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Asia Pacific Newsletter

March 2016 Volume 5 • Number 1 worldscinet.com/appn

Takaaki Kajita 2015 Physics Nobel Laureate

published by Institute of Advanced Studies, Nanyang Technological University (IAS@NTU) and South East Asia Association (SEATPA)

South East Asia Theoretical Physics Association Asia Pacific Physics Newsletter

March 2016 • Volume 5 • Number 1 A publication of the IAS@NTU Singapore and SEATPA

Asia Pacific Physics Newsletter publishes articles reporting frontier discoveries in EDITORIAL physics, research highlights, and news to facilitate interaction, collaboration and 3 cooperation among in Asia Pacific physics community. PEOPLE Editor-in-Chief 4 “Observing the Distant ” — Interview with Kok Khoo Phua Nobel Laureate Prof Associate Editor-in-Chief “Discovering the W and Z ” — Interview with Swee Cheng Lim Nobel Laureate Prof SEATPA Committee Christopher C Bernido Phil Chan Leong Chuan Kwek Choy Heng Lai Swee Cheng Lim Ren Bao Liu Hwee Boon Low Anh Ký Nguyên Choo Hiap Oh OPINION AND COMMENTARY Kok Khoo Phua 10 China’s Great Scientific Leap Forward: Completion of a Roh Suan Tung Preecha Yupapin planned ‘Great Collider’ would transform Hishamuddin Zainuddin Freddy Zen

Editorial Team NEWS Sen Mu 12 CityU’s Institute for Advanced Study will Champion Bold New Han Sun Chi Xiong Research Initiatives Case made for 'Ninth Planet' Graphic Designers Chuan Ming Loo Erin Ong

Cover Photo: " 5171- 2015" by Bengt Nyman - Own work. Licensed under CC BY-SA 4.0 via Commons - https://commons. wikimedia.org/wiki/File:Takaaki_ Kajita_5171-2015.jpg#/media/ File:Takaaki_Kajita_5171-2015.jpg High Temperature Superconducting Magnetic Lens Asia Pacific Physics Newsletter (APPN) Developed at IHEP is published jointly by Institute of Advanced From the Jade Rabbit to the Monkey King Studies, Nanyang Technological University (IAS@NTU) and South East Asia Theoretical New Structurally Perfect Candidate First Proposed for Physics Association (SEATPA) Quantum Spin Liquids IAS@NTU and SEATPA Address: 60 Nanyang View #02-18 ARTICLES Singapore 639673 Tel: +65 6513 7660 22 Statistical Physics in the Oeuvre of Chen Ning Yang Fax: +65 6794 4941 seatpa.org and the Origin of Mass ntu.edu.sg/ias Superfluidity and Symmetry Breaking— An Anderson Living APPN is distributed by Legacy World Scientific Publishing Co. Pte. Ltd. Takaaki Kajita — 2015 Physics Nobel Laureate Address: 5 Toh Tuck Link Oscillations: Discovery, Current Status, Future Singapore 596224 Directions Tel: +65 6466 5775 Fax: +65 5467 7667 worldscientific.com

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Authors CONFERENCE CALENDAR APPN welcomes articles with general 64 Upcoming Conferences in the Asia Pacific Region interests to the physics community. To recommend or contribute news, articles, history, book reviews, please write to: JOBS [email protected] 68 SOCIETIES The views expressed in this Newsletter 75 List of Physical Societies in the Asia Pacific Region belong to the authors, and do not necessarily represent those of the publishers.

Print ISSN: 2251-158X Online ISSN: 2251-1598

MCI(P)085/10/2015 EDITORIAL

This is the first issue of the Asia Pacific Physics Newsletter (APPN) in 2016. We plan to publish 3 to 4 issues this year, and continue to bring you important and latest discoveries and headline news in physics. In 2015, the physics society mourned the loss of Professor Yoichiro Nambu (1921-2015), a Japanese-born American Nobel Laureate, known for his contributions in the mechanism of spontaneous broken symmetry. Professor Thomas W. B. Kibble has shared his memories of Nambu in this issue, some never told before. In 2015, we also witnessed another Japanese Takaaki Kajita winning the for the discovery of neutrino oscillations. Professor Ngee-Pong Chang’s contributing article focuses on the importance of Professor Kajita’s works on neutrino oscillations, as well as the roles that Asian physicists play on the frontier of neutrino physics.

Also in other fields of physics, Asian countries have gained some international attention. Professors and discuss China’s scientific leap forward and how the completion of a planned ‘Great Collider’ could transform particle physics. [The article was first published in Wall Street Journal in September 2015]. As you can see in the News section, China has recently launched a satellite, the Particle Explorer for the detection of dark matter in our galaxy.

Let us not forget and the accelerating expansion of our ! We present the interview with Nobel Laureate Professor Brian Schmidt, who discovered the accelerating expansion of the universe through observations of distant supernovae. Back to great accelerators, another interview with Nobel Laureate Professor Carlo Rubbia highlights his work that led to the discovery of the W and Z bosons at CERN.

In this issue, you will also find brilliant articles like “Statistical Physics in the Oeuvre of Chen Ning Yang” by Professor and “Superfluidity and Symmetry Breaking— An Anderson Living Legacy” by Professor . The recently founded Institute of Advanced Study at City University of Hong Kong is also briefly introduced in the News. As always, we hope you enjoy reading this issue of APPN and give us feedback and suggestions!

Editor in Chief

Kok Khoo Phua President, South East Asia Theoretical Physics Association Director, Institute of Advanced Studies, Nanyang Technological University

March 2016, Volume 5 No 1 3 PEOPLE

“Observing the Distant Supernova” Nobel Laureate Prof Brian Schmidt

Brian Schmidt Research School of and at the Australian National University

Professor Brian Paul Schmidt is the 2011 Nobel Prize Laureate in Physics and is currently the Vice-Chancellor of the Australian National University. He was previously a Distin- guished Professor, Australian Research Council Laureate Fellow and astrophysicist at the University’s Mount Stromlo Observatory and Research School of Astronomy and Astrophysics. Professor Schmidt was awarded many notable awards such as the , the , and shared both the 2006 in Astronomy and the 2011 with and “for the discovery of the accelerating expansion of the Universe through observations of distant super- novae”. He was elected as a Fellow of the Royal Society in 2012.

From Wikipedia, we know that your father is a fishery to be great. A good personal relationship is also important. biologist. Do you think your father had a positive influ- More than that, your project must be interesting to you. In ence on you for you to become a scientist? my case, I chose where to go because I liked the supervisor, and he was very well known. But I didn’t like his project, so Yes. When I was a kid, my mother had to work a bit, and I talked with many people and looked for ideas. This one my father was still in his PhD. My father often babysat me came out and I knew that was what I wanted to do. Then while he was doing his research. From the earliest days I can one week later, I talked to my supervisor about the project remember, I had wanted to become a scientist, because I can I’m interested in. He thought the project I proposed was see how my father loved what he did. Absolutely, my father is actually better than the one he assigned to me. If you have the person who made me want to be a scientist. In the same some projects you are interested in, you could talk to your way, I help my sons. One of my sons wants to be a scientist, supervisor. As long as it’s reasonable, he will allow you to and the other one definitely does not want to be one. change. Talking about PhDs, would you give some suggestions Would you like to share with us how you found the about decisions about PhD? amazing people to form a group? The best way to make the best decision is by talking to people. Those are the people I worked with during my PhD. When Firstly, you need to find the correct person. People like me we realized it was the right time to do the project, we formed are very busy and may not be the best supervisor. (Joke) a group. The first person we invited was the one from Chile. The right supervisor must be someone who you respect, We also invited other people based on their expertise. Nick are interested in and someone who is also interested in you. was still doing another project with the other team. I had They must also be personable and have a good track record. time and energy, so he let me be the lead despite my young Track record is really important; they give you the resources age of 27.

4 Asia Pacific Physics Newsletter PEOPLE

Where is the fund from for your group? Can you share the experiences in leading the High-Z team and collaborating with Professor Adam Reiss, as We didn’t have much money when we started; we did it very well as competing with Professor Saul Perlmutter’s team cheaply. Most Nobel prizes don’t involve lots of money, but “Supernova Project”? are done when people are young, they have interest and energy. There is a lot of history here. They were a group of particle physicists. We were studying supernovae. They put a huge Were there any women in your team? amount of effort from 1988 to 1994, but didn’t discover anything. There were no women in our team. Within research on super- However, in 1994, a few things changed. A group in nova, there was literally one woman working in supernova Chile discovered how to make supernovae accurate distance area, who was in the other team. It was male dominated and indicators. That was the key thing. And Saul Perlmutter, is still male dominated. after six years, figured out how to discover the distance of When I arrived in Mount Stromlo, there was only one supernovae, that was the second thing, and the third thing female student out of 26. Now the number has increased to was the invention of Hubble Space telescope. Although 15 out of 30 in 2014. So the field has changed, for the better. finding supernovae is hard, once I knew Prof Saul Perlmutter That is an embarrassment that I’m trying to rectify. It’s getting could do that, I know we could do that too. We considered better. But we still have a long way to go. the option to work with Saul’s group, but we completely disagreed with each other on how to do things. So we had Compared to males, what do you think about females’ our own group, and I took the responsibility to write the competency to do science? software. It was not as good as we needed. The first year I see there are differences. The differences are not in your was really difficult for us. However, we were united, and the ability to do science, but in academic structure. Women can year was really intense. Three years later, we got the funny absolutely do a great job in science. There was a young female result that universe is accelerating. Saul’s team published a who was an undergraduate in our group, now she is one of paper in the middle of 1997, giving the results which were the great astronomers in Harvard. There are also other great sensible but totally different from ours. However, later they women in our field. published another paper and the data was the same as ours. However, there are some issues that affect both women Finally both of us made the same conclusion indepen- and men, but they affect women preferentially. I have a post dently. Despite the time issue, I think we both deserve this doc working one day a week and she is great. But when she prize. I also think that competition is actually good, to help goes on to the job market, she has all that time off spent on us work fast and check our results. babies and families; that is really difficult to account for, though we are getting better at it. Early this year the BICEP2 collaboration announced What we are looking at is not only how many publications that BICEP2 had made the first detection of the so-called they have, you have to figure out how much time this person B-mode polarization, a possible signature of in has worked, because what you care about is not what they the very early Universe and the existence of gravitational have done in the past when you hire them, but what they will wave. However the measurement from the team do in the future. Penalizing someone who just had a baby so suggests that the signal from dust scattering has the she works part time is not reasonable. same strength as that reported from BICEP2. Can you Due to this issue, it does happen in that 60 per comment on the BICEP2 detection? It is interesting to cent of biology undergraduates and 60 per cent of post docs notice that the media coverage for the BICEP2 detection are women, but only 30 per cent of biology professors are and your 1998 discovery seem to be a little different. women. Academia is male-focused. I am working very hard It’s a really interesting question. I am more sympathetic to on this issue in Australia. We cannot afford to have half the their situation than some, but I do think that they probably talent run off. We need bright people to do science, but the made a couple of mistakes. In 1998 we presented our work at bright women in Australia are usually doing law or medicine a conference at the end of February as we were submitting our so we need to fix this, it’s a big problem for us.

March 2016, Volume 5 No 1 5 PEOPLE paper to the journal. We did not do a press release, the science the or not, I don’t believe that god came before the media got on to it and made a big splash for us. We didn’t try big bang, but I cannot tell you god didn’t come before the to control the media or maximize the media coverage, yet we big bang; it’s not a question I can answer. still got big coverage by CNN. Did we manage it correctly? I For the people who are fundamentalist in religion and think we did, because we didn’t ever say “a discovery”, we said do not believe in scientific reasoning at all, there is almost “evidence for”. The BICEP guys didn’t say “evidence for”. They nothing you can do. Maybe you could tell them where they said “a discovery”. They said we nailed this. They thought used science in daily life. they had, so that’s the problem. They genuinely thought they cleanly measured the signal and had it dead to rights. If you What is your daily life like now? Is there any big change have a discovery that you believe is absolutely not going to after winning the Nobel Prize? go away, what they did was reasonable. The problem is that Yes. When you win the Nobel Prize, your voice becomes a they were wrong, so they didn’t have it dead to rights. They million times louder than it was. You get to meet the rich had miscalculated the importance of the dust. So what they and famous; your voice is amplified. One of the things I’m did is fine if they had the detection, but they screwed it up. pleased about was that people who know me don’t treat me People said in hindsight that they shouldn’t have done what differently. However, those people who didn’t know me do they did, but this is because they made a scientific mistake. think of me differently. This is a little bit frustrating because That is a tough call. People also said that they shouldn’t have whenever I meet new people, a Nobel Prize winner is always announced the discovery, but should we not have announced their first impression. the Higgs discovery? It is a discovery because they were sure Having a huge voice is empowering, but also scary. There that it won’t go away. That’s the difficulty in this one. They are certain things I can’t talk about. When I express my honestly thought that they had made a scientific discovery point of view on something, I get lots of attention. If I get a and they may well have. If this is real, it is huge. When I speeding ticket, it will be on the newspaper. (Joke) I have to saw their result, I thought that was interesting, and knew be very careful when expressing my own feelings. I can say immediately that they only looked at one frequency, and dust some problems that everyone more or less agrees with, like is going to be an issue for them. I have to admit that I was “women should be treated as equally as men”. However, for concerned. I was with (a dust analysis expert) climate change, I don’t talk about my own view, I can only three days later in Europe and I talked with him about the tell them the opinions from academia. problem, then I became very concerned. The mistake they I have to be careful, since the funding situation is tricky in made is that they did not have a dust expert. In my case every Australia. I could get lots of funds for astronomy, but I choose time we had something I didn’t understand, I brought an not to do that, because I think I have a responsibility to all expert in to make sure that we had that base covered, and of science. But that is hard, my field is under huge pressure that is why we had a theorist in our group. We had every right now, and many people want me to fix it. But if I fix it, base covered but they didn’t. It’s a small mistake and in the the rest of the physicists would get hurt. That’s challenging. end may cost them dearly. But that is the way science is done. That’s the way cookie crumbles. I want to emphasize, Would you share with us about your hobbies (on winery if I had to bet, I think their results are going to go away and and cooking)? I have bet with Lawrence Krauss. Though I would be glad to be wrong on this one, with a 25 per cent chance. I hope I I still enjoy my hobbies; I cook several days a week, and travel am overly pessimistic and I hope they are right. to the winery. I think having something you enjoy to do is very important. Scientists are usually too addicted to work. How do you communicate your studies on cosmology, If you are in a relationship with someone or if you have a your understanding about the universe, with people who family, they need you, and you need them. It’s very easy to have religions in situations like public lectures? work too much and ignore other parts of life. If all of one’s energy is devoted to science or work, he or she may have What I do is that I don’t try answering a question that is not nothing except work. When I describe to my students why scientific. There is no evidence for me to believe in god but they should not work too hard, I said that talent, the ability I’m also respectful of the fact that science cannot answer to do things in science, is maximized when you work under everything. If someone asks me whether God came before a normal load, say 35 to 45 hours a week. For me, if I work

6 Asia Pacific Physics Newsletter PEOPLE over 60 hours a week, I can see my creativity goes. In my vineyard, when I work on my grapes, I’m actually thinking, and that gives me inspiration.

Then did you follow your “less than 60 hours” rule when you were younger? Sometimes you do need to work really hard when you have to. But if you don’t have a deadline, then why go to the lab on Saturday? Go out for a walk, go swimming, clear your mind. However, since I won the Nobel Prize, my life has turned upside down. I’m working too hard, not because I’m addicted to it, but because I have deadlines every day. I’m working more than I have ever worked in my life. It has been non-stop for these years.

Experimental Studies of Neutrino Oscillations Memorial Volume for Y. Nambu by Takaaki Kajita (2015 Nobel Laureate) Edited by: Lars Brink (Chalmers University of Technology, Sweden), Lay Nam Chang (, USA), Moo-Young Han (Duke University, This volume of collected works of Kajita on neutrino oscillations provides USA), Kok Khoo Phua (NTU, Singapore) a good glimpse into the rise of Asian research in the frontiers of neutrino physics. is now a major force in the study of the three families of “I have only the fondest of memories of Nambu. He was a man of . Much remains to be done to clarify the Dirac vs. Majorana inordinate kindness, and there were many times that I felt I was a nature of the neutrino, and the cosmological implications of the neutrino. beneficiary of his consideration and generosity. Of course, the impact The collected works of Kajita and his Super-Kamiokande group will leave of his science was enormous.” an indelible footprint in the history of big and better science. H David Politzer Caltech 108pp Jan 2016 Nobel Laureate in Physics, 2004 978-981-4759-15-1 US$38 £25 978-981-4759-26-7(pbk) US$18 £12 200pp Sep 2016 978-981-3108-31-8 US$48 £32 978-981-3108-32-5(pbk) US$28 £18

March 2016, Volume 5 No 1 7 PEOPLE “Discovering the W and Z Bosons” Nobel Laureate Prof Carlo Rubbia

Carlo Rubbia CERN

Prof Carlo Rubbia is an Italian particle physicist and inventor who shared the Nobel Prize in Physics in 1984 with for work leading to the discovery of the W and Z particles, the elementary particles that mediate the inside atomic nuclei, at CERN. Rubbia studied physics at the University of Pisa and Scuola Normale in Pisa. He graduated on cosmic ray experiments in 1957 with Marcello Conversi. Rubbia obtained his PhD in 1958 from the University of Pisa. Following his PhD, then he went to the United States to do postdoctoral research, where he spent about one and a half years at performing experiments on the decay and the nuclear capture of muons. This was the first of a long series of experiments that Rubbia has performed in the field of weak interactions and which culminated in the Nobel Prize-winning work at CERN.

Broad and General Questions: mystery to me is the Big Bang. It is an incredibly exciting What is the one way Singapore can improve its position and mysterious moment in physics. as a leader in energy efficiency on the world stage? Singapore has an advanced system of transmitting power. What advice would you give a young researcher? Singapore is already advanced in its energy sector, however in Dick Feynman’s argument on originality comes to mind: my view geothermal energy is one solution Singapore should Never go where everybody else goes. If you go where choose to harness. It is economical and Singapore, being everyone goes, you never stand a chance. There is a lot of small, is capable of taking advantage of these geothermal competition. The probability of finding something exciting sources to introduce extra energy supply. It is also competi- is the same everywhere. As they say in France, ‘Vive la tive to other forms of energy, and there are adequate sources difference!’ of geothermal energy in the region. It works well, it is cheap, and I recommend it. What are your thoughts on the far future of energy science and energy technology? What unsolved mystery in physics strikes you as particu- Cheap natural gas is the winner of this situation. Renew- larly exciting due to progress in our current physical able sources will continue but will be slowed down by the understanding? competitive factor. The most exciting thing about natural In nowadays, there are all kinds of gas is eliminating carbon dioxide emissions. It sounds crazy initiatives that are exciting. Big bang cosmology used to be but it is true. It boils down to 80% of the energy coming theology half a century ago. There is a great deal of insights from hydrogen and 20% from carbon, which goes to carbon into the beginning of the Universe being made from the new dioxide from burning. If you don’t go to CO2 but stop at data from cosmological observations. The biggest unsolved black carbon, a solid material that has value and can be

8 Asia Pacific Physics Newsletter PEOPLE used in construction and other purposes, you avoid CO2 of chromosomes. Men have a Y and an X, women have two emissions. So this gives motivation to use natural gas all over X’s. A complementary exists between men and women in the planet without releasing CO2. a positive sense because both are essential. I can’t get too nitty-gritty over ‘yes’ or ‘no’ on whether the distribution What are your thoughts concerning a catastrophic should be more evenly divided. I can say that every human runaway greenhouse effect on Earth? being has the right to be respected and it is quite clear to me that a lack of respect is unacceptable. Assuming there are no Since we are living inside this small biosphere, we need differences between men and women in this issue and in to be careful. We should slow down to avoid a runaway my view is an oversimplification. There are a few activities greenhouse effect. We should be careful by not overdoing that are more appropriate to women and a few activities that CO2 production. It might be that CO2 is less dangerous than are more appropriate to men. It is a subtle issue to make a we expect, but I do not think that people really know. The judgement on gender distribution. Determining what the future of the climate is unpredictable and it is important to best distribution should be is unknown. be prudent. The average lifetime of CO2 in the atmosphere is about 30,000 years. The CO2 of the fires of Rome are still Question: The (LHC) has found in the atmosphere. Our effects are long lasting and its clear a Higgs-like particle two years ago, but no trace of super- to me that a sense of caution is warranted. symmetry. What do you think about the situation? In your view, at what point in the future will most people Interestingly, I am the person who, in one way or another, obtain their energy directly from renewable solar power? invented the word “LHC”. I was the one who brought in the word “LHC” through a discussion with a good friend Solar will grow, but it will not be the predominant energy of mine, who was an engineer who was saying that “LHC” source for a very long time. Fossils will be the primary was not what he wanted to have as a name. We had an argu- source for you and me and even our children. Those who ment because he claimed that “LHC” was the symbol for will depend primarily on solar energy have not yet been “Lausanne Hockey Club”. “Lausanne Hockey Club” would born. We cannot just throw away fossil use without concern. be much more important than “LHC” as an experiment Eventually solar will be there, but for now, the attention is therefore we should change to a different name! Actually on fossils. Don’t forget that the industrial revolution is only LHC was preserved this way and it is fine and it has been about 200 years old and is entirely based on fossils. There is a very successful endeavour. There is no doubt about never still awhile to go yet before solar power becomes primary. knowing when or where the next discovery will comes from

and it is not obvious to me that super-symmetry exists. Hard Questions! There may be bad news in the fact that super-symmetry has As a physicist, what are your thoughts on religion and a very small chance to be found at the LHC. Of course this science? Do you believe in God? all depends on the physics, maybe tomorrow it comes along, I like what Einstein said about nature and the order it has but it seems to be that super-symmetry at the LHC is getting in it. Nature has some universality to it. There are laws of tougher and tougher to find every day. If there is no signal nature. From that, to decide to use some specific religion or of super-symmetry, then nothing will oblige us to change another is the wrong way. The point is, even though I am our view about nature. It is like that. Maybe nature decides a member of the Pontifical Academy, they honestly respect that there is no super-symmetry. Today there is a very loud scientific views and are not imposing. There is a scheme, silence on super-symmetry from the theorists. They really there is a scenario, which is very important, very valid and don’t know what to say. So nature may decide either way. drives everything. The question about what it is in detail is a different story that everyone can interpret in different ways.

As a male physicist, what are your thoughts on the gender distribution in physics? Should the distribution be more evenly divided? I don’t know. This is a complex issue. There is a fundamental difference between men and women at the biological level March 2016, Volume 5 No 1 9 OPINION AND COMMENTARY China’s Great Scientific Leap Forward Completion of a planned ‘Great Collider’ would transform particle physics

David J. Gross and Edward Witten

hinese President Xi Jinping’s visit to Washington is an excellent opportunity to recognize China’s scientific contributions to the global community, and to foster Cmore cooperation between the U.S. and China in many areas of science, especially particle physics. The discovery of the Higgs particle at Europe’s Large Hadron Collider in 2012 began a new era. It confirmed an essential feature of the 40-year-old of particle physics, a missing ingredient that was needed to make the whole structure work. But the discovery also left many questions unanswered. These include the mass of the Higgs particle, the unification of all subatomic forces, and the incorporation of quantum gravity—issues that must be addressed if scientists wish to understand the origin of the universe. The Large Hadron Collider, which is funded and oper- ated by the European Organization for Nuclear Research, Atlas, one of two general-purpose detectors at CERN’s Large Hadron known as CERN, will provide important clues. But some Collider below the France-Switzerland border near Geneva. Photo: Getty Images big questions may require an even more powerful tool. Where might the next discovery take place? Physicists in the traditional centers of particle physics—the U.S., Europe study has yielded numerous surprises—was measured for and Japan—have exciting projects and proposals. But there the first time by a Chinese-American collaboration at the is a new player in the game: China. Daya Bay nuclear reactor in southern China. Most people know that after Mao Zedong’s death in Now, a group of Chinese physicists headed by Wang 1976, Deng Xiaoping began to liberalize China’s economy, Yifang, the leader of the Daya Bay experiment, has proposed putting the country on a far more productive path. Less an ambitious long-term plan for particle physics in China. known is another of Deng’s initiatives. He greatly extended The plan involves building what some have dubbed the the particle physics effort in China, authorizing in 1983 the “Great Collider.’’ Starting in the 2020s, this accelerator construction of the Beijing Electron- Collider, which will create very high-energy electron-positron collisions, began operation in 1988. revealing properties of the Higgs particle in much more For most of the past 30 years, particle physics advanced detail than will be possible at CERN’s Large Hadron Collider. in China at a steady pace. But lately Chinese particle physics Starting in the 2030s, the goal is to collide protons at ener- took a “great leap forward.” In March 2012 an important gies, again, far beyond the reach of the LHC to challenge our property of neutrinos—enigmatic neutral particles whose understanding and probe the unknown.

10 Asia Pacific Physics Newsletter OPINION AND COMMENTARY

Will China embark on this project? It is impossible to in China that attracts U.S. and international scientists. know. Crucial early decisions may be made soon. Competition and conflict between China and the U.S. could The total cost of this 30-year project will be great— easily spiral into a new Cold War where distrust becomes billions of dollars. But the benefits will also be great. In one the norm. Finding ways to cooperate and collaborate are fell swoop, China would leap to a leadership position in an essential. International facilities are marvelous settings for important frontier area of basic science. More practically, to such collaborations. build such a massive collider, China would need to develop CERN, which was founded in 1954, attracted scientists frontier technology in many fields, from superconducting from around the globe and played an important role in magnets to high-speed electronic detectors, attracting many establishing harmony in Europe after World War II. Scientific of the world’s top scientists and technologists. contacts between physicists in the U.S. and the U.S.S.R. There are also great potential benefits for U.S. science helped dampen the dangerous tensions between the two in collaborating on this project. Currently, the U.S. high- superpowers. With China emerging as a superpower in its energy physics program is concentrated on exploring the own right, U.S.-Chinese collaboration on the Great Collider properties of the mysterious neutrino, with no plan for a could play a similar role. large collider. But many of our high-energy experimenters, currently working at CERN, and a phenomenal amount of U.S. accelerator physics talent could contribute to and benefit *Reprinted with permission from the Wall Street Journal. http://www. from collaboration with the Chinese. wsj.com/articles/chinas-great-scientific-leap-forward-1443136976 There is another enormous benefit of a Great Collider (Sept. 24, 2015)

Mr. Gross is chancellor’s professor at the University of California at Santa Barbara and the recipient of the 2004 Nobel Prize in physics. Mr. Witten is a professor at the Institute for Advanced Study in Princeton, N.J., and a recipient of the U.S. National Medal of Science.

David J. Gross and Edward Witten

March 2016, Volume 5 No 1 11 NEWS CityU’s Institute for Advanced Study will Champion Bold New Research Initiatives

Communications and Public Relations Office City University of Hong Kong

he Institute for Advanced Study (IAS) at City Univer- community when I say how much I am looking forward to sity of Hong Kong (CityU) marks a new phase in the this new era of academia at CityU.” promotion of innovative research in Hong Kong by Professor David Yao, IAS Director, Tworld-leading scholars to address critical global challenges who works at Columbia University of today. and is a member of the US National IAS, which was launched on 22 November, is one of the Academy of Engineering, said IAS few such centres in the region. It aspires to be an international will attract some of the best minds in centre of excellence for the advancement of technology and science and engineering to spend time innovation by bringing together an interdisciplinary team of on the CityU campus. world-renowned scholars and researchers, including Nobel “The new initiative is dedicated to laureates and academicians, to contribute to the solutions of Professor David Yao pursuing curiosity-driven ideas and assumes the directorship pressing real-world problems. of CityU IAS. studies and conducting unfettered IAS will extend the frontiers of knowledge, and enhance research based on free and deep its global outreach by integrating research capabilities thinking, with the goals to seek truth, to advance knowledge informed by the sciences, technology and humanities to and to better humanity,” he said. develop innovative solutions for human betterment. It will Internationally acclaimed scholars appointed as IAS raise and invest resources to advance interdisciplinarity and Senior Fellows will work with and mentor other research innovation work with an initial focus on three themes: One fellows and students at CityU in problem areas of their Health, Digital Society, and Smart City. choice. Professor Way Kuo, CityU President, said at the inauguration The newly appointed IAS Senior Fellows are: ceremony that IAS would be the • Professor Philippe G. Ciarlet, Member of French perfect platform for spearheading the Academy of Sciences, French Academy of Technologies, University’s drive for excellence in Academia Europaea and Chinese Academy of Sciences interdisciplinary research that benefits • Professor Herbert Gleiter, Member of German National society. Academy of Sciences, US National Academy of Engi- “IAS will provide our faculty and neering and American Academy of Arts and Sciences Professor Way Kuo, students with an exciting environment CityU President, delivers • Professor , Nobel Laureate in Physics, the opening remark. in which to advance their work,” said Professor Kuo. “It will serve as a Member of French Academy of Sciences catalyst for many of the aspirations articulated in our new • Professor Way Kuo, Member of US National Academy Strategic Plan, and I am sure I speak for the entire CityU of Engineering and Academia Sinica in Taiwan; Foreign

12 Asia Pacific Physics Newsletter NEWS

Member of Chinese Academy of Engineering and Russian importance. Conferences, symposiums and workshops will Academy of Engineering also be organised to facilitate the exchange of ideas among academic communities in Hong Kong, mainland China and • Professor Jean-Marie Lehn, Nobel Laureate in Chem- overseas. istry, Member of French Academy of Sciences • Professor Pierre-Louis Lions, Fields Medalist, Member Reprint from CityU Newscentre, the City University of Hong Kong of French Academy of Sciences, Accademia dei Lincei and Academia Europaea About IAS director Professor David Yao: • Professor Liu Chain-tsuan, Member of US National Professor David D. Yao is the Piyasombatkul Family Academy of Engineering and Academia Sinica in Taiwan; Professor of Industrial Engineering and Operations Research and Foreign Member of Chinese Academy of Engineering at Columbia University, where he is the founding chair of the • Professor , Member of US National Academy Financial and Business Analytics Center at Columbia Data of Sciences and Academia Sinica in Taiwan, and Recipient Science Institute. In addition, over the last fifteen years he of the Shaw Prize in Astronomy has held part-time affiliations and special-term appointments with leading universities in Asia, including the Chinese • Professor , Fields Medalist & Wolf Prize University of Hong Kong, the City University of Hong Kong, Recipient and Member of US National Academy of National University of Singapore and Tsinghua University. Sciences His research and teaching interests are in operations • Professor David Yao, Member of US National Academy research, applied probability and stochastic systems, focusing of Engineering on resource control and risk analytics issues. Author/coau- thor of some 200 scientific publications, he is a principal IAS will also benefit immensely from the expert guidance investigator of over thirty grants and contracts from govern- of Professor David D. Ho, Scientific Director and CEO of the ment agencies and industrial sources, and a holder of eight Aaron Diamond AIDS Research Center and Member of US U.S. patents. His research and scholarly accomplishments Institute of Medicine and Academia Sinica in Taiwan, and Dr have led to numerous honors, including the Presidential Lee Kai-fu, Chairman and CEO of Innovation Works. They Young Investigator Award from the U.S. National Science have joined IAS as members of its International Advisory Foundation, Guggenheim Fellowship from the John Simon Board. Guggenheim Foundation, Franz Edelman Award from The work of IAS is organised in research fellowships to the Institute for Operations Research and Management enable world-leading visiting scholars to spearhead bold new Sciences, SIAM Outstanding Paper Prize from the Society for research initiatives and nurture postdoctoral/postgraduate/ Industrial and Applied Mathematics, Outstanding Technical undergraduate students in the pursuit of knowledge. It will Achievement Award from IBM Research, Great Teacher also explore partnerships with prestigious academic institu- Award from the Society of Columbia Graduates, and the IBM tions around the world in support of collaborative research Faculty Award. He is an IEEE Fellow, an INFORMS Fellow, that targets innovative solutions to global problems of critical and a member of the U.S. National Academy of Engineering.

March 2016, Volume 5 No 1 13 NEWS Case made for ‘Ninth Planet’*

Jonathan Amos BBC Science Correspondent

merican astronomers say they have strong evidence “And I’m really hoping that as we announce this, people that there is a ninth planet in our Solar System start a worldwide search to go find this ninth planet.” orbiting far beyond even the dwarf world Pluto. Strange swing AThe team, from the California Institute of Technology The group’s calculations suggest the object orbits 20 times (Caltech), has no direct observations to confirm its presence farther from the Sun on average than does the eighth - and just yet. currently outermost - planet, Neptune, which moves about Rather, the scientists make the claim based on the way 4.5 billion km from our star. other far-flung objects are seen to move. But unlike the near-circular paths traced by the main But if proven, the putative planet would have 10 times planets, this novel object would be in a highly elliptical trajec- the mass of Earth. tory, taking between 10,000 and 20,000 years to complete The Caltech astronomers have a vague idea where it ought one full lap around the Sun. to be on the sky, and their work is sure to fire a campaign to The Caltech group has analysed the movements of objects try to track it down. in a band of far-off icy material known as the Kuiper Belt. It “There are many telescopes on the Earth that actually is in this band that Pluto resides. have a chance of being able to find it,” said Dr Mike Brown. The scientists say they see distinct alignments among 14 Asia Pacific Physics Newsletter NEWS some members of the Kuiper Belt - and in particular two of his discovery of 2,236km-wide Eris in the Kuiper Belt in its larger members known as Sedna and 2012 VP113. These 2005 that led famously to the demotion of Pluto from full alignments, they argue, are best explained by the existence planet status a year later (Dr Brown’s Twitter handle is @ of a hitherto unidentified large planet. PlutoKiller). “The most distant objects all swing out in one direction At that stage, Pluto was thought to be slightly smaller than in a very strange way that shouldn’t happen, and we realised Eris, but is now known to be just a little bit bigger. the only way we could get them to swing in one direction Others who model the outer Solar System have been is if there is a massive planet, also very distant in the Solar saying for some years that the distribution of sizes seen System, keeping them in place while they all go around the in the objects so far identified in the Kuiper Belt suggests Sun,” explained Dr Brown. another planet perhaps the size of Earth or Mars could be a “I went from trying very hard to be sceptical that what possibility. But there is sure to be strong scepticism until a we were talking about was true, to suddenly thinking, ‘this confirmed observation is made. might actually be true’. Nasa’s chief scientist, Ellen Stofan, said she certainly The ‘ninth planet’ - where to look? needed telescopic evidence. The six most distant known objects in the Solar System “The intriguing point is: we’ve identified lots of planets with orbits exclusively beyond Neptune (magenta) all line up (beyond our Solar System) in this category of ‘super-Earth’ in a single direction. Why? Drs Brown and Batygin argue that with our Kepler telescope; over 5,000 planet candidates. The this is because a massive planet (orange) is anti-aligned with fact that we don’t have a planet in that size class between these objects. Can telescopes now find this planet? Could the Earth and Neptune makes us think, ‘well, maybe we are evidence already be in observational data but no-one has yet missing one’, and maybe they’ve predicted it,” she told BBC recognised it? The hunt is on. News. The idea that there might be a so-called Planet X moving Dr Brown and Dr Konstantin Batygin (@kbatygin) report in the distant reaches of the Solar System has been debated their work in The Astronomical Journal. for more than a hundred years. It has fallen in and out of vogue. *Reprinted with permission from BBC http://www.bbc.com/news/science- environment-35365323 What makes this claim a little more interesting is Dr Brown himself. Image By WP (Planets2008.jpg) [CC BY-SA 3.0 (http://creativecommons.org/ He specialises in finding far-flung objects, and it was licenses/by-sa/3.0)], via Wikimedia Commons from Wikimedia Commons

March 2016, Volume 5 No 1 15 NEWS High Temperature Superconducting Magnetic Lens Developed at IHEP*

High-Temperature Superconducting (HTS) This will be the first HTS lens used for an electron micro- magnetic lens developed by the Institute of High scope. HTS tapes made by a Chinese company were used to Energy Physics (IHEP) for Shanghai Jiaotong wind the coil. The HTS magnet uses conduction-cooling with AUniversity completed magnetic field measurement on one pulse tube refrigerator, so no liquid helium or nitrogen January 7, 2016, showing that the lens meets its design is used. The maximum operating temperature is about 50 requirements. K. The HTS lens will increase the resolution of the electron The HTS lens will be used in an accelerator-based microscope, reduce the overall size and weight of the device ultrafast transmission electron microscope capable of and give higher integration. producing a full field image in a single shot, with simulta- HTS magnet technology will promote the development neous picosecond temporal resolution and nanometer spatial of electron microscopes and HTS magnet research for future resolution. Transmission electron microscopes have played colliders. an important role in probing molecules, atoms, crystals and * Reprint with permission from Chinese Academy of Sciences http://english.cas. innovative new materials with atomic resolution. cn/newsroom/research_news/201601/t20160120_159006.shtml

Field mapping of the HTS magnetic lens (Image by IHEP)

16 Asia Pacific Physics Newsletter NEWS From the Jade Rabbit to the Monkey King

Chi Xiong Institute of Advanced Studies, Nanyang Technological University, Singapore

n December 17, 2015, China launched a satellite, for pure science research — the detection of dark matter. the Dark Matter Particle Explorer (DAMPE) with Dark matter is one of "two dark clouds in the sky of a Long March 2D rocket from the Jiuquan Satellite physics" in the 21st century. The other one is dark energy OLaunch Center; On December 21, stations in Kashgar, (see the interview with Brian Schmidt, this issue). According Miyun, Sanya successfully received data from the satellite to the most widely accepted theory of modern cosmology, and transferred them to the National Space Science Center only about 5% of the mass-energy content of our universe (NSSC). From the photos, it seems as if it was just the is ordinary matter, while dark matter accounts for 27% launch of another rocket carrying another satellite. However, and dark energy takes up the remaining 68%. Although it something is different this time — the satellite DAMPE, dominates in the matter world and plays an important role nicknamed "Wukong", is the first satellite launched by China in the formation and evolution of cosmic structures, we still

March 2016, Volume 5 No 1 17 NEWS

The mass-energy distribution of our universe. A schematic drawing of the satellite Wukong, hovering over the earth on a sun-synchronous orbit at an altitude of 500 kilometers and probing high energy gamma-ray and electrons which might result when dark matter candidate particles like WIMPs decay or annihilate.

do not know what dark matter is composed of. Therefore The Monkey King reminds one the most recent moon- the detection of dark matter is of great importance in both landing mission Chang'e 3 associated with another Chinese particle physics and cosmology. mythology. The lunar rover, called "Yutu" (玉兔 in Chinese) Besides direct detection through ground-based or the Jade Rabbit, the pet of moon goddess Chang'e (嫦 experiments, a few telescopes or satellites have been 娥 in Chinese), was designed to explore an area of about launched for indirect detection of dark matter. If the dark 1.2 square miles during its three-month mission. It carries matter within our galaxy is made of weakly interacting radars, spectrometers and cameras to inspect the soil massive particles (WIMPs), then in every second there composition and crust structure of the moon surface. might be more than millions of WIMPS passing through From Yutu to Wukong, it is not difficult to see the every square centimeter of the solar system. The unstable significant changes of the Chinese space science. While the WIMPs could decay into the Standard Model particles; Two Jade Rabbit is standing on the solid ground of the moon, WIMPs could annihilate to create gamma rays or particle- the Monkey King is taking a risky journey to the dark side antiparticle pairs in the Standard Model. Indirect detections of our universe. As one of the world's major space powers, search for the products of these decays or annihilations. China has so far only focused on the advanced engineering, These searches include the PAMELA experiment (launched technologies and applications rather than pure science. in 2006), the Fermi Gamma-ray Space Telescope (launched Wukong is the first in a series of space-science missions in 2008), and the Alpha Magnetic Spectrometer (AMS, planned by the Strategic Priority Program of the Chinese mounted on the International Space Station by the Space Academy of Science on space science. At least three other Shuttle Endeavour in 2011). Now the dark-matter hunting missions will follow up in 2016. "After the successful launch club has a new member, the Monkey King. of dark matter particle explorer satellite, next year we'll also The moniker Wukong is selected from 32,517 names launch a satellite for quantum science experiments, the hard solicited from the public. The winner Lin Lei, an astrophile, X-ray Modulation Telescope for bright and brief sources explained that Wukong, the monkey king and then the of radiation, and the Shijian-10 satellite for microgravity warrior in the 16th century Chinese classic fiction Journey research and space life science. Our exploration on sun, to the west, shares some common characteristics with the Mars and black holes are also on the way." says Bai Chunli, new satellite, such as being powerful and courageous when the director of Chinese Academy of Science. facing challenges, especially having golden eyes piercing Those are ambitious plans, but how good are these through the darkness. Interestingly, in Chinese "Wukong" detectors? (悟空) means "understand the space". Wukong has so far the widest observation spectrum

18 Asia Pacific Physics Newsletter NEWS and the highest energy resolution of any dark matter article by David Gross and Edward Witten in the Wall Street detector in the world. The satellite has ten times the Journal, reprinted in this issue) which also has a chance of energy observation spectrum of the AMS, and four times producing dark matter particles via high energy collisions the energy resolution of its international peers. Wukong's of protons, but will probably cost more than 1 billion payload consists of four parts: a plastic scintillator array US dollars each year for a couple of decades. In fact, our detector, a silicon-tungsten tracker, a BGO calorimeter, and universe itself is the greatest collider. It produces particles a detector. Together they can record the directions, with energy many orders of magnitude higher than those charges and energies of cosmic particles and make Wukong generated at any accelerators, and it would be a huge waste the most sensitive and accurate detector for dark matter if we do not make a good use of these high energy particles. designed to date. Will Wukong find dark matter? No one can be sure. What's the price? Wukong costs about 100 million US The design lifetime of Wukong is three to five years and dollars, while the AMS costs more than 2 billion US dollars. unfavorable scenarios could happen: There might be no The whole Wukong program is also "economic" compared dark matter at all and alternative explanations, for example with the disputable project "the Great Collider" (see the the modified gravity theory might be true; Even if dark matter really exists, its distribution in our galaxy might concentrate in the area close to the center of the galaxy and become too sparse to be detected in our solar system; There could be other sources in our galaxy producing the same products as those of dark-matter annihilation or decay, hence making it very hard to distinguish dark matter from other sources; Moreover there could be unexpected technical problems – let us not forget that after the first 14- day lunar night, Jade Rabbit the moon rover encountered operational problems and was unable to move after the end of second lunar night. These are the challenges that Wukong need to rise up to.

The structure of the satellite Wukong payload. Other parameters – Length "We are, of course, confident that DAMPE will contribute 1.5m, width 1.5m, height 1.2m, total weight 1.85 tons, payload 1.41 tons, to the dark matter search," says Philipp Azzarello, a Swiss orbital altitude 500km, design lifetime > 3 years. astrophysicist from University of Geneva who collaborated in the design of Wukong's detector. Professor Chang Jin, the chief scientist of the DAMPE collaboration and vice director of Purple Mountain Observatory, said they did not expect that Wukong will discover dark matter soon. "Searching for dark matter is our primary goal but at this stage we hope it functions well. The telescope is a window to things unbeknownst to the mankind. As long as you open it, you will see something new." So good luck, Wukong, find the dark matter, and leave the dark energy to another telescope which could be named "Wuneng" (悟能) after your fellow apprentice in the journey to the west. More interestingly, his name means "understand the energy".

Acknowledgment: The author thanks Professor Chang Jin and the DAMPE The Wukong payload successfully passed the vibration test, about 3 months before its launch. collaboration for the permission of using the pictures from its homepage http://dpnc.unige.ch/dampe.

March 2016, Volume 5 No 1 19 NEWS

The DAMPE collaboration is formed by leading research institutes and universities from China, Switzerland and Italy, including the Chinese Academy of Science (Institute of High Energy Physics, Institute of , National Space Science Center, Purple Mountain Observatory and University of Science and Technology of China), and University of Geneva, Switzerland and Istituto Nazionale di Fisica Nucleare (INFN) and University of Perugia, University of Bari and University of Lecce, Italy. This photo was taken during the 4th DAMPE collaboration meeting in Nanjing, China, October 2015, two months before the launch.

Photo of the DAMPE collaboration during the 3rd DAMPE collaboration meeting in Geneva, Switzerland, June 2015.

20 Asia Pacific Physics Newsletter NEWS New Structurally Perfect Candidate First Proposed for Quantum Spin Liquids#

cientists of a joint research team in China proposed a high-quality single crystals and the nonmagnetic reference

new structurally perfect quantum spin liquids (QSLs) single-crystals LuMgGaO4 for control experiments, such

candidate YbMgGaO4 for the first time, which is unique as extraction of the magnetic heat capacities from the total Sand excellent for future QSLs research. heat capacities of YbMgGaO . Furthermore, the Kramers 4 Quantum spin liquids (QSLs) are novel phases of matter, ground state double is well separated from the first excited where quantum spin fluctuations prevent any conventional double by an energy gap ~ 420K for Yb3+ ions. It has an spin freezing even at 0K, despite the significant spin-spin odd number of electrons per unit cell and it performs as a interactions. Studies on QSLs have aroused great interest of good insulator. All these factors make YbMgGaO4 an ideal researchers in since the resonating candidate for QSLs research. valence bond (RVB) states were proposed by Anderson in With the cooperation of Prof. CHEN Gang from Fudan 1980s. University, the study was conducted by a joint research These years, there are extensive studies on the most famous group led by Dr. LI Yuesheng and Prof. ZHANG Qingming

QSLs candidates, such as ZnCu3(OH)6Cl2, k-(ET)2Cu2(CN)3 of Renmin University of China by using the Electron Spin 3 and Yb2Ti2O7. However, some unavoidable structural “short- Resonance spectrometer (ESR), He-Magnetic Property comings”, such as magnetic defects, lattice distortions and Measurement System (MPMS) and low-temperature X-ray Dyaloshinskii-Moriya (DM) interactions, make extraction Diffractometer (XRD) in the Steady High Magnetic Field of the intrinsic physics from a real magnet difficult and lead Facilities (SHMFF) in High Magnetic Field Laboratory, Hefei to serious research divergence. As a result, the structurally Institutes of Physical Science, Chinese Academy of Sciences perfect QSLs candidates remain in urgent need. and dilution refrigerator Physical Property Measurement The joint research team found many structural advan- System (PPMS) in Fudan University. tages of the new candidate YbMgGaO4 over previously The above findings were published in Scientific Reports reported candidates. This new proposed candidate has entitled «Gapless quantum spin liquid ground state in perfect triangular lattices with R-3m symmetries and the the two-dimensional spin-1/2 triangular antiferromagnet concentration of magnetic defects is negligible (<0.04%). YbMgGaO4” and Physical Review Letters entitled “Rare-Earth Moreover, the antisymmetric DM interactions are symmetri- Triangular Lattice Spin Liquid: A Single-Crystal Study of cally forbidden and the interlayer magnetic interactions are YbMgGaO4”. negligible, compared to the intralayer nearest neighboring #Reprint with permission from Chinese Academy of Sciences http://english.cas. interactions. As for this candidate, it is available to gain both cn/newsroom/research_news/201601/t20160121_159046.shtml

March 2016, Volume 5 No 1 21 ARTICLES Statistical Physics in the Oeuvre of Chen Ning Yang

Michael E. Fisher Institute for Physical Science and Technology and Department of Physics, University of Maryland, College Park, MD 20742, USA [email protected]

tarting from his early years selected contributions of is actually a quasicrystal! Be that as it may, Yang’s first paper C. N. Yang to statistical mechanics are highlighted and in statistical physics was based on his Master’s thesis and the physics to which they led is briefly reviewed. published in The Journal of Chemical Physics in 1945: see S Fig. 3. This was submitted while he was a Research Fellow 1. First Publications of the China Foundation at the National Tsing Hua Univer- sity (which had been evacuated to Kunming owing to the From his earliest days as a student Chen Ning Yang — later Japan–China war, 1937–1945). Notable, and characteristic, known to friends in the West as Frank Yang — had been is that the paper develops a new formulation of the quasi- aware of mathematics; his father, Wu-Chih Yang, was, chemical method: “which is capable of yielding successively indeed, a professor of the subject. Not surprisingly, perhaps, higher approximations.” the first paper published by Cheng-Ning Yang (see Fig. 1) appeared in the Bulletin of the American Mathematical Society in 1944. Nevertheless, as a graduate student at the Southwest 2. The Ising Model and Onsager Associated University in Kunming in 1942–44, he became Doubtless already as a graduate student working on his intrigued by statistical mechanics. His advisor, Professor J. Master’s thesis, Yang had come across the Ising model of a S. Wang (who had studied in Britain with R. H. Fowler in ferromagnet. In its simplest form at each site, i, of a square the 1930’s) supervised his Master’s thesis under the title: lattice, in d = 2 dimensions (or a simple cubic lattice, if d =

“Contributions to the Statistical Theory of Order-Disorder 3) there is a “spin variable,” si which takes only the values +1 Transitions.” or −1. Nearest-neighbor spins, at sites i and j are coupled

Through his studies of order-disorder phenomena — one yielding a favorable energy ∆H = −Jsi sj while the magnetic of the most notable examples being the transition in beta- field,H , contributes −mHsi for each spin. To model a binary brass which is an alloy of copper and zinc close to a 50:50 AB alloy, the values si = +1 or −1 are merely associated with composition — the young Mr. Yang surely became familiar an atom A or B. with X-ray scattering observations such as that illustrated in Ernst Ising solved the model explicitly for d = 1 in 1924. Fig. 2. But here there is a bit of a cheat: the crystal studied in Too soon, however, he became a refugee from Hitler’s

Fig. 2 by and coworkers is actually Al6Mn Germany. Much later he worked for almost three decades, which, as might be concluded from the 10-fold symmetry, 1948–1976, as a Professor of Physics in Bradley University

22 Asia Pacific Physics Newsletter ARTICLES

Fig. 1. C. N. Yang’s first published paper based on Young’s paper in Fig. 2. Scattering observations illustrating the evidence for order in a Proc. London Math. Soc. 7, 157 (1908). The article appeared in Bull. crystal that can undergo an order-disorder transition. [After D. Shectman, Amer. Math. Soc. 50, 373–375 (1944). I. Blech, D. Gratias, and J. W. Cahn, Phys. Rev. Lett. 53, 1951 (1984).]

Fig. 3. The second paper published. Note that the author is now identified as “C. N. Yang.”

March 2016, Volume 5 No 1 23 ARTICLES

in Peoria, Illinois. But to solve the Ising model for d > 1 proved intractable for many years. Furthermore, as we now know well, the available approximate solutions were quite misleading! But Yang has related how one day in 1944–45, while still a Master’s student, his normally quiet and reserved advisor, Professor J. S. Wang, became quite excited, almost agitated. It transpired that he had just learned that (shown with C. N. Yang in Fig. 4) had exactly solved the square-lattice Ising model in zero magnetic field finding a logarithmic divergence of the specific heat at criticality! He told Yang about the paper: Phys. Rev. 65, 117 (1944); but Yang, like so many others, could not see how to go further: no “strategic plan” seemed evident. A little while later, when already in Chicago, significant progress still eluded him. Fig. 4. Chen Ning Yang and Lars Onsager together much later in March However, in November 1949, with a Chicago Ph.D. 1965. safely in hand, Yang had a chance conversation with J. M. Luttinger at the Institute for Advanced Study in Princeton. Through that he learned of Bruria Kaufman’s simplification

Fig. 5. The 1951 article providing the exact solution of the spontaneous magnetization of the square-lattice Ising model and establishing the critical 1 exponent β = ⅛. Note the author’s later remark! The basic transfer matrix is V1V2 where (in the notation of Bruria Kaufman who used H = J/kBT) V1 and V2 appear here in Eqs. (2) and (3).

24 Asia Pacific Physics Newsletter ARTICLES of Onsager’s approach in terms of a system of anticommuting hermitian matrices. Kaufman’s work1 opened the door to understanding Onsager’s solution and to an appreciation of how much had been learned about the Ising model on a square lattice, albeit in zero magnetic field. In January 1951 Yang realized that the spontaneous magnetization, M0(T ) as a function of the temperature T , could be derived from an off-diagonal matrix element between the two eigenvectors of the underlying transfer matrix that had the largest eigenvalues. Following that idea— Fig. 6. The spontaneous magnetization of a two-dimensional rectan- gular Ising model with vertical and horizontal couplings, J and J , related which entailed months of hard labour — led to the submis- 1 2 by n = J2 / J1. Note _that Tc is the critical point of the square lattice with sion in mid-September of the remarkable paper displayed J = J1 = J2 and xc = √2−1. [After C. H. Chang, Phys. Rev. 88, 1422 (1952).] in Fig. 5. Following a series of “miraculous cancellations” (including elaborate factors denoted, with bold originality, I, II, III, and IV), the calculation led to the surprisingly simple expression background occasion, recorded in Fig. 7, was the University of Kentucky Centennial Conference on Phase Transitions 2 2β 1 + x 2 4 ½ M0(T ) = ______(1 − 6x + x ) , (2.1) commemorating the founding of the university in 1865. [ 2 2 ] (1 − x ) While waiting after the meeting at the airport,3 Onsager where x = exp(−2J/kBT), while kB is Boltzmann’s constant. explained how, in succession, he had undertaken to diago- The crucial and universal critical exponent proved to beβ = nalize the transfer matrix by hand: first the 2 × ∞ matrix, ⅛, in strong contrast with nearly all previous approximate then the 3 × ∞, and so on! Eventually, by the 6 ×∞ case, he 6 theoretical treatments2 which yielded β = ½ — often called confirmed that the 64 = 2 eigenvalues were (essentially) all of the “mean-field value.” the form exp(±γ1 ± · · · ± γ6). That suggested an underlying The problem of a rectangular Ising model with distinct product algebra which, in turn, had led him to the elaborate values of J1 and J2 — already broached by Onsager — was structure of his original derivation. suggested to C. H. Chang (of the University of Washington, One may wonder what brought Yang and Onsager Seattle). His results (guided by Yang!) could be expressed together. It transpired that Onsager was an old friend of the in terms of the modulus, k, of the crucial elliptic integral as host at the Conference, W. C. de Marcus, who approached him for advice. Thus, indeed, it was Onsager’s approval that 2 β (2.2) brought Yang to the meeting! He also suggested Professor M0(T ) = (1 − k ) , Mark Kac (by then some years at the Rockefeller University where, with xi = exp(−2Ji /kBT) for i = 1, 2, in New York) and, in addition, as a junior speaker the Author of this article. All four, as shown in Fig. 7, were awarded a 2x1 2x2 ______special honor of the Commonwealth of Kentucky, that is to k = 2 2 . (2.3) 1 − x 1 1 − x 2 say, we were commissioned as Kentucky Colonels. A docu-

As expected, Chang found β = ⅛ for all values of n = J2 / J1; ment recording the author’s commission is reproduced in the striking behaviour of M0(T ; n) is shown in Fig.6. Fig. 8. In accepting the commissions on behalf of all four of us, Mark Kac expressed his belief that this “Southern Honor” was particularly appropriate in that Lars Onsager came from 3. Lars Onsager and C. N. Yang Southern Norway, Frank Yang hailed from Southern China, A year later Yang encountered Onsager at a 1953 –Kyoto 1 International Conference. But while Onsager spoke in his See: B. Kaufman, Phys. Rev. 76, 1232 (1949). 2 characteristic, somewhat vague style, punctuated by broad It is worth recalling, however, that , using an extrapola- tion of the exact low temperature series expansions for M (T), had, smiles, he did not address the Ising model. Thus it was only 0 in 1949, obtained the estimate β <~ 0.16 only 20% higher than Yang’s some twelve years later in March 1965 that Yang was able to exact result: see Proc. Roy. Soc. A 199, 199–221 (1949). learn, directly from Onsager himself, the reasons for all the 3As related in Chen Ning Yang, Selected Papers 1945–1980 With unobvious commutator calculations in the 1944 paper. The Commentary (W.H. Freeman & Co., San Francisco, 1983).

March 2016, Volume 5 No 1 25 ARTICLES

Michael Fisher was brought up in Southern England, while Chinese immigrant to the United States, namely, the talented he himself originated in Southern Poland! experimentalist, M. H. W. Chan. Moses as he is known in the West, was born in November 1946 in Xi’an but moved with 4. Two Dimensions in the Real World his family to Hong Kong in 1949 and came to America as a student, gaining his Ph.D. at . The critical exponent, β = ⅛ , found for the Ising model It was known that if one deposited a submonolayer of by Yang (and confirmed more broadly by Chang) was for methane, CH4, on graphite at a temperature below about 70K a “manifestly artificial model” — as the Ising model was it phase separated into a low density (or gaseous) “vapor” and generally regarded in the middle of the last century. Beyond a higher density “liquid.” At first sight this appeared to be other aspects, the “two-dimensionality” added to the sense an ideal lattice gas and so, reasonably described by an Ising of artificiality. But that was no serious obstacle to another model. But previous attempts to measure the coexistence

Fig. 7. Newly commissioned Kentucky Colonels with their host at the Conference on Phase Transitions.

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and experimental achievements the greeting shown in Fig. 11 was displayed.

5. Condensation and Circles in the Complex Plane In March 1982 a Sanibel Symposium was organized by Per-Olav Löwdin in Florida, in honor of Joseph Mayer (who died only a year later). In an interesting historical essay4 C. N. Yang has related how Mayer, in 1937, approached the problem of condensation of a fluid from a vapor to a liquid. Mayer developed systematic cluster expansions that, as Yang observes, “started an analysis of the mathematics5 and physics of such phenomena.” In fact, Mayer expected some sort of mathematical singularity at the condensation point (with, as a consequence, the failure of any analytical continu- ation of an isotherm beyond condensation). But conceptual puzzles remained: “How can the gas models ‘know’ when they have to coagulate to form a liquid or solid?” asked Born and Fuchs in 1938.”4 This was the topic that attracted Yang’s attention in 1952. It led to a collaboration with T. D. Lee and to the two-part articles shown in Fig. 12. Their recipe, as the figure states, was: “Go into the Complex Plane!”. As indicated in Fig. 12, Yang and Lee chose to examine the complex plane of the fugacity z. For a ferromagnet subject to a magnetic field, H, this is simply the corresponding Boltzmann factor; but for a fluid the chemical potential, Fig. 8. Document announcing the commissioning of Michael E. Fisher as a Kentucky Colonel on 17 March 1965 in the 173rd year of the μ, is involved. This variable is much beloved by chemists Commonwealth of Kentucky. but anathema to many physicists! However, in terms of z the grand canonical partition function, Ξ(z; Ω) for a finite domain Ω that contains N particles is merely a polynomial of degree N. Since Ξ(z) must be real and positive for positive curve as a function of temperature and hence determine the real z and T (or μ/T or H/T ) all zeroes of the polynomial Ξ(z) exponent β experimentally had, at best, proved inconclusive. must lie in the complex plane (or on the negative real axis). It was realized by Moses Chan, however, that the difficulty As a result, knowing the distribution of the zeroes amounts was closely associated with the steepness of the anticipated to a full knowledge of the thermodynamics. Consequently if “two-dimensional” coexistence curve, clearly evident in the zeroes approach the real axis as N → ∞, a singularity must Fig. 6. He realized that an optimal route is to determine the appear in the thermodynamic limit at the corresponding phase diagram by carefully measuring the specific heat at a value of μ and T. range of constant coverages, n: see the specific-heat traces in Fig. 9. On the coexistance curve at constant n 4C. N. Yang, Int. J. Quant. Chem.: Quantum Chemistry Symposium, 16, from the two-phase (vapor + liquid) region below Tc to the 21–24 (1982). See also pages 43–46 in Chen Ning Yang, Selected Papers supercritical fluid phase a clear break would be evident in II With Commentaries (World Scientific Publishing Co., Singapore, 2013). temperature plots of the specific heat. 5Among authors inspired to address the issues mathematically, Yang Using this approach, Chan (with his student H. K. cites L. van Hove, Physica 15, 951 (1949). Unhappily, however, as Kim) was able, in 1984, to determine the coexistence orginally pointed out by N. G. van Kampen and as I reported in Arch. curve displayed in Fig. 10. The fitted value, β = 0.127 ± Ratl. Mech. Anal. 17, 377–410 (1964), the second (but unnumbered!) 0.02, agrees remarkably well with Yang’s result of β = ⅛ = equation in the appendix of van Hove’s article is deeply flawed. This fact actually invalidates van Hove’s claim of a proof of the existence 0.125 — now clearly seen as a “prediction” thirty-two years of a well defined thermodynamic limit of the statistical mechanical before the observation! In celebration of these theoretical expression for the free energy of a system.

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In Part II of their article Lee and Yang explicitly consid- ered the Ising model and the lattice gas and found them to be completely equivalent mathematically. But the great surprise was the circle theorem! Specifically, as illustrated in Fig. 13, the zeroes of the grand canonical partition function for any pairwise ferromagnetic interactions whatsoever (of arbitrary range or structure, etc.) were proved to always lie on the unit circle in the complex z-plane. Equivalently, the zeroes are restricted to lie on the pure imaginary axis in the complex plane of μ, the chemical potential. It is worth stressing that, building on the work of Yang and Lee, we now know that Mayer’s vision of a singularity at condensation is, in fact, correct. At a first order transition 6,7 Fig. 9.(a) The coverage n versus temperature T, phase diagram of methane one must expect an essential singularity. Thus, all the nth deposited on graphite at low coverages as determined by (b) derivatives remain bounded but their behavior as n → ∞ is specific heat plots, C/NkB, versus T. (After H. K. Kim and M. H. W. Chan, Phys. Rev. Lett. 53, 170–173 (1984). insufficient to make the associated Taylor series converge. For many years it was felt that the Lee–Yang zeroes must basically remain unobservable — even though the density of zeroes, g(θ) near the real axis must influence the thermody- namics at condensation. Recently, however, Ren-Bao Liu,8 of the Chinese University of Hong Kong, and his coworkers have demonstrated how Lee–Yang zeroes may be investigated by “measuring quantum coherence of a probe spin coupled to a Ising-type spinbath.” Indeed, Dr. Ren-Bao Liu presented his results at the Yang–Mills Conference. Of course, as the saying has it: “What’s good for the goose is good for the gander!” Thus, as pointed out some time ago,9 the complex plane is also valuable for other variables, perhaps most notably the temperature. This leads to what have been called8 “Fisher zeroes.” For an Ising model on a rectangular lattice one knows from Kaufman1 that the canonical partition Fig. 10. Coexistence curve for temperatures from 62K to 69K of function for an m × n torus can be expressed as9 submonolayer methane on graphite to determine the critical exponent β. (After H. K. Kim and M. H. W. Chan, Phys. Rev. Lett. 53, 170–173 (1984). m n (1) 1 + υ2 1 + υ' 2 2υ 2πr 2υ' 2πs Z N = ______− ___ cos __ − ___ cos __ , (5.1) ΠΠ{ 2 2 2 2 } r=1 s=1 1 − υ 1 − υ' 1 − υ m 1 − υ' n 6See M. E. Fisher, IUPAP Conf. Stat. Mech. (Brown University, 1962) as recorded by S. Katsura, Adv. Phys. 12, 416 (1963); and Physics 3, 255–283 (1967). Note that the 1967 article is the text of the talk presented at the Centennial Conference on Phase Transitions held at the University of Kentucky, 18–20 March 1965 (as illustrated in Figs. 7 and 8, above). 7The concept of an essential singularity at condensation was indepen- dently advanced by A. F. Andreev, Sov. Phys, JETP 18, 1415 (1964). For a lattice gas the result was proved with full mathematical rigor by S. N. Isakov, Commun. Math. Phys. 95, 427 (1984): see also the discussion in M. E. Fisher, Proc. Gibbs Symp. (, 15–17 May 1989; 1990 American Mathematical Society), pp. 47–50. 8X. Ping, H. Zhou, B.-B. Wei, J. Cui, J. Du, and R.-B. Liu, Phys. Rev. Lett. 114, 010601 (2015); see also B.-B. Wei and R.-B. Liu, Phys. Rev. Lett. 109, 185701 (2012). Fig. 11. A good-will message from Moses Hung-Wai Chan to Professor Chen Ning Yang (as displayed on 28 May 2015 in the author’s 9M. E. Fisher, “The Nature of Critical Points,” in Lectures in Theoretical talk to the Conference at the Institute of Advanced Studies in Nanyang Physics, Vol. VIIC (Univ. of Colorado Press, Boulder, Colorado, 1965), Technological University). Secs. 13 and 19.

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Fig. 12. The two-part 1952 article by C. N. Yang and T. D. Lee addressing the statistical mechanical theory of phase transitions. This work established the significance of the complex plane for understanding how a sharp first-order could appear in a large system.

Fig. 13. Illustration of the Lee–Yang circle theorem for lattice gases or Fig. 14. Loci of zeroes of the canonical partition function of the square for ferromagnetic Ising models where z = exp(2H/kBT): all zeroes must lattice Ising model in the complex υ = υ' = tanh(J/kBT) plane. The critical lie on the unit circle. In the thermodynamic limit this implies that the points of the ferromagnetic and antiferromagnetic models are indicated. only possible singularities in the free energy — indicative of a phase transition — must be located in zero magnetic field (H = 0) or, for a lattice gas, on a unique locus μσ(T).

March 2016, Volume 5 No 1 29 ARTICLES together with three other quite similar products. Here the natural thermal variables, vanishing like 1/T as T → ∞, are 1 − x J 1 − x J υ = _____ 1 = tanh ____1 , υ' = _____ 2 = tanh ____2 . ( ) ( ) (5.2) 1 + x1 kBT 1 + x2 kBT

For the symmetric case υ = υ' (or J1 = J2) it is not hard to see, as illustrated in Fig. 14, that all the zeros of (5.1) lie on two circles in the complex υ plane. Where one of the circles crosses the real positive axis at Re(υ) < 1 corresponds to the ferromagnetic critical point. Conversely, where the other circle crosses the negative υ axis [at Re(υ) > −1], locates the critical point of the antiferromagnet (for which J < 0). If θ is an angle describing the circle centered at Re(υ) = −1, the density of zeroes varies as Fig. 15. Depiction of the Yang–Lee edges above the critical temperature,

Tc, when there is a real condensation locus, μσ(T). The real and imaginary g(θ) = | sin θ | F(θ) , (5.3) parts, (h', h"), of Δμ ≡ μ − μσ(T) are defined in the text; the Lee–Yang zeroes occur only on the plane h'= 0. where F(θ) is an analytic function periodic in θ. It then readily follows9 that the specific heat varies simply as A ln |T − Tc| — just as orginally found by Onsager! To this end, let us posit that the density of zeroes near the edge varies as 6. The Universal Yang–Lee Edge Singularity σ g(T, h") ~ [hYL(T) − h"] , (6.2) Let us identify μσ(T) as the locus of condensation in the plane of real chemical potential versus temperature. We may, for when h" → hYL(T) from below and enquire as to the value of convenience, write the critical exponent σ.

It follows that there is a singular contribution to the total Δμ(T) ≡ μ − μσ(T) = h'(T) + ih"(T) . (6.1) free energy F(T, h), near the Yang–Lee edge which behaves as

We then know, thanks to the circle theorem, that the 1+σ fs(T; h'=0,h") ≈ A± |hYL(T) − h"| , (6.3) Lee–Yang zeroes are confined to the imaginary plane Re{Δμ} ≡ h'(T) = 0; hence their density, g(T; h"), is a function where the amplitudes A+ and A− may, in general, depend only of h" ≡ Im{Δμ}. on the sign of h" − hYL. This implies that the susceptibility, Because of the essential singularity at h'(T) = h"(T) =0, 2 2 χ (∂ F/∂h ) diverges with an exponent γYL = 1 − σ where always to be expected below the critical temperature, Tc, the we have anticipated that σ is always less than unity. density g(T; h") must be nonvanishing for small h" when ∝ Indeed, it is natural to suppose that σ(d) depends only on T< Tc. On the other hand, when T increases above Tc there the dimensionality, d, of the system and is, thus, universal. must open up a gap, say hYL(T) > 0 that is free of zeroes (in This is, in fact, upheld by further investigation.10 For the thermodynamic limit). The gap function, hYL(T), serves d = 1 the results can be found exactly yielding σ(1) = −½ . to define the Yang–Lee edge as illustrated in Fig. 15. On Furthermore, one can check other aspects of criticality such grounds of symmetry we expect two equivalent edges located as scaling: specifically, that suggests the correlation function at h" = ±hYL(T). near criticality for an Ising (or more general) system — say Now, as noted by P. J. Kortman and R. B. Griffiths, Phys. with spins sO at the origin and sR at separation R — should Rev. Lett. 27, 1439 (1971) these edges must be branch points behave as of the free energy F(T, μ). We will call such branch points Yang–Lee Edge Singularities10 and, following Kortman and Griffiths, ask about their nature. It will be argued that they 10M. E. Fisher, Phys. Rev. Lett. 40, 1610–1613 (1978). See also D. A. should be treated as a potentially new class of critical points Kurtze and M. E. Fisher, J. Stat. Phys. 19, 205–218 (1978) and Phys. and analyzed accordingly! Rev. B 20, 2785–2796 (1979).

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G(R; T; h) ≡ sO sR − sO sR < > < > < > (6.4) νc d−2+η ≈ D(Rh )/R , when h, 1/R → 0. This can be checked precisely10 for d = 1 yielding the Yang–Lee values ηYL(1) = −1 and νc(1) = ½. Similarly, hyperscaling relations such as

______d − 2 + ηYL ______2 σ = and γc = , (6.5) d + 2 − ηYL d + 2 − ηYL are verified up to a borderline dimension that turns out to 10 be dYL = 6. Beyond that, consideration of mean-field or Landau-type theories demonstrates that Yang–Lee criticality should, indeed, be universal. However, in place of the standard field Fig. 16. Schematic view of the fugacity plane, (zA, zB), for the GMM theoretic φ4 analysis, it transpires that an iφ3 theory is needed! model showing, in the first quadrant, a first-order phase boundary on the axis of symmetry, zA = zB > 0, that terminates at a critical point. In the That being understood, a -group treatment third quadrant is a locus of repulsive-core singularities (which, in general, is possible and leads to may extend into the second and fourth quadrants).

__1 __1 __1 σ = − є and ηYL = − є , (6.6) 2 12 9 Sheng-Nan Lai labored.11 This consists of similar A and B to first order in є = 6 − d(> 0). (In second order the 1/9 for particles with interaction potentials 10 η is replaced by 43/81. A third-order calculation has been undertaken by Bonfim, Kirkham, and McKane, J. Phys. A uAA(r) = uBB(r) = 0 but 2 2 14, 2391 (1981); see also Ref. 11 and Fig. 17.) -r /r 0 (6.8) exp[−uAB(r)/ kBT] = 1 − e , It turns out, however, that this is not the end of the story! In 1984 a physical chemist at Johns Hopkins University, D. where r0 merely sets the scale of the repulsive potential. Poland, proposed [in J. Stat. Phys. 35, 341 (1984)] that both (Evidently the Mayer ƒ-function is Gaussian.) The singu- lattice and continum hard-core fluids are characterized, in larities arising in the (zA, zB) plane for this GMM model are the Mayer fugacity expansion of the pressure, by a universal shown in Fig. 16 (with d > 1). dominant singularity on the negative fugacity axis, say at The numerical values found for ϕ(d) as d varied strongly z=z0< 0. On introducing an exponent ϕ(d) for this singu- supported the natural hypothesis, namely, that the intrinisic larity, the pressure displays a contribution of the form ‘hardness’ (or otherwise!) did not matter at all! In other words, universality extended to whatever the nature of the ϕ(d) ps(T, z) ~ P(z − z0) , (6.7) particle repulsive cores that generated the singularity. (It is worth remarking that some form of repulsive cores are A subsequent study11 led to the exponent values ϕ(1) = ½, essential to maintain thermodynamic stability.12) ϕ(2) = 5/6 = 0.833 . . . , (derived from Baxter’s well-known In the same way, the similarity of the repulsive core 1980 exact solution of the hard-hexagon model) ϕ(3) ~_ 1.06, exponents as a function of d to the Yang–Lee exponents led11 and ϕ(4) ~_ 1.2. When d became large, it appeared that ϕ(d) to the explicit proposal approached 3/2 . A natural first question is: “How crucial is the ‘hard σ(d) = ϕ(d) − 1 . (6.9) core’ — implying an interaction potential, u(r), which is actually infinite over a finite range of particle separation A theoretical justification for this identification was r?” An answer can be found by studying models with a ‘soft originally lacking. However, with the aid of a field-theoretic repulsive core’ for which u(r) is always finite. A suitable approach which employed separate representations for the model, for which low-density series of significant length could be generated for arbitrary d turned out to be the 11S.-N. Lai and M. E. Fisher, J. Chem. Phys. 103, 8144–8155 (1995) Gaussian Molecule Mixture (GMM); on this my student and references therein. 12See, e.g., M. E. Fisher, Arch. Ratl. Mech. Anal. 17, 377–410 (1964).

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to Fermi’s pseudopotential approach. This soon led to joint work on the quantal many-body problem for Bose and Fermi systems. Ultimately Yang published some 15 or so papers on this topic, many involving a close collaboration with T. D. Lee. The first of these, together with four other early articles are shown in Fig. 18. However, unanticipated issues arose — as related in Yang’s much later commentary3 — and, in retrospect, these prove instructive illustrating the vicissitudes to which, even for the most talented scientist, research can lead in the real world! In the original paper ([A] in Fig. 18) the results for the

ground-state energy, E0, of a Fermi system proved satis- Fig. 17. Variation with dimensionality, d, of the universal repulsive- factory; but for a Bose system of dilute hard spheres the core singularity exponent, ϕ(d), now identified with the Yang–Lee edge exponent, σ(d) = ϕ(d)−1. The borderline dimensionality is d = 6; beyond pseudopotential approach resulted in that ϕ = 3/2 and σ = ½ . The continuous plot embodies an O(є3) expansion where є = 6 − d > 0. 2 4______πa(N − 1) __a __a 2 __ξ ... E0 = N 1 + 2.37 + (2.37) + (2N − 5) + ,(7.1) L3 { L L2[ π2 ]}

where a is the hard-sphere diameter, N is the number of repulsive and attractive parts of the pairwise interactions, spheres, L×L×L is the periodic box containing the system, such a demonstration was eventually constructed.13 (Note while ξ is a convergent sum over three integers, (l, m, n). For that particle–particle attractions are needed to yield conden- fixedρ = N/L3, as L → ∞ in the thermodynamic limit, however, sation, criticality, and a Yang–Lee gap, h"YL(T), above Tc.) the last term in (7.1) does not make sense: it behaves as Accepting (6.9), enables us to present, in Fig. 17 a combined ξNa2/L2 = ξLa2ρ and so diverges! This observation disturbed plot of the dimensional dependence of both the Yang–Lee the authors but they eventually decided to publish anyway. edge exponent, σ, and the repulsive core exponent ϕ. Of course, the pressure was then on to find an alternative Is that then the end of the story? Not really! Indeed, approach: this led to the binary collision expansion method separate investigations by many authors11 have shown not which was presented (under the names of all three authors) as only that ϕ(d) describes assorted square and triangular lattice a lecture by Yang at the Steven Conference on the Many-Body models of hard squares, hard hexagons (as mentioned), and Problem in January 1957. This is displayed as [C] in Fig. 18; dimers (with holes) but have also established the relations but publication was unhappily delayed for six years. The technique employs a summation of the most divergent terms:

ϕD(d) = ϕ(d − 1) and ϕI(d) = 1 + ϕ(d − 2) (6.10) applying this Lee and Yang found that the troublesome term identified in (7.1) dropped out after summation leading to for Directed Site and Bond Animals14,15 and Isotropic Site and —3 E0 128 ρa 16 __ = 4πρa 1 + ______+ ... . (7.2) Bond Animals or Branched Polymers. Note that in the case N [ 15 √ π ] of animals, etc., of size n one expects the numbers of animals to vary asymptotically as The correction term of order (ρa3)1/2 can be found merely by summing the most divergent terms (as shown in [C] of Fig. n −ϕD 3 3 an ≈ Aλ n , (6.11) 18). The next term, of order ρa ln(ρa ), was published first by T. T. Wu, Phys. Rev. 115, 1390 (1959) but soon confirmed (and similarly for isotropic animals, etc.) where A and λ by others. But T. T. Wu also found that in some cases are lattice-dependent, nonuniversal constants. The corre- summation of the most divergent terms — always a risky sponding singularities now lie on the positive real fugacity 13Y. Park and M. E. Fisher, Phys. Rev. E 60, 6223–6228 (1999). axis.11 14J. L. Cardy, J. Phys. A 15, L593 (1982). 15See D. Dhar, Phys. Rev. Lett. 51, 853 (1983), ibid. 49, 959 (1982), 7. The Quantal Many-Body Problem at Low T and H. E. Stanley, S. Redner, and Z.-R. Yang, J. Phys. A 15, L569 (1982)(and references therein). In Fall 1955 Kerson Huang became a member of the Institute 16See D. S. Gaunt, J. Phys. A 13, L97 (1980) and G. Parisi and for Advanced Study at Princeton and introduced C. N. Yang N. Sourlas, Phys. Rev. Lett. 46, 871 (1981).

32 Asia Pacific Physics Newsletter ARTICLES enterprize! — actually fails: see Phys. Rev. 149, 380 (1960). ground state, Boltzmann systems. It was noted that by a Meanwhile a defect had been found in the original appli- classic argument — which I first learned from the writings cation of the pseudopotential method; that invalidated (7.1). of — all the low-temperature expansions are Once it was understood that a careful technique of subtrac- likely to be of asymptotic character [allowing contributions tions was needed, it turned out that the pseudopotential like exp(1/ρa3)]. method could, in fact, yield the now well-established result Finally, in Fig. 18 the last article [E], by Lee and Yang, is (7.2). The details were published in [D], the penultimate the first in a series of five papers, published in 1959–60. The article exhibited in Fig. 18.While the various calculations last two articles represented the hope3 of revealing the true by different methods required thorough-exposition, once nature of the lambda transition to a superfluid in helium-4. the results were clear, it was wisely decided that a very But that was unsuccessful; progress in that direction had to short — less than two pages — “Progress Report” was called await more general findings regarding critical phenomena, for! That is the second article, [B], in Fig. 18. As more-or-less their universality and scaling, the renormalization group visible in the figure, this article essentially consists of a series, and the є = 4 − d expansion, and so on. (A) to (E), of explicit formulae for Fermi, Bose, and for the

Fig. 18. Papers published by Yang on the quantal many-body problem, initially with Kerson Huang and later with T. D. Lee. From the first, at the top, and downwards, the specific references are: [A] Phys. Rev. 105, 767 (1957); [B] Phys. Rev. 105, 1119 (1957); [C] pp. 165–175 in The Many-Body Problem, ed. J. K. Percus (-Interscience, New York, 1963); [D] Phys. Rev. 106, 1135 (1957); and [E] Phys. Rev. 113, 1165 (1959).

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8. Off-Diagonal Long-Range Order in the article shown in Fig. 20, he presented resulting general features for both Bose–Einstein and Fermi–Dirac Ever since Einstein accepted the ideas sent to him in 1924 particles. True to his customary meticulous regard for by S. N. Bose and applied them to an ideal gas, it has been proper credit, the first six references, reproduced in Fig. 20, hard to avoid the picture presented in Fig. 19. But how might refer to the previous studies of Penrose and Onsager as well it relate to the actual phenomenon of superfluidity in liquid as the less precise ideas of London for superfluids and, for helium? And, perhaps, also have some connection to superconductors, of Schafroth and others, including “BCS” superconductivity in metallic systems? and Bogoliubov. clearly matters; but in helium as in real metals, the interac- The essential step in defining ODLRO is to recognize tions between atoms are crucial and an ideal gas cannot be that a quantum mechanical system of N particles must be an acceptable model. described by a wave function, Personally, my first encounter with this central issue for many-body quantum mechanics was in 1954. Having ΨN = ΨN (r1 ,..., rN ; q) ~= ψˆ(r) , (8.1) rejoined King’s College, London now as a doctoral student after a couple of years of National Service in Her Majesty’s of appropriate symmetry in the positional co-ordinates Royal Air Force), I was sent to Cambridge by Cyril Domb, r1, . . . , rN, while q denotes the remaining co-ordinates of newly arrived as Professor of Theoretical Physics. The the closed system. Following the overall density reason for the visit was, I believe, related to my duties as matrix ρ is then Student Librarian in King’s for the Physics Department. At the end of the afternoon in Cambridge I looked up Oliver ρ(ri ; r'j) = dqΨ*N (ri ; q)ΨN(r'j ; q) , (8.2) Penrose, a close-friend of my brother-in-law-to-be, David ∫ Castillejo (the younger brother of Leonardo Castillejo of and reduced single-particle, two-particle, . . . density matrices some fame in high-energy physics arising from the “CDD” can be defined by integrating over the co-ordinates of (N − 1), paper by Castillejo, Dalitz and Dyson). To my fascination, (N − 2), . . . particles. Oliver Penrose told me of his thoughts, (already published In terms of the density operator, ψˆ(r) in (8.1), the off- three years previously) regarding the intrinsically “wave- diagonal matrix element of the single-particle density matrix mechanical” nature of the ‘order’ underlying superfluidity in behaves as real helium! Not long afterwards Oliver went, as a postdoc- † toral scholar, to work with Lars Onsager in Yale. Together in ρ1 ≡ ψˆ (r) ψˆ(r') →0 for T > Tc ,

1956 they published a basic paper in which, to quote C. N. < > ≈ Ψ*0(T)Ψ0(T) ≠ 0 for T < Tc , (8.3) Yang 3 they “were the first to give a precise definition of Bose condensation in the case of interacting Bosons.” when |r' − r| → ∞. Clearly Tc locates the transition at which Yang then introduced the name “Off-Diagonal Long- 2 ODLRO, embodied in n0(T) = |Ψ0(T)| , and Bose–Einstein Range Order” (or ODLRO) for the essential concept and, condensation sets in. For liquid helium it is natural to

identify, Tc ≡ Tλ, as the lambda point at which superfluidity appears and the specific heat exhibits its extremely sharp spike. More generally, to include superconductivity one

should, following Yang, consider at least ρ2 the two-particle reduced density matrix. Then large eigenvalues, ≥ O(N), and corresponding ODLRO, originate from pairs of , e.g., Cooper pairs of electrons, engaging in Bose–Einstein degeneracy. Thus, the smallest value of n for which ODLRO

appears in a reduced density matrix ρm(m ≥ n) identifies the “collection of n particles that, in a sense, forms the basic group exhibiting the long-range correlation.” In fact, the article Fig. 19. The theoretical picture of condensation in an ideal gas of N notes that although it customary to regard liquid helium as bosons. Above Tc the occupancy of the lowest eigenstate of energy remains negligible; but below Tc a finite fraction of the bosons are “condensed” a collection of helium atoms obeying Bose statistics, a “much into the ground state, the fraction approaching 100% as T → 0. better description is a collection of electrons and He nuclei.”

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fluids exhibit very sharp peaks at criticality well described by the form

± α CV(T ; ρc) ≈ A /|t| + B, t = (T − Tc)/Tc . (9.1)

This was in direct contradiction to van der Waals (or mean field) predictions. Rather, as Yang and Yang noted, the data were strongly reminscent of the close-to logarithimically divergent specific heat peak for the superfluid transition in helium found by Fairbank, Buckingham, and Kellers in 1957. We now know, however, that in argon and similar fluids, the exponent α introduced in (9.1) is close to 0.109 whereas in superfluid helium it is actually slightly negative with α ~− −0.013. (Note that a logarithmic divergence corresponds, via a simple limit, to α = 0.) Fig. 20. Yang’s fundamental paper on ODLRO, [Rev. Mod. Phys. 34, Yang and Yang then made a series of remarks of which the 694–704 (1962)], showing the first six references visible as footnotes on the title page. first — just visible in Eq. (3) in Fig. 21 — was a misleadingly simple thermodynamic formula, which we rewrite as

∂2p ∂2μ C total = VT ____ − NT ____ . (9.2) V 2 2 In the 1980’s Yang expressed3 his fondness for this paper (∂T )V (∂T )V but remarked that “it is clearly unfinished.” Indeed, there As they emphasized, this relation, based simply on is little doubt that in Yang’s mind were also the questions: SdT = V dp − N dμ, must hold in the two-phase region below “How best to define the observable superfluid density, ρs(T), Tc. Hence it must apply to the observations of Voronel and in microscopic terms?” and, ultimately related: “What is the coworkers in (9.1). Consequently, p and μ in (9.2) can be value of the corresponding critical exponent?” As regards replaced by the condensation loci, pσ (T) and μσ(T); thus one ODLRO it became clear that, in general, this is analogous to reaches the question posed pictorially in Fig. 22 (and stated 2 [M0(T)] for a ferromagnet; thus the appropriate exponent is verbally19 in the caption). 2β. It remained, however, for Josephson17,18 to convincingly Now, on the one hand, it is known that μ"σ (T) always argue that for ρs(T) the exponent is slightly different, namely, remains finite in the usual lattice gases in simple droplet models20 and in other exactly soluble systems.21 On the 2β − ην = 2 − α − 2ν = (d − 2)ν , (8.4) other hand in all these cases p"σ (T) becomes singular at Tc! 17B. D. Josephson, Phys. Lett. 21, 608 (1966). where the last equality is restricted to dimensionalities 18See also M. E. Fisher, M. N. Barber, and D. Jasnow, Phys. Rev. A d ≤ 4. In Eq. (8.4) the exponents α and ν describe, respec- 8, 1111–1124 (1973), where ρs(T) is identified as proportional to tively, the specific heat singularity and the divergence of the the so-called helicity modulus, Υ(T), whose definition requires the correlation length, while η < 0.05 is defined via the critical difference of free energies in finite-size systems with antiperiodic and point decay of the pair correlation function: see Eq. (6.4) periodic boundary conditions on the phase of the wavefunction (or its operator). above. And, finally, Yang himself drew attention, 35 years 19M. E. Fisher and G. Orkoulas, Phys. Rev. Lett. 85, 696–699 (2000); G. ago, to his conjectured formula for the penetration depth for Orkoulas, M. E. Fisher, and C. Üstün, J. Chem. Phys. 113, 7530–7545 superconductors in magnetic fields. (2000). 20M. E. Fisher, Physics 3, 255–283 (1967). More elaborate cluster- 9. Yang–Yang Thermodynamics and the Scaling interaction models are in M. E. Fisher and B. U. Felderhof, Ann. Phys. (N.Y.) 58, 176–216, 217–267 (1970); B. U. Felderhof and M. E. Fisher, Axes ibid. pp. 268–280. Nonetheless, some of the models described in Secs. When C. N. Yang visited Stanford in 1963 William Little told 7 and 8 of these articles do yield a divergence of μ"σ (Tc). him of the striking experiments by A. V. Voronel and workers 21It is worth noting here, that for ferromagnets (and other systems 2 2 in Russia. This led to the article with his brother, Chen Ping with a corresponding symmetry) the vanishing of (d μσ /dT ) cannot Yang, shown in Fig. 21. Voronel’s observations on argon and be questioned. Thus the chemical potential is replaced by the magnetic field, H, subject to the symmetry, H → −H, and the phase boundary, oxygen made it clear that the specific heats of ordinary μσ (T), becomes simply H = 0.

March 2016, Volume 5 No 1 35 ARTICLES

Fig. 21. Title and introductory paragraphs of a paper by C. N. Yang and C. P. Yang stimulated by specific heat measurements by Voronel and coworkers [M. I. Bagatskii, A. V. Voronel, and V. G. Gusak, Zh. Eksperimi. i Teor. Fiz. 43, 728 (1962)] on argon, shown in the graphs, and on oxygen a year later.

Experimentally, this as also true for H2O, CO2 and propane, where, up to second-order corrections, the three scaling 19 C3H8. For the hard-core square-well fluid this is likewise fields have the form confirmed by simulation. But as Yang and Yang remark: “For 2 2 real gases, it is more reasonable to expect that both (d μσ/dT ) p˜ = pˇ − k0t − l0μˇ + O2(· · · ) , (9.5) 2 2 and (d pσ/dT ) become ∞” — supposing α ≥ 0.

But why might this “detail” be significant? The answer is: μ˜ = μˇ − k1t , (9.6) “Because the orientations of the basic scaling axes depend 2 2 crucially on the behavior of (d μσ/dT ).” To understand this t˜ = tˇ . (9.7) we define the deviations from critically in the “space of fields” (p, μ, T), as Note that the dimensionless constants, k0, k1, and l0 (and, to

come below, ll, j0 and j1) serve to specify the nonuniversal p − pc μ − μc T − Tc pˇ = ______, μˇ = ______, t = ______, (9.3) orientation of the scaling axes for (p˜, μ˜, t˜) in the space of fields, ρckBTc kBTc Tc (9.2). Recall, however, that the exponents α, β, and γ — for Next notice that the full thermodynamics22 follows from the the specific heat [as in (9.1) and (8.4)], for the magnetization functional relation between p, μ and T. Consequently, the or coexistence curve [as in (2.1), (2.2), and (8.4)], and for presence of asymptotic scaling when pˇ, μˇ, and t → 0, can be the susceptibility or compressibility — should be universal. expressed as 22See, e.g., E. A. Guggenheim, Thermodynamics (2nd Edn., North p˜ μ˜ Holland Publishing Co., Amsterdam, 1950), Chap. II and, especially, Φ ____ , ____ = 0 , (9.4) p. 58; R. A. Sack, Mol. Phys. 2, 8 (1959). The corresponding partition ( 2 − α β + γ ) t˜ t˜ function might be described as “great grand canonical.”

36 Asia Pacific Physics Newsletter ARTICLES

measurements of the liquid and vapor phase boundaries,

ρliq(T) and ρvap(T), can determine the coexistence curve diameter. Scaling now predicts

1− α 2β ρdiam(T) = ρc[1 + c1− α l1|t| + c2β j2|t| + c1t + ...] , (9.12)

with unsuspected power-law correction terms, with ampli-

tudes c1, c2β, and c1− α . The correction proportional to l1 is Fig. 22. The Yang–Yang Question posed graphically! In words: “Given of order |t|0.89; the surprise is that pressure mixing induces a that the well-defined pressure locus of condensation pσ(T), exhibits a 0.65 divergent curvature (i.e., second derivative) at the critical point, is the new term, of order j2|t| , which dominates that previously same true (or not?) for the corresponding chemical potential locus, μσ(T)? And, if true, what is the appropriate19 dimensionless Yang–Yang ratio, known! Clearly, both power-law corrections dominate the Rμ, measuring the relative strength of the divergence of μ"σ(T)? Might Rμ anticipated term c1t, embodied in the Law of the Rectilinear even be negative? [The dashed lines at criticality indicate a well-defined slope, i.e., first derivative.] Diameter.

10. Yang–Yang and “Compressible” Fluid Models The coefficient k1 in (9.6) clearly serves to specify the slope

(dμσ /dTc): see dashed line Fig. 22. Studies of models, e.g., by It is natural to ask if there are models that might reveal 23 Mermin, established the need for a term −ll μˇ in (9.7); but, something about the origins of pressure mixing in the until the question raised by Yang and Yang was considered, scaling fields as is demanded by Yang–Yang anomalies both 19 25 that seemed adequate. However, a careful analysis19 of exten- observed and subsequently found in precise simulations. sive data for propane provided by Abdulagatov et al.24 — but To this end consider, first, the standard nearest-neighbor not available until the late ’90s — revealed the existence of a lattice gas (equivalent to a basic Ising model). As illustrated clear “Yang–Yang anomaly,” i.e., a divergence of μ"σ (T) at Tc! in Fig. 23(a), this can be regarded as representing a fluid of 19 Indeed, the Yang–Yang ratio was estimated as Rμ = 0.56 ± hard spheres of diameter a interacting via an attractive square 0.04 (propane). Examination of restricted data24 suggests a well of range b. Provided the lattice spacing is less than b, 2 which, in turn, must be less than the next-nearest neighbor negative ratio for CO (with Rμ ~− −0.4). Either way it is clear that “pressure mixing” is needed.19 lattice distance, the only approximation is the restriction of Thus the previously accepted equations (9.6) and (9.7) must the particles to lattice sites. 26 be supplemented to read But the lattice gas can be viewed instead as a “cell gas” [illustrated in Fig. 23(b)] in which one identifies adjacent

μ˜ = μˇ − k1t − j2pˇ , (9.8) lattice cells of volume υ0. A cell may be empty or (due to the hard cores) occupied by no more than a single particle

t˜ = t − l1μˇ − j1pˇ , (9.9) that can move freely in its cell. This motion contributes a Boltzmann factor exp(−pυ0/kBT) for each particle. The main with two further amplitudes j1 and j2 [as well as higher order approximation is that the attractive well comes into play only terms as in (9.5)]. between particles in nearest-neighbor cells and does not It is then straightforward to see that the condensation depend on their actual positions within the cells. boundaries have the form 23N. D. Mermin, Phys. Rev. Lett. 26, 169 (1971). 24 2− α 2 I. M. Abdulagatov et al., Fluid Phase Equilib. 127, 205 (1997); data μσ(T) = μc + μ1t + Aμ|t| + μ2t + ... , (9.10) for CO2 by I. M. Abdulagatov et al., J. Chem. Thermodyn. 26, 1031 (1994). 2− α 2 ... pσ(T) = pc + p1t + Ap|t| + p2t + . (9.11) 25Y. C. Kim, M. E. Fisher, and E. Luijten, Phys. Rev. Lett. 91, 065701 (2003). This work led to Rμ ~− −0.044 for the hard-core square-well ~ On returning to the Yang–Yang expression (9.2), one sees fluid (with b/a = 1.50 in Fig. 23) and to Rμ − 0.26 for the restricted primitive model of an electrolyte. See also: G. Orkoulas, M. E. Fisher, that both amplitudes Aμ and Ap specify the divergence (for and A. Z. Panagiotopoulos, Phys. Rev. E 63, 051507 (2001); Y. C. Kim, α > 0) of the specific heat at constant volume. The Yang–Yang M. E. Fisher, and G. Orkoulas, Phys. Rev. E 67, 061506 (2003). ratio then follows from Rμ = −j2/(1 − j2). 26This way of regarding a lattice gas was learnt from Benjamin Widom But a further surprise remains! Sufficiently accurate (private communication).

March 2016, Volume 5 No 1 37 ARTICLES

Fig. 23. Illustration of (a) the standard lattice gas and (b) its reinterpreta- tion as a cell gas which, in turn, suggests (c) the compressible cell gas model which, in general, yields a Yang–Yang anomaly.

How might this model be improved? Can one relax the “rigidity” imposed by the lattice structure? The alternative (c) Fig. 24. The components of the Yang–Yang relation (9.2) for a simple compressible cell gas on the simple cubic lattice yielding a negative ratio in Fig. 23 presents one such extension: Even in the absence Rμ. of particles the lattice volume may fluctuate and respond to pressure; thus individual cells are allowed to assume distinct (0) volumes, υi (i = 1, 2, . . . , q), that lead to corresponding (but (0) independent) Boltzmann factors exp(−pυi /kBT). The same “Exact Solution of a Model of a Two-Dimensional Ferro- idea may be used for singly-occupied cells, thus the model electric in an Arbitrary External Electric Field,” Phys. Rev. supposes that particle motion is restricted to a (possibly) Lett. 19, 588 (1967). (1) different set of cell volumes, υi . It is natural, but not neces- From a more mathematical point of view the analysis also (1) 29 sary, to suppose that each υi is smaller than the associated led specifically to the so-called Yang–Baxter equations. The (0) (1) (0) υi ; simplest is to take υi = υi − υσ for fixed υσ > 0. first publication where these equations appeared was by C. N. Now when the original lattice gas can be analyzed (say, Yang in: “Some Exact Results for the Many Body Problem in numerically) this Compressible Cell Gas (or CCG) proves One Dimension with Repulsive Delta-Function Interaction,” equally soluble! And the same applies to many of its exten- Phys. Rev. Lett. 19, 1312 (1967). But space did not allow sions and different versions.27 As an illustration Fig. 24 proofs of some of the crucial equations; complete details, (0) (0) 30 presents the simple case where q = 2 and υ2 = 2υ1 while however, were supplied by M. K. Fung in J. Math. Phys. (0) υσ = υ1 (the underlying lattice being simple cubic). Evidently 22, 2017 (1981). A fuller presentation of the 1D model had 27 the Yang–Yang ratio, Rμ , is now unmistakably negative (as, to wait over twenty years until the appearance in Commun. one may recall,19 seems so for carbon dioxide). However, Math. Phys. 122, 105 (1989) with first author Gu Chao-Hao, (1) positive ratio Rμ are found when the cell volumes υi are who visited the State University of New York at Stony Brook, coupled with distinct interaction energies, in particular when 27R. T. Willis and M. E. Fisher [poster], Thermo 2005 Meeting, Univer- smaller cells are associated with larger energies.27 sity of Maryland, 29–30 April 2005; C. A. Cerdeiriña, G. Orkoulas, and M. E. Fisher [abstract and poster], XV Congress of. Stat. Phys., Royal Spanish Phys. Soc., Salamanca, 27–29 March 2008; [abstract] 11. The Richness of Statistical Mechanics Proc. 7th Liquid Matter Conf., Lund, June 2008; to be published. 28H. A. Bethe, Zeit. Physik. 71, 205–226 (1931). Following his first paper in 1964, C. N. Yang wrote half a 29R. J. Baxter, Phys. Rev. Lett. 26, 832–833 (1971), solved exactly the dozen further articles with his brother Chen Ping Yang, in so-called eight-vertex model, see also Exactly Solved Models in Statis- the next five years. Many addressed anisotropic Heisenberg tical Mechanics (Academic Press, London, New York, 1982), Chaps. 9 spin systems, particularly in one-dimensional chains. Three and 10; and “Some Academic and Personal Reminiscences of Rodney papers, in particular; Phys. Rev. 150, 321, 327; 151, 258 James Baxter”, J. Phys. A Math. Theor. 48, 254001 (2015). 30 (1966), discussed, extended, and exploited the mathematics See C. N. Yang, Selected Papers II, With Commentaries (World Scientific Publishing Co., Singapore, 2013). originally introduced for Heisenberg spins by 31T. Y. Cao (editor), Conceptual Foundations of 28 over three decades earlier in 1931. A notable by-product, (Cambridge University Press, Cambridge, 1999), Presentations 1 to 26 published with B. Sutherland as first author, reported an: in parts I to X.

38 Asia Pacific Physics Newsletter ARTICLES from the Chinese University of Science and Technology in fermions in one-dimensional traps with Ma Zhong-Qi and, Hefei. Gu and Yang presented a 1D Fermionic model with concerning multicomponent fermions and bosons, with an explicitly factorized S matrix. The Yang–Baxter equations You Yi-Zhuang.30 ab for the related matrices X ij , namely, The main focus of the career of Chen Ning Yang—as also true of this meeting — has clearly been on quantum field ab cb ca ca cb ab X ij Xkj Xki = Xki Xkj X ij , (11.1) theory for the understanding of fundamental particles or “high-energy physics.” It may, hence, be appropriate to draw appeared as consistency conditions for the validity of Bethe’s attention to the proceedings31 of a meeting held in Boston hypothesis. University on 1–3 March 1996 concerning the foundations of An exposition of the essential steps in using the hypoth- quantum field theory. The two-day symposium, followed by esis had been presented in 1970 at a Winter School of Physics a workshop, was sponsored by the Center for Philosophy and in Kapacz in Poland.3 Much later, on reviewing his “Journey History of Science at Boston University. Among the speakers through Statistical Mechanics” in 1987 at the Nankai were David J. Gross, who featured here in Singapore, and I Institute of Mathematics,30 Yang pointed out the similarity myself. There were lively discussions and, as the Preface31 of the Yang–Baxter equations to the braid group relation put it: “interesting material about the tension between two ABA=BAB used in the classification of knots. The reader groups of scholars.” was invited to conclude that perhaps “these cubic equations C. N. Yang is almost unique in having contributed embody some fundamental structure still to be explored.” fundamentally to both the broader aspects of statistical After 33 years at SUNY in Stony Brook, Chen Ning mechanics and to central issues in quantum field theory. In Yang retired in 1999. Four years later, in December 2003 concluding my present contribution, I would like to draw he moved to Tsinghua University in Beijing. There he had attention to the article by David Nelson entitled: “What is the opportunity of developing his passion for the history of Fundamental Physics? A Renormalization Group Perspective” physics, especially as regards its philosophical and conceptual and the subsequent discussion (Sec. 18, pages 264–267, roots. Recall that, years earlier in 1982, while still in the in the proceedings31). Finally, I offer Fig. 25 as a pictorial United States, he4 had drawn attention to Joseph Mayer’s 1937 representation of the richness of statistical physics and the attack on the statistical mechanics of condensation in fluids. connections to quantum field theory. But still the stimulus of new experiments and the challenge of understanding them led once again to work in statistical Note: This article will also appear in “Proceedings of Conference of 60 years of Yang–Mills ‘Gauge Field Theories — C. N. Yang’s Contribu- physics or, essentially indistinguishable at the theoretical tions to Physics’, ” edited by: Lars Brink and Phua Kok Khoo (World level, “condensed matter physics.” Note in particular, a paper Scientific, 2006). alone in 2009 and further articles in 2009–2010 concerning

Fig. 25. The wide “Land of Statistical Physics” connected by a now sturdy bridge to the “Island of Quantum Field Theory”.

March 2016, Volume 5 No 1 39 ARTICLES 1 Yoichiro Nambu Nambu and and the the Origin Origin of Mass of ∗Mass*

Tom W. B. Kibble Blackett Laboratory, Imperial College London SW7 2AZ,Tom UK W. B. Kibble Blackett Laboratory, Imperial College

Abstract: This note summarizes and celebrates the important other forces could also be described by gauge theories. contributions of Yoichiro Nambu to the tricky question of the The first suggested beyond QED was that origin of particle masses. of Yang and Mills in 1954,5 intended as a theory of strong interactions based on a gauged version of the SU(2) isospin The origin of the masses of elementary particles has been a symmetry. The same theory was in fact written down in the major puzzle since the early days of particle physics, and same year by Ronald Shaw, a student of ’s in remains so today. For example, we have no real idea of Cambridge, although it was never published except as part where the quark masses come from. There has however of a Cambridge University PhD thesis.6 been important progress, including the very significant de- There was however an immediately obvious problem velopment of the idea of spontaneous symmetry breaking with this or any gauge theory of the strong or weak in- in gauge theories. In that development many of the key teractions. How could we understand the short range of early steps were taken by Yoichiro Nambu. In the excite- these forces, demanding massive intermediate force car- ment that followed the very probable discovery in 2012 of riers, when the gauge bosons are apparently naturally the Higgs at the LHC in CERN, most of the attention massless? Indeed it was widely seen as one of the suc- was on later theoretical developments, in particular the so- cesses of QED that gauge invariance correctly predicted called , and perhaps this important early the masslessness of the photon. The issue was somewhat work was unfairly neglected. clouded in the case of the Yang–Mills theory by the fact that isospin symmetry is only approximate. But this still left a 1. Physics after the Second World War big puzzle. It was well known that simply adding a mass term for the vector field into the Lagrangian would yield There was a great flowering of particle physics in the years a non-renormalisable, and hence inconsistent, theory. So following the end of the Second World War, when large how could the theory consistently accommodate massive numbers of physicists who had been working on military vector particles? projects returned to their university laboratories. The first person to note that gauge invariance does On the theoretical side the great triumph was the devel- not in fact require the photon to be massless was Julian opment of renormalisation theory independently in 1947 Schwinger in 1957.7 If the photon’s interaction were strong 1 2 by and by , and ear- enough it could in fact acquire a non-zero mass. lier, in 1943, by Sin-ichiro Tomonaga.3 This showed that calculations beyond the lowest order in the fine structure constant are possible in (QED). 2. Spontaneous Symmetry Breaking in At the same time, on the experimental side the beautiful Superconductivity experiments of Willis Lamb4 provided an extremely accu- Outside of particle physics, the great advance of the rate value for the in hydrogen, the separation nineteen-fifties was the work of Bardeen, Cooper and between the 2s1/2 and 2p1/2 energy levels. The theoretical Schrieffer8 that provided the first real understanding of the calculations were able to fit that result and the measured mechanism of superconductivity. The phonon-mediated anomalous magnetic moment of the electron with unprece- interaction can bind pairs of electrons with opposite mo- dented accuracy. menta and spins to form Cooper pairs. When the system is This triumphant success of QED encouraged particle cooled below the critical temperature, these form a Bose– physicists to search for similarly successful theories of the Einstein condensate, with macroscopic occupation of a sin- other forces, the strong and weak nuclear interactions. gle quantum state. Since QED is a gauge theory, and gauge invariance plays Prior to that development, a very useful phenomeno- an important role in rendering the theory consistent (via logical model of a superconductor was provided by the Ward identities), it was natural to ask whether the Ginzburg and Landau,9 with a scalar order-parameter field ∗This paper will also appear in Memorial Volume for Y. Nambu. φ(t, x) representing the Cooper pairs. Here |φ2| represents

40 Asia Pacific Physics Newsletter ARTICLES2 the number density of pairs. Since the pairs are formed of 3. The Superconductor Analogy two electrons, the appropriate gauge transformation is Nambu went on to suggest that elementary particle masses 2ieλ + ∇ φ → φe , A → A λ . (1) might be generated by a similar mechanism. He con- The Hamiltonian (with = c = 1) is structed a model to illustrate this possibility, though not a gauge theory. As a possible model of strong interactions, = 3 1 ∗ + H d x Dφ · Dφ V(φ) , (2) he envisaged a model based on a four- interaction, 2m  where the covariant derivative is with symmetries under both ordinary and chiral global transformations: Dφ = ∇φ − 2eAφ , (3) ψ(x) → eiαψ(x), ψ(x) → eαγ5 ψ(x) , (7) and the effective potential V is a function only of φ∗φ.

Near to the critical temperature Tc, it may be expanded as with corresponding conserved Noether currents: a power series, with temperature-dependent coefficients, jµ = ψγ¯ µψ , jµ = ψ¯iγµγ ψ . (8) keeping only the lowest terms, 5 5 1 By analogy with superconductivity, he suggested that the V = α(T)φ∗φ + β(T)(φ∗φ)2 . (4) 2 nucleon mass could be generated by spontaneous breaking As the temperature is lowered through Tc, α changes sign, of the chiral symmetry. and the bowl shape of V is replaced by sombrero shape, Nambu and Jona-Lasinio12 then constructed a specific where the minimum energy is found not at φ = 0 but model to illustrate this idea, based on the Lagrangian around the circle L = µ + 2 − 2 −α iψγ¯ ∂µψ g[(ψψ¯ ) (ψγ¯ 5ψ) ] . (9) φ∗φ = . (5) β Symmetry breaking occurs when a non-zero expectation So in the minimum-energy state, φ acquires a non-zero value �0|ψψ¯ |0� is formed. They showed that this would expectation value, somewhere around this circle, implying imply a non-zero mass for the quasiparticle, here identified a spontaneous breaking of the gauge symmetry. There with the nucleon. is a degenerate family of ground states, labelled by the A key feature of the model is the appearance of a phase of the order parameter. Moreover, because the cur- massless scalar boson. As shown by Goldstone,13 this is vature of the potential in the radial direction is non-zero, inevitable in a relativistic theory with a spontaneously an effective mass is generated for the gauge boson. The broken global symmetry. photon becomes a massive . At zero temperature, Of course, the Nambu–Jona-Lasinio model turned out the plasmon mass mpl is given by not to be the correct description of strong or weak interac- 2 tions, but it was nevertheless a very significant step on the 2 = e ne mpl . (6) ǫ0me way to developing one. It was widely believed in the particle physics com- In our units, mpl is the same thing as the plasma frequency munity that the same result must hold also for a local ωpl, the minimum frequency with which electromagnetic 14 waves can propagate within the superconductor. gauge theory, and that these massless Nambu–Goldstone This idea of broken gauge symmetry was quite con- bosons would necessarily appear. This seemed to present troversial at the time, with many physicists insisting that an insurmountable obstacle, since no such bosons had been the system must ultimately have a definite particle number seen, although they should have been easy to spot. It took and hence completely uncertain phase; the true ground a couple of years for particle physicists to understand how state must be a gauge-invariant superposition of these this could come about, via the so-called Higgs mechanism, degenerate states. It is now commonplace to talk of su- embodied in three independent papers published in Physi- perconducting states with definite phase, but that notion cal Review Letters in 1964.15–17 took a long time to be accepted. Nambu10 gave a par- ticularly clear account of the situation, using a modified 4. Conclusions form of the Hartree–Fock approximation, demonstrating the intimate connection between symmetry breaking and These three papers attracted very little interest — and quite the existence of an energy gap. In a closely related paper, a lot of scepticism — for the first two or three years, but Bogoliubov11 pointed out that quasiparticles do not have they laid another part of the groundwork for the develop- a definite charge; a quasiparticle is a linear combination of ment of the unified electroweak theory of Weinberg18 and an electron with momentum p and spin up, say, and a hole Salam,19 now an established component of the Standard in the state with momentum −p and spin down. Model and triumphantly vindicated by the almost certain

March 2016, Volume 5 No 1 41 ARTICLES 3 discovery in 2012 of the at the Large Hadron [7] J. S. Schwinger, A theory of the fundamental interactions, Annals Collider in CERN.20,21 Phys. 2, 407 (1957). [8] J. Bardeen, L. N. Cooper and J. R. Schrieffer, Theory of super- It is clear that Nambu made many of the essential conductivity, Phys. Rev. 108, 1175 (1957). early contributions towards the eventual development of [9] V. L. Ginzburg and L. D. Landau, On the theory of supercon- ductivity, Zh. Eksp. Teor. Fiz. 20, 1064 (1950). this theory, with unique insights into both particle physics [10] Y. Nambu, Phys. Rev. 117, 648 (1960). and superconductivity. Without his seminal work, it would [11] N. N. Bogoliubov, A new method in the theory of supercon- ductivity I, Sov. Phys. – JETP 7, 41 (1958) [J. Exper. Theor. Phys. surely have taken much longer to arrive at that goal. (USSR) 34, 58 (1958)]. [12] Y. Nambu and G. Jona-Lasinio, Phys. Rev. 122, 345 (1961). [13] J. Goldstone, Field theories with superconductor solutions, References Nuovo Cim. 19, 154 (1961). [14] J. Goldstone, A. Salam and S. Weinberg, Broken symmetries, Phys. Rev. 127, 965 (1962). [1] J. S. Schwinger, On quantum electrodynamics and the magnetic [15] F. Englert and R. Brout, Broken symmetry and the mass of gauge moment of the electron, Phys. Rev. 73, 416 (1948). vector bosons, Phys. Rev. Lett. 13, 321 (1964). [2] R. P. Feynman, A relativistic cutoff for classical electrodynamics, [16] P. W. Higgs, Broken symmetries and the masses of gauge Phys. Rev. 74, 939 (1948). bosons, Phys. Rev. Lett. 13, 508 (1964). [3] S. Tomonaga, On a relativistically invariant formulation of the [17] G. S. Guralnik, C. R. Hagen and T. W. B. Kibble, Global quantum theory of wave fields, Prog. Theor. Phys. 1, 27 (1946). conservation laws and massless particles, Phys. Rev. Lett. 13, 585 [4] W. E. Lamb and R. C. Retherford, Fine structure of the hydrogen (1964). atom by a microwave method, Phys. Rev. 72, 241 (1947). [18] S. Weinberg, Phys. Rev. Lett. 19, 1264 (1967). [5] C. N. Yang and R. L. Mills, Conservation of isotopic spin and [19] A. Salam, Elementary Particle Theory: Proceedings of the Nobel isotopic gauge invariance, Phys. Rev. 96, 191 (1954). Symposium, Lerum, Sweden, 1968, ed. N. Svartholm (Almqvist [6] R. Shaw, Invariance under general isotopic gauge transforma- & Wiksell, Stockholm, 1968), Conf. Proc. C, 680519, 367–377. tions, Cambridge University PhD thesis, Part II, Chapter III [20] ATLAS Collab. (G. Aad et al.), Phys. Lett. B 716, 1 (2012). (1955), unpublished. [21] CMS Collab. (S. Chatrchyan et al.), Phys. Lett. B 716, 30 (2012).

42 Asia Pacific Physics Newsletter ARTICLES1 Superfluidity and Symmetry Breaking — SuperfluidityAn Anderson Living and Legacy Symmetry Breaking

—Frank WilczekAn Anderson Living Legacy* Center for Theoretical Physics, MIT FrankCambridge, Wilczek MA 02139, USA Center for Theoretical Physics, MIT

Abstract: This is an eclectic survey of concepts around superflu- that I’ve been thinking about recently. I’ll save the idity and symmetry breaking, prepared for the celebration of Phil details for the main text; here I’ll just say that they Anderson’s 90th birthday in October 2013. I emphasize, through demonstrate the continued vitality of Anderson’s major examples, that the concepts Anderson pioneered in this ideas and style of thinking, as we bring them to bear field have very wide scope, penetrating in particular into many central issues of high energy physics: electroweak symmetry on new questions. breaking, confinement, , and Majorana Anderson’s work on the renormalization group has also mass. I also illustrate how Anderson’s pseudospin method can be had profound impact in high energy physics, but I will not used to exemplify breaking of time translation symmetry. discuss that here.

Phil Anderson doesn’t present himself as a high energy physicist, but he’s been a very influential one. In particular, 1. Canonical Models: Superfluidity and his focus on symmetry and its breaking, and the clarity of Superconductivity vision he achieved through his analysis of concrete prob- 1.1. Superfluidity: Symmetry breaking lems in magnetism, superfluidity, and superconductivity, have helped us to see many other things more clearly, and The simplest model for superfluidity involves a complex in new ways. We’ve come to appreciate that we live inside scalar field that supports a phase (U(1)) symmetry in its a cosmic superconductor. fundamental equations, but not in their stable solutions. The theory of symmetry breaking has two main aspects: This sort of theory describes the superfluidity of liquid 4He. macroscopic, and microscopic. The macroscopic part cen- In that context, the scalar field creates and destroys helium ters around the consequences of symmetry breaking, the atoms, and the (spontaneously broken) phase symmetry microscopic part centers around the mechanisms that cause is associated, through Emmy Noether’s famous theorem, it. Anderson made major contributions to both parts. with conservation of 4He atom number. Here, by way of tribute, I will discuss three things. The scalar field is subject to a potential

• First, I will present the distilled essence of global µ2 λ V(φ) = − φ∗φ + (φ∗φ)2. (1) and local symmetry breaking in two simple, canoni- 2 4 cal models. Those models arose by abstraction from The energy, as a function of the expectation value of the 4 superfluid He and standard superconductors, respec- field, is minimized at tively. They capture central aspects of the macroscopic |�| |�| = theory, and their ideas carry over to chiral symmetry φ v 0 (2) µ breaking in QCD and to electroweak symmetry break- v = √ (3) ing, respectively. λ • Second, I will discuss the theory of hadronic matter at and to minimize the kinetic (gradient) energy we must ultra-high density (large number, low temper- choose a single space-time constant value for �|φ|�. Whereas ature). The microscopic pairing theory pioneered by the potential, and the equations of motion of the theory BCS, which Anderson both clarified and generalized, as a whole, are left invariant under multiplication of the φ is beautifully adapted to this problem. It suggests a field by an arbitrary phase factor, those specific minimum form of symmetry breaking that leads, through the energy solutions are not. macroscopic theory, to some very striking results. In Deep issues arise around the precise realization of can- particular, the classic “hard” non-perturbative chal- didate states that support solutions of Eq. (2), in view of lenges of QCD, to demonstrate confinement and chiral the fact that φ is subject to quantum and thermal fluctu- symmetry breaking, are consequences. ations. The strength of the coupling, the dimensionality • Finally, I will briefly mention two new applications, of the system, and its volume are all relevant factors. *This article also appears in PWA: A Lifetime of Emergence

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Phil Anderson contributed greatly to our understanding easily moved. That is a heuristic way to understand super- of those issues, but that belongs to a branch of his work fluidity: Superfluidity is flow mediated by the soft modes (the renormalization group) that I won’t pursue here. The or Nambu–Goldstone bosons. basic upshot is that when the coupling is sufficiently weak, The ρ field, which parametrizes fluctuations in the am- the temperature sufficiently low, the dimension sufficiently plitude of the condensate, in more conventional. Consider- high, and the system sufficiently large — and only then! — ing Eqs. (6) and (7) we see that it represents√ a hard mode, we can justify the naive procedure. whose quanta are (quasi)particles of mass 2µ. The cubic To understand the consequences of Eq. (2), we expand and quartic terms in Eq. (7) represent self-interactions of 4 − µ around a typical one, where the expectation value is simply these quanta, and the numerical term 4λ represents the �φ�, with no phase factor, according to energy density gained through condensation. When the theory is coupled to gravity, it represents a contribution to φ ≡ + ρ iθ ≡ + ρ iσ/v (v )e (v )e . (4) the cosmological term, that can be profoundly problematic Here ρ and σ are fields, that vanish in the minimum (see below). energy state (ground state) we have chosen. We describe procedure as expanding around a condensate. Expressing 1.2. Superconductivity: Gauged symmetry the basic Lagrangian in terms of these fields, we have breaking

1 µ ∗ L = ∂ φ ∂µφ − V(φ) (5) Classic superconductors are described by a gauged version 2 2 of the same model. This is a case of “More is Different,” if 1 ρ µ 1 µ → 1 + ∂ σ∂µσ + ∂ ρ∂µρ − V˜ (ρ) (6) ever there was one. 2 v  2 √ We introduce gauge field degrees of freedom using the µ4 3 λ λ V˜ (ρ) = − + µ2ρ2 + ρ3 + ρ4. (7) Maxwell Lagrangian, and we replace ordinary by gauge co- 4λ 4µ 4 variant derivatives in the scalar kinetic terms. The potential The interpretation of Eqs. (6) and (7) is simple. The σ is unchanged. Thus we consider field occurs only in the first term of Eq. (6). Therefore it 1 µν 1 µ ∗ L →− F Fµν + (∇ φ) ∇µφ (8) represents a soft mode: Its variations carry zero energy, in kin. 4 2 the limit of infinitely long wavelength and low frequency. Fµν = ∂µAν − ∂νAµ (9) In a particle interpretation, it represents the field of a massless particle. Modes of this kind often arise when one ∇µφ = ∂µφ − igAµφ. (10) expands around solutions which have less symmetry than the underlying equations, and they are commonly referred Expanding the covariant derivative term in Eq. (8) we to as Nambu–Goldstone bosons.a One also has non-linear find 2 interactions, between the σ field and the amplitude fluctu- µ ∗ 1 ρ µ µ (∇ φ) ∇µφ → 1 + (∂ σ − gvA )(∂µσ − gvAµ) (11) ation field ρ. 2 v  The characteristic “superfluid” phenomenology of su- 2 2 2 = g v + ρ µ perfluid 4He is due to the existence of this mode. The 1 A˜ A˜ µ (12) 2 v  phase symmetry of the underlying equations, which is 1 spontaneously broken in our ground state, was meant to A˜ µ ≡ Aµ − ∂µσ. (13) gv encode conservation of 4He atoms. Of course, conservation of the number of 4He atoms is not really violated. Enclos- Once again the interpretation is simple, though at first ing any finite sample of 4He we can draw an enclosing encounter startling. It is natural, as in Eq. (13), to intro- surface, at which we can apply the reasoning that leads to duce a new field A˜ µ, wherein the gauge potential Aµ is − 1 conservation. But if we draw a surface within the sample supplemented by a longitudinal contribution gv ∂µσ. The we must worry about surface terms, and that changes new field is still governed by the Maxwell Lagrangian, the picture completely. The observable consequence of the since the longitudinal field cancels in Fµν. But, according mathematical violation, is that this quantum number is to Eq. (12), it has acquired mass gv. We also find non-linear interactions between A˜ µ and the amplitude fluctuations ρ. aThe naming of this, and of several other concepts I’ll be discussing, The σ field, which represented a soft mode in the theory itself involves a sort of spontaneous symmetry breaking. While never wholly inappropriate, the chosen names typically reflect historical without gauge symmetry, no longer appears as a separate choices among a number of valid possibilities, which have been degree of freedom. frozen into the literature in order to minimize some sort of ambiguity function. Rectification of names is a profound task, and I will not The characteristic macroscopic phenomenology of su- attempt it here. perconductors is largely implicit in this model, but subtle

44 Asia Pacific Physics Newsletter ARTICLES 3 to extract. The major bulk feature of superconductors in- of the effective Hamiltonian, derived phenomenologically, volves removing low-energy dynamics from the gauge field, begs to be explained by vector boson exchange. And the as epitomized by the Meissner effect. One also induces an universal coupling strength for very different particles, energy gap for the electrons, as I’ll discuss momentarily. So suggests an underlying gauge invariance. A major diffi- the bulk signatures are essentially negative. culty, that held up the fruition of this idea by several years, Reflecting this situation, on the formal side, we find was the apparent difficulty of reconciling gauge invariance that there is no proper bulk order parameter. The phase of with nonzero mass for the vector bosons. Anderson was the expectation value �φ� is gauge dependent, and gauge the first to articulate that this difficulty might be only dependent quantities are unphysical. Strictly speaking, the apparent, and he discussed several examples where it is Hilbert space of the gauge theory must be restricted, or pro- transcended. Brout and Englert, Higgs, and also Guralnick, jected, onto gauge-invariant states; for only in that sector Hagen, and Kibble showed that it could be transcended do we find a positive definite metric. at weak coupling and using Lagrangians well adapted to It is common to speak of “gauge symmetry break- the needs of particles physics, along the lines we reviewed ing,” but gauge symmetry actually represents a conve- above. The underlying equations would look very familiar nient mathematical redundancy in the physical descrip- to Landau and Ginzburg, or even London, from their mod- tion. Gauge symmetry must be factored out, and cannot eling of macroscopic superconductivity decades before; but be broken. We can and should speak instead of “gauged it required an audacious psychological leap, to picture the symmetry breaking”. When the gauge coupling is weak, world as a superconductor, seen from the inside. we can use the procedure above, based on adding the Modern electroweak theory incorporates an extension effect of gauge interactions to a model of global symmetry of the classic model described above, and the Higgs boson breaking, to draw approximate physical conclusions. That is essentially the ρ field of that model. As such, it is the is the intellectually respectable interpretation of gauged not the central player in the dynamics of spontaneous symmetry breaking. symmetry breaking, but an avatar. The same results for If we didn’t get to view them “from the outside” — if vector boson masses, specifically, would result if we had we didn’t have access to external electromagnetic fields, a different potential V, or if we had several scalar fields, surfaces, and weak links — then superconductors would keeping the appropriate weighted sum of contributions to be featureless. Fortunately, we do! A vast wonderland, the vector boson masses fixed. Nevertheless, in the spirit of largely charted by Anderson, featuring the Meissner effect Occam’s razor — or its generalization, the Jesuit Credo that (as a positive phenomenon), persistent currents, Josephson “It is more blessed to ask forgiveness than permission.” — effects, and many other phenomena both interesting and it makes good sense to analyze the consequences of the useful, opens before us. simplest possible model, to learn how well that approxi- mates observed reality, if it does at all. 1.3. Application to electroweak symmetry A picture of the discovery channel may afford the best breaking introduction to what’s involved (see Fig. 1). Since the primary couplings of the Higgs particle to But if some form of intelligent life evolved within a su- other fundamental particles in the standard model are perconductor, and experienced it only from the inside, the proportional to those particles’ masses, its direct, pri- accessible manifestations of gauged symmetry breaking mary coupling of the matter our accelerator accelerates — would be subtler. They might notice that there is a massive protons — is highly suppressed. For protons mainly con- vector excitation (the photon) with a simple pattern of cou- tain up and down quarks and antiquarks, whose mass is plings, and wonder whether it might be described using a very nearly zero, and color , whose mass is exactly model based on gauged symmetry breaking. If the model- zero. The main line of communication, as I discovered, ing went smoothly, and suggested new consequences that is through quantum fluctuations. In the picture, we see were verified, they might eventually convince ourselves that fact reflected in the virtual particle loop. Both gluons that they live inside a superconductor. and quarks couple efficiently to virtual — an- Something very much like that has occurred over the titop antiquark (tt¯ ) pairs: the gluons through their color last few decades of human history, culminating in the recent charge, the Higgs particle through their mass. Once the discovery of the Higgs boson. Higgs particle is produced, it can decay into two pho- The phenomenology of the weak interaction offered tons through a similar process, this time involving ei- + several clues that a description using gauged symmetry ther tt¯ or W W− virtual pairs. Although this is a small breaking would be appropriate. (Of course, this is much decay branch, it is very advantageous from an experi- clearer in retrospect!) The V−A current × current structure mental point of view, because energetic photons are both

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Fig. 2. This plot (courtesy of the CMS collaboration) of the production rate for two photons, as a function of their invariant mass, was among the first clear indications for the existence of a near-minimal Higgs particle, with mass close to 125 GeV. As you can see, itʼs very impor- Fig. 1. This stylized depicts the process through tant to understand the background quantitatively! Thus the discovery which the Higgs particle was discovered. As described in the text, it confirmed the accuracy of the standard model, as a description of brings many aspects of our deep theory of matter into play. To follow reality, and our ability to calculate its consequences, in many more the process in time, we advance from bottom to top. The beams at ways than one. the Large Hadron Collider contain rapidly counter-moving protons, that are brought into collision. Protons are constructed, according to QCD, from more basic building blocks, including gluons, whose 1.4. Conventional versus Majorana mass properties are simpler to analyze, and which (unlike holistic protons) support large energy-momentum flows. The core process, for Higgs production, involves collision of two gluons. (The remainders of the Before leaving this subject, I’d like to comment briefly on protons interact with one another and materialize in complex ways. the use of gauged symmetry breaking to generate fermion They constitute a dominant “background,” that one must control very masses. Here, there is a significant difference between the well in order to a extract meaningful signal.) These connect to the Higgs particle, which then decays into two photons. Photon pairs with standard model and superconductivity. I will gloss over invariant mass in the range of interest are relatively difficult to produce several technicalities, mainly highlighting one simple but by conventional standard model processes, so this signal rises above important, entertaining point. background. In the standard model, we move from couplings of the φ field to mass terms for fermions ψ basically as follows: quite distinctive and relatively difficult to produce in other ∼ ρ ρ yψφψ¯ → yv 1 + ψψ¯ ≡ mψ 1 + ψψ¯ . (14) ways. v  v  This is what the discovery plot looked like Fig. 2 repro- Together with the mass term, we have a proportional cou- duces the discovery plot. pling to the ρ field. Since the discovery announcement, the measurements In superconductors, the closest analogue to a mass term have become both more extensive and more accurate. In is the electron gap. It arises from electron-electron interac- particular, several additional production and decay chan- tions, when we have pairing into a condensate, basically as nels have been explored. follows: So far, all results are consistent with the minimal model. ∼ κe¯eee¯ → κ�e¯e¯�ee + h.c. (15) It remains important to keep pushing, because by its nature the Higgs particle opens a portal into several not implausi- The condensate e¯e¯, in the microscopic theory, supplies the ble forms of new physics. For example, considering the two φ field of the macroscopic theory. But the mass term is photon channel, there could be contributions from heavier of a different kind, involving particle number violation. particles, yet unknown, to the virtual particle loops. Also, Mass terms of this kind, though they do not arise in the if the Higgs sector is not minimal — if there’s more than standard model, are important in some of its possible one scalar field involved — the couplings of the observed extensions. They arise in the description of neutrinos, and particle will diverge from minimal expectations. It would in the description of various hypothetical particles that are be remarkable if the minimal model continues to survive introduced to implement supersymmetry. Particles whose close scrutiny, but I don’t expect it. mass is of this type can annihilate, at rest, in pairs. They

46 Asia Pacific Physics Newsletter ARTICLES5 are called Majorana fermions. We see that inside a super- In conventional superconductors it is quite subtle to conductor, near the nominal Fermi surface, electron/hole find an effective attractive interaction between electrons. quasiparticles are Majorana fermions. The primary interaction between electrons is the Coulomb (In metals the ordinary electron mass does not provide interaction, and it is of course repulsive. To find an at- a gap, of course. Formally, that is because it is cancelled by tractive interaction one must bring in phonons, retarda- the chemical potential.) tion, and screening, and concentrate on modes within a thin shell around the Fermi surface. For many “unconven- 2. QCD Meets BCS tional” superconductors, famously including the cuprates, the mechanism of attraction remains unclear. In all cases 2.1. Conceptual background the superconducting transition temperature (which reflects A wise principle states “It is more blessed to ask for- the attractive dynamics) is far below the melting tempera- giveness than permission.” In that spirit, we consider the ture (which reflects the primary dynamics). possibility of constructing a description of high-density In QCD it is more straightforward. The primary interac- QCD based on its elementary degrees of freedom, quarks tion can already be attractive. Two separated quarks, each and gluons. in the triplet 3 representation, can be brought together in Can we really bypass the forbidding complexities of nu- the antisymmetric 3¯. The disturbance in the field due clear physics, and use those elementary degrees of freedom to is then half what it was; since the field directly? At first sight that idea looks extremely plausible. energy has decreased, the force is attractive. By zeroing High density means large Fermi surfaces. Neglecting in- the spin — that is, once again, choosing the antisymmetric teractions, the low-energy excitations are associated with channel — we also remove the sources of magnetic distur- action near the Fermi surface: a mode just above the Fermi bance. Thus on very general grounds we expect a powerful surface, empty in the ground state, becomes occupied, or a attractive interaction between quarks in the channel where mode just below becomes empty. Since the Fermi surface is both colors and spins are antisymmetric. This intuition large, all the modes involved carry large momentum and is borne out by calculations using one-gluon exchange, energy. So scattering among these low-energy excitations instanton models, and direct lattice simulations. will either involve only small angles, and leave the distri- Thus color superconductivity occurs straightforwardly bution nearly unchanged, or else bring in large momen- and should be robust. What does it mean? tum transfers, and therefore weak coupling (asymptotic • Gluons acquire mass — that is a way to state the equa- freedom). It appears, therefore, that perturbation theory tions of the Meissner effect. If all the gluons acquire should work well; and perturbation theory is something mass, their exchange will no longer produce infrared we know how to do. divergences. But when you actually do the calculations, you run into • Quarks acquire mass — that is a way to state the infrared divergences. They arise from two sources: equations of the energy gap. If all the quarks ac- • The preceding argument only concerns the quarks. quire mass, Cooper’s infrared divergence will be Its central point is that Pauli blocking removes the removed. infrared divergences that usually arise through low- • Therefore the weak-coupling expansion should work, virtuality quarks. Gluons are not subject to any such as long as we start from the proper — color supercon- effect. Color electric forces are screened by the quark ducting — ground state. medium, but magnetic forces remain long-ranged, and • This ground state does not contain massless gluons lead to infrared divergences. nor exhibit long-range forces. In that sense, it exhibits • Interacting fermions are subject to the Cooper instabil- confinement. We also have the classic phenomenon of ity. One has many near-zero energy excitations at zero confinement — absence of fractional electric charge in momentum, associated with particle-particle or hole– the spectrum, as I’ll explain shortly. hole pairs with equal and opposite three-momenta ± p. • The energy gap for quarks suggests that chiral sym- Thus in perturbing around the free Fermi sphere one metry, which is associated with massless quarks, may is engaging in highly degenerate perturbation theory. be broken. As a general matter, degenerate perturbation theory In short, we have the prospect of a phase that exhibits can result in significant restructuring of the ground the main non-perturbative features of QCD — confinement state. In this specific context, Bardeen, Cooper, and and chiral symmetry breaking — in a transparent, fully Schrieffer (BCS) taught us that even a small attractive controlled theoretical framework. Let me emphasize that interaction will lead to a drastic re-arrangement of the here I am speaking of a phase of QCD itself, not of some ground state, by leading to pairing and superfluidity. idealization of a model of a caricature of QCD.

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Now let’s see how all this is embodied, concretely, in (so-called diagonal) symmetry group. Thus we arrive at equations. � α β�∼ǫαβ∗ǫ → ǫαβiǫ ∝ δαδβ − δαδβ qa qb ab∗ abi ( a b b a ). (16)

2.2. Ground state This condensate breaks local color times global flavor SU(3)×SU(3) to a diagonal, “modified flavor” global SU(3). To bring out the central issues and ideas, I will assume It also spontaneously breaks baryon number symmetry. To as the initial default that all quarks are massless, that a particle physicist encountering these ideas for the first they are subject to a common chemical potential, and that time, that might sound dramatic — and it is — but not electromagnetism can be treated as a perturbation. I’ll circle in the sense of allowing the material to decay. With the back to revisit these assumptions, in due course. sample enclosed in a finite volume, outside of which the Because the most attractive channel for quarks is anti- order parameter vanishes, there is a strict conservation law symmetric both in color and spin, Fermi statistics requires for the integrated baryon number. As in the theory of liquid another source of antisymmetry. One possibility is anti- helium-4, where one speaks of a condensate of helium symmetry in the spatial wave function of the quark pairs. atoms, the true implication is that there is easy transport of For example, we might have p-wave pairing. For simple, baryon number within the sample. More specifically, there purely attractive interaction potentials, s-wave tends to be is a massless Nambu–Goldstone field, which supports the favored, because it allows pairs from all directions over the supercurrents characteristic of superfluidity. Fermi surface to act in phase. So s-wave pairing, if possible, Now comes the full structure, in all its glory: is likely to be favorable. � |(qα)i (�k)(qβ)j ( − �k)| � The remaining possible source of antisymmetry is fla- 1 a L b L 1 vor. Thus we must pair off different flavors of quarks to = ǫij |�| δαδβ − δαδβ + |�| δαδβ + δαδβ v1( k )( a b b a ) v2( k )( a b b a ) take best advantage of the attractive interaction between  = −(L ↔ R). quarks. This can bring in some significant complications. Obviously, it means that the one-flavor case is not repre- Some further words of explanation are in order. The sentative, and that we cannot build up the analysis one mid-Latin indices i, j are for spin. The “L” and “R” are for flavor at a time. The two-flavor case also does not go left and right . The relative sign between left and smoothly. Antisymmetry in flavor and spin (and lack of right condensates reflects conservation of . The func- orbital structure) reduces the quark-quark channel to a � � tions v1(|k|), v2(|k|) are, for weak coupling, peaked near the single vector in color space. Therefore condensation in Fermi surface. Our preceding discussion anticipated v1, but this channel breaks color symmetry only partially, in the v2 is also allowed by the residual symmetry. It emerges pattern SU(3) → SU(2). Some gluons remain massless, from calculations based on the microscopic theory, though and some quarks remain gapless, so infrared divergences with v1 ≫ v2. remain. Simplicity and self-consistency (that is, consistent use of 2.2.2. Symmetry breaking and symmetry transmutation weak coupling) first arrive when we consider three flavors. Tracking chiral flavor symmetry and baryon number to- gether with color, the implied breaking pattern is: 2.2.1. Color flavor locking × × × → ∆ × I’ll describe the full structure of the condensate momen- SU(3)color SU(3)L SU(3)R U(1)B SU(3) Z2. (17) tarily, but since that’s a little intimidating let me begin The residual SU(3)∆ global symmetry, and the Z2 of with a sketch. Since the spin (singlet) and spatial (s-wave) fermion (quark) number, can be used to classify excitations. structures are unremarkable I’ll suppress them, and also There is no residual local symmetry: all the color glu- chirality. The favored condensate should be antisymmetric ons have acquired mass. A slightly more refined analysis in color and in flavor, which suggests the form shows that all the quarks have acquired gaps. � α β�∼ǫαβ∗ǫ Finally, as a consequence of the underlying (sponta- qa qb ab∗ neously broken) baryon number and chiral symmetries we where the Greek indices are for color, the Latin indices are also have the generalized ground states for flavor, and ∗ is a wildcard. Now by setting the wild � θ| α i � β j − � | θ� cards equal, and contracting, we maintain as much residual U, (qa )L(k)(qb)L( k) U, symmetry as possible. Any fixed choices for the wildcards = ǫij iθ |�| α β − α β + |�| α β + α β e v1( k )(Ua Ub Ub Ua ) v2( k )(Ua Ub Ub Ua ) will break both color and flavor symmetries. But by locking  color to flavor we maintain symmetry under the combined = −(L ↔ R)

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for an any SU(3) matrix U. Low-frequency, long- nicely onto the entries in the expected hadron spectrum. wavelength modulation of the fields θ and U, which repre- Even the superfluid mode makes sense, because we would sents slow motion within the vacuum manifold, generates expect, in this “”, pairing in the dibaryon the Nambu–Goldstone bosons. channel. Before leaving the ground state, one last comment. Throughout this discussion I’ve used the language of 2.2.4. Quark hadron continuity gauge symmetry breaking and gauge non-singlet order Since conventional (heuristic) “nuclear physics” and the parameters. This is quite familiar and traditional in BCS asymptotic (calculated) CFL state match so well with re- theory, and also in the standard model of electroweak gard both to their ground state symmetry and their low- interactions. Strictly speaking, however, it based on lies, for lying spectrum, it is hard to avoid the conjecture that there local gauge invariance is never broken, and gauge-variant is no phase transition separating these states. Consider expectation values always vanish. Indeed, the physical cranking up the chemical potential, starting from zero. First Hilbert space is defined by restricting to gauge-invariant there’s . At a critical value, nuclear matter appears, states. The usual procedures are a tool — a way of im- with a first-order transition. After that, there’s just smooth plementing favorable correlations in weak coupling. Their evolution. physical content emerges when we use them to draw This conjecture of quark-hadron continuity is both (super- consequences for gauge-invariant quantities, such as the ficially) paradoxical and powerful in implication. physical spectrum or expectation values of gauge-invariant It may seem paradoxical, when we consider that the operators. In the CFL, we can identify two nonzero gauge of conventional “nuclear physics” are supposed invariant vacuum expectation values that break chiral or to go over smoothly into excitations produced by directly baryon-number symmetries, of the types: by single quark fields. After all, baryons are famous for containing three quarks, and three can’t evolve smoothly � � qLqLq¯Rq¯R into one! Well, actually it can. When space is filled with �qqqqqq� a condensate of quark pairs, the difference between three and one is negotiable. with the color indices suitably contracted. They arise as Quark-hadron continuity is powerful, because it im- powers of the primary condensates. (Including instanton plies that the calculable forms of confinement and chiral effects, we also get �qLq¯R�.) By contrast conventional s-wave symmetry breaking we construct by adapting the methods spin-singlet BCS condensation, and also doublet conden- of BCS theory are in the same universality class as confine- sation in the standard electroweak model, do not support ment and chiral symmetry breaking at low energies, within true order parameters. nuclear (or rather “nuclear”) matter. In real-world QCD we do not have three massless 2.2.3. Elementary excitations species of quarks, but two that are nearly massless (u, d) We can analyze the elementary excitations from the point of and one whose mass in certainly not negligible, at the their spin and quantum numbers under the residual SU(3)∆ chemical potentials relevant to nuclear matter. Nuclear symmetry. There are three types: matter at zero pressure is a very different beast from the 1. Excitations produced by the quark fields: They are spin- CFL state, and does not seem amenable to similar theoret- 1 × ¯ → + ical analysis. Indeed, as mentioned previously, if we begin 2 fermions that decompose as 3 3 8 1 under by ignoring the s quark, we find that candidate color su- SU(3)color ×SU(3)flavor → SU(3)∆. The singlet turns out, at weak coupling, to be significantly heavier than the perconducting states do not induce gaps for all the gluons octet. and quarks, so we do not obtain a consistent starting point, 2. Excitations produced by the gluon fields: They are spin-1 free of infrared divergences. Although the CFL state is very bosons that form an octet. likely favorable at asymptotically high densities, where 3. Collective excitations: They are a pseudoscalar octet the s quark mass becomes negligible, it is separated from of Nambu–Goldstone bosons, plus the singlet super- nuclear matter by phase transitions, and one cannot draw fluid mode. continuous connections between their properties. Overall, there is a striking resemblance between this calculated spectrum of low-lying excitations and what one 3. Explorations might expect for the elementary excitations in the “nuclear 3.1. Exotic couplings of Nambu–Goldstone bosons physics” of QCD (that is, the nuclear physics of QCD with three massless flavors), based on standard phenomenology Because the theme of symmetry supports many interesting and modeling. The calculated elementary excitations map variations, so does the theory of symmetry breaking. I

March 2016, Volume 5 No 1 49 ARTICLES 8 will very briefly mention two that extend the spirit of our In superconducting systems the absolute frequency de- preceding discussion, and could become important: pendence is rendered ambiguous by the possibility of time- • Familons are hypothetical Nambu–Goldsone bosons dependent gauge transformations, or stated more simply associated with the idea that the difference between by the lack of a natural zero of energy, so it is simpler to particles in different families, which share most of discuss particle-hole pairing. their key properties (e.g., electron and muon) might For orientation purposes, let us begin by further spe- arise by spontaneous symmetry breaking. They par- cializing to the transparent case of two flat bands with ticipate in flavor-changing transitions, and could be energies ε1 <ε2, and the Hamiltonian + detectable even if their coupling is very weak. = ε2 ε1 + + H N (ε2 − ε1)S3 − g(S−S+ S+S−) • The concept of Majorana mass is usually considered in 2 1 ε + ε connection with spin- 2 particles only. But the essential = 2 1 + �2 2 N (ε2 − ε1)S3 − 2g(S − S ) (20) idea is more general, and simpler than it appears in 2 3

that context. Consider adding a second scalar field φ1 where = † + † to our canonical model, with the symmetry N bkbk ak ak (21) �k �k → iα (φ, φ1) e (φ, φ1) (18) is the total occupation number and = † broken by �φ� v condensation. Mass terms arising + = S bkak from the symmetric interaction �k = + = 2∗ 2 + 2 2 + ∗2 S1 iS2 Lm −κφ φ1 h.c. →−κv (φ1 φ1 ) = 2 2 2 = † −2κv ((Re φ1) − (Im φ1) ) (19) S− 1 will split the quanta produced by the real and imag- S = b†b − a†a (22) 3 2  k k k k inary parts of φ1, and thus tend to lift the degener- �k �k    acy between quanta that had opposite U(1) charge,   define hermitean pseudo-spin operators S1, S2, S3 that sat- and formed particle-antiparticle pairs, in the unbro- isfy the algebra of angular momentum and generate ken symmetry state. After symmetry breaking, they isospin-like rotations between the a and b modes. become two separate Majorana particles. �2 Since N, S , and S3 commute, we can construct the φ1 could also have an intrinsic mass, unrelated to minimum energy states for H, given N, by maximizing S symmetry breaking. In general, the relative impor- = (so S N/2) and choosing a state with definite S3. If S3 is tance of characteristic “Majorana” effects, which mix also allowed to vary, the minimum will occur for particle and antiparticle, is non-universal, and can be − = ε2 ε1 N large or small in different circumstances. �S3� Max − , − . (23) � 4g 2 � (The second alternative on the right-hand side, which satu- τ 3.2. Breaking (time translation) symmetry rates the population of the a modes, is essentially trivial.) On the other hand it can be appropriate to hold the ex- In 1964 Larkin, Ovchinnikov, Ferrell and Fulde (LOFF) pectation value of S fixed. We can imagine, for example, proposed that possibility of pairing with electrons at a 3 that the a and b modes correspond to states in distinct displaced momentum, i.e. electrons at momentum �k with layers, whose total occupations can be fixed independently. electrons at momentum −�k + δ. In the 21st century, several (Note that the assumed interaction term does not require probable realizations have been identified experimentally. interlayer tunneling — this is just another way of saying Because momenta, in the quantum theory, are proportional that it commutes with S .) As we can see by re-arranging to the wave vectors of electron wave functions, this sort of 3 ∼ pairing involves non-trivial spatial periodicity of the order † † →− † † ak bkbl al ak albl bk (24) parameter. Thus the LOFF states provide a new sort of the assumed interaction corresponds, roughly, to an effec- crystalline order. tive repulsion between density waves that does not depend It is natural to ask, whether one might have a simi- on momentum transfer. lar phenomenon, involving ordering with non-trivial time Now we can follow the classic BCS procedure, postu- dependence. To get oriented, I’ve found it very helpful lating a symmetry-breaking condensate. In this procedure, to recall Anderson’s pseudo-spin approach to BCS theory, we assume the ansatz which — after a simple generalization — supplies an illu- =∆ iθ minating model. Here I will sketch the essential idea. �µ, θ|S+|µ, θ� 0e (25)

50 Asia Pacific Physics Newsletter ARTICLES9

∆ with 0 a number, ultimately fixed self-consistently by the qualitative aspects of spontaneous symmetry breaking gap equation. Since to survive such generalizations. One can also consider = + + bosonic systems along the same lines. Indeed, related tech- [H, S+] (ε2 − ε1)S+ 2g(S3S+ S+S3) (26) niques have been applied to discuss dynamic and condensation in liquid 3He and density oscillations in two- d �S+� = i�[H, S+]� (27) component cold atomic gases. In both those contexts, very dt long-lived oscillatory states have been observed. consistent classical evolution for θ requires = + θ˙ ε2 − ε1 4g�S3�. (28) 4. Reflections This vanishes if �S � is fixed non-trivially by Eq. (23), but 3 By thinking hard and creatively about concrete problems not if that expectation value is pinned at a different value. of condensed matter physics, Phil Anderson achieved in- In the pseudo-spin formalism, this time dependence sights that have shaped, and continue to shape, our ideas has a simple interpretation: The condensate is an effective about the elementary structure of Nature. He achieved spin of fixed magnitude at a fixed angle to the z axis, and ˆ those insights by identifying physical phenomena that the ε − ε term supplies an effective magnetic field in the z 2 1 ˆ present essentially new features, and capturing their con- direction, which induces precession. ceptual essence. Their lessons could then be applied The BCS condensation ansatz is overkill for the flat- broadly, and orient us is wildly different physical regimes. band model, where all states with the total spin and ex- It is a beautiful thing, that inspires this birthday haiku: pectation value of S3 are degenerate eigenstates. Its virtue is its ability, at the price of more complicated algebra, to More is Different. accommodate more complex, momentum-dependent ener- Less is Different, too. gies and interactions than assumed in Eq. (20). One expects Same Difference.

March 2016, Volume 5 No 1 51 ARTICLES Takaaki Kajita 2015 Physics Nobel Laureate

Ngee-Pong Chang Physics Department, City College of CUNY

n Oct. 6, 2015, the Nobel Committee announced the Michigan Brookhaven) effort in the race to look for nucleon award of the 2015 Physics Prize to Takaaki Kajita decay. While IMB uses 8,000 tons of water with 2048 PMT, (Super-Kamiokande Collaboration) and Arthur Koshiba’s strategy was not to revise his proposal to ask the OB. McDonald (Sudbury Neutrino Observatory) in honor of government to build bigger, but to build better. Where the their key contributions to our understanding of the nature IMB used PMT of 12.5 cm (later upgraded to PMTs of 20 cm) and metamorphosis of the neutrino. in diameter, he convinced Hamamatsu to develop a 50 cm The volume of collected works1 of Kajita on neutrino PMT that enhanced the sensitivity by orders of magnitude. oscillations provides a good glimpse into as well as a record When Kamiokande succeeded in detecting the neutrinos of the rise and the role of Asian research in the frontiers of from the 1987A Supernova, the status of Japan was estab- neutrino physics. lished in the world of physics. The neutrino was proposed by W. Pauli in a postcard This was quickly followed by the first measurements of dated Dec. 4, 1930 to et al. (Radioactive Ladies the deficit of μν vs. νe in the atmospheric neutrinos, the first and Gentlemen),and Pauli gave a formal talk on this idea indication of neutrino oscillation. Kamiokande was quickly at the Solvay Congress 1933, Oct. 22–29. Fermi was at the upgraded to Super-Kamiokande I (SK-I), and the long Congress, and on Dec. 31, 1933 he published in Ricerca baseline neutrino oscillation experiment K2K (from KEK to Scientifica the first exposition on the 4-fermion theory of Kamioka) was started. Super-K was successively upgraded weak interaction. It was he who gave the name “little neutral to SK-II, SK-III, SK-IV. one” to this invention by Pauli. Interestingly, this first paper As the talks included in this volume show, they resulted had been rejected by Nature. in great strides in the study of solar neutrino, atmospheric Efforts to detect the mysterious little neutral one were neutrino, and inthe study of neutrino oscillations through not successful. The elusive neutrino was finally observed a T2K (Tokai to Kamioka). quarter of a century later by Reines and Cowan in 1956 at Japan is now a major force in the study of the 3 families the Savannah River reactor facility in South Carolina. They of neutrinos. Much remains to be done to clarify the Dirac used two tanks with 200 liters of water. vs. Majorana nature of the neutrino, and the cosmological This dwarfs in comparison to the size of detectors in the implications of the neutrino. ones employed at Kamiokande (a giant tank containing 3,000 The collected works of Kajita and his Super-Kamiokande tons of pure water and 1,000 photomultiplier tubes, PMT) group will leave an indelible foot-print in the history of big and even more outsized at Super-Kamiokande, with 50,000 and better science. tons of water and 13,000 PMT. One of the first people Kajita called after receiving news of the Nobel Prize was the 2002 Nobel Prize winner , his mentor and fellow neutrino researcher. It was References Koshiba’s insight and foresight to recognize how Japan [1] T. Kajita, Experimental Studies of Neutrino Oscillations could seize an opportunity to be ahead of the IMB (Irvine (World Scientific, Singapore, 2016)

52 Asia Pacific Physics Newsletter ARTICLES 1 NeutrinoNeutrino Oscillations: Oscillations: Discovery, Discovery, CurrentCurrent Status, Status, Future Future Directions Directions*∗ Takaaki Kajita ICRRTakaaki and IPMU, Kajita ICRR and IPMU, University of Tokyo

eutrino oscillation was discovered about 10 years 2. Discovery of Neutrino Oscillations ago. Since then, the knowledge on neutrino N masses and mixing angles have been improv- In the early 1980’s, several large underground detectors ing substantially. This article describes neutrino oscilla- were constructed. The main motivation for such detectors tion experiments; the discovery, the present status and the was the discovery of proton decays. These experiments did future prospect. not observe any evidence for proton decays. However, they observed a large number of atmospheric neutrino events, which are the most serious background for the proton 1. Introduction decay search. Therefore, these experiments studied these In 1933, at the Solvay conference, W. Pauli presented his atmospheric neutrino events. idea on neutrinos in public.1 75 years later, it is understood In 1988, Kamiokande, a 4500 ton water Cherenkov de- that neutrinos are still very important for the deeper un- tector, studied the number of e-like and µ-like events, which derstanding of elementary particle physics. Small but finite were mostly CC νe and νµ interactions, respectively. They neutrino masses are believed to be related to physics at found that the number of µ-like events had a significant a very high energy scale.2]–[4 The observed large neutrino deficit compared with the Monte Carlo prediction, while mixing angles might be the hint for understanding physics the number of e-like events had in good agreement with the at the very high energies. Furthermore, the physics of prediction.8 The flavor ratio of the atmospheric neutrino neutrino masses might be related to the baryon asymmetry flux, (νµ +νµ)/(νe +νe), has been calculated accurately (better of the Universe.5 As of this writing, neutrino oscillation than 5%) in the relevant energy range. Because of the experiments give one of a few experimental evidences for small (µ/e)Data/(µ/e)Prediction ratio, it was concluded: “We are “physics beyond the standard model”. unable to explain the data as the result of the systematic One of the most sensitive methods to observe small detector effects or uncertainties in the atmospheric neu- neutrino masses is to study neutrino flavor oscillations.6,7 trino fluxes. Some as-yet- accounted-for physics such as If neutrinos have finite masses, each flavor eigenstate (for neutrino oscillations might explain the data.” This result example, νµ) can be expressed by a combination of mass was the beginning of the serious interest in atmospheric eigenstates (ν1, ν2 and ν3). For simplicity let us discuss two neutrinos. The subsequent study by the same experiment flavor neutrino oscillations. The probability for a neutrino confirmed that the deficit of µ-like events was explained 9 produced in a flavor state να to be observed in a flavor state well by either νµ → ντ or νµ → νe oscillations. A consistent νβ after traveling a distance L through the vacuum is: result on νµ deficit was reported in the early 1990’s from the IMB experiment.10 1.27∆m2 (eV2)L(km) = 2 2 ij P(να → νβ) sin 2θij sin   , (1) Another important hint toward the understanding of  Eν(GeV)    atmospheric neutrino phenomena was given in the mid.   11 where Eν is the neutrino energy, θij is the mixing angle be- 1990’s. Zenith angle distributions for multi-GeV fully- tween the flavor eigenstates and the mass eigenstates, and contained events and partially contained events were stud- ∆ 2 mij is the mass-squared difference of the neutrino mass ied in Kamiokande. For detectors near the surface of the eigenstates. The above description has to be generalized Earth, the neutrino flight distance, and thus the neutrino to three-flavor oscillations. However, it is known that it oscillation probability, is a function of the zenith angle is approximately correct to assume two-flavor oscillations of the neutrino direction. Vertically downward-going neu- for analyses of the present neutrino oscillation data. There- trinos travel about 15 km while vertically upward-going fore, in this article, we mostly discuss two flavor neutrino neutrinos travel about 12,800 km before interacting in the oscillations. detector. The Kamiokande data showed that the deficit µ ∗This article was originally published in Int.J.Mod.Phys.A24, 3437 of -like events depended on the neutrino zenith angle. (2009). However, due to the relatively poor event statistics, the

March 2016, Volume 5 No 1 53 ARTICLES 2

100 200 1.8 80 150 1.6 60 1.4 100 40 1.2 20 50 1 number of events 0 0 0.8 -1 0 1 -1 0 1 0.6 cosT cosT SK1+2 Multi-GeV 1-ring e-like SK1+2 Multi-GeV 1-ring mu-like + PC 0.4 500 0.2 200 400 0 2 3 4 160 Data/Prediction (null oscillation) 1 10 10 10 10 300 120 L/E (km/GeV) 80 200

Number of Events L/E 40 100 Figure 2. distribution observed in Super-Kamiokande. The plot is updated from Ref. 15. The solid (blue), dashed (green), and dotted 0 0 -1 -0.6 -0.2 0.2 0.6 1 -1 -0.6 -0.2 0.2 0.6 1 (red) histograms show the best-fit predictions based on neutrino cos cosT T oscillation, decay and decoherence models, respectively.

Figure 1. Zenith angle distributions from Super-Kamiokande. The left and right panels show multi-GeV fully contained e-like events

] 4 and multi-GeV fully contained µ-like plus partially-contained events, 2 respectively. The top and bottom panels show the data as of 1998 and eV + -3 those of the full Super-K-I II data, respectively. ' [10 2 m ' 3 statistical significance of the up-down asymmetry in the Kamiokande data was 2.9 standard deviations, and there- fore the data were not conclusive. SK(zenith) 90%C.L. It was obvious that a much larger detector was re- SK(zenith) 68%C.L. quired to observe conclusive evidence for neutrino oscil- 2 SK(L/E) 90%C.L. MINOS 90%C.L. T lations with high enough statistics. In 1996, the Super- K2K 90%C.L.

Kamiokande experiment started. The detector is a 50 kton 0.5 0.6 0.7 0.8 0.9 1 2 water Cherenkov detector with the fiducial mass of sin 2T 22.5 kton. In 1998, the Super-Kamiokande experiment, with substantially larger data statistics than those in the previ- Figure 3. Allowed neutrino oscillation parameters from atmospheric neutrino data from Super-K and those from long baseline experiments ous experiments, concluded that the atmospheric neutrino (K2K16 and MINOS17). data gave evidence for neutrinos oscillations.12,13 The sub- sequent study confirmed that the oscillation was mostly 14 between νµ and ντ. 3. Long Baseline Experiments Super-Kamiokande has been accumulating the data. Figure 1 shows the zenith angle distributions for multi- Probably, atmospheric neutrino experiments are suited to GeV fully-contained and partially-contained events as the discovery of oscillations, since atmospheric neutrinos of 1998 (535 day exposure) and those of Super-K-I+II have a wide neutrino flight length distribution, a wide neu- (1489+799 day exposure). It is clear that the data statistics trino energy coverage, and the beam is the mixture of νe, νe, have been improved substantially. Furthermore, evidence νµ and νµ. On the other hand, long baseline experiments for the first oscillation minimum as expected by the sinu- have only one neutrino flight length, a controlled neutrino soidal oscillation probability has been observed as shown energy and an almost pure neutrino flavor. Therefore, in in Figure 2.15 Figure 3 shows the allowed neutrino oscil- general, the long baseline experiments are suited to the lation parameters from the Super-K atmospheric neutrino precise measurements of the oscillation parameters. data together with those from long baseline experiments. The first long baseline neutrino oscillation experiment The oscillation parameters are understood accurately. Es- was the . The baseline length was 250 km pecially, the atmospheric neutrino experiments contribute between KEK and Super-K. The experiment started in 1999 2 16 to the measurement of the mixing parameter (sin 2θ23). and finished in 2004. The MINOS experiment is the long 54 Asia Pacific Physics Newsletter ARTICLES 3

150 1.5 MINOS Far Detector Data - BG - Geo Qe Expectation based on osci. parameters Far detector data 1 determined by KamLAND No oscillations 100 1 Best oscillation fit 0.8 NC background

Events / GeV MINOS data 0.6 50 0.5 Best oscillation fit Ratio to null hypothesis Best decay fit 0.4 Best decoherence fit Survival Probability 0 0 0 5 10 15 20 30 50 0 5 10 15 20 30 50 Reconstructed neutrino energy (GeV) Reconstructed neutrino energy (GeV) 0.2

0 Figure 4. Left: Neutrino energy spectrum measured by the MINOS 20 30 40 50 60 70 80 90 100 experiment. Right: Ratio of the data and the no-oscillation expectation. L 0/E (km/MeV) Qe From Ref. 17. Figure 5. Ratio of the background subtracted reactor νe spectrum to the no-oscillation expectation as a function of L0/E. 2881 ton·year baseline experiment between Fermilab and the Soudan = of the KamLAND data are used. L0 180 km is assumed. (From mine. The baseline length is 735 km. The experiment Ref. 38.) started in 2005 and is still running. In both experiments, the deficits of νµ events were clearly observed. Even more con- vincing results have been obtained from the measurements the calculated event rate was due to fundamental pp solar of the energy spectra from these experiments. For example, neutrinos. These low energy solar neutrino experiments Figure 4 shows the neutrino energy spectrum measured also observed that the solar neutrino flux was lower than by the MINOS experiment.17 The event rate in the 1 to the SSM prediction. Although the solar neutrino deficit 2 GeV energy range has a significant deficit compared with was clearly observed in these experiments, the cause of the no-oscillation expectation. It is clear that the deficit that deficit was not firmly identified, partly because no depends on neutrino energy and is completely consistent experiment observed the νe and (νµ + ντ) fluxes separately. with the oscillation expectation. MSW mechanism was a serious possibility, but was not uniquely identified as the solution to this problem. 4. Solar Neutrino Problem and Neutrino The situation changed dramatically in 2001 and 2002. 8 Oscillations In 2001, the SNO heavy water experiment measured the B − 25 solar neutrinos by νe + D → e + p + p, i.e., by charged cur- The measurement of solar neutrinos was initiated by Ray rent νe interactions. At that time Super-Kamiokande mea- Davis Jr. and his collaborators in the 1960’s at Homes- sured the 8B neutrino flux precisely by neutrino-electron take.18 Soon after starting the measurement, they found scattering.26 By comparing these results, it was found that that the observed flux was much lower than the predic- the flux measured by Super-Kamiokande (assuming all the tion by the Standard Solar Model (SSM, see Ref. 19 for neutrinos are electron-neutrinos) was significantly higher the recent one). Various possibilities, including neutrino than that measured by SNO. This was a 3.3σ discrepancy, oscillations in the vacuum, were discussed to explain the and was concluded as evidence for solar neutrino oscilla- apparent inconsistency between the observation and the tions, since νµ’s and ντ’s generated by neutrino oscillations calculation. contribute only to the neutrino-electron scatterings. In the mid 1980’s, it was discovered that the effect of In 2002, the evidence was substantially strengthened by the solar matter might significantly enhance the neutrino the measurement of the total (= νe + νµ + ντ) neutrino flux oscillation probability even if the intrinsic mixing angle measurement in SNO. They observed νx + D → νx + p + was small (MSW mechanism).20,21 This mechanism natu- n.27 The observed total flux was consistent with the SSM rally explained the solar neutrino problem, and therefore prediction, confirming the solar neutrino oscillation at the had a significant impact to the solar neutrino physics. 5.5 standard deviation level. In 1989, Kamiokande observed the 8B solar neutrino Furthermore, a long baseline reactor neutrino exper- flux by neutrino electron scattering, νe → νe.22 This exper- iment, KamLAND, observed not only the deficit28 but iment confirmed that neutrinos are coming from the Sun also the spectrum distortion.29 See Figure 5 for the most and that the solar neutrino flux was significantly lower updated results from KamLAND. The observed spectrum than the SSM prediction. Subsequently, solar neutrino ex- distortion is regarded as very strong evidence for “oscilla- periments that used Gallium were carried out.23,24 These tions”. The mean flight length of the neutrinos detected by experiments were unique in the sense that about half of KamLAND was 180 km. The observed spectrum distortion

March 2016, Volume 5 No 1 55 ARTICLES 4

or accelerator neutrino beams. If a finite value of θ13 is solar observed, we understand the overall structure of the neu- 15

] trino mixing matrix (except for the CP phase). Thus, θ13 2 global should be measured with a high priority. Furthermore, the eV -5 10 measurement of θ13 is very important for future neutrino oscillation experiments, which will be discussed in the next [ 10 ฀฀

2 21 section.

m KamLAND 5 Reactor experiments try to observe νe disappearance (Eq. 2). At present 3 reactor θ13 experiments are under construction. Details of these experiments are discussed 0 0.2 0.4 0.6 0.8 in this conference.32 The expected sensitivities of these 2 2 experiments range between 0.01 and 0.03 in 2θ13. sin 12 sin The accelerator long baseline experiments try to ob-

Figure 6. Allowed region of neutrino oscillation parameters by the solar serve νe appearance. See Eq. 3 for the approximate ap- and the KamLAND experiments. (From Ref. 30.) pearance probability. The T2K experiment33 and the NOvA 34 experiment have high sensitivities to the νe appearance. T2K uses a high intensity, low energy (E < 1 GeV) together with the known flight length makes it possible to ν ∆ 2 neutrino beam produced by the 40 GeV PS in the J-PARC estimate the m12 parameters precisely. Figure 6 shows the ∆ 2 2 accelerator complex, which is under construction in Tokai, allowed m and sin θ12 parameters. These parameters are 12 Japan. The designed beam power is 0.75 MW. The proton already measured precisely. beam was successfully accelerated to 30 GeV as of this writing. The far detector is Super-Kamiokande. The base- 5. Future Directions line length is 295 km. The neutrino energy is tuned to the ∆ 2 = × −3 2 ∆ 2 2 ∆ 2 2 maximum oscillation energy. For m23 2.5 10 eV , the m , sin 2θ23, m and sin θ12 have been measured ac- 23 12 maximum oscillation energy is 600 MeV. To produce high- curately by the present generation experiments assuming intensity, narrow-band beam, the off-axis beam technique 2-flavor neutrino oscillations. However, we know that is used. The axis of the primary beam is displaced by 2.5 there are 3 neutrino flavors. Therefore, the neutrino oscilla- degrees from the direction to the neutrino detector. The tion studies should be generalized to 3-flavor oscillations. will start taking data in 2009. We discuss the possible future direction of neutrino oscilla- tion experiments. NOvA is the proposed long baseline experiment in the United States. This experiment plans to use the existing NuMI beam line at Fermilab. A beam power upgrade plan θ 5.1. Search for non-zero 13 to about 1 MW is under investigation. The far detector is For simplicity, we neglect the effect of the oscillations re- a 15 kton fully-active, finely-segmented liquid scintillator ∆ 2 detector. The baseline length is 810 km. In order to get the lated to m12. Under this approximation, there are only ∆ 2 =∆ 2 high flux at the oscillation maximum, this experiment also three oscillation parameters; θ13, θ23 and m ( m ). In 13 23 uses the off-axis technique. The peak neutrino energy is this case, for example, the νe → νe and νµ → νe oscillation probabilities in vacuum can be written as: about 2 GeV. The NOvA experiment is expected to start taking data in the early 2010’s. 1.27∆m2 L 2 θ = 2 2 13 These experiments have similar sensitivities in sin 2 13. P(νe → νe) 1 − sin 2θ13 sin , (2)  Eν  Assuming 5 years of data taking with the planned beam     intensities, these experiments can find clear evidence for 2 2 1.27∆m L a non-zero θ13,ifthetruevalueofsin 2θ13 is larger than = 2 2 2 13 P(νµ → νe) sin θ23 sin 2θ13 sin . (3) ∼ θ  Eν  0.02. If there is no evidence for a non-zero 13, they can   2   set the upper limit of ∼0.01 on sin 2θ13. The sensitivities 2 The CHOOZ experiment searched for νe disappearance in of these long baseline experiments on sin 2θ13 are similar the reactor νe flux based on Eq. 2. The observed flux was to or slightly better than the next generation reactor θ13 consistent with the no-oscillation expectation. The upper experiments. 2 31 limit on sin 2θ13 was ∼0.15. Finally it should be mentioned that these long base- |∆ 2 | 2 In the near future, various experiments that are much line experiments can measure m23 and sin 2θ23 pre- more sensitive to a small θ13 than the present experiments cisely. These experiments have the approximate sensi- 2 will start taking data. They use either reactor neutrinos tivities of 0.01 in sin 2θ23. It is especially interesting if

56 Asia Pacific Physics Newsletter ARTICLES 5 these experiments could find evidence for a non-maximal 6. Summary 2 sin 2θ23. “Atmospheric neutrino anomaly” and “solar neutrino problem” were beautifully resolved by neutrino oscilla- θ 5.2. Oscillation physics beyond 13 tions in 1998 and 2001(2), respectively. Since then, many experiments have contributed to the understanding of os- We assume that the next generation long baseline and re- cillations. Dominant νµ → ντ and νe → (νµ + ντ) are already actor experiments will observe evidence for a non-zero θ , 13 studied accurately. However, it is known that there are suggesting 2 2θ to be larger than ∼0.01. In this case, we sin 13 many interesting physics in the sub-dominant oscillations. know the approximate values of the three mixing angles. They include θ13, the CP violated and the mass hierarchy. However, we believe that this should not be the end of the Therefore there are large activities to study these effects. neutrino oscillation studies. In fact, there are still important The immediate goal is the search for non-zero θ13. Experi- and unknown neutrino oscillation parameters. One is the ments to search for non-zero θ13 will start within a year or CP phase. According to the leptogenesis scenario,5 the seed two. The subsequent big goals are the measurement of the of the baryon asymmetry in the Universe is generated from CP violation and the determination of the mass hierarchy. the CP violating decay of the heavy Majorana particles The world community is working hard for the best strategy of the see-saw mechanism. Therefore, it is generally be- for these measurements. lieved that the measurement of the CP violation in the neutrino sector is a very important step forward for the understanding of the baryon asymmetry in the Universe. Acknowledgments In addition to the CP violation, we should note that we do The author would like to thank the organizers of this not know whether the ν3 mass eigenstate is the heaviest conference for the kind invitation. This work was partly or the lightest. This is also an important question to be supported by the Grant-in-Aid in Scientific Research of addressed experimentally. JSPS. If θ13 is non-zero, future large-scale long-baseline exper- iments can address these questions. Various possibilities for these experiments have been studied. One possibility References for such experiments could be the Phase-2 of the T2K 33 [1] W. Pauli Septieme Conseil de Physique Solvay 1933: Noyaux project. The CP violation phase can be measured by Atomiques, Paris 1934, p. 324f. observing the difference in the neutrino oscillation prob- [2] P. Minkowski, Phys. Lett. B 67, p. 421 (1977). [3] T. Yanagida in Proceedings of the Workshop on Unified Theories abilities between νµ → ν and νµ → ν . To observe this e e and Baryon Number in the Universe, eds. O. Sawada and effect, a huge detector (0.54 Mton fiducial mass, Hyper- A. Sugamoto (KEK report 79-18, 1979). Kamiokande), and a beam power upgrade of J-PARC will [4] M. Gell-Mann, P. Ramond and R. Slansky in Supergravity, eds. P. van Nieuwenhuizen and D. Z. Freedman (North Holland, be required. Due to the relatively short baseline length of Amsterdam, 1979). 295 km and therefore due to a relatively small matter effect, [5] M. Fukugita and T. Yanagida, Phys. Lett. B 174, p. 45 (1986). [6] Z. Maki, M. Nakagawa and S. Sakata, Prog. Theor. Phys. 28, the mass hierarchy may not be determined in this setup. p. 870 (1962). The T2K experiment uses an off-axis beam. It is noticed [7] B. Pontecorvo, Sov. Phys. JETP 26, 984 (1968). that, with the present T2K beam-line configuration, the [8] K. S. Hirata et al., Phys. Lett. B 205, p. 416 (1988). [9] K. S. Hirata et al., Phys. Lett. B 280, 146 (1992). beam is simultaneously available in Kamioka (which is [10] R. Becker-Szendy et al., Phys. Rev. D 46, 3720 (1992). 295 km away from the target) and Korea (which is more [11] Y. Fukuda et al., Phys. Lett. B 335, 237 (1994). [12] Y. Fukuda et al., Phys. Rev. Lett. 81, 1562 (1998). than 1000 km away from the target). Studies have been [13] T. Kajita (For the Kamiokande and Super-Kamiokande collabo- carried out assuming the two detectors in Kamioka and rations), Nucl. Phys. Proc. Suppl. 77, 123 (1999). 35,36 [14] S. Fukuda et al., Phys. Rev. Lett. 85, 3999 (2000). Korea with 0.27 Mton fiducial mass for both detectors. [15] Y. Ashie et al., Phys. Rev. Lett. 93, p. 101801 (2004). The other study has been carried out in the United [16] M. H. Ahn et al., Phys. Rev. D 74, p. 072003 (2006). States, which assumed a 1300 km baseline between Fermi- [17] P. Adamson et al., Phys. Rev. Lett. 101, p. 131802 (2008). [18] R. Davis Jr., D. S. Harmer and K. C. Hoffman, Phys. Rev. Lett. lab and DUSEL at Homestake.37 The beam power could be 20, 1205 (1968). as high as 2 MW. The detectors used in this study are a [19] J. N. Bahcall and M. H. Pinsonneault, Phys. Rev. Lett. 92, p. 121301 (2004). 300 kton water Cherenkov detector and a 100 kton liquid [20] L. Wolfenstein, Phys. Rev. D 17, 2369 (1978). Argon detector. [21] S. P. Mikheev and A. Y. Smirnov, Sov.J.Nucl.Phys.42, 913 (1985). [22] K. S. Hirata et al., Phys. Rev. Lett. 63, p. 16 (1989). From these studies, it is understood that the CP phase [23] P. Anselmann et al., Phys. Lett. B 285, 376 (1992). and mass hierarchy can be determined by these future ex- [24] D. N. Abdurashitov et al., Phys. Lett. B 328, 234 (1994). 2 θ ∼ [25] Q. R. Ahmad et al., Phys. Rev. Lett. 87, p. 071301 (2001). periments if sin 2 13 is larger than 0.01 and if the baseline [26] S. Fukuda et al., Phys. Rev. Lett. 86, 5651 (2001). length is 1000 km or longer. [27] Q. R. Ahmad et al., Phys. Rev. Lett. 89, p. 011301 (2002).

March 2016, Volume 5 No 1 57 ARTICLES 6

[28] K. Eguchi et al., Phys. Rev. Lett. 90, p. 021802 (2003). [35] M. Ishitsuka, T. Kajita, H. Minakata and H. Nunokawa, Phys. [29] T. Araki et al., Phys. Rev. Lett. 94, p. 081801 (2005). Rev. D 72, p. 033003 (2005). [30] T. Schwetz, M. Tortola and J. W. F. Valle, New J. Phys. 10, [36] F. Dufour (2008), Talk presented at the 4th International Work- p. 113011 (2008). shop on Nuclear and Particle Physics at J-PARC (NP08), Mito, [31] M. Apollonio et al., Eur. Phys. J. C 27, 331 (2003). Japan. [32] Y. Wang in these proceedings. [37] V. Barger et al. (2007), arXiv:0705.4396 [hep-ph]. [33] Y. Itow et al. (2001), hep-ex/0106019. [38] S. Abe et al. (KamLAND Collaboration), Phys. Rev. Lett. 100, [34] D. S. Ayres et al. (2004), hep-ex/0503053. 221803 (2008).

Takaaki Kajita Professor Takaaki Kajita was awarded the 2015 Nobel Prize in Physics jointly with Professor Arthur B. McDonald. Professor Takaaki Kajita is the Director of Institute for Cosmic Ray Research, the University of Tokyo. Prof Kajita studied at the Saitama University and graduated in 1981. In 1986, he received his doctorate in the University of Tokyo, under the supervision of Professor Masatoshi Koshiba (2002 Physics Nobel Laureate).

Research Accomplishments Dr. Kajita has been working in Kamiokande and Super-Kamiokande experiments. In particular, he has been studying atmospheric neutrinos and neutrino oscillations. In 1988, they discovered the atmospheric muon-neutrino deficit (this was called atmospheric neutrino anomaly), which was confirmed to be due to neutrino oscillations 10 years later. In this study they showed that the nm/ne ratio observed in Kamiokande was only about 60% of the predicted ratio. Subsequently, in 1994, they discovered that the atmospheric muon- neutrino deficit depends on the zenith-angle or equivalently on the neutrino flight length through the study of multi-GeV atmospheric neutrino events observed in Kamiokande, which was the another indication for the neutrino oscillations. In 1996 the Super-Kamiokande experiment started. Dr. Kajita has been leading the studies of atmospheric neutrinos in this experiment. In 1998, by the study of the high statistics data from Super-Kamiokande, they concluded that the observed atmospheric muon-neutrino deficit was due to neutrino oscillations. The result was presented at the Neutrino 98 conference. They have been studying neutrino oscillations further. Recent major accomplishments are the confirmation of nmànt oscillations rather than oscillations to sterile neutrinos in 2000, the observation of sinusoidal muon-neutrino disappearance as predicted by the neutrino oscillation formula in 2004, and the first indication of appearance of tau-neutrinos which are generated by neutrino oscillations in 2006. In these studies they have established the standard neutrino oscillation generated by neutrino masses and mixing-angles.

58 Asia Pacific Physics Newsletter BOOKS

Memorial Volume for • Lars Brink • Lay Nam Chang Y. Nambu • Moo-Young Han Edited by: Lars Brink (Chalmers University of Technology, Sweden), • , Past and Future () Lay Nam Chang (Virginia Tech, USA), Moo-Young Han (Duke • Yoichiro Nambu: Visionary Theorist Who Shaped University, USA), Kok Khoo Phua (NTU, Singapore) Modern Particle Physics (Michael Turner) • Yoichiro Nambu (Peter G O Freund, Jeffrey Harvey, Emil Martinec, ) • Remembering Nambu (Jorge Willemsen) • Yoichiro Nambu (Louis Clavelli) • Yoichiro Nambu: Remembering an Unusual Physicist, a Mentor and a Friend (Giovanni Jona-Lasinio) • Pre- (Paul Frampton) • Yoichiro Nambu and the Origin of Mass (Tom Kibble) • Tohru Eguchi • Kazuo Fujikawa • Holger Bech-Nielsen • Appendix: Reminiscences of the Youthful Years of Particle Physics (Y Nambu)

Readership: University students and researchers interested in particle physics or the work of Professor Yoichiro Nambu.

“I have only the fondest of memories of Nambu. He We have lost one of the giants of the twentieth century was a man of inordinate kindness, and there were many physics when Yoichiro Nambu passed away in November, times that I felt I was a beneficiary of his consideration 2015, at the age of 94. and generosity. Of course, the impact of his science was Today’s Standard Model, though still incomplete in many enormous.” respects, is the culmination of the most successful theory H David Politzer of the Universe to date, and it is built upon foundations Caltech provided by discoveries made by Nambu in the 1960s: the Nobel Laureate in Physics, 2004 mechanism of spontaneously broken symmetry in Nature (with G Jona-Lasinio) and the hidden new SU(3) symmetry of quarks and gluons (with M-Y Han). In this volume honoring Nambu’s memory, World PWA90: A Lifetime of Scientific Publishing presents a unique collection of papers Emergence written by his former colleagues, collaborating researchers Edited by: Premi Chandra (Rutgers University, USA), Piers and former students and associates, not only citing Nambu’s Coleman (Rutgers University, USA), Gabi Kotliar (Rutgers great contributions in physics but also many personal and University, USA), Phuan Ong (Princeton), Daniel L Stein (New York private reminiscences, some never told before. University, USA), Clare Yu (UC Irvine) This book is a volume for all who benefited not only from Nambu’s contributions toward understanding the Universe In a remarkable career spanning more than six decades, but also his warm and kind persona. It is a great addition to Philip W Anderson has made many fundamental contribu- the history of contemporary physics. tions to physics. As codified in his oft-quoted phrase “More is Different”, Anderson has been the most forceful and Contents: persuasive proponent of the radical, but now ubiquitous, • Foreword viewpoint of emergent phenomena: truly fundamental • Profiles of Nambu (M Mukherjee) concepts that can and do emerge from studies of Nature at each

March 2016, Volume 5 No 1 59 BOOKS

• 40 Years of Quantum Spin Liquid: A Tale of Emergence from Frustration (Patrick A Lee)

• High Tc Superconductivity and RVB (Mohit Randeria) • Paired Insulators and High Temperature Superconduc- tors (T H Geballe and S A Kivelson)

• Special Properties of High Tc Cuprates, Radically Different from Other Transition Metal Oxides (T M Rice) • From Bacteria to Artificial Cells, the Problem of Self- Reproduction (Albert Libchaber) • Spin Glasses and Frustration (Scott Kirkpatrick) • Frustration and Fluctuations in Systems with Quenched Disorder (D L Stein) • Phil Anderson’s Magnetic Ideas in Science (Piers Coleman)

Readership: Students, academics and researchers in condensed matter. layer of complexity or energy scale. Anderson’s ideas have also extended deeply into other areas of physics, including the Anderson–Higgs mechanism and the dynamics of pulsars. PWA90: A Lifetime of Emergence is a volume of original Building the H Bomb scientific essays and personal reminiscences of Philip W A Personal History Anderson by experts in the field, that were presented as Kenneth W Ford (Retired Director, American , part of “PWA90: Emergent Frontiers of Condensed Matter” USA) meeting held at Princeton in December 2013 to highlight Anderson’s contributions to physics.

Contents: • Recollections of a Graduate Student (Khandker A Muttalib) • P W Anderson Seen Through the Eyes of a Student (Clare C Yu) • Random Walks in Anderson’s Garden: A Journey from Cuprates to Cooper Pair Insulators and Beyond (G Baskaran) • Some Reminiscences on Anderson Localization (Elihu Abrahams) • Anderson and Condensed Matter Physics (T V Ramakrishnan) • Superfluidity and Symmetry Breaking — An Anderson Living Legacy (Frank Wilczek) • Phil Anderson and Gauge Symmetry Breaking (Edward Witten) In this engaging scientific memoir, Kenneth Ford recounts • A Short History of the Theory and Experimental the time when, in his mid-twenties, he was a member of Discovery of Superfluidity in3 He (W F Brinkman) the team that designed and built the first hydrogen bomb. • Superconductivity in a Terrestrial Liquid: What Would He worked with — and relaxed with — scientific giants of It Be Like? (A J Leggett) that time such as , , Stan Ulam,

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John von Neumann, and John Wheeler, and here offers “Ford’s book is a valuable resource for anyone interested illuminating insights into the personalities, the strengths, in the history of the H bomb and its role in the Cold War, and the quirks of these men. Well known for his ability to and in how that work affected the life and career of an explain physics to nonspecialists, Ford also brings to life the individual involved.” physics of fission and fusion and provides a brief history of Physics Today nuclear science from the discovery of radioactivity in 1896 to the ten-megaton explosion of “Mike” that obliterated a “Personal memories are the book’s greatest strength. Ford Pacific Island in 1952. doesn’t glorify, or apologize for, his work on the H-bomb. Ford worked at both Los Alamos and Princeton’s Project He simply tells it as it was. As a result, this is an engagingly Matterhorn, and brings out Matterhorn’s major, but previ- human glimpse into the world of physics in the US in the ously unheralded contribution to the development of the H early 1950s.” bomb. Outside the lab, he drove a battered Chevrolet around Physics World New Mexico, a bantam motorcycle across the country, and a British roadster around New Jersey. Part of the charm of “This very readable book by Ken Ford is a welcome and Ford’s book is the way in which he leavens his well-researched worthy addition to the story of the development of nuclear descriptions of the scientific work with brief tales of his life weapons. This book deserves to be read by anyone inter- away from weapons. ested in the history of the H-bomb, its role in the Cold War, and how such work can affect the lives and careers About the author: of the individuals involved.” In 1950-1952 Kenneth Ford took a two-year break from his AIP Scitation graduate studies in physics at Princeton University to work on the H bomb, returning to earn his Ph.D. in 1953. Since In the News then he has conducted research in nuclear physics, taught Podcast — Building the H Bomb: A Personal History Hosted at several universities, and served as a college president and by Milt Rosenberg (1590 WCGO), 25 June 2015 as the head of a nonprofit organization. After retirement, Building the H-Bomb: The Big Idea APS News, June 2015 he taught high-school physics. In addition to his scientific (Volume 24, Number 6) papers, he has written textbooks and books explaining Behind the Making of a Super Bomb The Washington Post, quantum physics to nonscientists — as well as a memoir 22 May 2015 on flying small planes. His books have won two writing awards and some have been translated into other languages. Atomic Scientist From Philadelphia Claims His Book About In 2006, he was recognized by the American Association H-Bomb Isn’t Dangerous to U.S. CBS Philly, 6 April 2015 of Physics Teachers with that organization’s Oersted medal Does Philly Author Reveal Nuclear-Bomb Secrets? for contributions to teaching. He lives in Philadelphia with The Inquirer, 5 April 2015 his wife Joanne. They have seven children and thirteen Former New Mexico Tech President Writes Controversial grandchildren. Book KRQE NEWS 13, 26 March 2015

“It was a great treat to read a book that’s well-written, 美国氢弹专家书稿遭审查 怒在新加坡出电子版凤凰网, informative, and gets the science right. It is these personal 2015年03月25日 recollections and descriptions; the fact that it is a personal H-Bomb History Published Over Government Objections and first-hand account of a unique time in history and a Federation of American Scientists, 25 March 2015 remarkable scientific and technical achievement that made New Memoir by Participant in U.S. H-Bomb Program Sheds this book so enthralling. This is an engaging account of a on the Making of the First Test Device The National young scientist involved in a remarkable project.” Security Archive, 24 March 2015 P Andrew Karam Hydrogen Bomb Physicist’s Book Runs Afoul of Energy The Ohio State University Department , 23 March 2015

March 2016, Volume 5 No 1 61 BOOKS

A Singularly Unfeminine Contents: • Preface Profession • Beginnings One Woman’s Journey in Physics • Hollins and Paris: To Paris and Back Mary K Gaillard (UC Berkeley) • Brookhaven and Columbia • Paris Again: The Worst Year • CERN • Fermilab: Charm, The Delta I=½ Rule, Search for Charm • CERN Again: Two Weeks in the Soviet Union, The Higgs Particle, Gluon Jets, Bottom Quarks, Penguins and GUTs • Unrest: Annecy: Superguts • Returning • My Survival Mechanism • Afterlife: Physics at a Trillion Electron Volts, Physics at the Planck Energy • Reflections • Acronyms • Glossary

Readership: Students interested in women’s issues and/or particle physics, professionals interested in women’s issues and/or the history of the development of the Standard Model, In 1981 Mary K Gaillard became the first woman on the general public interested in women’s issues and/or particle physics faculty at the University of California at Berkeley. Her physics. career as a theoretical physicist spanned the period from the inception — in the late 1960s and early 1970s — of what is “Her frank autobiography is an honest, revelatory account now known as the Standard Model of particle physics and its of her many discoveries, made as she battled gender bias experimental confirmation, culminating with the discovery and faced the demands of raising three children …Gaillard of the Higgs particle in 2012. A Singularly Unfeminine became a grande dame of particle physics, with positions Profession recounts Gaillard’s experiences as a woman in a on many committees that shaped particle-physics research very male-dominated field, while tracing the development in the United States and, ultimately, the world. The story of the Standard Model as she witnessed it and participated is as much about a thrilling period in particle physics as in it. The generally nurturing environment of her childhood about Gaillard’s struggle to establish herself in a male- and college years, as well as experiences as an undergraduate dominated sphere … As a colleague comments in the in particle physics laboratories and as a graduate student at book: ‘She did it all!’” Columbia University — which cemented her passion for Nature particle physics — left her unprepared for the difficulties that she confronted as a second year graduate student in “It was clearly a hard time to be a successful theorist, and Paris, and later at CERN, another particle physics laboratory a woman, and Gaillard’s account makes for a compelling near Geneva, Switzerland. The development of the Standard tale. She was talented, determined and tough — she made Model, as well as attempts to go beyond it and aspects of early the system accommodate her. Life isn’t like that now, and universe physics, are described through the lens of Gaillard’s we have people like her to thank for it.” own work, in a language written for a lay audience. Times Higher Education

62 Asia Pacific Physics Newsletter BOOKS

60 Years of CERN Experiments • Highlights from High Energy Neutrino Experiments at CERN (W-D Schlatter) and Discoveries • The Discovery of Direct CP Violation (L Iconomidou- Edited by: Herwig Schopper (, Germany & Fayard and D Fournier) CERN), Luigi Di Lella (University of Pisa, Italy & CERN) • Measurements of Discrete Symmetries in the Neutral OPEN ACCESS Kaon System with the CPLEAR (PS195) Experiment (T Ruf) • An ISR Discovery: The Rise of the Proton–Proton Cross- Section (U Amaldi) • Deep Inelastic Scattering with the SPS Muon Beam (G K Mallot and R Voss) • Revealing Partons in Hadrons: From the ISR to the SPS Collider (P Darriulat and L Di Lella) • Properties of Antiprotons and Antihydrogen, and the Study of Exotic Atoms (M Doser) • Muon g–2 and Tests of Relativity (F J M Farley) • The Discoveries of Rare Pion Decays at the CERN Synchrocyclotron (G Fidecaro) • Highlights at ISOLDE (K Blaum, M J G Borge, B Jonson and P Van Duppen)

Readership: Graduate students and researchers in elemen- The book is a compilation of the most important experi- tary particle physics, and historians of science. mental results achieved during the past 60 years at CERN - from the mid-1950s to the latest discovery of the Higgs About the authors particle. Covering the results from the early accelerators Herwig Schopper is a former Director-General of CERN. at CERN to those most recent at the LHC, the contents He was the head of CERN Nuclear Physics Division in the provide an excellent review of the achievements of this 1970s. He returned to CERN in 1981 after chairing the outstanding laboratory. Not only presented is the impressive directorate of the German research center DESY for eight scientific progress achieved during the past six decades, but years. During his service as CERN’s Director-General, the also demonstrated is the special way in which successful Large Electron–Positron Collider (LEP) and its four detec- international collaboration exists at CERN. tors for the LEP experiments were constructed and installed.

Contents: Luigi Di Lella is an experimental physicist who has made • Foreword (R-D Heuer) most of his career at CERN. He has performed experiments • Preface (L Di Lella and H Schopper) at almost all CERN accelerators on a variety of subjects. At • The Discovery of the Higgs Boson at the LHC (P Jenni the CERN Intersecting Storage Rings he took part in the and T S Virdee) experiments that demonstrated the point-like structure of • Precision Physics with Heavy-Flavoured Hadrons (P the proton in the , and later he was one of Koppenburg and V Vagnoni) the leading physicists in the UA2 experiment at the proton- • Toward the Limits of Matter: Ultra-relativistic Nuclear antiproton collider which contributed to the discovery of Collisions at CERN (J Schukraft and R Stock) the W and Z particles. He has been a member of various • The Measurement of the Number of Light Neutrino international scientific committees both in the USA and in Species at LEP (S Mele) Europe. He has retired from CERN in 2002 and is presently • Precision Experiments at LEP (W de Boer) associated with the University of Pisa, Italy. • The Discovery of the W and Z Particles (L Di Lella and C Rubbia) • The Discovery of Weak Neutral Currents (D Haidt)

March 2016, Volume 5 No 1 63 CONFERENCE CALENDAR Upcoming Conferences in the Asia Pacific Region

MARCH 2016 APRIL 2016 ASCFD 2016 Asia Symposium on Computational Fluid Dynamics The 2nd Conference on Radio IUPAC International Symposium on Date: 15–17 April 2016 Science and Antenna Technology Photochemistry Location: Seoul, Korea, Republic of (RSAT 2016) Date: 3–8 April 2016 Organizers: ASCFD Date: 2–4 March 2016 Location: Ōsaka, Japan Event types: Conference, workshop Location: Beijing, China Organizers: The event has the objective of creating an Organizers: Engineering Information Institute Event types: Symposium international forum for academics, researchers and Event types: Conference The scientific program of 2016 IUPAC Photochem scientists from worldwide to discuss worldwide This Conference will cover issues on Radio Science will cover all of the major disciplines of results and proposals regarding to the soundest and Antenna Technology. It dedicates to creating a contemporary photochemistry-related science issues related to Computational Fluid Dynamics. It stage for exchanging the latest research results and including physics, biology, medicine, materials will include the participation of renowned keynote sharing the advanced research methods. The scope science, engineering, and technology. The scientific speakers, oral presentations, posters sessions and of RSAT 2016 covers both theoretical and practical committee represents a broad diversity of interests technical conferences related to the topics dealt areas of radio science and antenna technology. in photochemistry and, with their input, we are with in the Scientific Program. organizing an exciting array of scientific events ICKEM 2016 6th International composed by plenary lecture, invited talk, oral ICNPP 2016 International Conference on Key Engineering presentation, and poster session. Conference on Nuclear and Particle Materials Physics Date: 12–14 March 2016 ICSMA 2016 2nd International Date: 16–18 April 2016 Location: Hong Kong Conference on Sensors and Location: Bangkok, Thailand Organizers: ICKEM 2016 Mechanical Automation Organizers: ICNPP Event types: Conference Date: 7–8 April 2016 Event types: Conference The aim of ICKEM 2016 is to provide a platform Location: Bali, Indonesia It aims to bring together researchers, scientists, for researchers, engineers, academicians as well Organizers: ICSMA 2016 engineers, and scholar students to exchange and as industrial professionals from all over the world Event types: Conference share their experiences, new ideas, and research to present their research results and development ICSMA 2016 aims to bring together professors, results about all aspects of Nuclear and Particle activities in Key Engineering Materials. This researchers and students in the field of Sensors and Physics, and discuss the practical challenges conference provides opportunities for the delegates Mechanical Automation, making the conference encountered and the solutions adopted. to exchange new ideas and application experiences a perfect platform to share experience, foster face to face, to establish business or research collaborations across industry and academia, and D&P Forum: Characterization of relations and to find global partners for future evaluate emerging technologies across the globe. Tight Reservoirs collaboration. Date: 18–20 April 2016 28th Conference of the Nuclear Location: Manama, Bahrain Plasma for Functional and Societies in Israel Organizers: Society of Exploration Geophysicists, Engineered Materials and Surfaces Date: 12–14 April 2016 Middle East SMS Korea 2016 Location: , Israel Event types: Conference Date: 23–25 March 2016 Organizers: The Nuclear Societies in Israel This forum will focus on discussing the state of Location: Incheon, Korea, People's Republic of Event types: Conference, Exhibition the art on geophysical methods and workflows Organizers: SETCOR events The subjects to be discussed at the Conference that can be applied to improve well performance Event types: Symposium include Nuclear Reactor Physics and Technology, and reserve estimates in tight reservoirs. Recent We invite researcher and industrials to be part of Radiation Protection, Medical Physics, advances in wide azimuth 3D processing, elastic this symposium and show their latest results and Radiation Protection in Medicine, Radiation modeling, borehole geophysics, electromagnetics, discoveries that will inspire research towards the Dosimetry, Physical Properties of Nuclear micro-seismicity monitoring, time lapse methods next generation of plasma-derived functional Materials, Accelerators, Radiation Detectors and and their integration with reservoir geology materials and surfaces and their applications. Measurements, Nuclear Security and Nuclear and petro physics, provides the opportunity for Potential topics include, but are not limited to: Forensics, Non-Ionizing Radiation and Policy a step change in reservoir characterization and Plasma treatment for functional surfaces. Aspects, Simulations and Numerical Methods, monitoring. Radiological Risk Assessment, Natural Radioactivity, Operational Radiation Protection and Radioactive waste and the environment.

64 Asia Pacific Physics Newsletter CONFERENCE CALENDAR

8th International Seminar on Fire information on laser ignition and related sciences JUNE 2016 and Explosion Hazards and technologies. Date: 25–28 April 2016 The 8th International Kasetsart Location: Hefei, China ICRSA 2016 2nd International University Science and Technology Organizers: ISFEH International Organizing Conference on Remote Sensing and Annual Research Symposium Committee Applications Date: 2 - 3 June, 2016 Event types: Seminar Date: 20–22 May 2016 Location: Bangkok, Thailand This seminar is hosted by the State Key Laboratory Location: Chengdu, China Organizers: Faculty of Science, Kasesart University of Fire Science (SKLFS) from the University of Organizers: ICRSA Event types: Symposium Science and Technology of China (USTC). The ISFEH Event types: Conference, workshop The International Kasetsart University Science has been organized since 1995, and the previous The aim of ICRSA 2016 is to provide a platform and Technology Annual Research Symposium seminars were successfully held respectively in for researchers, engineers, academics as well (I-KUSTARS) will provide an excellent international Moscow (1995, 1997), Lake Windermere (2000), as industry professionals from all over the forum for sharing knowledge and results in theory, Londonderry (2003), Edinburgh (2007), Leeds world to present their research results and methodology and applications of Natural Science (2010), and Providence (2013). The 8th ISFEH development activities in the area of Remote and Applied Science. The symposium looks for will include invited lectures from the world’s Sensing and Applications. This conference provides significant contributions to all major fields of top fire and explosion hazards researchers and opportunities for delegates to exchange new ideas Science and Technology in theoretical and practical presentations of peer-reviewed papers. All accepted and research findings in a face to face environment, aspects. The aim of the symposium is to provide a and presented papers will be included in the to establish business or research relationships and platform for the researchers and students to meet seminar proceedings, which will be published by to find global partners for future collaboration. and share cutting-edge development in the field of the Press of USTC. Poster sessions will provide an science and technology. excellent opportunity to interact individually with ICCMST 2016 International researchers about their most recent work. Conference on Carbon Materials Stochastic Processes in the Cell Science and Technology Cycle Date: 21–23 May 2016 Date: 13 - 17 June, 2016 MAY 2016 Location: Taipei, Taiwan Location: , Israel Organizers: Ariel Amir ( ), ICEMA 2016 International Organizers: ICCMST Nathalie Q. Balaban (The Hebrew University) and Conference on Energy Materials Event types: Conference, workshop Naama Barkai (Weizmann Institute of Science) and Applications ICCMST 2016 is supposed to be the largest Event types: Workshop Date: 5–7 May 2016 technical event on Materials Engineering and The workshop will host a small group of scientists Location: Seoul, Korea, Republic of Nanotechnology in Taipei, Taiwan in 2016. This from Physics, Mathematics, Biology and Computer Organizers: ICEMA conference aims to together professors, researchers Science. By allowing significant amounts of time for Event types: Conference and students in the field of Carbon Materials discussions rather than talks, we hope to encourage ICEMA aims to be the leading international Science and Technology making the conference the initiation of novel collaborations between the conferences for presenting novel and fundamental a perfect platform to share experience, foster participants, and a real exchange of ideas across advancements in the fields of Energy Materials and collaborations across industry and academia, and disciplines. Applications. ICEMA 2016 scope covers, but not evaluate emerging technologies across the globe. limited to, the following topics: Energy materials, ICPCO 2016 2nd International Hydrogen energy, Hydrogen production, Fuel IWTAP-2016, International Conference on Power Control and cells, Biofuels, Solar energy, Alternative energy, Workshop on Theoretical and Optimization Photocatalysis, Supercapacitors, Photovoltaics, Applied Physics Date: 15–17 June 2016 Nanomaterials, Nanoenergy, Graphenematerials. Date: 28–29 May 2016 Location: Istanbul, Turkey Location: Chongqing, China Organizers: ICPCO Laser Ignition Conference Organizers: Scientific Cooperations Event types: Conference Date: 17–20 May 2016 Event types: Conference, workshop ICPCO conference is one of the leading Location: Yokohama, Japan International Workshop on Theoretical and Applied international conferences for presenting novel Organizers: The Optical Society Physics is a peer reviewed academic event held and fundamental advances in the fields of Power Event types: Conference annually. The workshop is a part of International Control and Optimization. ICPCO also serves to An international forum to discuss all aspects Conference of Basic Sciences which consists of three foster communication among researchers and of laser induced ignition: advances in novel separate workshops of different disciplines. practitioners working in a wide variety of scientific giant pulse micro-lasers, new insights into the areas with a common interest in improving Power phenomena of laser induced breakdown, and Control and Optimization related techniques. advanced combustion systems enabled by laser ignition. The purpose of this meeting is to share

March 2016, Volume 5 No 1 65 CONFERENCE CALENDAR

ICMMR 2016 3rd International AUGUST 2016 A special industry forum session is also planned Conference on Mechanics and with solicited presentations from key industry Mechatronics Research Synthetic Topological Quantum players in the field. Plenary presentations by Date: 15–17 June 2016 Matter leading authorities of the international photonics Location: Chongqing, China Date: 1–5 August 2016 community will provide an insightful update on the Organizers: ICMMR Location: Beijing, China state of the world photonics R&D and market, and Event types: Conference Organizers: Kavli Institute for Theoretical Physics address hot topics in the field. 2016 3rd International Conference on Mechanics China at the Chinese Academy of Sciences and Mechatronics Research (ICMMR 2016) is Event types: Conference ICOSM 2016 International the main annual research conference aimed at The major objective of the KITPC/PKU conference Conference on Sustainable presenting current research being carried out. The is to bring together leading researchers working Materials idea of the conference is for the scientists, scholars, on the topological phases for ultracold atoms, as Date: 25–27 August 2016 engineers and students from the Universities all well as condensed matter (and photonic) systems, Location: Chengdu, China around the world and the industry to present to report their latest findings in this area, and Organizers: ICOSM ongoing research activities, and hence to foster investigate the new issues particularly connecting Event types: Conference research relations between the Universities and the to the interacting or non-linear systems. The main The event has the objective of creating an industry. topics of this conference include new experimental international forum for academics, researchers and and theoretical results of synthetic spin-orbit scientists from worldwide to discuss worldwide CLOUDY Workshop coupling and gauge fields, quantum anomalous results and proposals regarding to the soundest Date: 20–24 June 2016 Hall effect, topological superfluid, topological issues related to MATERIALS. Location: Shandong, China flat band, Dirac and Weyl semimetals, topological Organizers: Shandong University superconductors, topological insulators, and Event types: Workshop topological Kondo physics. SEPTEMBER 2016 The workshop will cover observation, theory, and apply Cloudy to a wide variety of astronomical Spin-orbit-coupled quantum gases International Conference on environments, including the interstellar medium, Date: 1–19 August 2016 Molecule-Based Magnets AGB stars, Active Galactic Nuclei, Starburst Location: Beijing, China Date: 4–8 September 2016 galaxies, and the intergalactic medium. The Organizers: Kavli Institute for Theoretical Physics Location: Sendai, Japan lectures and hands-on sessions will be carried China at the Chinese Academy of Sciences Organizers: Tohoku University out by Gary Ferland. The sessions will consist Event types: Workshop Event types: Conference, Symposium of a mix of textbook study, using Osterbrock & It is a KITPC Program. Its main objective is to bring ICMM is the largest conference related to the Ferland, Astrophysics of Gaseous Nebulae and together leading researchers working in a rapidly molecule-based magnets. We anticipate fruitful Active Galactic Nuclei, and application of Cloudy. developing area of Spin-orbit-coupling (SOC) for discussions on the latest topics during several Participants will break up into small teams and quantum gases. In addition to leading theorists, the plenary, keynote, and invited lectures and poster organize research projects of mutual interest. Program will attract prominent experimentalists presentations. In addition, there will be pre- and working on the SOC, synthetic gauge fields and post-conferences for young researchers: “Rising Star related areas for ultracold atomic gases. This will Symposium” and senior researchers. JULY 2016 help to stimulate the work on the realization of a new generation of experiments with SOC in Bose International Conference of Near- OptoElectronics and and Fermi gases, in which the many-body effects Field , Nanophotonics and Communications Conference / play an essential role. Related Techniques International Conference on Date: 4–8 September 2016 Photonics in Switching IEEE International Conference on Location: Hamamatsu, Japan Date: 3–7 July 2016 Group IV Photonics Organizers: Shizuoka University Location: Niigata, Japan Date: 24–26 August 2016 Event types: Conference Organizers: Optical Society (OSA) Location: Shanghai, China NFO has been held every second year since 1992 Event types: Conference Organizers: IEEE at Besancon, France and NFO is now the most Topics of this conferece including, not limited too: 1. Event types: Conference established and outstanding conference focused Core/Access Networks and Switching Subsystems. The conference will feature an exciting program on near-field optics, nanophotonics, plasmonics, 2. Transmission Systems and their Subsystems. 3. with presentations organized in three topical related techniques, and interdisciplinary network Optical Fibers, Cables and Fiber Devices. 4. Optical sessions covering the breadth of Group-IV of scientists. Following the tradition of NFO Active Devices and Modules. 5. Optical Passive photonic research and spanning the range from conference, NFO-14 will provide great opportunities Devices and Modules. 6. Optical Switching System scientific curiosity and fundamental discovery to for information exchange and creation of new and Related Technologies. advanced applications and commercialization. science and technologies.

66 Asia Pacific Physics Newsletter CONFERENCE CALENDAR

International Conference on Highly NOVEMBER 2016 Frustrated Magnetism (HFM) Date: 7–11 September 2016 Aggregation Induced Emission Location: Taipei, Taiwan Date: 18–20 November 2016 Organizers: HFM Location: Guangzhou, China Event types: Conference Organizers: Royal Society of Chemistry This international conference will be a great Event types: Conference opportunity for scientists from around the world to The themes of this conference includes New share the most recent developments in the study of and efficient fluorescent and phosphorescent frustration in magnets. It will feature presentations luminogens; Advance functional luminogens in the reporting on experimental and theoretical studies solid-state; Biomedical applications of luminogens; of magnetic frustration, in all of its manifestations. Optoelectronic devices of high efficient luminogens in the solid state. International Iran Conference on Quantum Information Date: 8–11 September 2016 Location: Tehran, Iran, Islamic Republic of Organizers: Sharif University of Technology Event types: Conference The conference will feature the latest developments in theoretical and experimental quantum information science, feature talks by leading international researchers, and provide the opportunity for research discussions and collaborations between international and Iranian quantum information researchers.

2016 the 4th Int. Conf. on Optical and Photonic Engineering (icOPEN 2016) Date: 26–30 September 2016 Location: Chengdu, China Organizers: icOPEN 2016 Event types: Conference Following the success of icOPEN2015 in Singapore, OPSS is proud to bring this well received conference to Chengdu, China for the first time. icOPEN2016 will provide a timely platform to conduct a recap of the latest technologies and industry milestones, and promote optical and photonic engineering to a wider audience.

APPN CONFERENCE CALENDAR welcomes conference information in the Asia Pacific Region. To submit, send e-mail to [email protected]

March 2016, Volume 5 No 1 67 JOBS

LAB OFFICER/POSTDOCTORAL FELLOW • Ensure that results are scientifically robust and documented (IMAGE PROCESSING) • Consult and effectively communicate with researchers from varied backgrounds to determine optimal analysis solution for their data • Modify and customize existing analysis tools to provide additional functionality Work Location: Singapore or increase usability • Develop novel biological image processing, image analysis and data analysis Company/Institute: Institute of Bioengineering and Nanotechnology algorithm or software with GUI

Since 2003, IBN has carved out a unique niche at the interface of bioengineering Requirements: and nanotechnology. Led by Executive Director Professor Jackie Y. Ying, the B.Eng./ B.Sc./ M.Sc./ Ph.D. from Computer/ Computer Science/ Electrical Institute conducts interdisciplinary research bridging science, engineering and Engineering/ Physics/ Mathematics or related discipline medicine. IBN is focused on generating new knowledge and creating innovative • Knowledge and experience in bioengineering, data analysis or optical technology platforms that combine novel catalytic chemistry, biomaterials, sensing will be an added advantage nanofabricated devices, and microfluidic systems with biological and biomedical engineering. • MATLAB, C/C++, and LabVIEW software programming experience required • Experience in developing GUI of multiple platforms on Windows and other portable devices Mission • Relevant experience in an R&D environment or laboratory with product • Provide international leadership in establishing a broad knowledge base in development focus bioengineering and nanotechnology. • A good team player, motivated, proactive, independent and result-oriented • Conduct innovative research and create intellectual properties in these emerging fields, attracting top-notch researchers and business partners to Singapore. How to apply: • Play an active role in technology transfer and spinning off small companies, If you have a passion for innovation and the desire to be at the forefront of linking our research institute and industrial partners to other global scientific research, send or email your curriculum vitae to the following address. institutions. Please include a cover letter and three references. Only shortlisted candidates will be notified. • Foster an exciting, multidisciplinary research environment for the training of students and young researchers at the frontiers of bioengineering and nanotechnology. Professor Jackie Yi-Ru Ying Executive Director Institute of Bioengineering and Nanotechnology Corporate Values 31 Biopolis Way • Passion is the driving force behind our pursuit of excellence. We are The Nanos, #04-01 dedicated towards making an impact on humanity through our creative Singapore 138669 research and innovative technologies. • Integrity is central to what we do. We are trustworthy and accountable for Please send your CV to [email protected] our actions, always striving to make a difference through diligence, honesty and good character. • Dedication is the cornerstone of our actions. We are committed to improving lives through scientific discoveries and breakthroughs, and seek to fulfill our responsibilities to the best of our efforts and ability. • Teamwork is the fabric of our corporate culture. We pledge to collaborate and work together seamlessly in our multidisciplinary projects. TENURE-TRACK FACULTY POSITIONS OF • Commitment is intrinsic to our attitude. We take pride in our work and PHYSICS are devoted to IBN's mission and vision. Work Location: Kaohsiung, Taiwan Job Description: Implement and develop image processing solutions on existing optical detection system, biomedical devices and microscopic images Company/Institute: The Department of Physics at National Sun Yat- • Work with medical devices and microfluidic projects to identify and deliver sen University solutions for addressing key biological questions using image and data analytics National Sun Yat-sen University was established in 1980 along the Hsitzi Bay in • Characterize and develop models of related experimental results with the city of Kaohsiung, and has since been a thriving institution of higher learning. appropriate software There are six colleges: Liberal Arts, Science, Engineering, Management, Marine • Work with biologists, engineers, biochemists and physicians to analyze Sciences, and Social Sciences, and one general education center. Equal emphasis images through image enhancement, counting, signal extraction, analysis is placed on the teaching and research of humanities as well as science and and labelling engineering. Since 2006 NSYSU has been granted by the Ministry of Education

68 Asia Pacific Physics Newsletter JOBS through the “Aim for the Top University Plan” to improve teaching and research. TENURE-TRACK FACULTY POSITION IN Outstanding academic achievements exhibited by many departments have landed NSYSU among the world’s top universities in many academic rankings. PARTICLE THEORY PHENOMENOLOGY

Work Location: Daejeon, Korea, The Republic of The NSYSU campus is uniquely situated at the crossing of hills and sea, and adjacent to the Kaohsiung Harbor. Our strategic geography prompted our feature advancements in marine research, which heeds to Kaohsiung’s aspiration to Company/Institute: Center for Theoretical Physics of the Universe develop into a Marine Capital, as we become the leading academic institution (CTPU)/Particle theory and cosmology (PTC), Institute for Basic Science of marine sciences in Taiwan. The university encourages interdisciplinary collaboration between marine studies and other academic fields so as to Founded in November 2011 by Korea Government, the Institute for Basic Science stimulate new ideas and research directions. NSYSU is ranked in the top 200 (IBS) supports basic research within the entire range of natural sciences including by ESI in the fields of engineering, mathematics, and information engineering. physics, biology, chemistry, mathematics, earth science, and astronomy by We are also highly competitive in the fields of communications engineering, providing highly advanced, supportive, self-direct research environments. The electronic commerce, materials science, and optoelectronics. Institute for Basic Science (IBS) pursues excellence in basic science research. The goal of IBS is to advance the frontiers of knowledge and to train the leading NSYSU has sister-university agreements with over 160 universities from more scientists of tomorrow. than 30 countries around the world. Within these partnerships we engage in student exchange programs, dual degree programs, joint dissertation Accelerate Transformation through New Knowledge supervisions, research collaborations, and co-sponsorship of symposiums. We IBS was established in November 2011 as Korea’s first dedicated basic science are dedicated to creating an internationalized campus. Each year over 1,200 research institute. By studying the fundamental principles of nature, basic foreign students come to NSYSU for degree programs, exchange programs, science is essential in creating new knowledge from which significant societal research fellowships, or language learning. The vast array of activities provides transformations are derived. IBS promotes the highest quality of research that ample opportunities for domestic students and foreign students to interact and will increase the national basic science capacity and generate new opportunities bridge their understanding of different cultures. for this nation.

The campus is located in the scenic Hsitzi Bay and surrounded by the Longevity IBS specializes in long-term projects that require large groups of researchers. As Mountain and the Taiwan Strait. The spectacular beach offers a natural venue research in the 21st century requires more interdisciplinary collaborations from for recreation and water sports, and the sunset is the most popular scenery larger groups of people, scientists at IBS work together in the same laboratory sought by tourists from all over the world. base with a long-term perspective on research. We promote autonomy in research. IBS believes scientists unleash their creative potential most effectively Job Description: The Department of Physics at National Sun Yat-sen University, when they conduct research in an autonomous environment with world-class Kaohsiung, Taiwan, is seeking team-spirited and mission-oriented scientists research infrastructure, including a rare isotope accelerator to enable major of pedagogical inspiration to fill several faculty positions in the general areas scientific advances. By developing strong synergies from outstanding talents, including astrophysics, condensed matter physics, optical physics, biological autonomous research support systems, and world-class infrastructure, IBS is physics, and materials-related physics. The expected starting date is August steadily growing into a major basic research institute that meets the global 1, 2016. Qualifications include a Ph.D. in physics or closely-related fields, standards of excellence. demonstrated interest in mentoring students, abilities to teach physics core courses at all levels with some lectured all in English, and capabilities to secure Ensure Excellence in Research external funding for independent research. Some postdoctoral experience at By pursuing excellence in research, IBS has selected global leading scientists international institutions is preferred for junior-rank applicants. as directors of Centers through its competitive grant programs. These directors are operating 26 Centers of which research proposals are ranked highest in the How to apply: Application Materials Required: IBS peer review process. The review is carried out by a Review Panel composed • Cover Letter of independent and expert scientists from Korea and abroad. Directors choose the themes of their research and allocate funds accordingly. Generally, Centers • Curriculum Vitae operate projects with no fixed term for their duration as long as the quality of • Research Statement research is verified in evaluations. New Centers receive an initial evaluation five • Teaching Statement years after its launch, followed by three-year interval evaluations. • Publication List • Representative Works IBS has been inviting top scientists from around the globe and providing them • Reference full support for their relocations. Young scientists also enjoy unique research opportunities to collaborate with world renowned scientists and to organize and operate their own research groups, broadening their professional expertise. IBS Please send your CV to [email protected] brings together outstanding talents throughout all career levels to grow and inspire each other through close collaborations.

March 2016, Volume 5 No 1 69 JOBS

Stimulate Collaboration Without Boundaries 193 Munji-ro, Yuseong-gu, Daejeon 34051 IBS welcomes scientists from Korea and abroad seeking to work in a collaborative Republic of Korea research environment. IBS’ faculty researcher program and IBS’s affiliation with the founding body of University of Science and Technology (UST) help Please send your CV to [email protected] IBS scientists to reach out to and foster young talent outside the institution. Centers serve as a catalyst for research collaboration with universities and other government-funded research institutions through joint research and the sharing of research equipment. Other efforts are also underway to stimulate collaborations, including overseas training programs and visiting scientist programs. ASSISTANT OR ASSOCIATED PROFESSOR To disseminate research findings, IBS holds an “IBS Research Conference” and develops a global network with the world’s prominent research institutions Work Location: Beijing, China including the Gesellschaft (MPG) in Germany and the Royal Society in U.K. Company/Institute: Institute of Physical Electronics, Peking University We expect our work to make transformative changes outside as well as inside the institution. To realize this exciting vision, IBS will serve as a national R&D Peking University is a comprehensive and national key university. The campus, platform and accelerate the creation and use of new knowledge to support known as "Yan Yuan" (the garden of Yan), is situated at Haidian District in the universities, research institutions, and businesses. As a driving force for dynamic western suburb of Beijing, with a total area of 2,743,532 square metres (or 274 research collaborations, IBS will continually develop and refresh its science, hectares). It stands near to the Yuanmingyuan Garden and the Summer Palace. while always remaining receptive to outside talents and ideas. TPeking University is proud of its outstanding faculty, including 53 members of Continue its Endeavor to Make a Brighter Future the Chinese Academy of Sciences (CAS), 7 members of the Chinese Academy IBS shares the same passion as other great minds to investigate the nature of Engineering (CAE), and 14 members of the Third World Academy of Sciences of life in the universe for the development of humanity, as shown in its vision (TWAS). “Masking Discoveries for Humanity & Society”. The university has effectively combined research on important scientific subjects We are committed to realizing this vision through a phased endeavor as outlined with the training of personnel with a high level of specialized knowledge and in our Five-year Plan (2013 – 2017). We aim to: professional skill as demanded by the country's socialist modernization. It • Become a national hub for basic science research by 2017 strives not only for improvements in teaching and research work, but also for the promotion of interaction and mutual promotion among various disciplines. • Complete the construction of the rare isotope accelerator by 2021 • Evolve into one of the world’s top 20 basic research institution by 2030 (measured in terms of impact on research). Thus Peking University has become a center for teaching and research and a university of a new type, embracing diverse branches of learning such as basic and applied sciences, social sciences and the humanities, and sciences of By creating an integrated basic science effort that brings together the best minds medicine, management, and education. Its aim is to rank among the world's best across the borders, we will build an IBS Complex as an urban science park that universities in the future.The Institute of Physical Electronics (http://nano.pku.edu. will promote public outreach and community engagement. Our commitment to cn) grew out of the electron physics major in Department of Electronics, Peking enhance the quality of life and make sustainable progress continues every day. University. Since its establishment in 1959, this major has made significant contribution to the development of electron physics in China. In the recent Job Description: Center for Theoretical Physics of the Universe (CTPU) - decade, the Institute has made distinguished contribution to carbon nanotube Particle Theory & Cosmology Group at the Institute for Basic Science (IBS) in devices, in situ manipulating and characterizing nanotubes and nanowires, and Korea invites applications for a tenure-track faculty position in particle physics developing advanced functional nanomaterials and nanodevices. phenomenology starting anytime in 2016. We are particularly interested in the candidates with expertise in physics beyond the standard model with an The Institute of Physical Electronics (http://nano.pku.edu.cn) grew out of the emphasis on the astroparticle or cosmology implications. electron physics major in Department of Electronics, Peking University. Since its establishment in 1959, this major has made significant contribution to the How to apply: development of electron physics in China. In the recent decade, the Institute Applications should consist of a CV, a publication list, a research statement has made distinguished contribution to carbon nanotube devices, in situ and three or more letters of recommendation, and be submitted through manipulating and characterizing nanotubes and nanowires, and developing Academic Jobs Online. The search is open until the position is filled, but for advanced functional nanomaterials and nanodevices. full considerations, please submit the application and letters by February 29, 2016. Job Description: The Institute of Physical Electronics in the School of EECS at Peking University seeks for young talents to fill several new full-time tenure- IBS Center for Theoretical Physics of the Universe track positions at the assistant or associated professor rank in the following KAIST Munji Campus, Faculty Wing 3rd Floor research areas:

70 Asia Pacific Physics Newsletter JOBS

1) Nanomaterials aiming for nanoelectronic and optoelectronic devices addition to the four dimensions of space and time that are familiar to us. Other (including but not limited to functional nanomaterials design and fabrication, work in advanced algebra aims to develop laws that govern that description. characterization and novel device development). On the other hand, mathematicians use tools developed in string theory to 2) novel sensing and/or flexible devices and systems attack their own problems. 3) chip design, especially those based on nanoelectronic devices 4) semiconducting quantum devices String Theory. The pursuit of a unified theory that explains both , which describes the physics of gravity, and quantum mechanics, which describes 5) micro and nano biophotonics (including but not limited to single molecule/ the physics of elementary particles, may lie in string theory, which postulates single cell study and advanced biophotonics technology development) that matter at its most fundamental is comprised of vibrating strings. The close relationship between string theory and mathematics has inspired advances in How to apply: both fields, and collaborations at the Kavli IPMU are ongoing. To apply, please email the resume, statements of research, the names and contact information of at least three references to [email protected]. Early Neutrino Physics. Neutrinos are one of the fundamental particles in the submission is encouraged: universe and they must have played a role in the development of galaxies in the early universe, but little is understood about them. Experimental evidence Contact: Professor Qing Chen, +86-10-62757555 to date suggests that neutrinos have mass, but it has never been measured Email: [email protected] accurately. Two experiments involving researchers at the Kavli IPMU, called SuperKamiokande and KamLAND, both in a deep underground mine, are Postal Mail: attempting to detect and characterize neutrinos, while astronomical observations Department of Electronics, will constrain the neutrino mass as well. School of EECS, Peking University, Beijing 100871 Dark Matter. The Kavli IPMU researchers are involved in an experiment called China XMASS to detect the dark matter particles. Dark matter makes up nearly a quarter of the universe but it is completely unknown. Astrophysicists know of dark matter’s presence by its gravitational effects on galaxies and clusters of galaxies. But direct detection, if it is possible, will require close collaborations with particle physicists working on XMASS and other detection experiments.

POSTDOCTORAL FELLOW IN COSMOLOGY . A large view of the cosmos is needed to understand the nature and origin of its largest structures. Using the Subaru Telescope atop WITH GALAXY SURVEY Mauna Kea in Hawaii, the Kavli IPMU astronomers are involved in gravitational lensing studies – the phenomenon by which the gravity of foreground galaxies Work Location: Kashiwa, Japan and galaxy clusters distort more distant objects behind them. These and other studies, including a new project to install a wide-field camera on Subaru to conduct a wide-field survey of distant galaxies, will help astronomers better Company/Institute: the Kavli Institute for the Physics and Mathematics understand the nature of dark energy, which is causing the universe to expand of the Universe (Kavli IPMU), The University of Tokyo at an accelerating rate.

The Kavli IPMU, an institute within the University of Tokyo, brings together a The Kavli IPMU hosts international workshops and meetings on these and wide range of researchers – from pure mathematicians and string theorists other topics of interest, and over the years it has strengthened relationships to experimental particle physicists and observational astronomers – in a truly with other prominent research programs at U.C. Berkeley, Princeton University multi-disciplinary and collaborative environment. First established in 2007 and other institutions. Helping to fulfill its founding mission, the Institute has under a Japanese government initiative as the Institute for the Physics and also fostered increased awareness of cosmology through public talks and other Mathematics of the Universe (IPMU), the Institute received an endowment from activities, in Japan and abroad. The Kavli Foundation in early 2012 and became the Kavli IPMU.

Job Description: Applications are invited for a postdoctoral research position Housed in a research building at the University of Tokyo’s Kashiwa campus in at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli Chiba Prefecture outside of Tokyo, The Kavli IPMU is led by Hitoshi Murayama, IPMU), The University of Tokyo. The Postdoctoral Scholar will work primarily a particle physicist and ambassador for the Institute’s work. Of the Institute’s with Masahiro Takada (Cosmology), but also have an opportunity to work with nearly 200 principal investigators, faculty members, postdoctoral researchers, members at Kavli IPMU. Opportunities are available for a variety of pursuits in joint appointments and graduate students, more than half are from outside cosmology based on redshift galaxy survey (BAO and redshift-space distortion), Japan. Among the Institute’s main research areas: including theoretical and numerical studies, joint cosmological analysis of imaging and redshift galaxy survey data, and planning for the Subaru Prime Mathematics. The Kavli IPMU regards pure mathematics research as fundamental Focus Spectrograph (PFS) project. Kavli IPMU is one of the leading institutions to its quest to understand the universe. The Institute’s mathematicians, for of the Subaru Hyper Suprime-Cam (HSC) Survey and is leading the development example, are working on new geometric tools to help string theorists develop a of the Subaru PFS project. Furthermore, the institute is a full member of both new physical description of the universe that includes six extra dimensions – in the SDSS-III and SDSS-IV collaborations, which include the BOSS and eBOSS

March 2016, Volume 5 No 1 71 JOBS surveys. This position is supported by the grant “Why does the Universe • No need to relocate. As this is a freelance opportunity, we invite candidates accelerate? – Exhaustive study and challenges for the future – B03 group” from any location to apply. (MEXT Scientific Research on Innovative Area). Job Description: Cactus Communications employs a global team of highly Requirements skilled editors who are experts in various academic fields. We’re currently looking Candidates should have a recent PhD in Astrophysics or Physics with a strong for specialist freelance copyeditors and substantive editors. background in cosmology. Experience in large-scale structure theory and/or galaxy clustering analysis is highly desirable. Postdoctoral Scholar position Editors will be in charge of: is awarded for a minimum of two-year period and can be renewed up to a maximum of 4 years depending on achievements. • Edit manuscripts such that the final text is in standard scientific English and is free of unclear or unidiomatic sentences • Adhere to job-specific instructions and format manuscripts according to How to apply: the target journal when required The applications should include a CV, research statement, publication list, and at least three letters of recommendation. They should be uploaded at https:// • Ensure that all subject-specific conventions are followed academicjobsonline.org/ajo/jobs/6447. Applications will be considered, beginning on Dec 1, 2015, until the position is filled. Requirements A Post Doc/ PhD/Master's/ Bachelor's degree or expertise in one or more specialized subject areas in the life sciences, physical sciences and engineering, healthcare, medicine and surgery, and social sciences. Excellent English editing skills and attention to detail (prior editing experience would be great).

FREELANCE EDITORS - LIFE SCIENCES & How to apply: send your resume to [email protected] PHYSICAL SCIENCES

Work Location: Worldwide - Telecommute

Company/Institute: Cactus Communications POSTDOCTORAL FELLOW

CACTUS is a leading global provider of scientific and medical communication Work Location: Pohang, Korea services to researchers, authors, scholarly journals, publishers, academic societies, and pharmaceutical and device companies. Company/Institute: Asia Pacific Center for Theoretical Physics (APCTP) Our company mission is to enable growth through effective communication. In everything we do, we want to accelerate the development of global scientific Asia Pacific Center for Theoretical Physics (APCTP) is a close-knit, multi- research by helping science break through the confines of geography and disciplinary research environment that hosts scientists working on challenging language. To this end, we offer world-class editing, publication support, medical problems at the forefront of biophysics, condensed matter, quantum information, writing, translation, transcription, and researcher training services, to help astrophysics, cosmology and particle physics. The institute also plays a key role individuals achieve their communication goals. in Korea by inviting international scholars, acting as a conduit for collaboration through focus workshops and training young scientists. Since our foundation in 2002, we have set up offices in the US, Japan, India, South Korea, and China. Over 72,000 individuals across the globe trust us APCTP, whose previous presidents include Nobel Laureates C. N. Yang and R. because of our strong quality focus and expertise across over 200 scientific B. Laughlin, has a rich history and celebrates its 20th year in 2016. In 2008 and academic disciplines. APCTP established Junior Research Groups (JRG) under a previous president, P. Fulde, in collaboration with the in Germany, as a means to provide gifted young scientists with their first opportunity of managing research. Our full-time in-house staff consists of over 300 people and represents a The institute currently supports eight JRG groups. diverse group of people from India, China, Japan, South Korea, Taiwan, the US, Germany, and Brazil. We also work with 1000+ highly skilled contractors from around the world. We have 87 BELS-certified writers/editors in-house (BELS: APCTP is located at the Pohang University of Science and Technology (POSTECH), Board of Editors in the Life Sciences), one of the largest groups of certified which in addition to possessing established departments in both mathematics editors in the world. and the natural sciences, ranks globally within the top 100 universities. Moreover, the boutique campus currently boasts the POSTECH-Max Planck center for quantum materials, as well as four centers from the Korean government flagship Freelance Editors will enjoy the following benefits: Institute for Basic Science (IBS) program, spanning low-dimensional electronic • Flexibility to determine your schedule and work hours systems, immunology, self-assembly and notably, the only mathematics IBS • Potential to earn up to 3000 USD per month (based on regular availability) center to date. Further information on APCTP is available at www.apctp.org. • Performance-based bonuses of up to 20% extra

72 Asia Pacific Physics Newsletter JOBS

Job Description: The cosmology group at the headquarter of the Asia Pacific Job Description: The high energy physics group of Sun Yat-Sen University Center for Theoretical Physics (APCTP), Pohang, Korea invites applications for (SYSU) invites applications for several research scientist and postdoctoral a few postdoctoral fellow positions in theoretical cosmology. fellowship positions in neutrino physics. SYSU is currently participating Daya Bay (http://dayabay.ihep.ac.cn/), JUNO (http://juno.ihep.ac.cn/) and PANDA-III (gas Xenon neutrinoless double and liquid Argon dark matter) experiments The group is led by Jinn-Ouk Gong and has broad research interests, including and with possible participation of future dark matter and neutrinoless double particle cosmology, primordial inflation, cosmological perturbation, large scale beta decay experiments(nEXO). The research scientists and postdoc fellows are structure and dark energy. expected to play important roles in one or more aspects in the areas of data analysis with the Daya Bay experiment, design and construction of the JUNO The position is initially for two years, with the possibility of a third year depending experiment (including neutrino physics study, software development, R&D of on the research performance, mutual agreement or funding situation. The the liquid scintillator detector and the muon water Cherenkov detector, etc.), starting date of the appointments is negotiable, but it should not be later than R&D of future dark matter and neutrinoless double beta decay experiments, the end of 2016. as well as neutrino phenomenology. The successful applicants will be based in Guangzhou, China. Knowledge of Chinese language is not required. Foreigners and non-Chinese speakers are welcome to apply. How to apply: Interested applicants should submit their CV, a list of publications, and a statement of research interests to [email protected]. They should Requirements also provide the contact detail of three references who can write letters of Post doc candidates should have or expect to have a PhD degree by the time recommendation. Review of applications will continue until the positions are of appointment, in particle physics or in nuclear physics. Research scientist filled. Those who have strong backgrounds in astrophysics, gravitational physics, candidates require to have both PhD degree and post doc experience in those particle physics and string theory are encouraged to apply. fields.

How to apply: The candidate should submit a curriculum vitae, a statement of research interest and plan, a list of publications, and arrange to have three letters of recommendation, sent through emails to JUNIOR, POSTDOC Prof. Jiajie Ling Work Location: Guangzhou, China Prof. Wei Wang

Company/Institute: Sun Yat-Sen University (SYSU)

Sun Yat-sen University, originally known as Guangdong University, was founded in 1924 by Dr. Sun Yat-sen (also called Sun Zhongshan), a great democratic POSTDOCTORAL RESEARCHERS/YOUNG revolutionary leader of the 20th century. The University is located in Guangdong Province, an area neighboring Hong Kong and Macao, which is at the forefront SCIENTIST/VISITING PROFESSOR of China's reform and opening up. Work Location: Lanzhou, China Being one of the leading universities in the People's Republic of China, Sun Yat-sen University is a comprehensive multi-disciplinary university, including Company/Institute: The Institute of Modern Physics (IMP) the humanities, social sciences, natural sciences, technical sciences, medical sciences, pharmacology, and management sciences. The Institute of Modern Physics (IMP) of the Chinese Academy of Sciences was founded in l957. As of 2013, the institute had 892 staff members including 403 It has about 82,384 students studying on four campuses in Guangzhou and researchers, as well as 284 master's and doctoral students. Zhuhai. Benefiting from its location near Hong Kong and Macao and the regional advantage of opening and economic development, the university has become an important base for training high-level talents, scientific research, providing IMP operates the Heavy Ion Research Facility in Lanzhou (HIRFL), which consists services to society and inheriting cultural traditions. of the Sector Focusing Cyclotron, the Separated Sector Cyclotron, the Cooler Storage Ring (CSR), and a number of experimental terminals. After a half century of development, IMP has become the most important research center for heavy The University has also successfully built international cooperation and exchange ion sciences in China. We have established active and fruitful collaboration with relationships with many top universities in the world. According to the Times more than 40 institutions worldwide. Higher Education World University Ranking for 2010-2011, Sun Yat-sen University was ranked in the top 200 in the world. As a national laboratory, HIRFL is open to domestic and international users. HIRFL produces medium and high-energy ion beams from proton to uranium. At present, Sun Yat-sen University covers a total area of 5.972 square kilometers In recent years, HIRFL has operated 7,000 hours each year and delivered and has 4 campuses: Guangzhou South Campus, Guangzhou North Campus, 5,000 hours of beam time for experiments. To improve HIRFL’s beam intensity Guangzhou East Campus, and Zhuhai Campus.

March 2016, Volume 5 No 1 73 JOBS and operating efficiency, IMP has devoted much effort to accelerator physics nuclear power plants. IMP established a department dedicated exclusively to and technology R&D. the R&D of a high-intensity superconducting proton accelerator and spallation target system. Now the roadmap for the ADS project is fixed and the research program is on track. Using HIRFL, we conduct fundamental research in nuclear and . IMP’s main research focuses on nuclear reactions, nuclear spectroscopy, the properties of nuclear matter, the chemistry of super-heavy elements and Job Description: The Institute of Modern Physics (IMP) of CAS in China has synthesis of new super heavy isotopes, key reactions in stellar evolution, high several immediate openings for postdoctoral researchers/young scientist/ energy density physics, and highly charged heavy ion interactions. After the CSR visiting Professor to work on both Experimental/Theoretical dark matter physics. was put into operation in 2008, IMP set making precision mass measurements of short-lived nuclides as its highest priority research program at HIRFL. A The successful candidate is going to play a major role in data matter study. The batch of nuclear masses were measured with a precision of up to 10-7 using location of the position is expected to in Lanzhou of China. Applicants should isochronous mass spectrometry, and the implications for nuclear structures and have received their Ph.D. in experimental/theoretical high energy or nuclear nucleosynthesis in the rapid proton capture process of X-ray bursts have been physics, experiences with data analyses or simulation are strongly preferred for investigated. So far, this research has led to three main conclusions. 64Ge is experimental positions, experiences with satellite detector is a plus. certainly not a major waiting point in the rapid proton capture process in X-ray bursts. Aided by model calculations, no strong Ca–Sc cycle can be formed in X-ray bursts. Last but not least, a breakdown of the quadratic form of the mass The applications will be considered as soon as they are received and the positions equation for analogous states was found. will remain open until they are filled.

We have paid much attention to heavy ion applications. Cancer therapy has been IMP is an equal opportunity employer. developed at IMP since 2006, and so far 103 shallow-seated and 110 deep- seated tumor patients have been treated. In collaboration with local government Requirements agencies and hospitals, two dedicated heavy-ion treatment facilities are under B.Eng./ B.Sc./ M.Sc./ Ph.D. from Computer/ Computer Science/ Electrical construction in Lanzhou and Wuwei in Gansu Province. Engineering/ Physics/ Mathematics or related discipline • Knowledge and experience in bioengineering, data analysis or optical Mutation of sweet sorghum using heavy ion beam irradiation technology has sensing will be an added advantage also proved to be very successful. An early maturity variety was isolated, and • MATLAB, C/C++, and LabVIEW software programming experience required we expect large-scale planting in western China to benefit many people. • Experience in developing GUI of multiple platforms on Windows and other portable devices It is also worth noting that HIRFL provides an important platform for evaluating • Relevant experience in an R&D environment or laboratory with product single particle effects for devices used in space, and contributes to space development focus sciences in China. Another important application field is material irradiation, which may play a significant role in future nuclear energy development. • A good team player, motivated, proactive, independent and result-oriented

In 2010, IMP took charge of the Advanced Nuclear Fission Energy Program- How to apply: ADS Transmutation System, a strategic priority research program of CAS. In Contact: Prof Xurong Chen ([email protected]) for questions and application collaboration with other institutes in China, the project was approved by the form. central government at the end of 2010. This long-term project aims to build a demonstration facility for the transmutation of nuclear waste produced in

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74 Asia Pacific Physics Newsletter SOCIETIES List of Physical Societies in the Asia Pacific Region

South East Asia Theoretical Physics Indonesian Physical Society Association (SEATPA) President: Dr. Masno Ginting President: Prof. Phua Kok Khoo Address: d/a Komplek Batan Indah Blok L No 48 Serpong Tangerang Banten Address: Nanyang Executive Centre #02-18, 60 Nanyang View, 15314, Indonesia Singapore 639673 E-mail: [email protected] E-mail: [email protected] http://hfi.fisika.net http://www.seatpa.org Israel Physical Society Association of Asia Pacific Physics Societies President: Prof. Yaron Oz President: Seunghwan Kim Address: School of Physics and Astronomy, Tel Aviv University Address: Asia Pacific Center for Theoretical Physics/POSTECH, 77Cheongam-Ro E-mail: [email protected] Nam-gu, POSTECH, Pohang, Korea http://www.israelphysicalsociety.org E-mail: [email protected] http://www.aapps.org Physical Society of Japan President: Prof. FUJII Yasuhiko Australian Institute of Physics Address: Yushima Urban Building 8F, 2-31-22 Yushima, Bunkyo-ku, Tokyo President: 113-0034, Japan Address: PO Box 546, East Melbourne, Vic. 3002 E-mail: [email protected] E-mail: [email protected] http://www.jps.or.jp http://www.aip.org.au Japan Society of Applied Physics Bangladesh Physical Society President: Satoshi Kawata President: Prof. A. A. Ziauddin Ahmad Address: Osaka University Address: Dhaka Dhaka 1216 Bangladesh E-mail: [email protected] http://www.bdphs.org http://www.jsap.or.jp

Chinese Physical Society Korean Physical Society President: Zhan Wenlong President: Y. P. Lee Address: Institute of Physics, Chinese Academy of Sciences, Beijing 100190 Address: The Korean Physical Society, 635-4 Yeoksam-dong, Gangnam-gu, E-mail: [email protected] Seoul 135-703, Korea http://www.cps-net.org.cn E-mail: [email protected] http://www.kps.or.kr Physical Society of Hong Kong President: Ruiqin Zhang Malaysian Institute of Physics Address: Department of Physics and Materials Science President: Prof. Kurunathan Ratnavelu City University of Hong Kong, Hong Kong Address: INSTITUT FIZIK MALAYSIA (MALAYSIAN INSTITUTE OF PHYSICS) E-mail: [email protected] C/O Jabatan Fizik, Universiti Malaya, http://www.pshk.org.hk 50603 Wilayah Persekutuan Kuala Lumpur, Malaysia. E-mail: [email protected] Indian Physics Association http://ifm.org.my/ President: Dr. S. L. Chaplot Address: PRIP Shed, Room No. 4, B.A.R.C.,Trombay, Mumbai India 400085 Mongolian Physical Society E-mail: [email protected] President: Prof. Orlokh Dorjkhaidav http://www.ipa1970.org.in Address: Institute of Physics and Technology Enkhtaivan avenue 54b, Bayanzurkh district, Indian Physical Society Ulaanbaatar 13330, Mongolia President: Prof. Milan K. Sanyal E-mail: [email protected] Address: IACS Campus, 2A&B Raja Subodh Chandra Mullick Road, http://www.ipt.ac.mn/ Kolkata 700032, India http://www.iacs.res.in/ips

March 2016, Volume 5 No 1 75 SOCIETIES

Nepal Physical Society Institute of Physics Singapore President: Prof. Pradeep Kumar Bhattarai President: Prof. Sow Chorng Haur Address: Tri-Chandra Multiple Campus, Ghanta Ghar, Ranipokhari, Address: Institute of Physics, National University of Singapore, Kathamndu 2 Science Drive 3, Singapore 117542 Email: [email protected] E-mail: [email protected] http://www.nps.org.np http://www.physics.nus.edu.sg

New Zealand Institute of Physics Physical Society of the Republic of China President: Professor Peter Derrick President: Prof. Minn-Tsong Lin Address: Department of Physics Address: National Taiwan University, No.1 Sec. 4 Roosevelt Road, The University of Auckland 10617 Taiwan Private Bag 92019 E-mail: [email protected] AUCKLAND 1142 http://www.psroc.org.tw E-mail: [email protected] http://nzip.org.nz/ Thai Physical Society President: Dr. Amon Pakistan Physical Society Address: PO Box 217, Chiang Mai University, Muang District, President: Prof. Dr. M Zakaullah Chiang Mai 50202. Address: Room No 205, Technical Block, NCP, Islamabad, Shahdra Valley Road, E-mail: [email protected] Islamabad 44000, Pakistan http://www.thps.org E-mail: [email protected] http://pps-pak.org/ National Committee of Russian Physicists President: Dr. Leonid V. Keldysh Physical Society of Philippines Address: 119991 Moscow, Leninsky Prospekt, 32a President: Prof. Romeric Pobre E-mail: [email protected] Address: 3/F National Institute of Physics http://www.gpad.ac.ru University of the Philippines, Diliman 1101 Quezon City, Philippines E-mail: [email protected] Vietnam Physical Society http://www.spp-online.org/ President: Prof. Nguyen Ba An Address: PO box 607, Bo Ho, Hanoi, Vietnam E-mail: [email protected] http://www.iop.vast.ac.vn

76 Asia Pacific Physics Newsletter