Operator Algebras and Applications, Volume 38-Part 1
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A Short Survey of Cyclic Cohomology
Clay Mathematics Proceedings Volume 10, 2008 A Short Survey of Cyclic Cohomology Masoud Khalkhali Dedicated with admiration and affection to Alain Connes Abstract. This is a short survey of some aspects of Alain Connes’ contribu- tions to cyclic cohomology theory in the course of his work on noncommutative geometry over the past 30 years. Contents 1. Introduction 1 2. Cyclic cohomology 3 3. From K-homology to cyclic cohomology 10 4. Cyclic modules 13 5. Thelocalindexformulaandbeyond 16 6. Hopf cyclic cohomology 21 References 28 1. Introduction Cyclic cohomology was discovered by Alain Connes no later than 1981 and in fact it was announced in that year in a conference in Oberwolfach [5]. I have reproduced the text of his abstract below. As it appears in his report, one of arXiv:1008.1212v1 [math.OA] 6 Aug 2010 Connes’ main motivations to introduce cyclic cohomology theory came from index theory on foliated spaces. Let (V, ) be a compact foliated manifold and let V/ denote the space of leaves of (V, ).F This space, with its natural quotient topology,F is, in general, a highly singular spaceF and in noncommutative geometry one usually replaces the quotient space V/ with a noncommutative algebra A = C∗(V, ) called the foliation algebra of (V,F ). It is the convolution algebra of the holonomyF groupoid of the foliation and isF a C∗-algebra. It has a dense subalgebra = C∞(V, ) which plays the role of the algebra of smooth functions on V/ . LetA D be a transversallyF elliptic operator on (V, ). The analytic index of D, index(F D) F ∈ K0(A), is an element of the K-theory of A. -
April 2010 Contents
International Association of Mathematical Physics News Bulletin April 2010 Contents International Association of Mathematical Physics News Bulletin, April 2010 Contents Reflections on the IAMP Geography 3 Aharonov-Bohm & Berry Phase Anniversaries 50/25 5 The 25th anniversary of the founding of HARL 8 An interview with Huzihiro Araki 10 Shing-Tung Yau the Wolf Prize laureate 2010 in Mathematics 14 News from the IAMP Executive Committee 22 A new associated member: PIMS 26 Bulletin editor Valentin Zagrebnov Editorial board Evans Harrell, Masao Hirokawa, David Krejˇciˇr´ık, Jan Philip Solovej Contacts [email protected] http://www.iamp.org Cover photo (courtesy of Professor A.Tonomura): From double-slit experiment to the Aharonov-Bohm effect. See a comment at the end of the page 7. The views expressed in this IAMP News Bulletin are those of the authors and do not necessary represent those of the IAMP Executive Committee, Editor or Editorial board. Any complete or partial performance or reproduction made without the consent of the author or of his successors in title or assigns shall be unlawful. All reproduction rights are henceforth reserved, mention of the IAMP News Bulletin is obligatory in the reference. (Art.L.122-4 of the Code of Intellectual Property). 2 IAMP News Bulletin, April 2010 Editorial Reflections on the IAMP Geography by Pavel Exner (IAMP President) The topic of today’s meditation was inspired by complaints of American colleagues about the shaky position our discipline enjoys in the U.S. True, such woes are ubiquitous since com- petition for resources in science was and will always be tough. -
Perturbative Algebraic Quantum Field Theory
Perturbative algebraic quantum field theory Klaus Fredenhagen Katarzyna Rejzner II Inst. f. Theoretische Physik, Department of Mathematics, Universität Hamburg, University of Rome Tor Vergata Luruper Chaussee 149, Via della Ricerca Scientifica 1, D-22761 Hamburg, Germany I-00133, Rome, Italy [email protected] [email protected] arXiv:1208.1428v2 [math-ph] 27 Feb 2013 2012 These notes are based on the course given by Klaus Fredenhagen at the Les Houches Win- ter School in Mathematical Physics (January 29 - February 3, 2012) and the course QFT for mathematicians given by Katarzyna Rejzner in Hamburg for the Research Training Group 1670 (February 6 -11, 2012). Both courses were meant as an introduction to mod- ern approach to perturbative quantum field theory and are aimed both at mathematicians and physicists. Contents 1 Introduction 3 2 Algebraic quantum mechanics 5 3 Locally covariant field theory 9 4 Classical field theory 14 5 Deformation quantization of free field theories 21 6 Interacting theories and the time ordered product 26 7 Renormalization 26 A Distributions and wavefront sets 35 1 Introduction Quantum field theory (QFT) is at present, by far, the most successful description of fundamental physics. Elementary physics , to a large extent, explained by a specific quantum field theory, the so-called Standard Model. All the essential structures of the standard model are nowadays experimentally verified. Outside of particle physics, quan- tum field theoretical concepts have been successfully applied also to condensed matter physics. In spite of its great achievements, quantum field theory also suffers from several longstanding open problems. The most serious problem is the incorporation of gravity. -
Arxiv:1306.6519V5 [Math-Ph] 13 May 2014 5.1 Vacuum State
Construction of KMS States in Perturbative QFT and Renormalized Hamiltonian Dynamics Klaus Fredenhagen and Falk Lindner II. Institute for Theoretical Physics, University of Hamburg [email protected], [email protected] Abstract We present a general construction of KMS states in the framework of pertur- bative algebraic quantum field theory (pAQFT). Our approach may be understood as an extension of the Schwinger-Keldysh formalism. We obtain in particular the Wightman functions at positive temperature, thus solving a problem posed some time ago by Steinmann [55]. The notorious infrared divergences observed in a di- agrammatic expansion are shown to be absent due to a consequent exploitation of the locality properties of pAQFT. To this avail, we introduce a novel, Hamiltonian description of the interacting dynamics and find, in particular, a precise relation between relativistic QFT and rigorous quantum statistical mechanics. Dedicated to the memory of Othmar Steinmann ∗27.11.1932 †11.03.2012 Contents 1 Introduction 2 2 Perturbed dynamics 4 3 Time averaged Hamiltonian description of the dynamics 7 4 KMS states for the interacting dynamics: General discussion 13 4.1 The case of finite volume . 13 4.2 The case of infinite volume . 17 5 Cluster properties of the massive scalar field 19 arXiv:1306.6519v5 [math-ph] 13 May 2014 5.1 Vacuum state . 20 5.2 Thermal equilibrium states . 23 6 Conclusion 29 A Proof of the KMS condition 31 1 B Propositions for the adiabatic limit 34 1 Introduction According to the standard model of cosmology, the early universe was for some time in an equilibrium state with high temperature. -
Dark Matter and Weak Signals of Quantum Spacetime
PHYSICAL REVIEW D 95, 065009 (2017) Dark matter and weak signals of quantum spacetime † ‡ Sergio Doplicher,1,* Klaus Fredenhagen,2, Gerardo Morsella,3, and Nicola Pinamonti4,§ 1Dipartimento di Matematica, Università di Roma “La Sapienza”, Piazzale Aldo Moro 5, I-00185 Roma, Italy 2II Institut für Theoretische Physik, Universität Hamburg, D-22761 Hamburg, Germany 3Dipartimento di Matematica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica, I-00133 Roma, Italy 4Dipartimento di Matematica, Università di Genova, Via Dodecaneso 35, I-16146 Genova, Italy, and INFN Sezione di Genova, Genova, Italy (Received 29 December 2016; published 13 March 2017) In physically motivated models of quantum spacetime, a Uð1Þ gauge theory turns into a Uð∞Þ gauge theory; hence, free classical electrodynamics is no longer free and neutral fields may have electromagnetic interactions. We discuss the last point for scalar fields, as a way to possibly describe dark matter; we have in mind the gravitational collapse of binary systems or future applications to self-gravitating Bose-Einstein condensates as possible sources of evidence of quantum gravitational phenomena. The effects considered so far, however, seem too faint to be detectable at present. DOI: 10.1103/PhysRevD.95.065009 I. INTRODUCTION but their superpositions would, in general, not be—they would lose energy in favor of mysterious massive modes One of the main difficulties of present-day physics is the (see also [6]). lack of observation of quantum aspects of gravity. Quantum A naive computation showed, by that mechanism, that a gravity has to be searched without a guide from nature; the monochromatic wave train passing through a partially observed universe must be explained as carrying traces of reflecting mirror should lose, in favor of those ghost quantum gravitational phenomena in the only “laboratory” modes, a fraction of its energy—a very small fraction, suitable to those effects, i.e., the universe itself a few unfortunately, of the order of one part in 10−130 [5]. -
Annals of K-Theory Vol. 1 (2016)
ANNALSOF K-THEORY Paul Balmer Spencer Bloch vol. 1 no. 4 2016 Alain Connes Guillermo Cortiñas Eric Friedlander Max Karoubi Gennadi Kasparov Alexander Merkurjev Amnon Neeman Jonathan Rosenberg Marco Schlichting Andrei Suslin Vladimir Voevodsky Charles Weibel Guoliang Yu msp A JOURNAL OF THE K-THEORY FOUNDATION ANNALS OF K-THEORY msp.org/akt EDITORIAL BOARD Paul Balmer University of California, Los Angeles, USA [email protected] Spencer Bloch University of Chicago, USA [email protected] Alain Connes Collège de France; Institut des Hautes Études Scientifiques; Ohio State University [email protected] Guillermo Cortiñas Universidad de Buenos Aires and CONICET, Argentina [email protected] Eric Friedlander University of Southern California, USA [email protected] Max Karoubi Institut de Mathématiques de Jussieu – Paris Rive Gauche, France [email protected] Gennadi Kasparov Vanderbilt University, USA [email protected] Alexander Merkurjev University of California, Los Angeles, USA [email protected] Amnon Neeman amnon.Australian National University [email protected] Jonathan Rosenberg (Managing Editor) University of Maryland, USA [email protected] Marco Schlichting University of Warwick, UK [email protected] Andrei Suslin Northwestern University, USA [email protected] Vladimir Voevodsky Institute for Advanced Studies, USA [email protected] Charles Weibel (Managing Editor) Rutgers University, USA [email protected] Guoliang Yu Texas A&M University, USA [email protected] PRODUCTION Silvio Levy (Scientific Editor) [email protected] Annals of K-Theory is a journal of the K-Theory Foundation(ktheoryfoundation.org). The K-Theory Foundation acknowledges the precious support of Foundation Compositio Mathematica, whose help has been instrumental in the launch of the Annals of K-Theory. -
Lie Groupoids, Pseudodifferential Calculus and Index Theory
Lie groupoids, pseudodifferential calculus and index theory by Claire Debord and Georges Skandalis Université Paris Diderot, Sorbonne Paris Cité Sorbonne Universités, UPMC Paris 06, CNRS, IMJ-PRG UFR de Mathématiques, CP 7012 - Bâtiment Sophie Germain 5 rue Thomas Mann, 75205 Paris CEDEX 13, France [email protected] [email protected] Abstract Alain Connes introduced the use of Lie groupoids in noncommutative geometry in his pio- neering work on the index theory of foliations. In the present paper, we recall the basic notion involved: groupoids, their C∗-algebras, their pseudodifferential calculus... We review several re- cent and older advances on the involvement of Lie groupoids in noncommutative geometry. We then propose some open questions and possible developments of the subject. Contents 1 Introduction 2 2 Lie groupoids and their operators algebras 3 2.1 Lie groupoids . .3 2.1.1 Generalities . .3 2.1.2 Morita equivalence of Lie groupoids . .7 2.2 C∗-algebra of a Lie groupoid . .7 2.2.1 Convolution ∗-algebra of smooth functions with compact support . .7 2.2.2 Norm and C∗-algebra . .8 2.3 Deformation to the normal cone and blowup groupoids . .9 2.3.1 Deformation to the normal cone groupoid . .9 2.3.2 Blowup groupoid . 10 3 Pseudodifferential calculus on Lie groupoids 11 3.1 Distributions on G conormal to G(0) ........................... 12 3.1.1 Symbols and conormal distributions . 12 3.1.2 Convolution . 15 3.1.3 Pseudodifferential operators of order ≤ 0 ..................... 16 3.1.4 Analytic index . 17 3.2 Classical examples . -
Arthur Strong Wightman (1922–2013)
Obituary Arthur Strong Wightman (1922–2013) Arthur Wightman, a founding father of modern mathematical physics, passed away on January 13, 2013 at the age of 90. His own scientific work had an enormous impact in clar- ifying the compatibility of relativity with quantum theory in the framework of quantum field theory. But his stature and influence was linked with an enormous cadre of students, scientific collaborators, and friends whose careers shaped fields both in mathematics and theoretical physics. Princeton has a long tradition in mathematical physics, with university faculty from Sir James Jeans through H.P. Robertson, Hermann Weyl, John von Neumann, Eugene Wigner, and Valentine Bargmann, as well as a long history of close collaborations with colleagues at the Institute for Advanced Study. Princeton became a mecca for quantum field theorists as well as other mathematical physicists during the Wightman era. Ever since the advent of “axiomatic quantum field theory”, many researchers flocked to cross the threshold of his open office door—both in Palmer and later in Jadwin—for Arthur was renowned for his generosity in sharing ideas and research directions. In fact, some students wondered whether Arthur might be too generous with his time helping others, to the extent that it took time away from his own research. Arthur had voracious intellectual appetites and breadth of interests. Through his interactions with others and his guidance of students and postdocs, he had profound impact not only on axiomatic and constructive quantum field theory but on the de- velopment of the mathematical approaches to statistical mechanics, classical mechanics, dynamical systems, transport theory, non-relativistic quantum mechanics, scattering the- ory, perturbation of eigenvalues, perturbative renormalization theory, algebraic quantum field theory, representations of C⇤-algebras, classification of von Neumann algebras, and higher spin equations. -
The Top Mathematics Award
Fields told me and which I later verified in Sweden, namely, that Nobel hated the mathematician Mittag- Leffler and that mathematics would not be one of the do- mains in which the Nobel prizes would The Top Mathematics be available." Award Whatever the reason, Nobel had lit- tle esteem for mathematics. He was Florin Diacuy a practical man who ignored basic re- search. He never understood its impor- tance and long term consequences. But Fields did, and he meant to do his best John Charles Fields to promote it. Fields was born in Hamilton, Ontario in 1863. At the age of 21, he graduated from the University of Toronto Fields Medal with a B.A. in mathematics. Three years later, he fin- ished his Ph.D. at Johns Hopkins University and was then There is no Nobel Prize for mathematics. Its top award, appointed professor at Allegheny College in Pennsylvania, the Fields Medal, bears the name of a Canadian. where he taught from 1889 to 1892. But soon his dream In 1896, the Swedish inventor Al- of pursuing research faded away. North America was not fred Nobel died rich and famous. His ready to fund novel ideas in science. Then, an opportunity will provided for the establishment of to leave for Europe arose. a prize fund. Starting in 1901 the For the next 10 years, Fields studied in Paris and Berlin annual interest was awarded yearly with some of the best mathematicians of his time. Af- for the most important contributions ter feeling accomplished, he returned home|his country to physics, chemistry, physiology or needed him. -
17 Oct 2019 Sir Michael Atiyah, a Knight Mathematician
Sir Michael Atiyah, a Knight Mathematician A tribute to Michael Atiyah, an inspiration and a friend∗ Alain Connes and Joseph Kouneiher Sir Michael Atiyah was considered one of the world’s foremost mathematicians. He is best known for his work in algebraic topology and the codevelopment of a branch of mathematics called topological K-theory together with the Atiyah-Singer index theorem for which he received Fields Medal (1966). He also received the Abel Prize (2004) along with Isadore M. Singer for their discovery and proof of the index the- orem, bringing together topology, geometry and analysis, and for their outstanding role in building new bridges between mathematics and theoretical physics. Indeed, his work has helped theoretical physicists to advance their understanding of quantum field theory and general relativity. Michael’s approach to mathematics was based primarily on the idea of finding new horizons and opening up new perspectives. Even if the idea was not validated by the mathematical criterion of proof at the beginning, “the idea would become rigorous in due course, as happened in the past when Riemann used analytic continuation to justify Euler’s brilliant theorems.” For him an idea was justified by the new links between different problems which it illuminated. Our experience with him is that, in the manner of an explorer, he adapted to the landscape he encountered on the way until he conceived a global vision of the setting of the problem. Atiyah describes here 1 his way of doing mathematics2 : arXiv:1910.07851v1 [math.HO] 17 Oct 2019 Some people may sit back and say, I want to solve this problem and they sit down and say, “How do I solve this problem?” I don’t. -
2003 Jean-Pierre Serre: an Overview of His Work
2003 Jean-Pierre Serre Jean-Pierre Serre: Mon premier demi-siècle au Collège de France Jean-Pierre Serre: My First Fifty Years at the Collège de France Marc Kirsch Ce chapitre est une interview par Marc Kirsch. Publié précédemment dans Lettre du Collège de France,no 18 (déc. 2006). Reproduit avec autorisation. This chapter is an interview by Marc Kirsch. Previously published in Lettre du Collège de France, no. 18 (déc. 2006). Reprinted with permission. M. Kirsch () Collège de France, 11, place Marcelin Berthelot, 75231 Paris Cedex 05, France e-mail: [email protected] H. Holden, R. Piene (eds.), The Abel Prize, 15 DOI 10.1007/978-3-642-01373-7_3, © Springer-Verlag Berlin Heidelberg 2010 16 Jean-Pierre Serre: Mon premier demi-siècle au Collège de France Jean-Pierre Serre, Professeur au Collège de France, titulaire de la chaire d’Algèbre et Géométrie de 1956 à 1994. Vous avez enseigné au Collège de France de 1956 à 1994, dans la chaire d’Algèbre et Géométrie. Quel souvenir en gardez-vous? J’ai occupé cette chaire pendant 38 ans. C’est une longue période, mais il y a des précédents: si l’on en croit l’Annuaire du Collège de France, au XIXe siècle, la chaire de physique n’a été occupée que par deux professeurs: l’un est resté 60 ans, l’autre 40. Il est vrai qu’il n’y avait pas de retraite à cette époque et que les pro- fesseurs avaient des suppléants (auxquels ils versaient une partie de leur salaire). Quant à mon enseignement, voici ce que j’en disais dans une interview de 19861: “Enseigner au Collège est un privilège merveilleux et redoutable. -
Quantum Field Theory: Where We Are 3
Quantum Field Theory: Where We Are Klaus Fredenhagen1, Karl-Henning Rehren2, and Erhard Seiler3 1 II. Institut f¨ur Theoretische Physik, Universit¨at Hamburg, 22761 Hamburg, Germany [email protected] 2 Institut f¨ur Theoretische Physik, Universit¨at G¨ottingen, 37077 G¨ottingen, Germany [email protected] 3 Max-Planck-Institut f¨ur Physik, 80805 M¨unchen, Germany [email protected] Summary. We comment on the present status, the concepts and their limitations, and the successes and open problems of the various approaches to a relativistic quantum theory of elementary particles, with a hindsight to questions concerning quantum gravity and string theory. arXiv:hep-th/0603155v1 20 Mar 2006 1 Introduction Quantum field theory aims at a synthesis of quantum physics with the prin- ciples of classical field theory, in particular the principle of locality. Its main Contribution to: An Assessment of Current Paradigms in the Physics of Fun- damental Phenomena, to be published by Springer Verlag (2006). 2 Klaus Fredenhagen, Karl-Henning Rehren, and Erhard Seiler realm is the theory of elementary particles where it led to a far reaching under- standing of the structure of physics at subatomic scales with an often amaz- ingly good agreement between theoretical predictions and experiments. Typ- ical observables in QFT are current densities or energy flow densities which correspond to what is measured in particle physics detectors. The original aim of QFT was to compute expectation values and correlation functions of the observables, and to derive scattering cross sections in high-energy physics. In the course of development, QFT has widened its scope, notably towards the inclusion of gravitational interactions.