole is a generalization of the exchange of an ordinary spin-J particle to complex values of the spin. The analysis of the t-channel unitarity condition in [17, 18] revealed that Regge poles can be assigned by speciﬁc values of quantum numbers such as signature, parity, baryon charge, and isospin, the residues at these poles satisfying factorization relations for various channels. This served as a basis for representing a Reggeon as a virtual particle-like object of non-integer orbital angular momentum. This object is characterized by interaction vertices and a propagator that depends only on the properties of the Reggeon itself. As a result, the two-particle amplitude for the process a+b → c+d

cIn perturbative QCD, a singularity that has a negative signature, which is C-odd, and whose intercept is close to unity (odderon) arises in the complex plane of angular momentum j. This singularity could lead to the violation of Pomeranchuk’s theorem. Experimental searches for the odderon are of great importance for obtaining deeper insight into the nature of singularities in the j plane in QCD. dThe method of complex angular momenta was ﬁrst proposed by T. Regge for potential scattering in nonrelativistic quantum mechanics [15]. In relativistic ﬁeld theory, the possibility of an analytic continuation of scattering amplitudes to complex values of energy and angular momentum was proven on the basis of the Mandelstam representation [12, 16]. – K.B. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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Figure 1. Diagram of one-Reggeon exchange.

can be represented as the sum of Regge pole contributions (Fig. 1), i s αi(t) i Tab→cd(s,t)= gac(t) η αi(t) gbd(t) , (1) s0 i

2 where αi(t) is the Regge pole trajectory, which, at t = MJ ,isequal to the spin J of the corresponding particle. The function 1+σ exp (−iπα(t)) η αi(t) = − , sin (πα(t))) which is referred to as a signature factor, arises because of the need for considering, in relativistic ﬁeld theory, an analytic continuation of partial-wave amplitudes to complex values of j foreven(apositive signature, σ = +1) and odd (a negative signature, σ = −1) values of J individually. Regge pole trajectories. The Regge pole amplitude (1) involves asetofpolesint at α(t)=J (for even or odd J, depending on the signature) that are characterized by deﬁnite quantum numbers. Each such pole individually corresponds to the t-channel exchange of a spin-J particle (resonance), the respective contribution being s J proportional to ( /s0) and, hence, violating the Froissart bound [19] for J 2 . However, the contribution of the Reggeon pole is pro- s portional to ( /s0) α(t) and, in the case where the intercept α(0) is smaller than unity or equal to it, the contradiction with the Froissart bound is removed. The method of complex angular momenta establishes an important relation between high energy scattering and the hadron spectrum in the crossed channel. Data on two-particle reactions at large s April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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give us information about Regge pole trajectories for t 0 , while experimental data on the hadron spectrum carry information about Regge pole trajectories in the region of positive t. For all trajectories associated with experimentally established mesons, αi(t) 0.5 for t 0 . Their contributions to cross-sections for various processes, including the contribution to the total cross-section, decrease with increasing energy. Therefore, the corresponding Reggeons are considered as secondary ones. The astounding linearity of secondary −2 trajectories in t with a universal slope of αi ≈ 1GeV is one of their remarkable properties. Usually, this property is interpreted as a manifestation of confinement and as an indication of the string nature of quark–antiquark interaction at large distances. This led to developing dual-resonance and string models of hadron interactions. A number of other properties of meson trajectories, such as exchange degeneracy and isospin degeneracy, are also in agreement with dual-resonance models. An analysis of backward baryon scattering within the Reggeon approach led to the emergence of fermion trajectories [20]. Ex- perimental data on the baryon spectra also reveal linearity of relevant trajectories in t, the slope taking the same universal value −2 of αi ≈ 1GeV , which is natural if a baryon is represented as a string having a quark and a diquark at its√ ends. Fermion trajectories must be analytic functions of W = t . Using the analyticity properties of partial-wave amplitudes, one can show that there must exist pairs of opposite-parity fermion trajectories that satisfy the re- 2 lation α+(W )=α−(−W ). The linearity of trajectories in t = W then means their degeneracy in parity. Many opposite-parity baryon states of the same spin that have very close masses are observed experimentally, but the nucleon and the delta isobar, which are the lowest states on these trajectories, do not have partners in parity. The degeneracy between meson and baryon trajectories (phenomenological “supersymmetry”), which was revealed in [21], is an intriguing fact that has not yet been understood completely. Possi- bly, this is one of the specific manifestations of chiral dynamics. The secondary poles determine only the asymptotic behavior of the differences between the total cross-sections of interactions. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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As it has already been indicated, the main contribution to total cross-sections comes from the exchange of the Pomeranchuk pole (Pomeron). It is also referred to as a “vacuum” pole, since it has vacuum quantum numbers: positive signature, parity, and G (or C) parity and zero isospin. In the framework of QCD it is usually assumed that the Pomeron is associated with t-channel gluon exchanges (see Section 4). Hence, states lying on the vacuum trajectory at positive t are associated with glueballs (bound states of gluons). The magnitude of the Pomeron intercept plays an important role in the Regge theory. Originally, it was assumed that all total cross- sections of the interactions go to a constant limit, i.e. αP(0) = 1. The first experimental data on the behavior of total cross-sections (a weak decrease at energies below 30 GeV) were indicative of an effective αP(0) value slightly below unity. Data from the Serpukhov accelerator revealed a reduction of the rate of decrease and then its slow growth (“Serpukhov effect”). As a result, the effective value of Δ = αP(0) − 1 changed sign (Δeff ∼ 0.07 – “James Bond effect”). The presently observed growth of total cross-sections is consistent 2 s with the ln ( /s0) behavior (Froissart regime [19]). Because of this, now the model which is generally considered is that of a supercritical Pomeron for which αP(0) > 1. In order to obtain in this model a behavior which is not contradictory, it is necessary to take into account, in addition to Regge poles and moving branch-points (see Section 1.3) also Pomeron–Pomeron interactions (see Section 5). Inelastic processes in multi-Regge kinematics. In the beginning, the Reggeon approach was applied only to two-particle processes. To some extent, this was because the Regge theory originated from the investigations of analytic properties of the amplitudes. For two-particle amplitudes these properties are relatively simple and understandable. At the same time, the properties of multi-particle diagrams are rather complicated. Because of this, the Regge description of the latter, which was first proposed by Ter-Martirosyan [22], was a highly nontrivial step at that time. For the simplest inelastic process a + b → c + d + e, the asymptotic behavior is determined by the amplitude where, now, two Reggeons (Fig. 2) enter the vertex ik γd (t1 ,t2) . This result can easily be generalized to multi-Reggeon April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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Figure 2. Diagram of two-Reggeon exchange.

processes a + b → n particles. Investigating multi-Reggeon processes lead for the first time to the appearance of the concept of Reggeon diagrams including propagators and vertices of several Reggeons. In the case of multi-Pomeron processes, the configuration of inelastic processes corresponds to large pair masses of the particles, i.e. to large gaps in the rapidity space. Since the energy dependence of multi-Pomeron processes involves additional logarithms of energy, first there was a hope that these were processes making the main contribution to the total cross-section. However, experimental data favored the so-called multiperipheral kinematics characterized by smaller rapidity gaps and higher multiplicity (see Section 3). The growth of multi-Pomeron diagrams must be screened by Pomeron branch-points (see below). It should be noted that the observation of particle production or the production of systems of particles in, for example, two-Pomeron kinematics makes it possible to obtain information about the quantum numbers of the produced particle system since Pomerons have vacuum quantum numbers. In particular, this could be a serious advantage for the detection of Higgs bosons in this doubly diffractive kinematics [23].

1.3. Moving branch-points At the ﬁrst stage of the development of the theory, it was assumed that there are only poles in the angular-momentum plane, since only pole singularities follow straightforwardly from t-channel unitarity. The ﬁrst indications that the simplest (so-called nonenhanced) branch-points may appear on the j plane came from an analysis May 15, 2013 10:49 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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of the simplest Feynman diagrams [24]. Mandelstam showed [25] that, although the diagrams considered in [24] do not give an asymptotic contribution, since, at high energies, there arise cancellations in them, there exists yet another class of diagrams (nonplanar diagrams) generating moving branch-points.e After that, a new problem appeared: the determination of a general asymptotic behavior of scattering amplitudes on the basis of unitarity conditions and minimal analyticity assumptions, which are usually satisfied in any reasonable field theory. An approach to solve this problem was developed in the well- known papers of Gribov, Pomeranchuk, and Ter-Martirosyan [26]. This approach required assumptions about the structure of an analytic continuation of multiparticle unitarity conditions to complex values of j. Here, for the first time, enhanced branch-pointsf corresponding to Reggeon number-changing t-channel transitions were introduced along with nonenhanced branch-points. A method for analyzing Reggeon amplitudes directly in the s- channel proved to be simpler. This program was carried out by Gribov in [27], where the author performed an analysis of asymptotically significant (nonplanar) field-theory diagrams, which contained Reggeon amplitudes as internal elements. The paper had a strong impact on the further development of the theory. The considered field theory was assumed to be “soft,” i.e. the integrals off the mass shell were assumed to be converging quickly.g As a result, rules for constructing Reggeon diagrams were obtained in the form corresponding to the so-called Reggeon field theory. In addition to interaction vertices for colliding particles and Reggeons, the Lagrangian

eSo called planar diagrams (they can be plotted in a plane without the intersection of lines), for which the third spectral function in the terminology of the Mandelstam representation equals zero. In diagrams that are similar to those considered in [24], but which are nonplanar, there is no such cancellation. The physical distinction between the space-time picture for planar and nonplanar diagrams is considered in Section 3.4. – K.B. f Enhanced branch-points involve a pole singularity in addition to a branch-point. gIn calculating the asymptotic behavior of complicated Feynman integrals, it is important to choose adequate variables. Gribov made use of the Sudakov variables [28], and it turned out that the application of these variables is highly eﬃcient for a broad range of problems concerning interactions at high energies. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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of this theory contains vertices corresponding to the interaction of Reggeons themselves (see Section 5). This way one reproduces the total set of Reggeon diagrams, which includes both nonenhanced and enhanced branch points.

2. Two-body Processes A description of the behavior of the total cross-sections for the interaction of hadrons and for two-particle reactions was the first testing ground for Reggeon theory. It was necessary to reconcile a power-law decrease with the difference of the total cross-sections and the differential cross-sections for charge-exchange reactions with increasing energy, their behavior being controlled by the values of intercepts of secondary Regge poles. The Pomeranchuk singularity has a positive signature and, hence, makes the same contributions to the total cross-sections for particle and antiparticle interactions. The differences of the total cross- sections, Δσ(hN)=σtot(hN¯ ) − σtot(hN) , are related to the contributions of secondary poles having a negative signature (ρ,ω)and an intercept less than 1; therefore, these differences must decrease accordingtothepowerlaw,Δσ ∼ sαR−1,R = ρ,ω. Since the isospin of the Pomeranchuk singularity is zero, we similarly conclude that the differences of the cross-sections for the interaction of hadron h withaprotonandaneutronaredeterminedbytheρ and A2 singularities. Therefore, these differences must also decrease according to a power law. In addition, the momentum-transfer (t) dependence of the Pomeron trajectory, αP(t), leads to the shrinkage of the diffraction cone with increasing energy in the case of elastic hadron–hadron scattering. New experimental data from the Serpukhov accelerator and then from the ISR accelerator began to appear precisely within this passionate period (the late 1960s). These data were expected eagerly (even bets were made sometimes) and were immediately analyzed in terms of the Reggeon scheme, which successfully passed experimental tests. The next step was to reveal qualitative effects associated with Regge branch-points. We have noted that up to now there exist a April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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Figure 3. Contributions of intermediate states to vertices of Reggeon branch-points.

phenomenological point of view according to which the simple Regge pole parametrization is sufficient for describing experimental data, while the presence of branch-point contributions is not obvious and has not been proven rigorously (see, for example, [29]). This naive approach seems strange, especially since the presence of branch-points in the j plane was proven both on the basis of an analysis of Feyn- man diagrams and on the basis of the t-channel unitarity condition (see Section 1.3). Moreover, the lower limit of the branch points in elastic scattering was obtained by Gribov and A. A. Migdal [30] from the analysis of the Reggeon unitarity condition. This limit corresponds to taking into account only the pole contribution in the intermediate state for the amplitude of Reggeon-particle scattering (see Fig. 3). Taking into account only the pole contributions for multi-Pomeron vertices leads to the well-known eikonal approximation. The approximation where corrections due to other intermediate states (so-called shower corrections) are taken into account in the framework of the simplest model was called the quasieikonal approximation [31]. Shower corrections, which determine the deviations of the branch-point contribution from that at the lower limit, are related to the cross-sections for the diffractive production of low-mass multiparticle intermediate states. Their estimates for pion–nucleon and nucleon–nucleon interactions were obtained by Kaidalov [32] from an analysis of experimental data on inelastic diffractive production, and turned out to be of the order of 20–40%. There are a number of phenomena demonstrating the important role of moving branch-points in binary processes (see [33,34]). These May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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include: (i) the “crossover” phenomenon, i.e. the difference of the differential cross-sections for particle and antiparticle scattering on nucleons (for example, π− and π+ scattering on nucleons orpp ¯ and pp scattering) change signs – in the Regge pole model, this phenomenon is impossible, since it requires the change in the sign of the square of the residue (in pp scattering), but it naturally arises upon the inclusion of branch-points [34]; (ii) the appearance of polarization in the charge-exchange reaction π−p → π0n [35] (in the Regge pole model, this process receives a contribution only from the ρ-meson pole, but, for one pole, the phase of the helicity-flip amplitude is identical to the phase of the non- helicity-flip amplitude, so that the polarization is zero); and (iii) narrow forward peaks in the differential cross-sections for the np charge-exchange reaction and the process γp → π+n (in the Regge pole model taking into account the pion pole and the ρ-and A2-meson poles, one expects minima for |t|→0 in these processes. Taking into account the branch-points, we get an explanation for the above phenomena [33, 36, 37]). It should be noted that, in all of the mentioned processes the branch-point contributions are in agreement with the results of the calculations based on the Reggeon technique. After testing qualitative predictions and describing individual reactions by the group of Ter-Martirosyan at ITEP, they addressed the problem of constructing a complete self-consistent description of all experimental data available at that time for two-particle elastic- scattering processes and charge-exchange reactions induced by nucleon, pion, and kaon beams. Within the quasi-eikonal approximation, these data were described successfully and a set of parameters that characterize Regge trajectories, residues, and branch-points were obtained [38]. At that time (1970), this comprehensive description was unique. It should be emphasized that, to a considerable extent, this description owed its success to an extensive use of computer calculations, which was rare in theoretical physics at that time. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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Figure 4. Ladder diagram appearing in φ3 ﬁeld theory and corresponding to a Regge pole.

3. Multiparticle Production Processes 3.1. Multiparticle structure of the Pomeron Although Regge poles were originally introduced formally via the analytic continuation of the partial wave expansion from the t-channel to the s-channel, it soon became clear that, since the s-channel asymptotic behavior of the amplitude corresponds to the interaction radius growing with the energy as R2(s) ∼ ln s, the Reggeon amplitude must correspond to complex multiparticle interactions. The ladder diagrams in Fig. 4, which reproduce a power-law asymptotic behavior (at small coupling constants), provide the simplest example of such a multiparticle structure of the Reggeon. The total cross- section, which is proportional to the imaginary part of the ladder diagram, corresponds to multiparticle processes in the so-called multiperipheral kinematics, where the transverse momenta of secondary particles are finite and where the logarithms of their longitudinal momenta (rapidities) differ by a finite quantity (which does not grow with energy), so that the mean multiplicity of secondary particles is proportional to the logarithm of the energy, n∼ln s.Starting from the work of Chew and Low [39], pion exchange has been considered as a dominant mechanism because of the proximity of the pion pole to the physical domain owing to the smallness of the pion mass. The contribution to the total cross-section from peripheral processes including pion exchange was discussed in early papers of physicists from ITEP [40] and the Lebedev Institute of Physics (Moscow) (see, for example, the review articles quoted in [41]). A very important contribution was made in the studies of a group including Amati April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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a b

Figure 5. Pion-exchange diagrams: (a) ρ-meson production and (b) total blocks of pion–pion scattering.

and Fubini (see [24, 42]), where the multiperipheral mechanism of multiparticle production processes was discussed in connection with the Regge pole approach – the ladder diagram including t-channel pion exchanges and ρ-mesons in the s-channel intermediate state was associated with the Pomeron.

3.2. Meson-cloud model In the original formulation of the multiperipheral model [24], blocks of elastic pion–pion scattering were used only in the resonance region (see Fig. 5(a)). This led to an insufficient value of the iterated kernel and, consequently, to a cross-section decreasing with energy. Work on developing and refining this model with the aim of obtaining a quantitative description of experimental data on multiparticle production processes was carried out by several groups. The first task was to construct a self-consistent quantitative description of nondecreasing total cross-sections and logarithmically growing multiplicities. At the same time, the appearance of new experimental data posed a much more complicated problem of describing the features of particular processes at various energies. A model combining the peripheral and the statistical mechanism was proposed by a group from the Lebedev Institute of Physics (I. M. Dremin, I. I. Royzen, E. L. Feinberg, D. S. Chernavsky et al. – see [41]). A multiparticle kernel was introduced there under the assumption of pion production via a thermodynamic mechanism. This made it possible to obtain a nondecreasing total cross-section, on one hand, and to ensure a rather high multiplicity, on the other hand. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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InthemodeldevelopedbyE.M.LevinandM.G.Ryskin[43],a resonance character of the kernel was preserved, but the pion-exchange contribution was supplemented with exchanges of other Reggeons (ρ , ω ,etc.). In the OPER model developed by a group of physicists from ITEP (K. G. Boreskov, A. B. Kaidalov, and L. A. Ponomarev) [44], the main contribution comes from the exchange of a Reggeized pion, while the enhancement of the kernel contribution is due to taking into account all masses in the block of elastic pion–pion scattering, including the region associated with the exchanges of secondary Reggeons and a Pomeron. The possibility of an absolute normalization of model predictions at low momentum transfers is an advantage of this model. The model is formulated in terms of multiperipheral diagrams (see Fig. 5(b)) containing on-mass-shell two-particle blocks of pion–pion (or pion–nucleon) scattering that are parametrized by using experimental information, including information from a partial-wave analysis of pion–pion and pion–nucleon interactions. The off-shell behavior of the pion is described in terms of phenomenological form factors. Owing to the fact that two-particle blocks contain both resonance and Reggeon contributions, the model provides, despite its compact formulation, a quantitative description of data in various regions of the phase space over a broad energy range – in particular, it describes specific exclusive reactions, processes of diffractive dissociation, multiparticle production processes, and inclusive spectra. The OPER model made it possible to describe quantitatively a formidable amount of experimental data on exclusive and inclusive pion-production processes over the entire kinematical domain of importance. It is interesting to note that the pion-exchange model made it possible to explain [45] the spin structure of the amplitude for pion– nucleon scattering – the small value of the spin-flip amplitude for isoscalar exchange (Pomeron) and its large value for isovector exchange (ρ-meson Reggeon) in relation to the non-spin-flip amplitude. The observed structure is explained theoretically by the cancellation of the nucleon and the delta-isobar contributions in the irreducible pion–nucleon block and is closely related to the isovector nature of April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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the pion. Due to the good description of soft processes within the model, it can be taken as a basis for describing the structure of a rapidly moving hadron at long distances. In calculating its structure at short distances, one can then make use of this model in formulating initial conditions for the QCD evolution equation. The quarks and antiquarks (predominantly valence ones) of the pion cloud determine the structure and the size of the quark sea of the nucleon. This program was realized in the papers of Arakelyan et al. [46], who were able to describe both nucleon structure functions and Drell–Yan processes, the production of mesons containing heavy quarks, and some other processes in the region of not very high virtualities. In particular, the model predicts the ﬂavor and spin structure of the quark sea.

3.3. Cutting rules for Reggeon amplitudes Thus we have seen, from the point of view of s-channel unitarity, that elastic scattering in the Regge pole approximation corresponds to a multiperipheral chain of secondary particles whose multiplicity depends logarithmically on energy. The question is, to what multiparticle configurations correspond more complicated diagrams – for example, diagrams including nonenhanced branch-points. A breakthrough in this region was due to the work of Abramovski˘ı, Gribov, and Kancheli (AGK) [47], where rules for the cuts of Reggeon amplitudes were formulated in a simple form on the basis of the Cutkosky rules [48] applied to the case of high energies. Since Reggeon diagrams are nonplanar, one can cut simultaneously any number of Pomerons, the AGK rules fixing unambiguously the relationships between the contributions of different intermediate states. Figure 6 shows examples of inelastic processes corresponding to various inelastic cuttings of the two-Pomeron diagram in Fig. 3.

3.4. Space-time interpretation of Reggeon diagrams The multiperipheral structure of Pomeron exchange indicates the complicated nonlocal nature of the high-energy hadron interaction. May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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Figure 6. Inelastic processes corresponding to various inelastic cuts of two-Pomeron diagrams.

A qualitative space-time pattern of such interactions that corresponds to multiperipheral kinematics was given by Gribov [1]. The basic idea underlying this pattern is that a fast hadron of momentum p (or rapidity y ln (2p/m)) interacts with a target via quantum- mechanical fluctuations including slow particles. The structure of the simplest fluctuation (which corresponds to a ladder diagram) has a multiperipheral character – that is, it includes about ln p intermediate particles (rungsh) uniformly distributed over rapidities. In the impact-parameter plane, partons in a fluctuation are distributed in accordance with the diffusion equation, where a fast hadron plays the role of a source. Only partons of low momentum (about a few hundred MeV) interact directly with the target. Fast partons in the fluctuation appear to be spectators.i The time of the development of such a multiperipheral fluctuation is proportional to the initial energy.j This means that the space- time structure of a ladder diagram (see Fig. 7(a)) is very strongly

hFor the sake of brevity, we will call them soft partons or merely partons. – K.B. iWe note that this interpretation of Reggeon diagrams in terms of partons is possible in any Lorentz-invariant system, although the parton structure of a fast hadron depends on the reference frame in which it is observed. For example, the multiplicity of partons in the simplest fluctuation of each hadron depends logarithmically on its momentum, ni(pi) ∼ p ln ( i/mi ), i =1, 2, whereas the total multiplicity in an interaction event is Lorentz- s invariant: n(s)=n1 + n2 ∼ ln( /4m1m2). This property is conserved also for more complicated fluctuation dynamics, including the splitting and fusion of multiperipheral ladders. – K.B. jThe growth of longitudinal distances significant in the interaction with increasing energy was first indicated by Gribov, Ioffe, and Pomeranchuk [49]. – K.B. May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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a b c

Figure 7. Space-time structure of Reggeon diagrams in the laboratory frame (time scales of the upper parts of ladders are proportional to the initial energy): (a) Regge pole diagram, (b) planar two-Reggeon diagram, and (c) nonplanar two-Reggeon diagram.

extended in time and in the longitudinal coordinate.k Therefore, it becomes clear why the contributions of Regge branch-points stem only from nonplanar diagrams. In such diagrams, several multiperipheral fluctuations develop simultaneously at the same longitudinal distances (see Fig. 7(c)), but, in a planar diagram (Fig. 7(b)), fluctuations develop successively in time, so that slow particles from the second fluctuation are far off the target. If, however, the target dimensions are rather large (the case of a heavy nucleus), there is a critical energy of about a few GeV below which the main contribution to the interaction comes from planar diagrams and above which the main contribution stems from nonplanar diagrams. Gribov demonstrated [50] that the transition from one regime to the other is smooth, and this explains the applicability of the Glauber approximation formulas [51] at energies much higher than the critical energy in spite of the fact that the continuous rescattering on nucleons of a nucleus is negligible in the Regge regime. Such a consideration of the hadron–nucleus interaction at high energies is referred to as the Glauber–Gribov approach. In [52] it was shown that the transition at the critical energy is smooth not only for the total cross-section but also for individual multiparticle processes leading to different final states. Nevertheless, there are processes for which the transition of the regime via Ecrit changes the observed pattern qualitatively. In particular, let us note

k At a given instant of time, partons in a ﬂuctuation of the√ ladder type are nevertheless in a Lorentz-compressed disk of transverse radius R ∼ ln p and longitudinal size about 1/k,wherek is the parton longitudinal momentum. – K.B. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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that in the production of systems containing heavy quarks, the critical energy scale is proportional to the mass of the produced system and may be as large as tens or hundreds of GeV [53].

3.5. Diffraction processes The investigation of the diffraction scattering gives us important information on the structure of hadrons, and about the mechanisms of their interactions [54]. The theory of the diffractive dissociation of hadrons was formulated in the well-known papers of Pomeranchuk and Feinberg [55]. From the point of view of the s-channel consideration, the diffractive dissociation of hadrons is associated with a different absorption of different components of the fast-hadron wave function and, hence, with the unitarity condition. In the t-channel approach the diffraction dissociation (also in the case of large masses) is described in terms of Reggeon diagrams including both poles and branch-points. In accordance with the AGK rules [47], the diffraction dissociation processes are contained in various discontinuities of the elastic scattering amplitude. For example, diffraction dissociation to small-mass final states corresponds to cutting the nonenhanced diagram in Fig. 7(c) between Pomerons. As to diffraction dissociation to large-mass final states, it corresponds to the cutting of so-called enhanced diagrams, the simplest of which is presented in Fig. 8.

Figure 8. Diﬀractive production of large masses in terms of cutting a three-Reggeon diagram.

Thus, cross-sections for diﬀraction dissociation processes with small masses characterize deviations of the contribution of Reggeon branch points from the eikonal approximation (shower corrections, May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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which were discussed in Section 2). Cross-sections for diffraction dissociation processes with large masses (or, what is the same, inclusive spectra in the region x → 1) are determined by the three-Reggeon coupling constants,l and the presence of these processes indicates directly that it is necessary to take into account multi-Reggeon diagrams in Reggeon field theory. Triple-Pomeron coupling constants, including the fundamental triple-Pomeron coupling constant rPPP , were first determined from an analysis of inclusive spectra [56]. The triple Pomeron coupling constant proved to be comparatively small, rPPP gP .Thises- timate was also confirmed by a direct calculation within the one- pion-exchange model [57], in accord with a successful description of inclusive spectra on the basis of this model.

3.6. Deep-inelastic processes Deep-inelastic scattering [58] at small values of the Bjorken variable xB forms an important class of inelastic processes. In such processes, dynamics depends not only on the energy of a virtual photon but also on the value of its virtuality Q2, so that one can consider “soft” and “hard” diffractions. Data on deep inelastic scattering processes make it possible to obtain information about the distributions of partons (quark and gluons) in nucleons and nuclei depending on the longitudinal momentum fraction x = xB . Recent experimental investigations at the HERA collider revealed two regularities of importance: a fast growth of the parton density with decreasing xB and quite an intense diffractive production in the processes studied there. In Reggeon theory, this growth is related to the intercept αP(0) = 1 + Δ of the leading Pomeranchuk singularity: the quark distribution (xq(x)) or the gluon distribution (xg(x)) is proportional to 1/xΔ. In the parton model, this growth is associated with the cascade increase in the parton density with decreasing x.At higher parton densities, however, it is necessary to take into account nonlinear effects of their interaction, which lead to a decrease in the

lIn principle, more complicated diagrams including multi-Reggeon interactions also contribute. – K.B. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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rate of growth of the number of partons and, in the limit x → 0, to their saturation [59–61]. In Reggeon theory, this problem is related to Pomeron–Pomeron interactions (see Section 5). In [62], it was assumed that the experimentally observed increase in the effective intercept of the Pomeron with increasing Q2 is due to a decrease of shadowing corrections – that is, to the reduction of multi-Pomeron effects. According to AGK rules, cross-sections for diffraction processes are related to the contributions of n-Pomeron exchanges. Thus, in order to construct a self-consistent theoretical model, it is necessary to describe not only the total cross-sections for γ∗p interaction but also cross-sections for diffraction processes. An explicit model for the rescattering contribution to the amplitude for elastic γ∗p scattering was constructed in [62,63]. This model made it possible to describe quantitatively the mentioned energy dependence tot 2 of σγ∗p for various values of Q and cross-sections for diffraction dissociation processes including real and virtual photons. The model predicts a definite character of parton density saturation. A fairly good description of proton structure functions in deep inelastic scattering was also obtained in the dipole model of the Balitsky–Fadin–Kuraev–Lipatov (BFKL [64]) Pomeron (see Sec- tion 4). In the small-xB region, shadowing effects are enhanced in the case of interactions with nuclei (in proportion to A1/3). The Glauber–Gribov approach makes it possible to calculate corrections to the cross-section for photon–nucleus interaction in terms of diffractive photon–nucleon interaction, which was considered above. Rele- vant theoretical predictions [65] are in excellent agreement with experimental data on structure functions for nuclei at very small values −2 −3 of the Bjorken variable, xB ∼ 10 − 10 . One can hope that this approach will make it possible to advance toward the region of still smaller values of xB , which will play an important role in the dynamics of heavy ion interactions at ultrahigh energies – for example, in experiments at the Large Hadron Collider (LHC).

4. Quantum Chromodynamics and the Pomeron The Reggeon approach is a very general one, since it is based on such fundamental properties as unitarity and analyticity. However, April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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the analysis of strong interactions at short distances proves convincingly that quarks and gluons are true degrees of freedom and that quantum chromodynamics (QCD) is the microscopic theory which describes their interactions. From this point of view the Reggeon theory, which describes interactions at long distances (soft processes), is a phenomenological theory dealing with effective color-singlet degrees of freedom. In the region of large distances, the strong-interaction coupling constant is not small, so that methods of perturbative QCD are inapplicable. To a considerable extent, interaction dynamics is determined by the confinement phenomenon and nonperturbative condensates of gluon and quark fields. Since the Pomeron does not carry quantum numbers, it is usually associated with gluon bound states of a nonperturbative origin (glueballs). However, even the simplest QCD diagram with an exchange of two gluons reveals some properties inherent in the Pomeron, giving a contribution to the elastic-scattering cross-section not decreasing with energy. Taking into account higher order diagrams (gluon ladders) leads to some increase in the intercept and to a nonzero slope of the Pomeron trajectory. The properties of the phenomenological Pomeron, such as the proximity of the intercept to unity (Δeff ≈ 0.08) α ≈ . and the smallness of the slope of the Pomeron trajectory ( P 0 2), as well as the smallness of the triple-Pomeron coupling constant (rPPP/g 1), may suggest that the properties of the Pomeron are determined to a considerable extent by short-distance dynamics. One can consider special high-energy processes for which it is natural to expect that the interaction at short distances plays a dominant role – for example, the scattering of heavy quarkonia on each other. In this kinematics, the small parameter x also plays an impor- 2 tant role in addition to the parameter ΛQCD/Q , which is typical of hard processes. Therefore, it is necessary to sum all diagrams which contain αs ln(1/x) . In the leading-logarithm approximation, the summation of ladder gluon diagrams featuring the exchange of Reggeized gluonsm at a fixed coupling constant αs leads to the emergence of a BFKL Pomeron – a singularity (branch-point) whose intercept is

mThe Reggeization of gluons and quarks is a typical property of QCD. May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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larger than unity [66]: Δ ≡ αP(0) − 1 0.9Nc αs .Atαs ≈ 0.2, this leads to a value of Δ ≈ 0.5 . The calculated nonleading corrections n (of order αs ) reduce the value of Δ significantly [67]. Even for these processes, however, the role of large distances may prove to be of fundamental importance. In [68], it was shown that, for x → 0, low transverse momenta of gluons begin playing a significant role in the ladder diagram for the running coupling constant, so that it is illegitimate to remain within perturbation theory.o In recent years, the investigation of the properties of the perturbative BFKL Pomeron has been carried out in the following directions. The calculation of higher order corrections in αs to the leading BFKL contribution is being continued, along with the generalization of the BFKL Pomeron to multi-gluon states. Yet another line of investigation applies the s-channel parton pattern, where partons are chosen to be natural from the QCD point of view. In one case, this is the color-dipole model proposed by Nikolaev and Zakharov [69] and independently by Mueller [70], where the BFKL Pomeron is reproduced in the limit of an infinite number of colors. In this model, the pattern of fast-hadron interaction is very clear and corresponds to a collision of two chains (strings) formed by color dipoles of fluctuating dimensions. The inclusion of multiple interactions and multichain states in wave functions is quite natural in this pattern. One can hope that all higher order Reggeon diagrams will be correctly reproduced within this approach. In the approach developed by McLerran et al. [71], it is proposed to use gauge fields themselves as partons. Possibly, this pattern is valid at high gluon densities (for example, in heavy-ion collisions), in which case relative fluctuations of the parton density are small, so that one can apply the quasi-classical approximation. The 1/N-expansion method [72] was an important step that made it possible to bridge the gap between the Reggeon theory and non-

nThe magnitude of these corrections to Δ depends on the renormalization scheme. – K.B. oHere the character of the Pomeron singularity also changes – the branch-point transforms into a series of poles condensing toward the point Δ = 0, the dynamics of the emergence of these poles being determined to a considerable extent by the region of long distances. – K.B. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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a b

Figure 9. (a) Planar and (b) cylindrical diagrams.

perturbative QCD. In this approach, one considers the number of colors, Nc, and the number of light ﬂavors, Nf , as large numbers

and expands amplitudes in series over 1/Nc and 1/Nf . The approach in question is also referred to as a topological expansion because the individual terms of this expansion correspond to an infinite set of Feynman diagrams that can be arranged (without line intersection) on a surface having a definite topology. The first term of the expansion corresponds to a planar diagram of the type in Fig. 9(a). The boundary of such diagrams is formed by lines of the valence quarks of the hadrons participating in the reaction being considered, while the interior of the diagrams is filled with gluon lines and quark loops. At high energies, the exchanges of secondary Reggeons composed of light quarks (ρ, A2 , ω, etc.) correspond to these diagrams. The cuttings of a planar diagram determine multiparticle processes in the s-channel, which have the same properties as in the multiperipheral model [73]. Such a process can be interpreted as the formation of a color tube or a string, which then decays to final state hadrons [7, 73–75]. Within a topological expansion, diagrams of the cylindrical type (Fig. 9(b)) for which there is no transfer of quantum numbers in the t-channel correspond to the Pomeron. Multiparticle configurations associated with cutting cylindrical diagrams correspond to the production of two chains (color tubes or strings), each having the same structure as in the case of planar diagrams. The fragmentation of each string has the same properties as in the planar case. Since in the Pomeron case two strings are formed, we can conclude that the density of the produced hadrons in the central rapidity region is approximately two times larger in this case than in the planar case. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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The string-to-hadron fragmentation functions can be determined theoretically on the basis of the correspondence with various Reggeon asymptotic expressions [7,73,74]. The corresponding model of quark- gluon strings possesses a correct triple-Reggeon limit for x → 1and a correct two-Reggeon limit for x → 0 and satisfies all conservation laws. This model has made it possible to describe quantitatively [75] a large amount of data on multiparticle processes in collisions of hadrons and nuclei over a very broad energy range – specifically, multiplicity distributions, inclusive cross-sections over the entire x range, strange- and charmed-particle production, and so on. Quali- tative changes in distributions with increasing energy (for example, a strong violation of the Feynman scaling at small x and its moderate violation in the fragmentation region at x 0.1) were also described. This permitted deriving reliable estimates in the energy region of new accelerators and for cosmic-ray physics.p By and large, the model of quark-gluon strings provides a fully adequate description of basic features of multi-particle hadron production at high energies. There also exist Monte Carlo realizations of the model of quark-gluon strings [76]. Thus, the Pomeron can be considered as a nonperturbative object that consists basically of gluon fields and whose structure at short distances is determined by perturbative QCD – for example, it may correspond to the BFKL Pomeron. Some properties of the Pomeron (in particular, its nonperturbative component) can be studied at positive t by applying the same methods as those that are used in low-energy QCD. In this case, various gluonia lying on the corresponding trajectory must be associated with the Pomeron. In order to solve this problem, one may use various methods, including numerical lattice calculations. The effect of phenomena not described within perturbative QCD on the Pomeron trajectory and the relationship between the Pomeron and the glueball spectrum were examined in [77]. In the small-t region, the leading gluon trajectory proved to be close to the quark–

pIn cosmic-ray physics, the model of quark-gluon strings is considered as a standard model for basic calculations. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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antiquark trajectories f and f . In view of this, the effect of mixing of these trajectories appears to be significant – it leads to a strong nonlinearity of the Pomeranchuk trajectory at small t and to a phe- nomenologically reasonable value of its intercept. The concept of the Pomeron as a finite-radius gluon tube was developed in the works of Vladimirsky [78] (see also [79]).

5. Pomeron Interaction As it was discussed in Section 1, the set of Reggeon diagrams is much wider than the set of simplest rescattering diagrams and includes, in addition to nonenhanced branch-points, Reggeon–Reggeon interactions. Gribov showed [27] that one can associate a total set of Reggeon diagrams with the perturbative expansion of nonrelativistic (2+1) field theory (specified by a non-Hermitean Lagrangian), where Reggeon coordinates in the impact-parameter plane correspond to spatial coordinates and where the rapidity plays the role of the evolution parameter (time). In this case, Reggeons can also be split and scattered. They can also undergo fusion. A large number of investigations were devoted to analyzing various regimes of Reggeon field theory and the asymptotic properties of the corresponding scattering amplitude. The simplest case, where the Pomeron intercept is less than 1 (Δ = αP(0) − 1 < 0), proved to be unrealistic. The regime in which the Pomeranchuk singularity is exactly at the point j = 1 (critical Pomeron regime) is of great interest from the theoretical point of view since all branch-points occur at the same point, so that there arises the infrared problem of summation of diagrams in the theory with massless particles. The problem reduces to calculating anomalous dimensions of the theory. One of these quantities, η, characterizes the energy dependence of the total cross-section, σtot ∼ lnη s ,where0 η 2. Gribov and Migdal [30] analyzed this problem both for Hermitean interactions which are related to condensed matter physics, and for the non-Hermitean case corresponding to Reggeon theory. In the case of Reggeon dynamics, however, they gave preference to the so-called weak-coupling regime [80], where Pomeron interaction vertices vanish at low momenta. Subsequent experiments that considered diffractive May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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dissociation to large-mass final states did not show any signs of the disappearance of these processes at low t. Later, Migdal, Polyakov, and Ter-Martirosyan [81] (and independently Abarbanel and Bronzan [82]) reanalyzed the strong-coupling regime, this time by means of the ε-expansion technique.q For the 2 exponent η, they obtained η = ε/12 + O(ε ) ≈ 1/6. However, this beautiful theory is likely to be at odds with experimental data. Avail- able data suggest a much faster growth of the cross-section, η ≈ 2. Moreover, this scheme predicts the fulfillment of the asymptotic re- el lation σ /σtot ∼ 1/ln s, which also contradicts experimental data. A complete analysis of the behavior of cross-sections and inclusive spectra is likely to favor a Pomeron intercept value larger than unity. This is also corroborated by calculations within perturbative QCD. For this reason, the supercritical Pomeron regime, for which Δ > 0, is supposed to be the most realistic at present. Taking into account only the pole diagram with supercritical Pomeron exchange leads to a violation of the s-channel unitarity condition. The simplest way to avoid this violation is to sum the Reggeon diagrams corresponding to the eikonal (or quasieikonal) approximation. The resulting amplitude corresponds to the scattering on a black (or gray) disk of radius growing as R ∼ ln s (Froissart regime). However, it then appears that the effective number of Pomeron exchanges grows as a power function of energy (in proportion to sΔ), so that it is necessary to take into account Pomeron– Pomeron interactions when the Pomeron density becomes sufficiently large. The Pomeron coupling constants extracted from data on diffractive-production processes proved to be relatively small compared to the hadron-Pomeron residues. Because of that, at relatively low energies, effects of Pomeron interactions manifest themselves only in diffractive processes, where these interactions play a

qIn the case where the transverse dimension is d = 4, anomalous dimensions do not arise in the theory. In the case of diﬀerent numbers of transverse dimensions, anomalous dimensions can be calculated via an expansion in the parameter ε =4− d. The ﬁrst term of the expansion in ε was calculated in [81, 82], while the second-order term was found in [83]. – K.B. May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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dominant role. However, the quantity (r/g)sΔ is a characteristic parameter since the Pomeron is supercritical, so that the role of these effects becomes more pronounced with increasing energy. In the case of interaction with heavy nuclei, the Pomeron–Pomeron interaction is additionally enhanced since the number of Pomerons is proportional to the factor A1/3. A quantitative analysis of the supercritical regime is a very complicated problem, since it is necessary to sum sign-alternating series whose terms grow. The result of such a summation can in principle depend on the order of summation. Therefore, it is important (and even crucial) to choose physically justified methods of analysis. Cardy [84] and Dubovikov and Ter-Martirosyan [85] considered a scheme where any propagator of the supercritical Pomeron was uni- tarized within this rapidity interval by parallel Pomeron exchanges, leading, as a result, to an amplitude that corresponds to scattering on a black disk of a logarithmically growing radius (Ter-Martirosyan called it a Froissarton).r By using such an amplitude as a single element, one can then construct diagrams including the interaction of Froissartons. A convenient scheme for calculating the contributions of Froissarton diagrams at finite energies was constructed tot in [86]. The energy dependence of the total (σNN) and elastic- el scattering (σNN) cross-sections for nucleon–nucleon interaction and of the cross-sections√ for diffraction dissociation was calculated up to s ∼ 5 √energies of 10 GeV. It was shown that, for energies in the s<104 GeV interval, the predictions of the theory that takes into account the interaction of supercritical Pomerons characterized by Δ=αP(0) − 1=0.21 differ only slightly from the results of the calculations that include only the contributions of nonenhanced diagrams but at an effective intercept of Δeff 0.12 . In the case of

rCardy [84] considered a disk that has a sharp boundary, while Dubovikov and Ter- Martirosyan [85] took into account effects of the smearing of the boundary and the two-pion threshold singularities of the Pomeron contribution. Boundary effects are especially important in analyzing diffraction dissociation processes, which are associated predominantly with large impact parameters. In order to go over from Pomerons to Froissartons, it is necessary to assume that the vertices rmn for the transition of m to n Pomerons are analytic in m and n.–K.B. May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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higher energies, these predictions for the total cross-sections grow still more slowly. Thus, the contributions of higher order Reggeon diagrams significantly reduce the rate of growth of cross-sections. reff The effective triple-Pomeron vertex, PPP , which is responsible for diffraction dissociation processes, proves to be significantly smaller than the bare triple-Pomeron vertex because of shadowing effects. An alternative method for summing Pomeron diagrams consists in taking into account continuously the Pomeron fusion, which prevents the growth of the Pomeron density in the transverse plane.s This regime also leads to the Froissart behaviort – that is, to scattering on an almost black disk of logarithmically growing radius, as in the (quasi)eikonal approximation, where only shadowing effects are taken into account. In order to discriminate between the saturation and shadowing regimes, it is therefore insufficient to analyze the experimentally observed shape of the scattering amplitude T (b), but it is necessary to invoke data on the multiplicities and inclusive spectra of secondary particles. We note that, at high densities of Pomerons, their splitting and subsequent fusion can occur within such narrow rapidity intervals that the very concept of the Reggeon loses its asymptotic meaning. Probably, the application of parton models will make it possible to resolve this problem. The problem of determining the structure of the Pomeron amplitude – in particular, the problem of calculating the asymptotic value of its opacity – has not yet been solved. We note that the parton model where the mean parton virtuality grows with energy leads to an asymptotically black Froissart disk [89]. Effects that are associated with Pomeron–Pomeron interaction are of particular importance in the case of heavy-ion interaction since the Pomeron density depends on the number of nucleons in a nucleus.

sFor this it is suﬃcient, in principle, to take into account only triple-Pomeron interactions. Parton saturation in the context of QCD is discussed in detail elsewhere [59]. – K.B. tIt is convenient to analyze this regime on the basis of the probabilistic parton model [87, 88]. In this model, an analysis of Reggeon ﬁeld theory is replaced by a mathematically equivalent consideration of a classical-parton system, whose evolution with time (rapidity) includes random walks in the transverse plane and the fusion and splitting of partons. – K.B. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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Information about the Pomeron density is contained in the spectra of secondary particles, their A dependence becoming weaker owing to saturation eﬀects. Even at RHIC energies, the predicted value of the secondary-particle density is approximately one-half as great as that which is obtained by taking into account only nonenhanced branch-points [90], and this was corroborated by experimental data. At LHC energies, these eﬀects are still stronger. It should be emphasized that knowledge of long-distance dynamics in the interactions of nuclei is of great importance for revealing, against the background of these mechanisms, phenomena of new, nonstandard physics – in particular, for diagnosing the formation of quark-gluon plasma.

6. Conclusions In retrospect, we can see that, after forty years, the Reggeon theory still remains the only general approach to describing strong interactions at high energies. The theory passed flourishing periods and periods of fading interest; however, both its successes in describing experimental data and its theoretical achievements are unquestionable. The Reggeon approach made it possible to transform a chaotic pile of different experimental data into a systematized set of results that are basically understood. Attempts to interpret general properties of Reggeon dynamics in terms of concrete mechanisms led to constructing dual-resonance models and string theory.u The concept of Reggeized exchange also proves to be useful in analyzing a broader class of gauge theories and gravitational interactions. The development of the Reggeon approach within QCD requires obtaining deeper insight into the color- confinement mechanism. Only under this condition can one hope for an ab initio calculation of basic parameters of Reggeon theory.

uIt took a short time for the string theory to go beyond the strong interactions, becoming the main candidate for the “theory of everything” – that is, a theory that describes the structure of strong, electroweak, and gravitational interactions at scales of the order of the Planck mass. April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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Aknowledgments We are grateful to Yu.A. Simonov for his interest in this work and stimulating discussions. This work was supported in part by the Russian Foundation for Basic Research (Project No. 04-02-17263). It was also funded with grants from the Foundation for Support of Leading Scientiﬁc Schools (No. 1774-2003.2) and from CRDF (No. RUP2-2621-MO-04).

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42. L. Bertocci, S. Fubini, and M. Tonin, Nuovo Cimento 25, 626 (1962) . 43. E. M. Levin and M. G. Ryskin, in Elementary Particles (1st ITEP School in Physics) (Atomizdat, Moscow, 1973), Issue 2, p. 42, 82 . 44. K. G. Boreskov, A. B. Kaidalov, and L. A. Ponomarev, in Elementary Par- ticles (1st ITEP School in Physics) (Atomizdat, Moscow, 1973), Issue 2, p. 94 ; L. A. Ponomarev, Fiz. Elem.´ Chastits At. Yadra 7, 186 (1976) [Sov. J. Part. Nucl. 7, 70 (1976)] . 45. K. G. Boreskov, A. A. Grigoryan, A. B. Kaidalov, and I. I. Levintov, Yad. Fiz. 27, 813 (1978) [Sov. J. Nucl. Phys. 27, 432 (1978)] . 46. G. G. Arakelyan, K. G. Boreskov, and A. B. Kaidalov, Yad. Fiz. 33, 471 (1981) [Sov. J. Nucl. Phys. 33 247 (1981)] ; G. G. Arakelyan and K. G. Boreskov, Yad. Fiz. 41, 416 (1985) [Sov. J. Nucl. Phys. 41, 267 (1985)] ; K. G. Boreskov and A. B. Kaidalov, Eur. Phys. J. C 10, 143 (1999) . 47. V. A. Abramovski˘ı, V. N. Gribov, and O. V. Kancheli, Yad. Fiz. 18, 595 (1973) [Sov. J. Nucl. Phys. 18, 308 (1973)] . 48. R. E. Cutkosky, J.Math. Phys. 1, 429 (1960). 49. V. N. Gribov, V. L. Ioﬀe, and I. Ya. Pomeranchuk, Yad. Fiz. 2, 768 (1965) [Sov. J. Nucl. Phys. 2, 549 (1965)] . 50. V. N. Gribov, Zh. Eksp. Teor. Fiz. 56, 892 (1969); 57, 1306 (1969) [Sov. Phys. JETP 29, 483 (1969); 30, 709 (1969)] . 51. R. J. Glauber, in Lectures in Theoretical Physics, Ed. by W. E. Britten (Interscience, New York, 1959), Vol. 1, p. 315. 52. K. G. Boreskov, A. B. Kaidalov, S. M. Kiselev, and N. Ya. Smorodinskaya, Yad. Fiz. 53, 569 (1992) [Sov. J. Nucl. Phys. 53, 356 (1992)] . 53. K. Boreskov, A. Capella, A. Kaidalov, and J. Tran Thanh Van, Phys. Rev. D 47, 919 (1993) . 54. A. B. Kaidalov, Phys. Rep. 53, 157 (1979) . 55. I. Ya. Pomeranchuk and E. L. Feinberg, Dokl. Akad. Nauk SSSR 93, 439 (1953); E. L. Feinberg and I. Ya. Pomeranchuk, Nuovo Cimento, Suppl. 3, 652 (1956) . 56. A. B. Kaidalov, V. A. Khoze, Yu. F. Pirogov, and N. L. Ter-Isaakyan, Phys. Lett. B 45, 493 (1973) ; A. B. Ka˘ıdalov, Yu. F. Pirogov, N. L. Ter-Isaakyan, and V. A. Khoze, Pis’ma Zh. Eksp.´ Teor. Fiz. 17, 626 (1973) [JETP Lett. 17, 440 (1973)] . 57. K. G. Boreskov, A. B. Kaidalov, and L. A. Ponomarev, Yad. Fiz. 19, 1103 (1974) [Sov. J. Nucl. Phys. 19, 565 (1974)] . 58. B. L. Ioﬀe, L. N. Lipatov, and V. A. Khoze, Hard Processes ( North-Holland, Amsterdam, 1984) . 59. L. V. Gribov, E. M. Levin, and M. G. Ryskin, Phys. Rep. 100, 1 (1983) . 60. I. P. Ivanov, N. N. Nikolaev, W. Schafer, et al., arXiv:hep-ph/0212161v2 . 61. A. H. Mueller, presented at INFN Eloisatron Project 44th Workshop on QCD at Cosmic Energies: The Highest Energy Cosmic Rays and QCD Erice, Italy, 2004 [arXiv:hep-ph/0501012v1]. 62. A. Capella, A. Kaidalov, C. Merino, and J. Tran Thanh Van, Phys. Lett. B 337, 358 (1994) . April 5, 2013 16:45 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

522 K. G. Boreskov et al.

63. A. Capella, E. Ferreiro, A. B. Kaidalov, and C. A. Salgado, Nucl. Phys. B 593, 336 (2001) ; Phys. Rev. D 63, 054010 (2001) . 64. N. N. Nikolaev and V. R. Zoller, in Villefranche-sur-Mer 2000, Quantum Chromodynamics, p. 102, [arXiv:hep-ph/0009189]. 65. A. Capella, A. Kaidalov, C. Merino, et al., Eur. Phys. J. C 5, 111 (1998) . 66. K. A. Kuraev, L. N. Lipatov, and V. S. Fadin, Zh. Eksp. Teor. Fiz. 71, 840 (1976) [Sov. Phys. JETP 44, 443 (1976)] , Ya. Ya. Balitski˘ı and L. N. Lipatov, Yad. Fiz. 28, 1597 (1978) [Sov. J. Nucl. Phys. 28, 822 (1978)] . 67. V. S. Fadin and L. N. Lipatov, Phys. Lett. B 429, 127 (1998) . 68. L. P. A. Haakman, O. V. Kancheli, and J. H. Koch, Nucl. Phys. B 518, 275 (1998) . 69. N. N. Nikolaev and B.G. Zakharov, Phys. Lett. B 327, 157 (1994) . 70. A. H.Mueller, Nucl. Phys. B 425, 471 (1994) . 71. L. McLerran and R. Venugopalan, Phys. Rev. D 49, 2233, 3352 (1994) ; A. Kovner, L. McLerran, and H. Weigert, Phys. Rev. D 52, 3809, 6231 (1995) . 72. G. ’t Hooft, Nucl. Phys. B 72, 461 (1974) ; G. Veneziano, Phys. Lett. B 52, 220 (1974) ; Nucl. Phys. B 117, 519 (1976) . 73. A. B. Kaidalov, Surv. High Energy Phys. 13, 265 (1999) . 74. A. B. Kaidalov, Phys. Lett. B 116, 459 (1982) . 75. A. B. Kaidalov and K. A. Ter-Martirosyan, Phys. Lett. B 117, 247 (1982) ; Yad. Fiz. 39, 1545 (1984) , 40, 211 (1984) [Sov. J. Nucl. Phys. 39, 979 (1984); 40, 135 (1984)] . 76. N. S. Amelin, Yad. Fiz. 51, 512 (1990) [Sov. J. Nucl. Phys. 51, 327 (1990)]; N. S. Amelin, K. K. Gudima, S. Yu. Sivoklokov, and V. D. Toneev, Yad. Fiz. 52, 272 (1990) [Sov. J. Nucl. Phys. 52, 172 (1990)] . 77. Yu. A. Simonov, Phys. Lett. B 249, 514 (1990); A. B. Kaidalov and Yu. A. Simonov, Phys. Lett. B 477, 163 (2000); Yad. Fiz. 63, 1507 (2000) [Phys. At. Nucl. 63, 1428 (2000)] . 78. V. V. Vladimirski˘ı, Yad. Fiz. 39, 493 (1984) [Sov. J. Nucl. Phys. 39, 310 (1984)] . 79. V. A. Abramovski˘ı, E. V. Gedalin, E. G. Gurvich, and O. V. Kancheli, Yad. Fiz. 48, 1805 (1988) [Sov. J. Nucl. Phys. 48, 1086 (1988)] . 80. V. N. Gribov and A. A. Migdal, Yad. Fiz. 8, 1002 (1968) [Sov. J. Nucl. Phys. 8, 583 (1968)] . 81. A. A. Migdal, A. M. Polyakov, and K. A. Ter-Martirosyan, Phys. Lett. B 48, 239 (1974) . 82. H. D. I. Abarbanel and J. B. Bronzan, Phys. Lett. B 48, 345 (1974) . 83. M. Baker, Phys. Lett. B 51, 158 (1974); J. B. Bronzan and J. W. Dash, Phys. Rev. D 10, 4208 (1974) . 84. J. L. Cardy, Nucl. Phys. B 75, 413 (1974) . 85. M. S. Dubovikov and K. A. Ter-Martirosyan, Nucl. Phys. B 124, 163 (1977) . 86. A. B. Ka˘ıdalov, L. A. Ponomarev, and K. A. Ter-Martirosyan, Yad. Fiz. 44, 722 (1986) [Sov. J. Nucl. Phys. 44, 468 (1986)] . 87. P. Grassberger and K. Sundermeyer, Phys. Lett. B 77, 220 (1978) . May 10, 2013 12:22 WSPC/Trim Size: 9in x 6in for Proceedings 12d˙Kancheli˙YaF˙Nyiri

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88. K. G. Boreskov, in Multiple Facets of Quantization and Supersymmetry. Michael Marinov Memorial Volume, Ed. by M. Olshanetsky et al. (World Sci., Singapore, 2002), p. 322 . 89. O. V. Kancheli, About the structure of the Froissart Limit in Quantum Chro- modynamics,[arXiv:hep-ph/0008299]. 90. A. B. Kaidalov, Phys. Usp. 173, 1121 (2003) . April 5, 2013 16:22 WSPC/Trim Size: 9in x 6in for Proceedings 12e˙Anselm-Shifman

ANSELM’S DISCOVERY OF THE GROSS–NEVEU MODEL IN 1958

M. SHIFMAN William I. Fine Theoretical Physics Institute University of Minnesota Minneapolis, MN 55455, USA [email protected]

The Gross–Neveu model comprises quantum field theory of N Dirac fermions interacting via four-fermion interaction in one spatial and one time dimension. It was introduced in 1974 (shortly after quantum chromodynamics was discovered) by David Gross and André Neveu [1] as a toy model which mimics two crucial features of quantum chromodynamics: asymptotic freedom and spontaneous breaking of a chiral symmetry. The model is based on N Dirac (i.e. complex two-component) fermions, ψ1,ψ2, ..., ψN . The Lagrangian of the Gross–Neveau model is 2 2 N µ g k L = ψi∂¯ µγ ψ + ψ¯k ψ . (1) 2 k=1 In two dimensions, it is renormalizable. When N = 1, the Lagrangian (1) represents the Thirring model [2] famous due to its sine-Gordon duality [3]. The focus of Gross and Neveu was on the large N limit, and the effect of the spontaneous chiral symmetry breaking in this limit. The Lagrangian (1) is invariant under the discrete γ5 transformation, ψk → γ5 ψk . (2) The condensate ψψ¯ = 0 breaks this symmetry.

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Anselm’s Discovery of Gross–Neveu Model 525

Gross and Neveu calculated the β function in the model (1) for arbitrary N (see Eq. (3.7) in their paper). The β function turned out to be negative (assuming positivity of g2 in (1)), implying asymptotic freedom. Anselm’s work [4] dates back to rather gloomy days for field theorists, after Landau’s discovery of the so-called “zero charge,” or, infrared freedom in modern terminology. Extensive searches for asymptotically free field theories (known at that time as “theories without zero charge”) in the set of available four-dimensional theories failed. That’s when Anselm suggested a two-dimensional theory (1), with N = 2. To be more exact, the Lorentz structure of the four-fermion interaction in [4] was somewhat different, but this difference plays no role in the β function calculation.a Anselm’s paper is reprinted below. The crucial result is Eq. (14). In comparing this result with [1] one should make the following identification: g g g | g2 . 1 = 2 = 3 Anselm =2 Gross−Neveu (3) Equation (14) and the discussion around this formula show that the asymptotic freedom regime for positive g2 was clearly understood and emphasized. Moreover, I checked that the β function following from (14) is exactly that of Gross and Neveu, with N =2. Why Anselm did not return to his model immediately after the discovery of asymptotic freedom in QCD in 1973 remains a mystery.

References 1. D. J. Gross and A. Neveu, Dynamical symmetry breaking in asymptotically free ﬁeld theories, Phys. Rev. D 10, 3235 (1974). 2. W. Thirring, Ann. Phys. (N.Y.) 3, 91 (1958). 3. S. R. Coleman, The quantum Sine-Gordon equation as the massive thirring model, Phys. Rev. D 11, 2088 (1975). 4. A. A. Anselm, A model of the ﬁeld theory with nonvanishing renormalized charge, Sov. Phys. JETP 9(36), 608-611 (1959) [Russian original: ZhETF, 36, 863-868 (1959)].

aIt is important, however, for the issue of the spontaneous chiral symmetry breaking which was not addressed by Anselm. April 5, 2013 16:24 WSPC/Trim Size: 9in x 6in for Proceedings 12f˙Anselm˙statya

A MODEL OF FIELD THEORY WITH NONVANISHING RENORMALIZED CHARGE∗

A. A. ANSELM Ioﬀe Physical-Technical Institute, Academy of Sciences, USSR

Two fermion fields are considered in a space of one dimension (and in time), with interaction of each field with itself and of the two with each other. The first term in the expansion of the vertex part in an asymptotic series of well known form is obtained. It is shown that within certain limits the renormalized charge can have an arbitrary (nonvanishing) value.

In a number of papers [1–3] attempts have been made to deal with a relativistically invariant model of a field theory – the one- dimensional four-fermion interaction. It was expected that the relation between the renormalized and bare charges in this theory would be such that the renormalized charge would not vanish when one goes to the limit of a local interaction [2]. A more detailed examination showed, however, that on account of a certain special cancellation of terms in the perturbation- theory series the theory contains no divergences at all, so that there is no charge renormalization and the question of the vanishing of the charge simply does not arise. In the present paper we consider two spinor fields in a one-dimensional space,a with interaction of the four-fermion type between the two fields and of each field with itself. There is then a logarithmic divergence in the vertex part, and consequently an infinite charge renormalization. Unlike the various three-dimensional types of field theory, however, in which up to now

∗Published in Russian in ZhETF 36, 863-868 (1959). Submitted to JETP editor on September 13, 1958. Translated from Russian by W. H. Furry; the English translation is published in Sov. Phys. JETP 9(36), 608-611 (1959). aOne time and one spatial dimension.

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it has not been possible to avoid the vanishing of the renormalized charge in the local-interaction theory, in the present model it is possible to construct a renormalized solution (or, more precisely, its asymptotic form for large momenta) with an arbitrary value of the renormalized charge.

1. The Equations for the Vertex Part Let us consider two fermion fields ψ and χ that depend on a single space coordinate x and the time x0 . In our case the Hamiltonian canbechosenintheform: g1 g2 H = ψσ¯ μ ψ ψσ¯ μ ψ + χσ¯ μ χ χσ¯ μ χ μ 4 4 (1) g3 + ψσ¯ μ ψ χσ¯ μ χ , σμ×σμ = σ×σ − 1×1 . 2 μ The product μ σμ × σμ is a mixture of interaction types −S + P + V, which in the one-dimensional case is the only completely antisymmetric type of interaction [2]. For the first two terms in Eq. (1) this spinor form is necessary; in the third term σμ×σμ can in principle be replaced by an arbitrary invariant operator Oj×Oj so that σμ×σμ has been kept here just for simplicity. Thus we are dealing with the one-dimensional analogue of the “universal interaction” of the type proposed by Feynman and Gell-Mann. The introduction of terms of the type ψσ¯ μ χ ψσ¯ μ χ into the Hamiltonian makes the problem much more complicated, and this case is not considered here. We now introduce a field ψ Φα = χ with the components ψ and χ. Then Eq. (1) can be rewritten in the form g1 g2 H = Φ¯ σμ τ1Φ Φ¯ σμ τ1Φ + Φ¯ σμ τ2Φ Φ¯ σμ τ2Φ μ 4 4 (2) g3 10 00 + Φ¯ σμ τ Φ Φ¯ σμ τ Φ ,τ= ,τ= . 2 1 2 1 00 2 01 April 5, 2013 16:24 WSPC/Trim Size: 9in x 6in for Proceedings 12f˙Anselm˙statya

528 A. A. Anselm

The matrices τi act on the “isotopic” index of the function Φα . The most general form of the vertex part is Γ= αik(τi×τk) (σμ ×σμ) , i, k μ

where αik is a set of scalar functions, and τi and τk are all possible two-rowed matrices. It can be shown, however, that the equations for Γ are satisﬁed by the following spinor form:b Γ= α1(τ1 ×τ2)+α2(τ2 ×τ2)+2α3(τ1 ×τ2) σμ ×σμ . (3) μ

A method for obtaining an integral equation for Γ in the asymptotic region p2 m2 has been developed by Dyatlov, Sudakov, and Ter- Matirosyan [4]. In the present case we have to deal with a situation entirely analogous to that considered in Ref. [2]. Carrying out some simple algebraic manipulations, we get the following system for the “lying” and “standing bricks” (the deﬁnition of these functions and some explanations about the equations are given in Ref. [2]):

L L

1 2 1 2 2 f , , (ξ)= − α , , (z) dz, ϕ , (ξ)= α , (z)+α (z) dz, 1 2 3 2π 1 2 3 1 2 2π 1 2 3 ξ ξ L 1 ϕ (ξ)= α (z)+α (z) α (z) dz, 3 2π 1 2 3 ξ p2 Λ2 αi = gi + fi + ϕi ,ξ=ln ,L=ln , (4) m2 m2

Λ is the maximum momentum, and all the momenta entering and leaving the vertex part are of the order of p. In Eq. (4) the Green’s function is taken equal to its zeroth approximation, since it is in general free from divergences [2]. From Eq. (4) it at once follows

b This is a consequence of the conservation law of the number of particles ψ and χ,which follows from the Hamiltonian (1). – A.A. May 10, 2013 13:46 WSPC/Trim Size: 9in x 6in for Proceedings 12f˙Anselm˙statya

Field Theory with Nonvanishing Renormalized Charge 529

that

L L 1 1 α (ξ)=g + α2(z) dz, α (ξ)=g + α2(z) dz, 1 1 2π 3 2 2 2π 3 ξ ξ (5) L 1 α (ξ)=g + α (z)+α (z) − α (z) α (z) dz. 3 3 2π 1 2 3 3 ξ

2. Solution of the Integral Equations Combining the ﬁrst and second equations of the system (5), we get the following system, which includes the third equation:

L f ξ λ 1 ϕ2 z dz, ( )= + π ( ) ξ (6) L 1 ϕ(ξ)=ν + f(z) − ϕ(z) ϕ(z) dz. 2π ξ

Here we have introduced the notation

f = α1 + α2 ,ϕ= α3 ,λ= g1 + g2 ,ν= g3 . (7)

Since the independent variable does not appear explicitly in Eq. (6), it is convenient first to try to find f as a function of ϕ . The first equation of the system (6) then has the form

ν dξ f λ 1 ϕ2 dϕ . = + π dϕ (8) ϕ

From the second equation it follows that dϕ ϕ = −(f − ϕ) , (9) dξ 2π April 5, 2013 16:24 WSPC/Trim Size: 9in x 6in for Proceedings 12f˙Anselm˙statya

530 A. A. Anselm

that is, ν ϕdϕ f(ϕ)=λ − 2 , (10) f(ϕ) − ϕ ϕ or df ϕ 2 . dϕ = f − ϕ (11) Equation (11) is a homogeneous equation; integrating it in the usual way, we easily get

(f − 2ϕ)(f + ϕ)2 =(λ − 2ν)(λ + ν)2 ≡ G3. (12)

Let us consider the important case G =0.Herewehaveeither (a) λ =2ν, g1 + g2 =2g3 , f =2ϕ, or else (b) λ = −ν, g1 + g2 = −g3 , f = −ϕ. In each case we can substitute ϕ,expressedintermsoff,inthe ﬁrst equation of (6); we thus easily get the following expressions for the vertex parts: 2ν ν (a) f(ξ)= ,ϕ(ξ)= , 1 − (ν/2π)(L − ξ) 1 − (ν/2π)(L − ξ)

g1 − g2 ν α1(ξ)= + , 2 1 − (ν/2π)(L − ξ)

g1 − g2 ν α2(ξ)=− + , 2 1 − (ν/2π)(L − ξ) −ν ν (13) (b) f(ξ)= ,ϕ(ξ)= , 1 − (ν/π)(L − ξ) 1+(ν/π)(L − ξ) ν g1 − g2 /2 α1(ξ)= − , 2 1+(ν/π)(L − ξ) ν g1 − g2 /2 α2(ξ)=− − . 2 1+(ν/π)(L − ξ) When ν = 0 we have for both sets of relations between the constants the results α1 = g1 , α2 = g2 , α3 = 0, in agreement with the results obtained in Ref. [2]. April 5, 2013 16:24 WSPC/Trim Size: 9in x 6in for Proceedings 12f˙Anselm˙statya

Field Theory with Nonvanishing Renormalized Charge 531

If g1 + g2 < 0, then for the usual reasons the renormalized charge goes to zero, but if g1+ g2 > 0 the zero charge does not appear. Fur- thermore, the connection between the renormalized and bare charges is given by the following relation (for example, in the case (a), see (13)):

ν g1 − g2 ν νc = ,g1c = + , 1 − (νL/2π) 2 1 − (νL/2π) (14) g1 − g2 ν g2c = − + , 2 1 − (νL/2π) and the expressions for the renormalized vertex parts have no non- physical pole: ν g − g ν ϕ ξ c ,αξ 1c 2c c , c( )= ν ξ 1c( )= + ν ξ 1+( c /2π) 2 1+( c /2π) g − g ν (15) α ξ − 1c 2c c . 2c( )= + ν ξ 2 1+( c /2π) Let us now go back to the determination of the functions f and ϕ in the general case G =(λ − 2ν)1/3(λ + ν)2/3 = 0. Equation (12) in principle makes it possible to express the function ϕ in terms of f, after which the first of the equations (6) reduces to a quadrature. We shall, however, proceed in a different way, which allows us to get the solution in a more compact form. We define F (ξ)bytherelation λ ν f ϕ + , + = F (16a) and then from Eq. (12) we get

f − 2ϕ =(λ − 2ν)F 2, (16b)

from which we have 2(λ + ν) 1 λ − 2ν f = + F 2, 3 F 3 (17) λ + ν 1 λ − 2ν ϕ = − F 2. 3 F 3 Substituting these expressions in the first equation of (6) and differ- entiating it with respect to ξ, we find a differential equation for F. April 5, 2013 16:24 WSPC/Trim Size: 9in x 6in for Proceedings 12f˙Anselm˙statya

532 A. A. Anselm

Separating the variables and integrating, we ﬁnd

F dx G 3α2 = L − ξ , x3 − α3 2π 1 1/3 λ + ν 1/ 2/ α = ,G= λ − 2ν 3 λ + ν 3, λ − 2ν (18) F dx 1 (F − α)2(1+ α + α2) √ 2F + α 3α2 = ln − 3arctan √ x3− α3 2 (F 2 + αF + α2)(1− α)2 α 3 1 √ 2+α + 3arctan √ . α 3

Together with the (17), Eq. (18), which implicitly determines F, gives the solution of our stated problem. We shall now show that the solution we have obtained has the property of normalizability, and shall carry out the renormalization program explicitly. We introduce the renormalized charges λc and νc as the values of the vertex parts f and ϕ when the incoming and outgoing momenta are real (p2 = −m2, ξ =0): λ ν λ − ν λ 2( + ) 1 2 F 2, c = + 0 3 F0 3 λ ν λ − ν ν + 1 − 2 F 2, c = 0 3 F0 3 (19) F 0 dx G 3α2 = L. x3 − α3 2π 1 From this we have λ − 2ν λ + ν =(λ + ν )F ,λ− 2ν = c c , (20) c c 0 F 2 0 and

G = Gc ,α= αc F0 . (21) April 5, 2013 16:24 WSPC/Trim Size: 9in x 6in for Proceedings 12f˙Anselm˙statya

Field Theory with Nonvanishing Renormalized Charge 533

These formulas enable us to eliminate from Eqs. (17) and (18) the renormalized charges and the logarithm of the cut-oﬀ L,namely, F dx G 3α2F 2 = − c ξ, c 0 x3 − α3F 3 π c 0 2 F0 2(λ + ν ) F λ − 2ν F 2 (22) f = c c 0 + c c , F F 2 3 3 0 λ + ν F λ − 2ν F 2 ϕ = c c 0 − c c . F F 2 3 3 0

Introducing the quantity Fc(ξ)=F (ξ)/F0 , we can verify that the renormalization invariants fc = f, ϕc = ϕ canbeexpressedinterms of the renormalized quantities only: λ ν λ − ν f ξ 2( c + c) 1 c 2 c F 2 , c( )= + c 3 Fc 3 λ ν λ − ν ϕ ξ c + c 1 − c 2 c F 2 . c( )= c 3 Fc 3 (23) F c dx G 3α2 = − c ξ. c x3 − α3 π c 2 1 We have still to examine the problem of the zero charge in the general case. For this purpose we rewrite Eq. (19), which deﬁnes the function F0 , in the following form: − α 2 α F α2F 2 √ α 1 (1 c) (1+ c 0 + c 0 ) − 2+√ c ln 2 2 3arctan 2 (1+ αc + α )(1− αcF0) α 3 c c (24) √ α F G 2+ √c 0 c L. + 3arctan = π αcF0 3 2

For L→∞ the right member of this equation goes to +∞ for Gc>0 c and to −∞ for Gc<0. The left member can go to +∞ if 1−αcF0→0. Thus for G>0, A>2ν the zero-charge situation does not arise, and

c α2F 2 α F → F If c 0 + c 0 +1 0, then 0 is complex and the theory is non-Hermitean. – A.A. April 5, 2013 16:24 WSPC/Trim Size: 9in x 6in for Proceedings 12f˙Anselm˙statya

534 A. A. Anselm

the bare charges approach the following limiting values [cf. Eq. (20)]: λ ν λ ν → c + c G ,λ− ν → λ − ν α2 G , + = c 2 ( c 2 c) c = c αc that is

λ → Gc ,ν→ 0 . (25) This limiting behavior can be understood in a qualitative way. All the divergence in the theory is due to the presence of the third term in the Hamiltonian (1) (cf. Ref. [2]). When this term is absent (ν =0,νc =0), λ requires no renormalization, λ=λ c . In the general case the renormalization of λ still turns out to be a ﬁnite one.

3. Conclusion Various attempts to construct a consistent physically useful ﬁeld theory with nonvanishing renormalized charge have so far been unsuccessful [5, 6]. Therefore the idea has been put forward recently that a consistent relativistically invariant Hermitean theory with a local interaction is impossible in principle. We have analyzed here an example of such a theory, though of course it is of no use for the description of physical phenomena. It seems to us that the very fact of the existence of such a scheme shows how complicated the problem is of proving rigorously the zero-charge result.

References 1. W. Thirring, Ann. of Phys. 3, 91 (1958) . 2. A. A. Anselm, Zh. Eksp. Teor. Fiz. 35, 1522 (1958) [Sov. Phys. JETP 8, 1065 (1959)] . 3. M. E. Maier and D. V. Shirkov, Joint Institute of Nuclear Research Preprint (1958) . 4. I.T. Diatlov, V.V Sudakov, and K.A. Ter-Martirosyan, Zh. Eksp. Teor. Fiz. 32, 767 (1957) [Sov. Phys. JETP 5, 631 (1957)] . 5. I.Ya. Pomeranchuk, V.V Sudakov, and K.A. Ter-Martirosyan, Phys. Rev. 103, 784 (1956) . 6. A.A. Abrikosov, A.D. Galanin, L.P. Gorkov, L.D. Landau, I.Ya. Pomeranchuk and K.A. Ter-Martirosyan, Phys. Rev. 111, 321 (1958) . May 15, 2013 10:51 WSPC/Trim Size: 9in x 6in for Proceedings 13˙Index

INDEX

Abramovsky 279 Ellis, John 435 Abrikosov 13, 50, 135 Esin 398 Agasyan 55 Alikhanov 36, 384, 389, 398 Feinberg 266 Amusya xix Fermi 423 Anisovich 442 Ferrel 340 Anselm, Alexei 355, 524, 526 Feynman 72, 134, 141, 421 Anselm, Ludmila 367 Filonov 169 Flerov 415 Badalyan 178 Fock 9, 172, 186 Belyaev 55, 67, 81 Fradkin 269 Berestetsky xv, 204, 382 Frenkel, A. 181, 284 Frenkel, Ya. 199 Berezinsky 338 Fuchs, Klaus 148, 149, 405 Bergelson 229 Fulde 340 Bogolyubov 42, 78, 408 Bolotovsky 223, 243 Gaidar 263 Boreskov 488 Gaillard, Mary K. 435 Breidenbach, Joanna 437 Galanin 13, 135 Bronshtein 55, 171 Galitsky 69, 76, 81, 98 Bruk 223 Galkin 229 Budker 81, 93, 135, 388, 395 Ganelin 228 Gell-Mann 134 Calogero 178 Gershtein 30, 123, 302, 399 Chirikov 394 Ginzburg 136, 223, 244 Chukovskaya 172 Goldman xix Gribov 192, 277, 437, 488 Danilov 215 Gross 355 Diakonov 355 Gurevich 149, 151 Di Bartini, Roberto Oros 408 Domokos 181, 189 Hawking 136, 281 Dokshitzer 285, 287, 442 Houtermans 425 Drobantseva-Landau xx, 24 Dykhne xix, 480 Imshennik 141

535 May 13, 2013 15:48 WSPC/Trim Size: 9in x 6in for Proceedings 13˙Index

536 Index

Ioﬀe 5, 135, 209, 279, 296, 381 Nyiri, J. 189, 285, 307 Ivanenko 45 Nyiri, P. 194, 437

Jenik 286 Okun 55, 83, 147, 382, 395, 426, 439, 444 Kallosh 269 Orlov, Yu. 118, 381, 445 Kaidalov 488 Ovchinnikov 332, 340, 345 Kamenev 345 Kancheli 279, 488 Peshkov 403 Kapitsa 3, 4, 26, 34, 383 Petrov, Yu. 139, 306 Khalatnikov 13, 50, 135 Pokrovsky 336, 465 Khodel 88 Polievktov-Nikoladze 70 Khodorkovsky 350 Poloz 245 Khriplovich 106, 135 Polyakov 114, 202, 362 Kirzhnits xvii, 223, 226 Pomeranchuk 117, 175, 278, 297, 386, Knizhnik 433 430 Krylov 340 Ponomarev 138, 140 Kobzarev 103 Pontecorvo 83, 281, 396, 399 Kolker 371 Potanin 226 Komarov 171 Puzikov 183 Korets 26, 32 Kurchatov 104, 129, 151, 164, 387, 404 Ratner 228 Kushner 372 Ritus 223, 246 Kvitko 229 Rudas, Serge 435 Rudik 14, 381 Landau 5, 116, 135, 164, 200, 228, 278, Rumer 22, 34, 411 297, 384, 465 Ryndin 174, 183 Larkin, Alexander 318 Larkin, Anatoly 74, 116, 313, 340 Sagdeev 336 Lifshitz 36, 39 Sakharov 74, 77, 103, 118, 257, 319 Linde 223, 266 Sapershtein 55 Lipatov 280, 290 Schmid 325 Shifman xiii, 203, 347, 428, 524 Markish 229 Shiryaeva 154 Mezentsev 391 Shmushkevich 277, 303 Migdal 55, 313, 336, 417 Shpatakovskaya 223 Miller 244 Silin 244 Mochan 367 Simonov 178, 204, 431 Sivashinsky 157 Nambu 116 Sliv 86 Neveu 355 Smilga 207 Nevzorov 212, 219 Smorodindkaya 163, 219 May 13, 2013 15:48 WSPC/Trim Size: 9in x 6in for Proceedings 13˙Index

Index 537

Smorodindky 163, 171, 174, 411 Vainshtein 299, 434 Solzhenitsyn 261 Vaks 101, 116, 314, 336 Sudakov 48, 130, 200, 391 Varlamov 344 Suranyi 181 Vilenkin 184 Voronov 249 Tamm 243, 248, 252 Ter-Martirosyan xv, 199, 277, 303, 488 Winternitz 183 ’t Hooft 269 Tretyakov, Evgeny 393 Zaitsev 215 Tsvelik 349 Zeldovich 40, 103, 106, 123, 155, 288 Tukhachevsky 235 Tupolev 411 Tyutin 269