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Interview of Mikhail Shifman by David Zierler on July 7, 2021,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Interview with Mikhail Shifman, Ida Cohen Fine Professor of Theoretical Physics at the William I. Fine Theoretical Physics Institute at the University of Minnesota. The interview begins with Shifman’s thoughts on the differences between the physics community in Russia versus the US, as well as his thoughts on the future of supersymmetry. Then Shifman turns to his family history and memories of growing up Jewish in Russia under Communist rule. He describes his early interests in math and physics, and he recalls that reading Feynman’s lectures (translated into Russian) swayed him toward physics. Shifman recounts his undergraduate education at the Moscow Institute for Physics and Technology, where he had access to many great Russian physicists. He discusses his decision to focus on high energy physics and his graduate studies at the Institute for Theoretical and Experimental Physics (ITEP). Shifman recalls the November Revolution and its implications for his PhD research which led to the penguin mechanism. Then Shifman discusses being hired by ITEP after his PhD, and he overviews his research areas such as gluon condensate, axions, and his work connecting Yang-Mills with supersymmetry. Shifman recalls his decision to immigrate to the US and the offer that led him to the University of Minnesota, as well as the cultural shift and transition that came with that move. He recounts the honor of receiving the Sakurai Prize, as well as his many book projects. Toward the end of the interview, Shifman talks about his more recent work in supersymmetric solitons, shares his thoughts on the future of the Standard Model, and reflects on the impact of SVZ sum rules.
This is David Zierler, oral historian for the American Institute of Physics. It is July 7th, 2021. It is my great pleasure to be here with Professor Mikhail Shifman. Misha, it’s great to see you. Thank you so much for joining me.
Thank you, David.
Misha, to start, let’s go right to your nickname. How long have you gone by Misha, and is that a traditional nickname for the proper name “Mikhail?”
Yeah, it’s like in English, the full name may be Michael, but everyone would address the person as Mike. So Misha is a normal abbreviation for Mikhail in Russian.
A more official question, Misha—please tell me your title and institutional affiliation.
I'm Ida Cohen Fine Professor of Theoretical Physics at the William I. Fine Theoretical Physics Institute at the University of Minnesota.
Misha, just as a snapshot in time right now, what are you personally working on? And more broadly, what is interesting to you in the field?
Well, if you ask me what I am doing right now, it is a rather technical work. I am preparing the second edition of my big textbook, Advanced Topics in Quantum Field Theory. A deadline before which I should submit if I want it to be published in 2022 is August 30. I decided that summertime is the best time to do this work. In a broader aspect, if you ask me what I'm doing in my research right now—well, there are some traditional topics, like topics from the strong interaction theory. It’s called quantum chromodynamics, QCD for short, which was born at the very beginning of my career. So I am working on a problem from quantum chromodynamics. And then I am thinking on an exotic problem—it has a relation to the theory of gravity at very short distances, of the order of the Planck scale. We don’t know gravity well enough at such distances, and surprising things can happen. I am thinking about possible violations of causality at very short distances. If they exist, are there any observable consequences, for us, in our life?
A very broad question as it relates to your expertise in high-energy physics—is your sense currently observation and experiment is leading theory, or is theory leading experimentation?
Frankly, speaking now, I would say that in my area theory is way ahead of experimentation. And that’s not a good situation, to my mind. And that’s not what physics used to be, for centuries, starting from Galileo. Usually people observed something in nature, and then other people tried to interpret what was observed and build a theory, and then with a new theory, make new predictions, and verify the theory. That was the traditional way in physics. It is still the case in many areas of physics. Like in condensed matter. It’s mostly driven by experiments, which are abundant. Also in astrophysics, experiments are abundant and that’s very good, especially for young people. But if you ask me what’s happening in high-energy physics, which was my beloved area from the beginning of my career, I would say that the situation has changed, and there’s a reason for that. Large colliders needed for exploring shorter and shorter distance physics are very expensive. In the current global economic and political climate expectations for a new one seem dim.
The last one of this type was built in 2008 at CERN in Geneva, actually at the border between Switzerland and France. It brought a couple of great results. For example, the Higgs boson was discovered in 2012. This was expected. But since then, no new breakthrough experimental results. Only a couple of smaller colliders exist in the world, in China and in Japan. Basically, there are no large colliders of the traditional type in the United States. The flux of experimental data in high-energy physics dries out. It’s not totally dry, because there are still non-accelerator experiments, for instance, neutrino experiments in underground laboratories, proton stability experiments, astroparticle observations, and so on. But they are few. Theory is developing ahead of experiment for over twenty years, which is not so good conceptually, and not so good for young researchers who enter this area.
Misha, I’d like to ask a cultural question, one that might punctuate our discussion. Do you feel that culturally you bring a specifically Russian or even Soviet approach to physics?
Well, physics is an abstract international science. However, some nuances exist —or better to say existed—some nuances in the way how physicists were approaching their work, their goals, in the Soviet Union and in the Western countries. Physics community in the Soviet Union was not large and very isolated. I was a part of it from the time I entered the ITEP graduate school in 1972, until the time the USSR collapsed in 1991. To stay afloat special measures had to be taken. For instance, in ITEP we had three seminars a week. The task was not just to listen to the speaker for an hour as an indifferent listener but to understand each and every point in speaker’s presentation. We had to overcome many obstacles with publication of our results in the Western journals. International journals used to arrive at ITEP with a significant delay. We had to be very careful with selecting new students in theoretical physics. Selecting them was an elaborated multistage process. Physicists in Moscow were used to relying mostly on themselves, used to avoid researching topics which lied at the surface of the current development. Rather, they tried to find something which had a chance not to be discovered in the West immediately. That is why communications between each other in the community and help from colleagues were absolutely necessary. You could not survive in a small isolated community unless it is a very neatly tied community of colleagues and friends aspiring to excel in physics. I think, for the same reason the Soviet tradition was to be quite aggressive toward the speakers during the seminars and presentations. It was the kind of criticism which in principle was very welcome and needed. But on the other hand, at times, it was becoming too offensive, I would say.
When many Soviet physicists found themselves in the Western countries after the demise of the USSR in 1991, it was natural that they brought some of their culture here, in the West. At first it was a very strongly expressed tradition, strongly expressed feeling, strongly expressed criticism. But on the other hand, it was always accompanied by a desire to communicate with a colleague, to help out if necessary. Some speakers referred to our physics seminars in Minnesota as “Russian seminars”. But with time—you know, 30 years passed, and that generation of physicists who came in the early 1990s to the USA or other Western countries, they are getting close to retirement, or even past retirement. With newer generations––young men and women from modern Russia educated at least in part in the United States—the old traditions gradually fade away. They are being diluted with the passage of time.
Misha, a question that inevitably looks to the future—are you optimistic that you will live to see supersymmetry?
I want to be optimistic, and I want to see supersymmetry. After all, it permeates a half of my scientific life. When I came to high-energy physics–– as I said, it was in 1972—I was rather passionate. I'm still a rather passionate person, but at that time, I was incredibly passionate. I had two passions. In the beginning, my passion was quantum chromodynamics which was just born almost simultaneously with my entering the graduate school at ITEP. It was a little too late for me to participate in its making but it instantly became my passion. I worked a lot on it, and worked very hard, as was normal in the USSR. When supersymmetry came, eventually I also became passionate about supersymmetry. But not about phenomenology aspects. We––I mean my informal teachers Vainshtein and Zakharov––and myself were intrigued by less obvious issues in supersymmetry, which were not so popular. It was the early 1980s when we started. And I'm still deeply immersed in supersymmetry until these days. It is a fascinating theory, and unique in some aspects. This is one of my main preoccupations. From time to time, I make forays to other areas. In general, I like to be relatively broad. I don’t like to limit myself to one issue forever. So, I make detours to some other areas, but there is a main highway, on which I like to drive, and this, to date, is supersymmetry––non-perturbative supersymmetry to be more exact.
Misha, this is as much a philosophical as it is a scientific question, but until supersymmetry is experimentally verified, does it exist more in the realm of belief, or do you feel that the theory is so strong that it’s definitely there; we just lack the tools to see it currently?
First of all, it’s not quite right to say that supersymmetry is kind of a phantom of our imagination. Yes, that’s true that in nature so far we don’t see traces of supersymmetry. But it exists as a tool for solving deep problems in strongly coupled Yang-Mills theories also known as non-Abelian gauge theories. You know, they run our world. Quantum chromodynamics belongs to this class. Supersymmetry proved to be a unique tool which will stay with us forever. The idea to use supersymmetry as a tool of explorations of gauge field theories dates back to the early 1980s. Some first results were obtained in our group. The culmination of this idea occurred in 1994 after the Seiberg-Witten paper on confinement. The area of applications of this supersymmetry-based method so far is not as wide as it was hoped for in the very beginning. The development goes slowly. The advances do not come every month. What do you want–– it’s a very difficult area. Everything that’s strongly coupled is very difficult for theoretical studies, even in classical physics. For instance, take turbulence which is crucial, among other things, for weather forecasts. In principle, it is described by a classical Navier-Stokes equation known since the 1820s. And still, today, we don’t have an analytic theory, only numerical predictions. Even with all the power of modern computers, the numerical solution of the Navier–Stokes equations for turbulent flow is far from being precise. That’s why reliable predictions don’t expand for more than two or three days. Even for two or three days, sometimes they don’t come true. So it shows that strongly coupled systems, even in classical physics, are intrinsically difficult to analyze. Quantum field theory as well as quantum gravity, are examples of such quantum theories whose complexity is way higher than in classical systems. That’s why it is notoriously hard to study them, and the progress is so slow. And, nevertheless, we understand now a lot more than let’s say 40 years ago. But obviously it’s not the final solution. So people still are working on that. This work is facilitated by supersymmetry-based methods.
Misha, to broaden it out a little bit, where do you see the overlap and where do you see the subfields as distinct, with the other supers, namely superstring theory and supergravity? Where do you see them fit in overall with supersymmetry?
Both disciplines you’ve just mentioned are based on supersymmetry. In string theory, supersymmetry was first “discovered” in two dimensions, or as they say, on the string world sheet, that’s why I use quotation marks. Appropriate string theories are consistent and theoretically treatable only if there is superconformal symmetry on the string world sheet. The first supersymmetric field theory in four dimensions––supersymmetric quantum electrodynamics––was invented in early 1971 in Moscow by Golfand and Likhtman.
As I know from pioneers of string theory, the relationship between superstrings and supersymmetry in our four-dimensional world was not immediately realized. In our world supersymmetry must be broken since we don’t see supersymmetry at “our” energies. I don’t think that this part of the string theory is worked out in earnest. Moreover, superstrings are consistent in ten-dimensional space-time, and they predict supersymmetry in the ten-dimensional world. Now, you want to reduce it down to our world which has one time and three spatial dimensions and no visible supersymmetry, but there is no easy way to do so. I would say, no unique generally accepted solution exists so far. The dream of string theory pioneers did not come true. Is this bad? I do not think so. For many years string theory was advertised as the theory of everything. But if everything is already derived and understood, then physics dies. It’s like with geography of our planet. It died with the discoveries of the last rocks in the oceans, after its glorious times of 15th, 16th century, maybe 17th century. What it is now to do for the geographers on Earth? Assume that a theory of everything is created, no new phenomena ever to be discovered in our world… Logically, that’s an option. But I personally do not believe that humans will ever know everything about nature. I hope people will continue to observe new phenomena, theorists will continue to incorporate them in new theories, and so on. My conjecture; take it or leave it.
As for supergravity it can be viewed as a direct generalization of four-dimensional gravity which emerges after addition to gravitons their superpartners––gravitinos.
[laughs] Misha, last question on a current events issue—how has, for better or worse, the mandates of remote work during the pandemic affected your science? On the one hand, has it given you more opportunity to work on long-standing problems? And on the other, has it really been problematic to be physically isolated from your collaborators?
I don’t know, it probably depends on the particular person. At first, I took it okay, I could work at home. But when you work at home in isolation for a month, two, three months, for half a year, it becomes as little depressing. Because physicists, theoretical physicists used to have discussions. They are fruitful. Discussions are much better in person, than via Zoom. It’s just depressing. And the more it continued, the more depressing, personally, for me it was. So I feel myself very happy that it’s close to completion. I am again going to my office at the U, and I am talking to people, to other people who come there. We discuss physics news. Soon seminars will start. So I think that COVID was a challenge, in general—such a long period of isolation, basically a year and a half, maybe a little bit more. But, it’s over.
Misha, let’s take it all the way back to the beginning. Let’s start first with your parents. Tell me about them.
My father was a civil engineer, and my mother was a family doctor. They were born in the early 1920s into poor Jewish families in a small shtetl. Both were first-generation college educated. My father didn't have time to finish the university before the onset of the Second World War. In the Soviet Union, the war started on June 22nd of 1941. At that time, he was 19 years old, and he immediately was drafted in the Army and sent to the front line. He spent four years on the front lines and ended in Berlin, one of few men of this generation who survived. If you look at the statistical data, in this generation in Soviet Union, maybe one of 10 or 20 men c?me back at the end of the war. After the war my father returned back and resumed his studies at the university. And then he met my mom. They got married. And that’s how I appeared in 1949.
Life at that time was very hard in the Soviet Union. Especially hard it was for Jews. You maybe know that shortly before his death, Stalin launched an atrocious anti-Semitic campaign. Jewish culture was completely eradicated at that time. Many Jewish writers, poets, newspaper men were arrested and either sent to gulag or killed. My mom and my dad were afraid of being fired, they expected this to happen every day. So the first years of my life were not so smooth…. But, well, Stalin died in 1953—I was four years old at that time—and life started becoming a little better. It was still quite hard, in terms of making ends meet in the family. Unlike American doctors, doctors in Russia worked long hours and their salary was small. But okay, they tried to give me as good education as they could, and I think they succeeded eventually. I was able to go to a very good university in Moscow. It’s called Moscow Institute for Physics and Technology. It’s a very small university, much smaller than let’s say Moscow State University. But it had very strict requirements for the students and excellent curriculum. Only the best students were selected through quite challenging entrance examinations. I was very lucky to be admitted. Excellent professors taught us a lot of things, some of them are not even mentioned in many universities. So that’s all about my father and my mother, they were both university educated. If you go one generation back, my grandparents had at best a few years of heder (Jewish school) in a shtetl in the western part of Belarus, and they were extremely poor. So, that’s it about my background.
Misha, as Soviet Jews, were your parents aware, do you think, of what was happening to Jewish people elsewhere in Europe during the war, or they were not aware of that?
Well, yes and no. By 1950s, Holocaust was known, but not its full scale. At the same time many—you wouldn’t believe it –– many words which seem normal in English were kind of avoided at that time in the Soviet Union. For instance, saying that such and such is Jewish was considered to be very rude. The very word “Jew” became derogatory. Also, details of the Holocaust were not mentioned in full in the Soviet literature until mid-1960s. Only then evidence about Holocaust, and in particular its part that happened in the occupied territories of the Soviet Union, started dribbling into the public space. I remember when Evgeny Evtushenko managed to publish his poem “Baby Yar” in the mid-1960s it was like a bomb explosion. Before, by and large it was kind of a taboo subject. They would never say, “In Auschwitz, three million Jews perished.” Or in Baby Yar. They would say that, “In Auschwitz, many Soviet citizens were killed by German fascists.” Of course, now archives are open, and everything is known.
Misha, growing up, what are some of the big things about the Cold War that stands out in your memory?
I lived through Cold War from its beginning to the end. I remember posters in elementary school depicting what we should do if the American aggressors drop nukes on our cities. Americans were always referred to as American imperialists and Israelis as Israeli militarists. The Soviet Communist Party propaganda was omnipresent in the Soviet Union. It taught us that everything what was happening in the West was bad, and draw it only in black colors. And then they would say that everything what was happening in the Soviet Union is great, and even perfect. I remember the time when genetics and cybernetics were referred to in the Soviet media as bourgeois pseudo-sciences used to oppress the American working class. I remember the Caribbean crisis of 1962. It was not mentioned until it was actually resolved. My grandfather after retirement bought a short-wave radio set and would listen to BBC Russian service every evening, despite terrible noise produced by jamming devices. He would tell me the other side of the story.
August 20, 1968, the day of the Soviet invasion in Czechoslovakia, is a black day in my memory. It was Tuesday. On this Tuesday I finally fully realized that socialism with the human face is an absolute Utopia. Frankly, I cried, probably the last time in my life. Of course, at a certain point, people who could see around realized that the communist propaganda is not even a fairy tale. It was obvious that by far not everything happening in the Soviet Union was good. For instance, food shortages. As long as I remember myself—maybe from mid-1950s—there were food shortages, and, basically shortages of everything. When I got married, I felt it especially strongly, because I had two daughters, and my wife and I, we had to feed them somehow. It was a never-ending hunting expedition. You get up early in the morning; the first thing you do, you go to the nearby groceries. And maybe at one grocery you can find a piece of meat, and in another, a piece of cheese. But okay, there was no famine, fortunately. It was not like during the war—or before the war. You probably heard that in Ukraine, there was a huge manmade—Stalin-made—famine, in the 1930s. Millions of peasants died of starvation. In my time, there was no famine, but there were shortages. TV tells you we have food and prosperity. It is getting better by day… And then you look around and see a total discrepancy between what you hear on TV and what you see. It made me nervous, [laughs]. It was humiliating.
Misha, growing up, did you ever get the feeling that your science education had an ideological or even Communist component to it? That physics was something that was in service to the state?
This question has two aspects. If you mean physics students education, all students in the Soviet universities, physics students including, had to take such courses as Marxism-Leninism, dialectic materialism, scientific communism (whatever it might mean) and pass examinations. You could not avoid them. All five years when you are a university student these courses were mandatory. And if you don’t get good grades, you are not admitted to grad school. So ideological indoctrination was not only on TV; it was in our lives. But okay, this is depressing. With surprise I see that some American students take such courses voluntarily, so to say, to indoctrinate themselves. It became a fashion. Of course, the degree of this indoctrination in the Soviet Union was much deeper because there it would start already in the elementary school. As to the other aspect of your question, if I understood it correctly, we all knew that physics is so much cherished in the Soviet Union because it had military applications. And moreover, all our teachers, those teachers whom we respect very much, they all went—in the late 1940s, 1950s, maybe early 1960s––through some military projects, top secret, related to the atomic project or something else. For instance, Landau, Zeldovich, Ginzburg––all of them. And they were the same highly esteemed people who founded my university.
Misha, did your family ever want to express its Judaism and was prevented from doing so, or were they were more secular and it wasn’t a big deal for them?
You know, my grandparents were religious, and they would go—mostly my grandfather––to the synagogue for every Jewish holiday. It was not easy since only one synagogue remained opened in Moscow, the city of seven or eight million population–– probably half a million Jews. As for my parents, they grew up in the time when being religious, no matter Jewish or Christian would be a major block for any career. They did not go to synagogue, neither they knew Hebrew. In our family, at home we had celebrations for major Jewish holiday, like Passover or Yom Kippur. But this was not expressed publicly. It was behind closed doors in our apartment.
Were you Bar Mitzvahed? Did you go to synagogue?
No, no. I was not Bar Mitzvahed. I never went to synagogue. My children went to the synagogue for the first time only when we came to the United States. Me, too. So you know, although the religion was forbidden for 70 years in the Soviet Union, it lived somehow deep in the hearts and minds of people, even those who never went to synagogue. I don’t know how this phenomenon could occur.
The Yiddish term is “pintele yid,” if you've ever heard that.
[laughs] Misha, when did you start to get interested in science?
Rather early, I would say. My parents were too busy with their works, and basically, at school I had to educate myself. I loved to read. At first I read everything I could find on our family bookshelves. This was not much, but I still remember that at the age maybe 10, 11, or 12 years old, I read correspondence between Stalin, Roosevelt, and Churchill, which was published in Russian, and somehow my father bought it. But then, I decided to find a library. I looked around in the vicinity and found a small public library. I got enrolled at this library, and I started reading books more systematically. Then I came across the shelf with science fiction, and the shelf with the popular science books. In the early 1960s science fiction was very popular in the Soviet Union. They started translating American authors and also popular books. Eventually I read everything which I could find on these two shelves. So that was the onset of my interest in physics and math.
At first, I didn't know what I liked more, so I read both on physics and on math. The decisive event occurred in 1966 when I was about to graduate from high school. What happened in early 1966? Feynman’s lectures on physics were translated in Russian and published in the Soviet Union. In Russian, the course was published in ten volumes. In America, in three volumes, but in Russia, in ten volumes. I bought all ten volumes, started reading and could not stop. Feynman’s lectures impressed me, immensely. I thought that some pages were like poetry. He was such an inspirational man, Feynman. He was in love with physics and managed to pass his excitement and inspiration to the reader, at least to me. After reading these books I understood that that’s what I wanted to do. Another event which pushed me in the same direction was accidental. A friend of mine told me “Jews are not admitted to Math department of the Moscow University”, do not even try.
Misha, was it physics from the beginning that you wanted to study in college?
I still hesitated a little bit. So when I went to college, the first years I was taking both physics and math on the same footing. Also, remember, in the Soviet system there was no choice, at least during the first three years. I even got a special prize for solving contrived math problems. But with time passing, I directed myself more and more to the physics side.
Tell me about your undergraduate education. What was most exciting as your professors conveyed it?
Well, first of all, in Russia, the educational system in universities followed the German pattern rather than American. So the division between undergraduate and what you might call graduate was different. In Soviet universities, undergraduate education lasted for five years, and after these five years you would receive an equivalent of Master’s degree in the US. In my university, MIPT, it was six years. The last two years were devoted to working on the Master’s degree. The graduate school (aspirantura in Russian) normally consisted of three years. If you were successful enough and lucky, you could get PhD after these three years in aspirantura.
So my undergraduate education as I said, happened in Moscow Institute for Physics and Technology. The best thing about it, was that we had access to the best Soviet physicists in various areas. MIPT’s students were offered (actually obliged to take) a wide spectrum of courses: several levels of topics on quantum mechanics, theoretical physics, mathematical physics, nuclear physics, numerous problem solving sessions, etc. In the last two years a number of special disciplines were offered such as Einstein’s gravity, quantum electrodynamics and particle physics. A specific feature of the so-called “socialist” countries was the absolutely distinguished role of the capital city. That’s because everything was regulated by the government in Moscow. Government was omnipotent. So all intellectual forces of the country gravitated towards the capital. On the practical side, the food which was delivered to Moscow was a little better than it was everywhere else. Let’s say Novosibirsk University is also famous, but they had much more severe food shortages than in Moscow. Most of the best professors were in Moscow, not necessarily at MIPT where I had my undergraduate education, but they were within reach. They all knew each other. And if I need some kind of a consultation, I could ask my professor, “How could I reach Professor X?” and they would tell me. This was a great advantage. We had excellent professors in mathematics whom I remember until this day, all of them, and I am extremely grateful. I remember my physics professors too. For instance, in my courses on general physics, we had Goldin who died a few years ago. He was not just excellent; he was superb. Out of scale. The first course on quantum mechanics was delivered by Gershtein.
This was 55 years ago, but I still keep my notes of his course. Theoretical physics was taught by Berestetskii. We had Okun and other well-known physicists. In some way, MIPT could be compared with MIT. If you are a student at MIT, you can reach Harvard professors, but not only Harvard—because Boston University is nearby, Tufts is nearby, and so is Brandeis university, you can also talk to all of them, and meet at seminars. I believe MIPT was very good. It was hard in terms of details of everyday life, but my education was good.
Misha, was it always theory? Did you ever consider pursuing experimentation?
I am not very good at doing things with my hands. [laughs] I tried maybe a couple of times, but it ended in failure. So I decided to better focus on theory.
What areas of theory were most interesting to you as an undergraduate and may have informed what you wanted to pursue for graduate school?
At MIPT I started at the Department of Applied Physics, which was more focused on applications. Like cosmic space studies, fluid and gas dynamics, and so on. But then I decided to switch to more fundamental areas at the Department of General Physics. And there, I had two options, either to focus on condensed matter or on high-energy theory. First, I tried to approach a condensed matter professor but he showed no interest. Then I approached a high-energy physics professor and he was more perceptive. I started in high-energy theory under Professor Berestetskii, it was my fourth year as an undergrad. The fifth and the sixth years I spent mostly doing research in high-energy physics.
What was the process to establish a relationship with your graduate advisor?
Well, some elements are the same as in the United States. First you identify a professor whose lectures impressed you most. Usually there are not so many of them—two or three professors resonate with your mind. So then you try to approach them and ask them, “Do you want me to become your student for the Master’s degree?” Or, “I would like to do this and this and this. Is it of any interest to you?” Not much difference. Except that it’s not so easy—after you get your Master’s degree, if you want to continue working on PhD you have to be admitted to grad school (aspirantura) which is not automatic. Even if you have all best grades and your Master’s degree is exemplary, it was not so easy, because there was also an ideological element in admission of students to grad school. You had to show yourself very loyal and have excellent grades in all this Marxism-Leninism stuff. A letter of recommendation from the local Communist party committee was required, even if, like in my case, you have not been a party member. And if you did something which was considered inappropriate by the Young Communist League, you won’t get a good letter. And then you wouldn't be admitted to the graduate school. I had some problems with admission, but I was helped a little by Professor Berestetskii, a very well-known theorist. He talked to some people, you know, behind the scene negotiations.
Eventually in October of 1972 I got admitted to the graduate school at ITEP, Institute of Theoretical and Experimental Physics, and Berestetskii became my first graduate advisor. Unfortunately, he had a heart attack shortly after that, and then for some time, I was left alone, which was bad for a grad student. Eventually I found a formal adviser, Boris Ioffe. Also I was very lucky to find informal advisors, two of them: Valentine Zakharov, who is nine years older than me, and Arkady Vainshtein, who is seven years older than me. By that time, when I entered the grad school, they were already recognized theoretical physicists, with vast experience in high-energy physics. They agreed to take me in their collaboration as the youngest member. And they taught me a lot.
How provincial was your physics world as a graduate student? In other words, were you aware of what was going on with, for example, the November Revolution at SLAC, or grand unification at Harvard? Were these things on your radar at all?
ITEP had a strong theory group and was better connected to the outside world. For instance, as far as I remember, the news that ‘t Hooft had proved renormalizability of the Weinberg-Salam model reached ITEP in September of 1972. A relatively short time delay, isn’t it? It was immediately understood that something very exciting happened. The November Revolution of 1974 became known almost immediately. This news came from ITEP experimentalists working at CERN. At that time I was already working on quantum chromodynamics, so we––I mean Vaisnhtein, Zakharov and myself––delved into this subject. In a sense, the November Revolution was a turning point in my career. It lead to the development of the SVZ sum rules a few years later. In late 1974 the charmed quark discovered in the November revolution played a major role in the penguin diagrams.
It was helpful that some ITEP theorists were allowed to travel abroad once in a while, and we had visitors from the West such as J. Bjorken, John Ellis, David Gross, Daniele Amati and others. By the way, in November of 1974 the ITEP theory group worked almost in the non-stop regime, seminars lasted till late at night. It is rare that people are born in time to witness the advent of new physics. I was very lucky.
Did you call it the penguin mechanism? Because my understanding was that this term comes from John Ellis.
You are right. We (SVZ) just invented a new mechanism for non-leptonic decays which today are called flavor changing weak decays. This mechanism was overlooked by other researchers because it couldn't be imagined before the advent of QCD. This was my first serious work as a graduate student. Our work grew from a paper by Mary Gaillard and Ben Lee; they pioneered in applying QCD in such decays. They made the first step in the mystery of the Δ? = ½ enhancement but missed a key element resulting from the penguin diagrams which they missed too. We discovered this class of diagrams but in our paper they did not look like penguins. You should understand, at that time, even c quark was not yet firmly established, let alone b or t. It is only November of 1974, people have just started truly believing in the charmed quark’s existence. We published a brief paper in a Russian journal. Very short, because in Russian journals page limits existed since time immemorial. Soon, we wrote a larger more understandable paper and sent it to Nuclear Physics. They rejected it outright, saying, “This is not possible because it is not possible.” We replied and correspondence started. Correspondence between the Soviet Union and the Western countries was very slow. Because if you wrote a letter to the editorial office of, say, Nuclear Physics, before it could be mailed you had to obtain clearance from a secret department. So each exchange of letters was around three months.
Finally, after a year or so of fruitless correspondence, we appealed to the editor. I think at that time it was David Gross. David Gross said, “It’s an okay paper,” and so he authorized its publication. For that, I am grateful to David. It was John Ellis who named our mechanism penguin. He redrew the diagrams in such a way that they started looking like penguins. We made them from straight lines, and John curved the lines appropriately. Why did he do that? He lost the game of darts with Melissa Franklin. The condition was that the one who loses is obligated to insert the word penguin in the next paper.
Misha, you mentioned David Gross. What about the discovery of asymptotic freedom and QCD? Did that register for you in real time as well?
Of course, of course. It was 1973. I was already a graduate student. When the news of the Gross-Wilczek-Politzer discovery came it was like an earthquake. There was a lot of commotion in the ITEP theory division, especially among the older generation. You may ask why? In the late 1950s, after the Landau zero charge in QED was discovered, all ITEP theorists got involved in the search of asymptotically free field theories. Of course, they failed –– Yang-Mills theories which had been just discovered were not yet ready for loop calculations. Ironically, the opposite sign in Yang-Mills compared to that in QED was discovered in the Soviet Union in 1969, by Khriplovich, a theorist from Novosibirsk. He calculated the first loop in Yang-Mills theory in the Coulomb gauge and observed asymptotic freedom, but he didn't pay any attention to this phenomenon. His paper was published in Russian. Nobody besides his closest friend knew about it. Sometimes I quote it in my papers. I ask myself what would happen if the ITEP theorists paid due attention to Khriplovich’s calculation. The history of physics could be different now. Anyway, Gross, Wilczek and Politzers’s triumph occurred only in May of 1973. Now, I return to the summer of 1973. Given the previous exposure to this problem due to Landau, it is not surprising that the ITEP theorists were in a euphoric mood. Okun immediately summoned all his students and instructed them to forget about their current problems and start learning Yang-Mills and the Faddeev-Popov quantization. The discovery of charmed quarks only enhanced the feeling that a great breakthrough was taking place and we had a chance to participate. This was a wonderful feeling. Such breakthroughs do not occur often.
Misha, tell me about your own thesis research. What did you see as some of your primary contributions and findings?
For PhD, you mean? Or my research after PhD?
For your PhD.
Oh. I started from applying QCD to various weak decays. The heart, the core of my PhD is the work on the penguin mechanism and its extensions. As I mentioned, the penguin mechanism, on which three paper were published by Vainshtein, Zakharov, and myself—was my first serious research project. I published a few papers before that, but they were not as important as this one. So I decided to build my PhD thesis around penguins. I added some new considerations, new applications, some extensions to compare to what had been already published by that time. Now I understand that it was a good solid thesis.
Misha, what did you do after you defended? Was it a postdoc position? Was it a faculty appointment?
You see, neither postdoc nor faculty. Because again, in the Soviet Union, the system was different. There were no postdocs. Even now, there are very few universities in the Soviet Union who employ postdocs. Maybe a few in the whole country. So postdoctoral positions are a new phenomenon for Russia. Normally, what you would do after PhD defense, you go to some university or research center, preferably to a large research center. With luck you could be admitted, roughly speaking, as a junior researcher, which would be equivalent to assistant professor or something like that in the United States. As you know, in the Soviet Union, the salaries were so low, hiring a junior person was not a big deal. It’s not like in the United States; even an assistant professor will cost tens of thousands of dollars per year. In the Soviet Union, my first salary was around 150 rubles per month, roughly the price of a pair of winter shoes for my wife. If you want to compare with the US, say 1,400 USD per year. It’s not a big deal. My wife’s salary and mine were barely enough to cover rent and food, and that’s it. I do not complain, that was normal. I was very lucky, because I was hired by ITEP, Institute of Theoretical and Experimental Physics, where I knew everybody and people knew me already. At least for the first 10 years, I was quite comfortable there.
Just so I understand, either for graduate school or your first professional opportunities, as a Jew in the Soviet Union, did you ever feel like your options were limited, or did you ever experience any discrimination professionally?
Of course, they were limited. I knew it and everybody else knew it. The situation with Jews oscillated with time. Under Stalin, it was awful, especially, after 1948. At times it was life-threatening. But then, when Khrushchev came to power he sort of relaxed the regime down to bearable limits. The situation with Jews improved from mid-1950s to mid-1960s, during the Khrushchev’s thaw. That’s why I managed to become a student of Moscow Institute for Physics and Technology in 1966. It was a relatively good year. In 1967, the Six Days War happened in Israel. Israel won the war completely defeating the United Arab Armies in six days. The Arabs were the best friends and allies of the Soviet Union. Somebody at the very top got very angry with Jews, probably—I don’t know. No documents are found in archives till now—but apparently there was an oral communication at the very top, maybe it was Brezhnev who ordered to bar Jews from good universities, especially those in which Jews could get quality education in natural sciences and such disciplines as diplomacy and so on. Since 1968, for a Jew, getting a position became very problematic, no matter where, with the exception of manual labor such as sweeping the streets, and all that. In ITEP, in 1977 I was crossed out from the list of participants of Neutrino-77 conference which was attended by foreign physicists. It was a small conference, but I felt myself humiliated. In modern Russia it is different––because practically all Jews left Russia and those few who remained there are probably not considering themselves as Jews. In the 1970s and 1980s the tacit no-Jews rule was enforced with more rigor. This tendency lasted until perestroika launched by Gorbachev when he became General Secretary in March of 1985. With him, the above rule started fading away.
Misha, back to the science, as we get to the later 1970s, tell me about how you got involved with gluon condensate.
?hat was a natural continuation of our work on the penguin mechanism and other weak decays. You have mentioned the November Revolution in 1974, in which the charmed quark was discovered. At that time, the charmed quark was still an exotic object, noticeably heavier than the previously known quarks. It could be treated as almost non-relativistic. Some semi-quantitative properties of charmonium could be obtained from this side. In 1977-78 we used the large mass of the c quark as an expansion parameter to develop a rather precise sum rule method for charmonium mass calculations––a precursor to the SVZ sum rules––SVZ stands for Shifman, Vainshtein and Zakharov. In 1978 an alleged para-charmonium was observed. Its mass was measured to be 2.83 GeV, and this particle was called X(2.83). Some theorists accepted this “discovery”. Our sum rules predicted––I emphasize here the prefix pre––3.00 GeV with the error bars 0.02 GeV. We firmly believed in our number, and in the early 1978 published a paper in Phys. Lett. Shortly after, a new experiment showed no traces of X(2.83), it just disappeared into thin air. Later, the paracharmonium was found at 2.98 GeV. This was before the gluon condensate. Inspired by this triumph we started thinking about expanding into the realm of light-quark hadrons. In the course of this work we came to the idea that there is a nonvanishing gluon condensate which plays a key role in the dynamics of quarkonia. The numerical value of the condensate was extracted from c quarks and then applied as an input to a huge variety of light quarkonia. The success was overwhelming.
The next year, you became more involved in axion research. How did that happen?
Well, let me try to remember. Maybe I don’t remember all the details, but I remember a conversation with our friend c, an outstanding physicist. Now, he’s at Princeton, but at that time he was my neighbor in Sokolniki in Moscow. Every theorist in the world knows him. Once he told me that according to his intuition the problem of CP conservation in QCD might be solved by itself, through QCD confinement. That’s exactly what’s happening in three-dimensional Yang-Mills theory that he had considered. Polyakov discovered that confinement in three dimensions makes the theta term unobservable and CP naturally conserved. So we started thinking whether Polyakov’s mechanism might work in four dimensions, and it turned out that it does not. This draw our attention to axion. By that time it was already known that the Weiberg-Wilczek axion contradicted experimental data. There was no way out for us––we had to invent an invisible axion. We called it phantom axion but people preferred invisible. OK. I remember that this work did not take two much time, perhaps, 2-3 weeks, and a part of it was carried out in Novosibirsk in Siberia, at Arkady Vainshtein’s institute. Thank god, that was spring, the early spring of 1979. They had miracle typewriters there. A mechanical typewriter was ingenuinely connected by a wire to a primitive computer and could type papers by itself. Like today’s printer but slower. At that time this was a miracle unheard of in Moscow. Thus we proved that Polyakov’s conjecture is not applicable in four dimensions––four-dimensional confinement does not screen the theta term––and introduced the invisible axion. Simultaneously and independently the latter part was done by Jihn Kim in South Korea. In the former part of this project we invoked some ideas which my coauthors knew very well, the so-called called soft-pion technique. Invisible axions present a good mechanism for solving the CP problem. In addition, as it turned out, they may constitute dark matter! Currently axions and the so-called ALPS––axion-like particles–– are a very hot topic.
Did you see this as possibly a contender for dark matter, either early on?
Well, people do discuss axions as a candidate for dark matter. I think one of the first to put forward this idea was Pierre Sikivie at around 1983. In 1980 we definitely did not anticipate this application for invisible axions. For a long time it was believed that a heavy super-partner was the number one candidate. Now, after LHC’s failure to produce super-partners it seems quite unlikely that they play a role in dark matter. They faded away. At the same time, the invisible axions are not ruled out. There’s still a window of parameters allowing them to materialize as dark matter. Unfortunately, laboratory experiments do not see axions so far. Their experimental sensitivity is not enough to rule them out either. We have to wait and see––maybe in the future it will be confirmed that dark matter is built of axions after all.
Misha, tell me about some of your work connecting Yang-Mills with supersymmetry in the early 1980s.
Okay! I mentioned that I had two passions in my career. The first one was nascent QCD. I was very lucky to begin my research in this euphoric time in our area. This does not happen too often. Now, you are addressing my second passion. In fact, I could have come to it earlier, in the mid 1970s. But I was too preoccupied with my first passion to pay attention to other developments. Why I could have paid attention to supersymmetry earlier? That’s because in fact supersymmetry in four dimensions was not invented by string theorists; it was invented by two people, Golfand and Likhtman in Moscow in early 1971. Golfand was a professor at Lebedev Physical Institute. Likhtman was his grad student. They discovered the superalgebra for the first time in a dedicated search, and also constructed the first four-dimensional supersymmetric model: the four-dimensional supersymmetric quantum electrodynamics. This happened even before QCD. But the story of Golfand and Likhtman was tragic, very shortly after their great discovery Golfand was fired from the Lebedev Institute because of his allegedly low productivity. This was already after their seminal paper had been published.
Supersymmetry in four dimensions was rediscovered by Wess and Zumino in 1973, from a totally different side. The Golfand/Likhtman publication was in 1971. Golfand tried to find new employment at some other university or elsewhere, but it was a bad time for Jews to look for employment. For a couple of years, he couldn't find any—nobody would take him. He had no means of survival. Being desperate, he decided to apply for immigration to Israel. And that completely destroyed him, because it was a very bad time for people who wanted to immigrate to Israel. Not only his application was denied, he was blacklisted, and his grad student was blacklisted, too. Perhaps, this sad turn of events diverted attention from the beauties and merits of supersymmetry in the Soviet Union for a couple of years.
I was lucky though to attend Golfand’s seminar at ITEP, so the word supersymmetry was at the back of my mind. In 1972 a preprint by Volkov and Akulov was released. I remember it vividly because it was titled “Is the neutrino a Goldstone particle?” This was shocking. When phenomenological supersymmetry captivated the world in the mid-1970s, it came back to the USSR. I got interested in some aspects of supersymmetry in strongly coupled problems, in four-dimensional field theories. In earnest, this work started after 1980. There were not so many people at that time who were interested. I remember only one publication by Affleck, Harvey and Witten devoted to a strongly coupled three-dimensional problem and released in 1982. Which was good for us. I worked with Zakharov and Vainshtein, and sometimes with Victor Novikov too.
Around 1980 Valya Zakharov pointed out a certain contradiction between instantons and fermions in the instanton background, on the one hand, and supersymmetry on the other. If you consider massless fermions and instantons simultaneously you will observe multifermion vertices called the ‘t Hooft vertices. But they had no bosonic partners! For two and a half years I could barely think about anything else, even at night I saw instantons with the fermion legs attached to them. This paradox tortured us immensely. And then, after two years came an understanding of how everything, all pieces of the puzzle can come together, and we understood not only consistency of instantons with supersymmetry, but many other wonderful application that came with this consistency. It is hard to make ‘t Hooft vertices consistent with supersymmetry but paradoxically just because of this circumstance some special quantities in supersymmetric field theories at strong coupling can be exactly determined.
The first papers on the NSVZ beta functions appeared in Nucl. Phys. in 1983. That was the beginning. Then several papers on further developments followed. In one of them Vaishtein and I found an exact formula for the gluino condensate setting holomorphy as a basic method. It is widely used today. Of course in the 1980s I also made detours to some other areas when something else interesting would show up. For instance, with Misha Voloshin, on heavy quark symmetry. It is called the SV limit––SV may mean either Shifman-Voloshin or small-velocity. But supersymmetry was my main occupation. In 1996 Gia Dvali and I, when I was on sabbatical at CERN, we carried out an important project. It’s about domain walls in strongly coupled supersymmetric Yang-Mills theories, and central charges. We derived an exact relation for the wall tension in terms of the gluino condensate. Since 2003, I've worked mostly on supersymmetric solitons. I am happy to have an excellent coauthor, my friend Alexei Yung from Saint Petersburg, who visits us in Minnesota on a regular basis. This work is still in progress. I never stop thinking on that.
Misha, how did the end of the Cold War and the opening to the West affect you professionally?
Well, it affected a lot. Even before the collapse of the Soviet Union, a new spirit introduced by Gorbachev was felt almost immediately. Maybe not quite immediately, but by 1988. I was allowed, for the first time, to travel to some Western countries, first to CERN in Geneva and then to Hamburg in Germany. I made there a lot of new friends among my colleagues. This enlarged my horizons. I started thinking about problems which otherwise I would not have appreciated. And also, psychologically it was like a breath of fresh air. If you're in a country which forms kind of robots out of its citizen, and then all of a sudden you have an opportunity to travel elsewhere you feel fresh air in your lungs. It makes your spirits higher. It makes you happier. At first I was very happy because Gorbachev from the very beginning was remarkable. However, by the end of 1980s dark forces nearly blocked him. You probably don’t remember; you are too young. The Communist Party machine opposed Gorbachev, and that made me very nervous. I think the fact that I came to the United States in 1990, 31 years ago, was a life-saving event for me, because I was at the verge of a nervous breakdown in 1989.
When did you start thinking about immigrating to the United States, and what opportunities were available that made that happen?
Well, in principle, this was on the back of my mind for a long time, in a form of a nebulous dream. When I was younger, it was practically impossible. Because my father, by that time, became kind of a director of a civil construction organization, and he would be immediately fired if I would attempt to immigrate. And also, after I got married, I had to think not only about myself, but about my wife and I had two daughters, very shortly after I got married. And, as I told you, in the 1970s, it became virtually impossible. The people, like I told you the fate of Golfand, and I had other friends who applied for immigration, and they all lost their jobs and living, which I couldn't do it for my family. But when it became clear that the situation in the Soviet Union becomes more and more lax, I returned to this idea again. And in the late 1989, I wrote a few letters to my friends in the United States asking them about a possible position for me. I got an encouraging letter from Larry McLerran, who at that time was a director of a newly organized institute––Theoretical Physics Institute at the University of Minnesota. They have many vacancies at that time, so he suggested that they might consider me. That’s how eventually I got an offer from Larry McLerran. We came to the United States in September—no, late August, 1990. And since then, I am still at the University of Minnesota.
How was your English? Were you pretty proficient just because in contact with people? Or you really needed to learn it?
When I was at school, we had a very good course of English language. By far not every school in Moscow had the language classes at this level. Many students in other schools would graduate knowing maybe 20 or 50 words. But our school was very special in this respect. We had classes of English language I think from the sixth year, several times a week. So by the time I graduated from the school, I knew English pretty well. Maybe not so many words as I know now, but my pronunciation at that time was much better than it is now. We were taught the British pronunciation, the classical education. English taught at schools in the Soviet Union was British English. I still remember. I remember the Trafalgar Square and Big Ben topics, lorries, blokes and other British words. Lorry is the same as a truck in British English. When we arrived to the US I could understand everything from the moment of arrival. And my wife also, she was a student at the same school, but a few years younger than me. Eventually my beautiful British pronunciation evaporated—you see, we had so many Russian physicists in our Institute in Minnesota, that this was inevitable [laughs].
Now when you got here, what was the timing when you won the Sakurai Prize? Were you already in Minnesota, or this was before?
I was already in Minnesota for nine years. It was in 1999. And this was my first prize, the prize of the American Physical Society. I value it very much, because it’s one of a few prizes which are still given for achievements in particle physics, not in “high” theory or in mathematical physics, but for achievements in physics related to experiment. And this was, as I have told you, my first passion. I started with the experiment-related physics, and these were probably the happiest days of my life.
What did it feel like when you won the Sakurai Prize?
First of all, all three of us—Vainshtein, Zakharov, and myself––we got this prize, and of course I was very proud, as it was my first experience. Some people get dozens of prizes. For them, it’s just nothing. Just another line in their resume or CV. But when you get a prize of this level for the first time, of course it’s exciting.
Now, at this point, at the turn of the century, were you already involved in non-Abelian flux tubes and confined monopoles?
Not exactly, but I was already involved in supersymmetric solitons. I have already mentioned the 1996 work with George (Gia) Dvali, about domain walls in super Yang-Mills theories. A transition from the domain walls to flux tubes was smooth. In order to say that these particular walls exist and they are supersymmetric, you need to employ a certain property of supersymmetry algebra, which is called the central extension—at that time, we called it central extension––nowadays, some people prefer more accurate term brane extension. Very shortly after our paper with Dvali appeared, Edward Witten observed from certain specific properties of the wall that it can be interpreted as a string-theory brane. In the field theory I'm talking about such central/brane charges were not known. So, the supersymmetric domain wall in minimal supersymmetric Yang-Mills theory was the first example where this brane extension was found. Why it was found so late? Because it is not seen at the classical level. It appears due to the so-called anomaly in supersymmetric Yang-Mills theory. By the way, the beta functions (known as the NSVZ beta functions) which we found in 1983 are also related to a similar anomaly. So in a sense, for many years, I am working with anomalies [laughs] in supersymmetric Yang-Mills theories. It was very natural then to start looking for similar phenomena beyond the simplest domain walls, in some more complicated solitons. I started thinking in this direction. An enormous boost was provided by Alexey (Alyosha) Yung who is a visiting professor at our institute. In 2003 we published our first joint paper on flux tubes and started a project which lasts already for 18 years. Each year he comes from St. Petersburg, Russia, for a few months.
Misha, what were some of the cultural things that you needed to learn scientifically within physics when you joined the faculty at Minnesota?
Well, first of all, I had to learn more extensive teaching than I had been doing in the Soviet Union. I did teach in the Soviet Union, too, but usually these were short courses and not on a regular basis. From time to time, I was asked to lead some lecture course on a newly nascent topic. When I came to the United States, I had to learn how to do proper teaching with students being quite demanding on the one hand and not always well prepared on the other. As it happens, newly arrived professors are given at first undergraduate classes, with a huge number of students. This was my experience, too. Once I had a class on introductory algebra-based physics for premeds. I started teaching them the way it would have been taught at MIPT in Moscow. Grading on the curve was never heard of there. Grading was an absolute notion. In the case when the best students in the group could not solve, say, two problems out of five, they would get C while those with less solved problems would get F (3 and 2 in Russia, respectively). Partial credit was not used either. If a student solved a problem with a mistake, be it even in the last line, he or she didn't solve it, period. The basic principle was: “You cannot do this? Not prepared? Then you should leave and go to another university which is not as demanding as ours.” It took me some time to realize that the American educational principles are somewhat different. In my first year as a lecturer too many students failed on quizzes, and even more so on the finals. This was a total disaster. I was told by people who were professors before me that that’s not the proper approach, that I could not flunk so many students, that I must grade students on the curve, etc.
I attended lectures of other professors and worked out another strategy more appropriate for the American realities. According to this strategy during the given semester you identify a group of the best students and a group of the worst students, and then draw an interpolating curve gradually decreasing from A to F starting from the best and moving toward the worst. In the US if a students write in the first line the Maxwell equation correctly he or she gets some partial credit. In terms of science and education, this was the strongest cultural shock to me.
[laughs] Misha, tell me about the edited anthology project, At the Frontier of Particle Physics, and what some of the advances in QCD were, and specifically why you were inspired to do this on the occasion of your advisor Boris Ioffe and his 75th birthday.
Boris Ioffe was my formal advisor. But our interaction, especially in the first years of my grad school, was rather limited because he left Moscow for Czechoslovakia for a year or so. In his youth Ioffe had two chairs to sit on. On the one hand, he was particle theorist. On the other, he participated for a short while in the Soviet nuclear project and became an expert in nuclear reactors for power plants. So sometimes he would be given a task for the power plant department of ITEP. And when I just entered the grad school, shortly after that he was sent to Czechoslovakia to design their power plant, and to supervise its construction. Once he was out of Moscow I couldn't interact with him. But then he returned, and our interactions resumed, maybe more on a personal level rather than scientifically. He told me stories about his life under Stalin, what he did for the nuclear bomb project and how he interacted with Landau. He taught me life lessons. He also supported me in my career. He managed to make my salary a little bit larger than it was originally, but anyway it was helpful. I had personal feelings to Ioffe, and when it was his anniversary, I decided to edit this collection of mostly review papers from people—first of all, from those who knew Boris Ioffe, and second from people in his area of research. I wrote letters to many people. My original expectation was that perhaps one third of them would answer positively. I was very much surprised that almost all colleagues whom I addressed wrote me back, “Yes, I will write something.” It was an exciting experiment.
Were there advances specifically in QCD that you wanted to capture in this project?
Of course. This project was devoted to new areas of QCD. In the 1990s, QCD was still rapidly developing. Now it continues to evolve, but frankly, quite slowly. This is because all problems relatively easy for solutions had been already solved, and whatever remains defies analytic solution for years, even decades. These are really hard aspects. Some of these hard concepts were addressed with success through supersymmetry. Here I can mention the Seiberg-Witten confirmation of the Mandelstam-Nambu-‘t Hooft conjecture of the confinement mechanism. When I started working on Ioffe’s collection, the heavy quark physics was a hot topic. Many young physicists were working on heavy quark physics, the so-called heavy quark expansion, and the physics of heavy mesons and baryons, constructed of heavy quarks. Among more general topics were chiral models, instantons, renormalons, etc. So, it was quite timely to prepare such an extensive “Encyclopedia” in four volumes! It was well appreciated in the community.
And then later on, tell me about your inspiration to write the book about Felix Berezin.
Well [laughs]… My memory functions in a strange mode. Many episodes from my Moscow life are deeply imprinted but still dormant. Then an event or a conversation can wake up a certain memory and I feel an urge to react. In the past 20 years I worked on a number of not-entirely-physics books, starting from “You failed your math test, Comrade Einstein”, a collection devoted to discrimination of Jews in the admission policy at Moscow University and other best universities in the USSR. A method of “selection” was used to this end. Entrance examinations for Jewish boys and girls were much harder than for others, with the so-called killer problems or questions. Around 2006 I received a letter from a colleague of mine, Dmitri Gitman, who at that time had a position in Brazil. Berezin’s widow Elena Karpel was his friend. Elena wrote a very moving recollection of life and death of Felix Berezin, an inventor and pioneer of supermathematics. In her recollections one can read about many facts of his personal life, the hardship he had to overcome, how hard it was for him to publish his papers, and he never was allowed to travel to any conference outside of the Soviet Union, and so on. Gitman kindly sent me a photocopy of her manuscript. After I read it, I thought all of a sudden, “What a story! It is a shame nobody knows about Berezin’s life.” At that time, Karpel’s memoir written in Russian was not published. So, I decided that it had to be published, this way or that way, in order for people to know.
I personally knew Felix Berezin. He was not my close friend, but I attended some of his seminars at Moscow University. Once in a while––rather rarely, though–– he would give a talk at ITEP. His seminars on supermathematics and its applications to physics were intriguing. They become a part of my inspiration when later on I started working on supersymmetry. I don’t know how it’s with other people, but for me Karpel’s memoir was a chance which I could not miss. Berezin, as you probably heard, was a very talented mathematician, but he died very early, in 1980, while rafting in Magadan area in the Soviet Far East. In Stalin’s time Magadan was a notorious GULAG “capital.'' In my spare time, I started collecting relevant materials from books. I wrote to his close friends and co-authors, soliciting recollections or notes about him. All of them told me that it’s a very good idea, that this collection should be published. At that time Elena Karpel resided in La Rochell?, in France. In summer I went there to visit her. We had long conversations. I arranged Karpel’s memoir of 100 pages to be translated in English. Then around ten additional recollections arrived and I compiled them in this book. It was very well accepted. Ironically, a few years later the book was published in Moscow in Russian. Also, recently a French edition was released. It’s amusing that the book devoted to the outstanding Russian mathematician, the mastermind of supermathematics, first appeared in English, in the Singapore Publishing House.
Another book question, Misha—tell me about your interest in supersymmetric solitons, and why this required book-length treatment.
This is a different story. I started working on supersymmetric solitons in earnest in 1996, but it was almost exclusively domain walls. Alexei Yung arrived to Minnesota for the first time in 2003, and we started working on flux tubes. Next year he sort of infected me with supersymmetric flux tubes and beyond. The project, originally modest in size, grew fast. By 2008 we realized that if we do not systemize our initial results we will drown in them. We drafted a note for ourselves. Simon Capelin, then a Cambridge University Press Editor, learned about this not? and suggested to publish it as a monograph. It was released in 2009. Even now, if I need something specific about supersymmetric solitons in Yang-Mills theory, instead of looking at the original papers, searching for them, I open this book and find there what I need. Of course, at present we know much more about supersymmetric solitons than 12 years ago. Also, our monograph is far from being perfect. If we worked on it today, it would be written differently.
What were some of the advances in quantum field theory at this point? What were you interested in?
The answer to your question depends on where you put the starting point. Quantum field theory (QFT) experienced several revolutions. The first revolution, when it was born. Well, I don’t like the word “revolution,” because for me it has negative connotations. Let us say, QFT emerged from quantum mechanics in the early 1930s. Then it developed for around ten years until the Second World War started. Many things were understood but much more questions related to quantum corrections remained unanswered. The “terrible and mysterious infinities” in quantum corrections which people didn't know how to treat blocked further development. Then there was a break for 5-6 years due to the Second World War. The work on QFT resumed shortly after the end of the Second World War. The second wave of gigantic developments, was associated mainly with Richard Feynman. He was the first to realize what to do with infinities and how they can be hidden in a renormalization procedure. Feynman explained that if you calculate a physically measurable quantity and express the result in terms of parameters relevant to the energies of the given experiment––the renormalized constants––all infinities will disappear. Also Feynman invented Feynman diagrams which became the language of particle physics. As the third wave we may consider the famous Yang-Mills advance of 1954, the discovery of Yang-Mills theories. The years that followed were the years of accumulation of knowledge which culminated in 1967, with the construction of the Weinberg-Salam model of electroweak interactions and the subsequent discovery of quarks. Approximately at the same time Faddeev and Popov figured out how to quantize Yang-Mills in a covariant way. The fourth wave started from two breakthrough discoveries––renormalizability of Yang-Mills theories in the Higgs regime (‘t Hooft, 1972) and asymptotic freedom of Yang-Mills theories (Gross, Wilczek, and Politzer, 1973)––which gave rise to QCD and the Standard Model, the theory of our world. I consider these two events as the beginning of the Modern Era in QFT. String theory was born approximately at this time too, but I won’t comment on this development.
I believe—this is my personal opinion––that the most important advances in QFT since the early 1970s are related to our growing understanding of what happens in Yang Mills theory at strong coupling (in particular, in QCD) and the advent of supersymmetry-based methods. The progress in this area was enormous. Many of the theoretical discoveries made since then are directly related to natural phenomena, to the world in which we live, while others (such as axions) are expected to show up in experiment in the future. In the last 10 years or so QFT development somewhat slowed down. Since 1990 a number of strong and creative theorists moved to string theory and elsewhere but now they are returning back. The same tendency is seen in model- building and phenomenological supersymmetry. New horizons in QFT are open now. When people realized that supersymmetry can be used as a tool in the studies of strongly coupled theories, such as QCD, they had great expectations. At least some of them came true.
Here I mention again the Seiberg-Witten breakthrough of 1994 and hundreds of papers that followed since then. Of course, not all of them are of paramount importance, but some are. Another impetus came from string theory after it was realized that some qualitative aspects of the latter can be reinterpreted in field theory in purely field-theoretic terms. For instance, dualities known in string theory were reinterpreted by Seiberg and others in terms of field theories. Quite recently, a couple years ago, a totally new type of anomalies was discovered by a group of people. Among this group there was Kapustin, Seiberg, Komargodski, and some others. These are the so called 1-form and higher-form anomalies, which were proven to be very fruitful in understanding subtle aspects in strongly-coupled field theories, not only in QCD but well beyond. They significantly generalize what is known as the ‘t Hooft anomaly matching. I know you spoke with Gerard, and I suppose he told you about his wonderful idea of 1980 to exploit anomalies to make predictions for QCD-like theories. Now the ‘t Hooft matching is world classics. However, 40 years after ‘t Hooft people uncovered another class of the same nature! The modern class of higher-form anomalies is conceptually close to ‘t Hooft’s, except it’s totally different technically and has its own range of application. You see, the current stage of QFT developments continues more or less uninterrupted for half a century. And I expect it to continue, at least in the near future.
I'm very curious—it’s an interesting title, when you talked about Physics in a Mad World. What was mad, exactly?
Well, I think I have already told you. It was a mad world. I could also refer to it as “between two evils”.
The book you mention is not entirely my book. I only wrote 100-page introduction reflecting the knowledge acquired after 1996. The core of the book is a translation from Russian of a 1997 booklet written by a Russian historian of science Victor Frenkel and published in Russian as a preprint. Again, I came across it accidentally. Somebody brought it to me from Russia, I read it, and I was fascinated by its remarkable, hardly believable story Of Fritz Houtermans. The second part of the book is devoted to life and destiny of Yuri Golfand, the discoverer of supersymmetry. I started working on both stories. I found new sources, some of them were from various archives. I reached out to people who were involved or their relatives and friends all over the world, on four continents.
The book is titled Physics in a Mad World because the world I describe––the Soviet Union and Germany between two wars, and the postwar USSR––was mad. Both regimes, the Soviet socialism and the German national socialism were sick to the bottom. This was a glorious time for physics and for young physicists. They lived and worked there and then. I am proud that in a few years I worked on this book I managed to collect enough data to depict suffering of human beings under totalitarian regimes and, at the same time, the highest achievement of the human spirit, of young physicists which transcended the horrors they lived through despite all odds.
The first larger part, is about the Austrian-German scientist whose name is Friedrich (Fritz) Houtermans. He was the first to suggest in the late 1920s—when quantum mechanics was just brought into life––that the stars burn and emit energy because of thermonuclear reactions of nuclear fusion in their cores. He didn't do precise calculations which at that time were hardly possible, even neutron was discovered only in 1932, and we are talking now about the late 1920s. But the idea was formulated in this paper of Houtermans. In 1933, Hitler became the chancellor of Germany with all consequences which ensued. Houtermans was quarter Jewish. Worse than that, he was a rather ardent Communist, and had some special assignments from the German Communist Party. Don’t know exactly what he was doing, probably industrial espionage for the USSR. And this was really dangerous, because of course Gestapo knew about his Communist activities, so he had to flee Germany as soon as possible. He first went to the United Kingdom. He found a pretty good job in the industry, in the research department of a big company which was working on television. The first public TV broadcast occurred, I believe, a year or two later. Houtermans was half experimentalist and half theorist. In principle this research department would suit him. But he was not the kind of person who would love to come every day by 8:00 am in the office and stay there until five or six.
After a year in Britain, he decided that it’s not for him. He got an invitation from the Soviet Union and accepted this invitation to a new institute just being built in Kharkiv, at that time the capital of Ukraine. He went there with his wife and a child. The first year or two, everything was nice. He had a free apartment, and his salary was way higher than that for Russian employees. Most importantly, he had the opportunity to start working on nuclear physics. So he was very excited about that.
I remind you, in Germany he was a Communist. At first he mulled joining the Soviet Communist Party too. The year of 1937 was the beginning of the Great Terror. The Kharkiv institute was hit hard. Many leading scientists were arrested by the NKVD during a pogrom at the institute, they were either sent to gulag or executed by firing squad shortly after their arrest. Konrad Weisseberg, Lev Rozenkevich, Lev Shubnikov, Vadim Gorsky, Valentin Fomin––this is an incomplete list of executed. At a certain point, Fritz and his wife, Charlotte, understood that they had to immediately flee. First they had to get permission to exit from the Soviet Union. They went to Moscow to get the paperwork done for this permission. Houtermans was arrested at the moment he was passing the customs. Charlotte found herself in Moscow, with no documents, no money, no place to stay, and with two small children. The story of her escape from the USSR and the subsequent misadventures reads like a thriller. Houtermans himself spent a few years in NKVD prisons under tortures, and then in 1940 extradited to Gestapo. To make a long story short, he survived the Nazi regime. I just could not pass by this incredible story of which, I think, a good movie could have been made.
Now, Misha, I know what the mad world is. Your subsequent book on physics in troubled times—Standing Together in Troubled Times—what were the troubled times that you were thinking about, and what was the importance of standing together?
In essence, this was a continuation of Physics in a Mad World. It so happened––accidentally as it usually happens with me––that the daughter of Fritz and Charlotte Houtermans, Giovanna, lived in a small town Northfield an hour drive from Minneapolis. At that time, she was alive. I wrote to her, asking whether she would be willing to tell me something about her mother, something that was not yet published in the literature. She kindly agreed, “Yes, sure, just come visit me.” In a long conversation Giovanna mentioned that her mother was a close personal friend of Wolfgang Pauli. Pauli even participated in her marriage ceremony at an exotic location. “I keep their personal correspondence, about two dozen letters, somewhere in my attic, and maybe I can find them. Then I could give them to you.” When I touched this stack of old letters, on yellowish paper, from a quantum genius of the 20th century to Giovanna and her replies to Pauli I felt awe. Even expert historians were not aware of their existence. Giovanna also gave me the original Charlotte’s diary. In the book Standing Together in Troubled Times these treasured documents were published in English. They narrate a story of friendship which lasted for decades, until Pauli’s death in 1958. Pauli did what he could to help Charlotte and her children to find safe heaven in the USA. You know, she was penniless in the middle of the war. In these letters Pauli and Charlotte discuss rather subtle details of their lives—not intimate but subtle. I got in touch with experts. “We have never heard of any private letters, written by Pauli to Charlotte Houtermans. That’s a totally new page in the Pauli’s saga.” This book is not large. Added are some other relevant letters, for instance, from Oppenheimer. Oppenheimer was her close personal friend too. It is clear from Charlotte’s diary that at a certain point Oppenheimer was kind of in love with her and courted her. Professional historians who work on Pauli’s correspondence asked me for the originals of these letters, so they will publish them in German. I sent to them all these originals, because, of course, they belong to history, not to me.
[laughs] Misha, I wonder if you can compare what it felt like to win the Pomeranchuk Award, and then the Dirac Medal, later on.
Well, I think we speak too much of the awards. But since you ask me, I—
Specifically with Pomeranchuk, if it was special given your background?
Yeah, it was a very special award, because it was given by ITEP, the institute of my youth. On the other hand, it was bitterness in this award, because by that time ITEP started dying. Eventually, good theorists and experimentalists were pushed out. As far as the Dirac Medal is concerned, it’s the most prestigious award I ever got. I got it with Arkady Vainshtein and Nati Seiberg. This gives it a special dimension, a special feeling, because Arkady was one of my informal teachers. Even after we both moved to the United States, once in a while he would teach me about some forgotten idea, or find a reference which he still remembered while I was unaware. And also Nati Seiberg, who is younger than me by seven years. He was very—his works were very influential in my career. As I have already mentioned, we worked in overlapping areas, and the fact that he was responsible for many pioneering discoveries helped me, too. Especially inspiring was the seminal paper of Seiberg and Witten of 1994 where they basically analytically solved the problem of confinement in a supersymmetric cousin of QCD. To receive the Dirac Medal in such company, it’s an honor for me.
Misha, as we move closer to the present, what has been most important in high-energy physics for your physics agenda?
For my current agenda, or in general?
Since the past five years.
Okay! In the past five years, I was working mostly on supersymmetric solitons. This is not an extremely popular area right now, but still, if you compare to what it was in the beginning, two decades ago, there are quite many young people who now work in this direction. There is a large group in Japan, a group in Italy, some work is being done in the United States and elsewhere. So far, the program on supersymmetric solitons which I have been pursuing for a long time did not give “practical” results—I mean, results of the type of transistor or graphen. However, we definitely achieved a better understanding of some aspects of Yang-Mills at strong coupling. My dream is to acquire a deeper understanding of the phenomenon of confinement in QCD-like theories. Qualitative insights were provided by Seiberg and Witten in 1994. They analyzed supersymmetric Yang-Mills theories and not just supersymmetric. To use the power of supersymmetry they had to address the so-called extended supersymmetric Yang-Mills theory, with the so-called N=2 supersymmetry. It is not QCD, not even a sibling of QCD, and probably not even the first cousin. There is a resemblance, the basic principles are the same, but we–– Alexey Yung and myself–– strive to understand details. Our idea is to come as close as possible to the actual QCD-like theories, with less supersymmetry or no supersymmetry at all. This is a long shot. There is a certain progress in this direction, for instance in theories with non-extended supersymmetry. A new type of vortex strings used in dense QCD and in condensed matter physics were identified. I still continue working on the latter with graduate students. To my mind, it’s a promising area. I plan to continue for the next few years and see what happens, with the hope of positive outcomes, of course.
Do you think there will be major advances at CERN in this regard?
Unfortunately, my intuition—my gut feeling—is that there will be no more breakthrough discoveries at LHC. Some discoveries may come from non-accelerator or small accelerator physics. You probably heard that there are anomalous measurements in the muon magnetic moment and discrepancies in heavy quark physics. It is too early to decide whether they are significant until confirmed by other groups. In my career, which lasts almost 50 years from 1972 till today, I saw many examples when there is certain deviation in experimental number from a theoretical prediction, say, by three or four sigmas. But later, the experiment is repeated by another group, and the discrepancy disappears. I saw maybe a dozen of such instances during my career. I think we have to wait more. Anyway, we waited for almost ten years after the discovery of Higgs till today; maybe, we should wait another three or four years and see what happens.
[laughs] Misha, that’s a perfect segue to the last part of our talk. Now that we've worked up to the present, I’d like to engage you a little more broadly about the state of play with regard to the standard model. First, broadly, how do you see your research contributing to the creation of the standard model? And is your sense right now we're still working to build out and understand the standard model as it currently exists? Or do you think we're really on the threshold of new physics and breaking beyond the standard model?
[exhale] You see, for the time being, the standard model basically describes everything we see in experiment. It perfectly fits everything. A few new additions to the standard model supported by data were accepted. They are the non-vanishing neutrino mass––more exactly, the mass matrix––and the theta angle and the associated axion, etc. The standard model (SM) was essentially created by Weinberg, Salam, and Glashow, and it was before my time. As I mentioned, I entered grad school in 1972. QCD was incorporated in the Weinberg-Salam- Glashow model in 1973, giving rise to SM. In fact, the color of quarks had been already incorporated before QCD. Gluons when they were added in 1973 opened new opportunities. In this sense, the penguin mechanism can be viewed as a contribution to the standard model. Also, I made some very early predictions about the Higgs particle––their decays into two photons. Invisible axion can be viewed as a contribution to SM too, although axion is not a part of the original standard model. On the other hand, it might play a role in the dark matter mystery. Dark matter currently is the most serious challenge to SM. This is the only established fact in nature which tells us something else has to be added for the description of our world to become complete.
At the same time––I should be honest––the standard model still doesn't satisfy aesthetic feelings of many theorists. Indeed, the standard model has around 30 free parameters. The quark and lepton mass matrices seem random. They are not understood, and so are the mixing angles. How they emerged the way they are? No answer. Inclusion of axion brings in extra parameters. Many people believe that it’s not aesthetic to have a model with so many free parameters. Minimal supersymmetric extension would be a nightmare, with over 100 free parameters. People say we should go beyond SM, say, embed it in string theory, maybe in something else, so that all these free parameters become derivable. I don’t know. Human curiosity is infinite. But does it mean we will be able to answer all questions right now? For the time being I can live with some free parameters. It was always the case in physics, that there were some God-given parameters. As physics develops, we are able to understand these parameters in terms of some new parameters, of which existence we just didn't know previously. This is the so-called Matrioshka-like structure, that there are many layers in the world.
Of course, it would be great to have just two or three free parameters, with all others drivable from them. However, nature does not care of what we feel about it. The original string theory idea was that they will build a unique string theory, string theory-based model which will completely and unambiguously describe our world. “The Theory of Everything”–– that’s how it was originally referred to by its enthusiasts. In other words, dozens of free parameters will emerge by themselves from some deep geometry of the string theory. Well… so far, this did not happen. On the contrary. What happened is that string theory allows almost any set of parameters, so that string theorists came up with the idea that there are many, many universes. Each has its own set of parameters, they are distributed chaotically, and our multiverse is just a conglomerate of these universes not connected with themselves by causality. Then there are many, many disconnected worlds, and by accident, we live in this one, most suitable for our life. This is a serendipitous accident—that we can exist, are intelligent and make observations. If you accept that that’s the case, there is nothing else to think of. We arrive at the anthropic principle. If you’d ask yourself, why, say, the electromagnetic coupling constant is around 1/137, you’d say––because were it not 1/137 but let’s say 1/250th or 1/37 the world which will correspond to such a value would not have observers to measure it. Maybe such a world exists in the multiverse, but we will never know. This is a possible option but since there is no way to confirm Multiverse or rule it out experimentally, you may believe in it like people who believe in a religion.
I still hope that there is less chaos in our world, more reason for a specific structure, which is more understandable. The fact that we don’t see explanations now doesn't mean that they do not exist at all. This way of development was traditional way in the history of physics, from Galileo’s time. First, we observe, then develop a theory, then make predictions and confirm theory or prove it falsify. I hope that future observations or experiments will teach us more about physics of nature and will open the doors to the next level of theories. Maybe not now, not at the LHC. The cost of accelerators became so high that a new accelerator, which would be meaningful to build, can only be built in good economic times, through cooperation of all major world powers. None of these two preconditions exist today. But what do we know of our future? Can we be sure that the Second Cold war is not around the corner?
I hope not, Misha.
There are some signs that we are moving in this direction. The relation between Russia and the rest of the world rapidly deteriorates. China also doesn't want to compromise on any issues and tries to impose their rules in trade, and so on. This seemingly prevents the American economy to develop more harmoniously than it does now. What we saw in the beginning of the COVID pandemics was not nice. In the stores, one could not buy tissues or toilet paper, or hand sanitizer because all of this stuff was produced in China, and there was no connection between China and the U.S. for several months. Some shelves in the stores became empty as it used to be in the USSR. This is a lesson––you don’t build all your factories in one particular corner of the world to exploit poor people there for a miserable salary. This is risky, dangerous and unethical. This is a direct road to Cold War.
Misha, let’s stay on the happier note of science. To the extent that the standard model is somewhat stuck right now, I wonder if you've reflected on how your research is of relevance more broadly in astrophysics or even cosmology?
The only thing which I might think of now is the axion physics. Axions might be viable candidates for dark matter. I think that they have chances. Another application in astrophysics might be the so-called cosmic strings —people discuss all sorts of cosmic strings. Originally a particular example of the cosmic string was invented by Witten. They were searched for in nature but so far, not found. Now we know that different types of cosmic strings or flux tubes may exist. Some were discussed by Alexey Yung and myself. With luck, maybe they have more chances to be discovered somewhere in outer space. I don’t know. If the tension of the cosmic string is below some critical value, with our observational capabilities today, we won’t see it. Great discoveries usually happen accidentally. Like the November Revolution, which you have mentioned, happened totally accidentally. Nobody expected it to come.
Where do you see the future of soliton research? Your current project. Where is this headed, do you think?
I have already mentioned that solitons, in particular, supersymmetric solitons are of importance, already today. They provide a connection between string theory and field theory The flux tubes are in the focus of the Seiberg-Witten solution. Solitons are very important in condensed matter physics, for instance in some nanomaterials which is now a big deal not only in science but in industry. Spin properties in condensed matter can be related to Skyrmions––a subclass of solitons. I work on all of the above. In high-energy physics, for the time being, I think that solitons are useful in understanding strongly coupled theories like QCD. As I’ve mentioned, QCD is not analytically solved. Numerically, there are many indications that the QCD flux tube are formed, but how they could be formed, what there features are, what the underlying dynamics are, how the QCD string could be excited, what are the properties of these excitations—all these questions are asked but not yet answered because it is difficult to answer them in numerical studies. I believe studying the solitonic flux tubes from the supersymmetry side eventually will help answer at least some of the above questions. Maybe next time I talk to you or your colleagues we will see more applications.
Misha, for my last question, I’d like to ask you to reflect on the significance of your work on the SVZ sum rules. Why do you think it resonated so powerfully, and how might it be updated as the field progresses into the future?
Historically, this was the first method of quantitative analysis of the hadronic properties which was invented in quantum chromodynamics. We worked on it in 1978, published in 1979. First we had to adjust the general Wilson operator product expansion to apply it in QCD. Simultaneously, we introduced a crucial operator of dimension four, the gluon condensate. The quark condensate was already known from Gell-Mann, Oakes and Renner. Finally, we analyzed a huge amount of static hadronic properties, analyzed them within the SVZ sum rules and, quite remarkably, our results described the hadronic family with reasonable accuracy. A priori we did not expect the method to work so successfully. We came across a few exceptional cases which also taught us a lot. A published paper on the latter finding was titled “Are all hadrons alike?” Of course now, in most of these cases—not in all of them––lattice calculations give better accuracy. Especially this is true if you don’t include light quarks. In nature, there are three light quarks—u, d, and s. The last quark called “strange” is semi-light but u and d are real light. Their masses are of the order of a few MeV, much lighter than a typical QCD scale.
Dealing with light quarks on the lattices is difficult. Even with modern computers, it takes a lot of time. So whenever you want to calculate something with light quarks with high precision—something about pions or eta-prime—it’s at the borderline between what is doable with precision on the lattice and what is not doable. Let’s say you need pion form factors as functions of the momentum transfer, or b to π transitions, or even more contrived amplitudes. Lattice people determine them numerically, but in a number of instances the numeric accuracy is not good enough. On the other hand, the SVZ sum rules, which had been modified and amended in the 1990s and then in the early 2000s are useful in such cases. Now SVZ “descendants” are called the light-cone sum rules. Light-cone refers to massless or nearly massless particles. They are still competitive with the numeric lattice calculations. This is not the most important heritage of the SVZ sum rules, however. Sooner or later computers will become more powerful, and eventually they'll overcome the light quark difficulty and acquire the needed accuracy. But what you cannot do on the computer, you cannot infer qualitative features of the QCD vacuum, subtle features of, say, hadron decays, or the behavior of highly excited hadrons. Vacuum—unlike laymen would think––is not a void. It has a complicated structure which we need to know. If you understand the vacuum of some theory, you understand almost everything. Numerically, you cannot do that. I have just mentioned there are some hadrons, being analyzed by virtue of SVZ, they turn out to be exceptional. This is an indication that the QCD vacuum is contrived. In this way we learned some qualitative things. This knowledge will stay with us forever.
And as a subset to that, Misha, you mentioned geopolitics. What do you think it will take for collaborations to come together so that there can be accelerators or other projects that can fruits for future theories?
Well, if you disregard all political and economic issues which are typical for our time, all you’d need is good will. By and large, physicists are benevolent people and love what they do. There were better times in the past, for instance the very existence of LHC is a proof of a remarkable global cooperation. Many young people which enter our area today are talented scientists. You need young scientists, because construction of a new accelerator will take a lot of time. We are speaking about young people who are in their early thirties. I have no doubt about the common desire in the physics community to have the next-generation accelerator. This is doable in the time of prosperity and reasonable political climate. When people live happily, when they are free and there are no wars, no hatred, they are much more inclined—taxpayers are much more inclined to say, “Let’s do it, for the benefit of the humankind, for the benefit of the future generations.” I hope this time will come soon, although I cannot be certain, because what I see now does not please me. I hope that people will value reason above all, that challenges such as the environmental pollution will be overcome, that no more crazy social experiments will be carried out. I don’t see any serious animosities between physicists of various countries. Even in the most problematic countries, with totalitarian regimes, physicists have never been aggressive. But you need to convince the governments. You need the support from taxpayers …
The way you put it, it sounds almost doable, and I hope it happens.
I hope, too. I hope to see at least the beginning of the construction. And let us not forget, there is a chance that some new principles of acceleration will be invented, which will allow us to build an accelerating machines with lower costs. I remember when I was young there was such a famous Russian accelerator physicist, Vladimir Veksler, who proposed a collective method of acceleration––it was called smokotron––which allegedly could lead to higher energies at a lower price. Veskler died in 1966. At that time smokotron was considered to be impractical. He also thought about acceleration inside crystals. Who knows, maybe someone will look at these ideas from the modern perspective or invent something even more powerful.
Misha, it has been a great pleasure spending this time with you. I'm so glad we were able to do this. I’d like to thank you so much.