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Credit: University of Florida, Dept. of Physics
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In footnotes or endnotes please cite AIP interviews like this:
Interview of Pierre Ramond by David Zierler on April 13, 15 and 22, 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 Pierre Ramond, Distinguished Professor of Physics at the University of Florida. Ramond recounts childhood in Paris, he describes his family’s experiences during World War II, and he explains that opportunities that led to his education in electrical engineering at the New Jersey Institute of Technology. He discusses his graduate degree in physics at Syracuse University to focus on general relativity and his first exposure to the earliest iterations of string theory. Ramond describes his work at Fermilab on Veneziano modelling, his postdoctoral research at Yale, and his subsequent work at Los Alamos. He describes Gell-Mann’s interest in grand unified theories and the influence of Ken Wilson. Ramond explains the excitement regarding the muon anomaly experiment at Fermilab, and he narrates his decision to join the faculty at the University of Florida. He explains how the department’s stature has risen over the past forty years, and he reflects on his involvement with the superstring revolution in 1984. Ramond describes the difference between effective and fundamental theories in particle physics and he conveys the productive intellectual ferment at the annual Aspen conferences. He describes his service work on the faculty senate and he describes his leadership position at the APS during the discovery of the Higgs. Ramond explains why he thinks supersymmetry would have been detected at a completed SSC and he reflects on receiving the Dirac medal in 2020. At the end of the interview, he discusses Einstein’s misgivings on quantum mechanics, he imagines how string theory might be testable, and he explains why he remains interested in CP violation.
OK, this is David Zierler, Oral Historian for the American Institute of Physics. It is April 13, 2021. I'm delighted to be here with Professor Pierre Ramond. Pierre, it's great to see you. Thank you for joining me.
Thank you. Glad to be here. We'll see.
To start, would you please tell me your title and institutional affiliation?
University of Florida. I'm a Distinguished Professor of Physics.
When did you attain the honorific title, Distinguished Professor?
Oh, God, I don't know. Maybe around 2000 or so.
A question we're all dealing with right now, for you as a theorist, how has the last year in the pandemic been in terms of your science and collaborations?
Awful. I still have two graduate students. And for me, it's awful, but I have tenure, it doesn't matter. But for them, it's even worse because they have to graduate. They were supposed to graduate. Communicating by Zoom is linear, and the possibility of feedback occurring with face-to-face interactions is not there. And it has been very distracting, not only because of the worry at the beginning. In my age group, it's worrisome. The virus is a killer. But at the same time, it was extremely abrupt. I was teaching undergraduate quantum mechanics, and I started one week, and by the end of that week, I was on Zoom.
Alternatively, working at home, the social isolation, has that given you any additional bandwidth or mental headspace to work on longstanding theoretical problems that you might otherwise not have been able to do?
Yeah, but I think age doesn't help in that respect. Because it takes a bit longer to get up to speed for concentration. And so, the only time I really had time was during the summer, when I was not teaching. And I did a lot of research, but I got nowhere. Nothing came out. I usually benefit a great deal from conversations with people. That's why I like very much the Aspen Center for Physics, where I've been forever. And so, innocent or uncorrelated conversations sometimes lead to very interesting insights. And a change of scenery. So with age, one tends to ossify. In other words, not be as daring as one was at some point. And then, you end up doing things that you are familiar with. And that's exactly what you should not be doing in research. And so, it's not very good. On the other hand, once in a while, you have insight, but then it's not the same. We are remarkably routine people. You would think that perhaps isolation would be better. Maybe it was good for Einstein. [laugh] But not everybody's Einstein.
Let's take it all the way back to the beginning. Let's go back to France. Tell me about your parents.
Well, my father was a civil engineer. He graduated from one of the Grandes Ecoles in France, the “Ponts et Chaussees”. So he was in a war, even though he was in France. Although, I never got any details from him. And then, after that, he never settled down and traveled all over the world. And his thing was building concrete pipes for water conduits all over the place. And so, I spent a lot of my youth in boarding school in Paris. And they were traveling all over the place. Although, I spent two years in Africa at some point when I was a kid. So I had a very mixed youth. But my father wanted to be, I think, a mathematician. He never was, and he never could settle down, but he was a very smart man. And so was my mother. It was an unusual childhood.
Of course, you were too young to remember the war yourself, but what were your earliest memories that made you realize the suffering that France went through during the war?
There are several beautiful gardens in Paris, but there's a garden called The Garden of Plants, the Jardin des Plantes. And we lived very close to it. There was a normal playground, and close to that, there was a house that had been bombed. I remember seeing it. It was in ruins, and it took a long time for it to be rebuilt. And that was very impressive. But most of the memories had to do with my parents and grandparents, who, basically, had been completely upended by the war. And especially in France, I think they felt that they were safe, things were OK. And then, in the space of a month, the world got totally destroyed. My grandfather was a war hero. He had fought in the first World War. And unfortunately, he died of his wounds in the early 50s. He was only 51 years old at the time. But in the family, there was a lot of talk about the war. And the war was the big event. Not only the first World War, but the Second World War, the occupation, the rationing of food, and everything else. So I grew up in that atmosphere, although mostly by osmosis. I could not imagine what actually had happened until much later, when I started reading.
What neighborhood in Paris did you grow up in?
Well, I grew up close to the Jardin des Plantes. It's a little bit in the south part. It's very close to the Luxembourg Garden and the Jardin des Plantes. And I was born in Neuilly-sur-Seine, one of the suburbs of Paris. So I was told by my mother, come to think of it, I was born on January 31 of 1943, and she remembered it because that night, there was a Renault factory, which they bombed the hell out of, although they missed everything. Because they were making, I guess, tanks for the Germans at that time. But also, I learned later on that was the day of the German surrender at a Stalingrad. Thank God. So that was, in a sense, the beginning of the end, although it took a long time.
What kind of schools did you go to as a young boy?
Well, the boarding school was a Jesuit boarding school. One of my grandfathers is Jewish, although I never knew it until I was an adult. So we went into the Jesuit school, which was a fantastically good education. It's one of the rather famous high schools outside of Paris called Sainte Croix de Neuilly. Looking back, it's somewhat prejudiced. They didn't like too many things that were not like them. But it didn't matter too much at the time. But it was a fantastic education. And I remember that one of the professors there talked to us about the tectonic theory as if it were a fact. It was a fantastic education.
When did you start to get interested in science specifically?
Oh, from the beginning, I think. As long as I can remember. I was always looking at pieces of machinery. I was totally turned off, though, by the physics education in France. We had to take, basically, three years of physics. And the first year, I was so pleased, and it was all definitions. For example, I remember the physics professor, we learned about Newton's law, but he never said Newton, he said New-ton. I used to go on the banks of Paris. There were a lot of booksellers there, and we were very poor. And I had a little bit of money, and I bought this little book, which had something on parabolic mirrors. I don't know why, but parabolic mirrors just turned me on something crazy. So I was drawing, and there is a cartoon that I have somewhere, that I drew of parabolic mirrors in class. And then, I went to the physics teacher, and I asked him about parabolic mirrors. And he said, "There is no such thing." And I said, "Really?" I said, "I'm doing it." "No, there's no such thing." And later on, I understood--this is why it was so stupid--that, basically, it was not in the coursework, and therefore, it did not exist, which is unbelievable. So yeah, I was always interested.
In the high school system, how early do you declare a focus, a specific subject to look at?
Well, remember, this was before 1968, at which time, there were many reforms in France. First of all, you were screened at some point, about four years before the end of high school, to go to a lesson track to learn a trade or something. Although, you may become richer, but at least it was a lesser track. And then, after that, you had to opt between different versions. One version was math-intensive, you learn ancient Greek, Latin. And then, after a while, I got thrown out of the Greek class because I wasn't paying any attention. I'm a bit weird that way, but I was somewhat rebellious. And the Jesuits didn't like that too much. And then, the last year of high school, you could opt between philosophy or math, elementary mathematics.
And then, you have a course all ready for you, given your age. You prepare for the École Normale Supérieure or Polytechnique, etc. And it was tremendously ossified, and I hated it because it was based very much on memorization. And when I came to the United States, and I'll come back to this later, I was absolutely amazed to see how open the faculty was talking to the students. In those days, in France, the faculty didn't talk to the students.
It was too formal.
It was too formal and impersonal. Memories are coming back upon talking to you. I guess you're good at this. So in the last year of high school, we had several mini courses. One course was in number theory, one course was in astronomy. And I love number theory, and I loved astronomy, and at the end of that mini course, there was an oral examination. I walk into the room, there's a guy there, and I remember him. He looked very cold, and he said, "Monsieur Ramond, what is the difference of two numbers?" I gave him an example, "5 - 3 = 2, that's the difference." And he doesn't say a word.
And the French expression for being at the blackboard and feeling like a fool is called sécher. Sécher means to dry. Your mind dries up. And that's what I felt. And at the end, 15 minutes pass, and he said, "Thank you very much." And before getting up, I said, "What should I have said?" And he said, "It is the number, which added to the smaller one, gives the largest one." And you have no idea how furious I was. And it was a very good system, but that part of it was tremendously awful. And I think it changed somewhat, but you still see this rather formal aspect in much of France's science. It was formalized by Napoleon at some point, and everything by Napoleon is kind of like a religion.
When did you consider leaving France for your education?
Ah, well, that had to be with my parents. So what actually happened is, I went to Africa with my father, I learned African dialects--which I don't remember, but I'm told I knew them. And then, he went to South America to build some water stuff, then he went to Peru to build some water stuff, then he worked for an American company. And the American company asked him to head their research center in West Orange, New Jersey. So there they are. And at the end of high school, I was thrown out as a boarder and lived with my maternal grandmother in Paris. The other grandparents, we didn't talk to them because when they learned that my father was dating a Jew, he was thrown out of the house. I never quite understood this until much later, of course, but the relations with that part of the family were not extremely warm. Those little vignettes that are part of everyday life, unfortunately.
So my father said, "Well, after high school, why don't you come to the US?" And of course, I was very excited to go. When I was in Peru for the summer, I had known a lot of Americans who worked for the CIA, I think, tracking satellites. I'm not sure they worked for the CIA, perhaps the Smithsonian, but I think that's what they were doing. And I liked Americans a great deal. My mother's best friend had married a US soldier after the war and he said to her about the land of cowboys and everything. So I go to live with them in New Jersey, but I wanted to keep on going to school. And my father said, "OK, I'll ask my friends." And his friends were all engineers. And in New Jersey, the place that engineers were excited about was Newark, the Newark College of Engineering (NCE), now known as New Jersey Institute of Technology.
Well, I get there, and at first, it was a disaster. I knew English very well from the point of view of grammar, but I couldn't speak it, which is normal. But then, when I got to the Newark College of Engineering, I met some fantastic teachers. I was totally lucky. Especially a math teacher, and then some physics teachers later on. And it was an adventure. I loved it because not only were they interested in what you were doing, but they gave you more suggestions. In other words, there was a life outside the classroom. And I loved it. However, the clock was ticking in France. Because if I wanted to get into École Normale, because I was good in physics and math, there was an age limit. You couldn't take the entrance exam after a certain age. So I had to make a decision early on. And with my experience at NCE, Newark College of Engineering, I just said, "The hell with it."
Yeah, "I will stay."
Did you realize at the time that that decision might mean something longer term, that you'd make an entire life for yourself in the United States?
No. You don't think that way at that age. You think, but not about that. It was obviously the better thing to do. I've done that several times in my life. I've made unusual moves that way, which at the time, sounded better. Some of them were better, some were not. But that's the way it goes. So what happened is, I decided to stay. Furthermore, I was with my parents. I had not been with my parents since I was 10 years old. So that was it. But also, I met all these teachers, who were fantastic. And I owe them an enormous debt of gratitude because they really encouraged me and directed me to things beyond what I was learning. At the end of the four years at NCE, my wife, who's also an engineer, we met there. She's of Ukrainian origin. So boom, you get tangled up. And then, a few years later, one of my friends asked me if I wanted to go back to France, and they had a CNRS position ready for me, apparently. And I said no. However, I remained French. I speak French, I'm full of French culture, etc. But I'm truly a half- breed. It's both sides.
Your major at Newark was in electrical engineering? How much of a physics curriculum did you have?
Well, first of all, there were no electives at that time. We all had to wear ties because this was a professional attire for engineers. And what happened is, I remember, as a freshman, I wanted to get out of freshman physics. And the guy asked me, "Do you know what a “free body diagram is?" And I said, "No." He said, "Then, you must take this course. End of story." And that was extremely formalized. When I got to NCE, I was in the worst section because I was asked to take the SAT exam, and I'd never taken an exam like that in my life. In France, you always had exams which contained some coursework, which you had to repeat verbatim, and then a problem. The notion of a speed test, I'd never heard of. So I was put in that. But at the end of that session, whenever there was a difficult mathematical question, the instructor was asking me for the answer.
So the second semester, I was put in another section. And in the other section, the mathematics was fantastic. And the teacher, Dr Achilles E. Foster was from Tennessee with a fantastic southern accent, one of the best teachers I ever had. He was not a researcher. But anyway, so I first started learning physics on my own. I was asked by the chairman of the physics department to grade problems that he was assigning to high school teachers in quantum mechanics. In that time, the NSF was actually training high school teachers in modern topics. This is long gone, I think. And I was the grader for that. And I learned quantum mechanics that way, although I didn't really understand it. But later on, it worked very well for me because I was interviewed for a Wilson Fellowship. Now, I'm going to brag.
And I go to Princeton for an interview. I go there, and I go to the Nassau Inn, which you probably know, and I'm directed to a room in which there is a portable blackboard, and there are a bunch of guys sitting there. He said, "Mr. Ramond, why don't you teach us quantum mechanics?" Well, I don't remember what I said. I really have no memory. But I'd been teaching myself all that stuff. I never took a formal course in quantum mechanics as an undergraduate. And I got a Woodrow Wilson. The only one, I must say, from Newark College of Engineering to this day. So that was big. My self-esteem went up.
Did you always have academic ambitions? Or did you ever think about entering industry with a degree in electrical engineering?
That's a good question. So I had summer jobs, and between my junior and sophomore year, I had a jobs at Bell Labs in Holmdel. After that, I was offered a free ride. And the free ride was, they would get me after I graduate from NCE and have me as an employee. But then, they would pay all my education towards a PhD at NYU. This was something Bell Labs was doing. And I refused and said I wanted to do physics. And the reason for that was, I'd noticed there were Dover Books. Dover Books, for me, were a godsend because they were cheap, and some of them were damn good. And I'd been reading many of them, and I noticed their simplicity, which I guess I must've known was happening, but I'd never seen it written in such a nice way as in some of those books. And so, I knew I wanted to do physics. I did not know what it took to do physics, but I knew the next step was to go to graduate school.
What kind of programs did you apply to? What kind of advice did you get about being a non-physics major and where would make the most sense for you for graduate school?
I got no advice whatsoever. I applied to Princeton because it was near Jersey. I applied to Yale. I applied to Syracuse, and the reason I applied there is because a former student of Peter Bergmann was the chairman of the math department, and he'd recommended me to this guy. I didn't apply to too many others because it was expensive, and I'm not exactly with it with those things. So what happened is, Princeton rejects me. I remember my mother being horrified because a friend of hers was Mrs. Newberry of 5 & 10 Newberry, and he was on the board at Princeton. And she thought, using the old-world stuff, that I would be a shoo-in. Well, it didn't work. And in a sense, it was a great favor because I simply was not prepared. Yale put me on the waiting list, and Syracuse basically accepted me. And then, I was kind of amazed because Syracuse offered me, very soon afterwards, a National Defense Education Act four-year fellowship.
Now, the NDEA was a federal program, which basically got people to study science at the frontier of it, in whatever the frontier is. I was not even an American citizen. And that's another thing I felt really good about the US. And by the way, I was saved by physics from going to Vietnam. Because I graduated in 1965. At that time, the US was getting heavily involved, but they needed French speakers. And when I was asked in 1961 when I left France for military service, which one I would opt for--the French were waging war in Algeria at that point, so I didn't want to go there. So I said, "The US." There was a choice. But then, in 1965, I could have been drafted into the US Army.
As a US citizen?
As a French citizen, yeah. Because I'd taken this option. But then, this National Defense Education Act stuff came, and I was put in a different category, and I never went to Vietnam. Although, a few of my friends went there. None of them got killed, but nevertheless, it scarred them. But I did not know there was such a thing as a profession. Very early on in my life, in Paris, there were several science museums, but there was one where, basically, they had Crookes tubes, and I was very young, probably less than 10. And I went there, and I was endlessly fascinated by the Crookes tubes. And this is the question about simplicity. It looks very mysterious but produces very reproducible results. And it's got to be simple because it's a simple thing. This from here to there. And so, the importance of museums is incredible. Because it shows you that there's a way to go forward.
Coming into graduate school, what kind of physics did you want to do
I wanted to do general relativity.
So you knew you wanted to do theory.
Definitely theory, yeah.
Which is interesting, coming from an electrical engineering background.
Yeah, but electrical engineering could be very mathematical.
Why were you interested in GR at that point?
Well, because of the equations. I always liked the equations. I learned in those books that everything was ruled by equations. And the equations were much simpler than the phenomena they described. I didn't learn from my high school physics because that teacher was more interested in definitions than in concepts. So I knew about Newton's law, but I never had a visceral understanding of that. Because it was just a definition.
Was there a general relativist on Syracuse's faculty?
Yes, it's a very famous group. That's why Peter Bergmann was there. There was a man there, who is very old now, called Josh Goldberg, who is a fantastic man, to whom I owe a great deal, actually. Ashtekar was there much later at some point. It has a long reputation. And Peter Bergmann had been the last assistant to Einstein, and Henry Zatskis, being a student of Peter Bergmann, that's how--life is full of these little bifurcations. If you would've asked me if was aware that some of these bifurcations would have such long-lasting effects, I would've said no. It would be completely different if I had gone one way or the other.
Did Syracuse see a lot of activity with regard to the Vietnam War movement and other things?
Yes, there was, towards the end. In fact, I was just talking to some of my friends from graduate school there. First year of graduate school, I never worked harder in my life. Because I took a course in quantum mechanics. Now, I'd taught myself quantum mechanics, but the course that was given didn't look at all like what I knew. Quantum mechanics is very complicated. So the first two years, I was working very hard. And in the second year, you had to take a qualifying exam. And in physics departments, qualifying exams were very big. Either you were cleared to PhD, or you were given a master's and a goodbye. Nowadays, it has been watered down tremendously. But the important thing is, for probably one week in my life, I knew more physics than at any other time. Because you were basically cramming in one brain all these facts, most of which are irrelevant, but you had to know them. And that was good, in the end. But it was physically and mentally exhausting. But that was the way.
After the second year, I had friends in the humanities, but what was more prevalent were drugs. I remember very well a fellow graduate student in physics whose friend was a chemist, and he blew his mind on LSD. I saw him before and after. And that made a big impression, of course. And then, came the assassinations. MLK and Bobby Kennedy. And of course, when I was an undergraduate, there was JFK. But that didn't affect me too much. I was too busy writing lab reports in engineering. But that's the way it was. In Syracuse, the weather was terrible, but I still have a few good friends from there. They're all over the world, but we still talk once in a while. It's a good university, but their forte was the general relativity group. But then, I got an advanced course that was basically particle physics. And there was nothing happening in general relativity at that time. People were just writing solutions to Einstein's equation under these or those conditions. It looked like a very dry field. It's totally different today, of course. But particle physics was extremely exciting. Things were happening. So I got into particle physics, and I became a student of George Sudarshan, who was the big theorist there. And so, that's how it happened.
What was particularly exciting in particle physics at that time?
Good question. I think the fact that there were patterns waiting to be understood. There were, again, a lot of simple things. Particle A decays into particle B. There were all kinds of nice things, but it's like Humpty Dumpty. There are a lot of pieces, and you know they have to fit together at some point. So there was a lot of a detective story in it. But it was very hard. It was extremely hard. And my advisor, George Sudarshan, who felt all his life that he had been cheated out of his discovery of the V-A theory by Gell-Mann and Feynman, which is not true because I now know both sides. But he never recovered, and he was a very smart man, but he tried the rest of his life to show that V-A was not the correct theory, cutting off his nose to spite his face. It was tragic.
And so, I changed advisors because he went on sabbatical in India for a year, and he gave me a problem. And in the process of learning the problem, I learned a lot, but I didn't solve the problem. But then, he asked me to work on something else to disprove this V-A theory. It became a numerical mess, and I just quit. I changed advisors, and I went to this man called Balachandran as my advisor, and he put me on a lot of S-matrix theory and stuff, which I did not like. So at the end of the day, when I left graduate school, I thought I was going to go back to engineering. So I applied for a job, and I didn't get it. And then, the people at Fermilab, Bob Wilson, who was the big shot there, decided to form some sort of a theory group. And the theory group did not have any senior person in it, just juniors. And he formed a committee, and I was one of the leftovers, the people who were interesting, but not interesting enough to hire. And I went there. It was like an adventure. So what happened is, my advisor did one very good thing for me, he got me a three-month appointment in Trieste at Abdus Salam Centre. And there, I ran into a bunch of physicists who were working on string theory.
Who was working on string theory at that point that you met?
Well, first of all, the way we learned of string theory was because of the Veneziano amplitude. Particle physics looked like too much stuff on the momentum plane, on the complex plane, a lot of mathematics, etc. Geoffrey Chew had this program called the S-matrix theory. You look at the invariance of the S-matrix for the strong interaction, and if you put all these invariances together, maybe you'll get a unique answer. That was the program. And when you put all kinds of things together, you got some sort of an answer, but not the full thing. There were four people in Israel looking at a certain set of crossing relations with amplitudes. It's a long story. But what happened is, Virasoro and Veneziano wrote this amplitude where there was an extra criterion for the amplitude that the S-matrix people were not aware of.
And so, people thought, "A-ha. We're going to solve strong interactions." And that was called the dual resonance model. Dual because the s-channel and t-channel amplitude were related by the structure of the mathematics. Then, later on, this led to what is string theory. That was the beginning of it. So that's what we learned of it. But I knew of it by osmosis, mostly. What I was very intrigued by, there was a man called Joe Schechter, who was coming in as an assistant professor, and Joe told me, "Look at this paper of Steve Weinberg called A Theory of Leptons." And I said, "OK." My God, I sweated blood, to use a Hungarian expression. Because in it, there were gauge theories, spontaneous breaking, none of which I knew. And it was very difficult. But it looked pretty, again. But then, I was told, "Coleman thinks it's not renormalizable, so it's not really physical." And if Coleman said that, this is the way it was. But in Trieste, I met Hirotaka Sugawara, and I met John Nuyts, whom I had collaborated with through Balachandran before, and they turned me on to this thing, and I noticed that there was a mixture of physics and mathematics. And it completely changed my life. Because I was ready to go back to engineering. Because I felt graduate school had not been very good. But I was wrong in many respects. But at the time, that's how I felt.
When did you first become aware of what John Schwarz and Michael Green were doing?
Fifteen years later! Well, I had been aware of it around that time. My good friend, Lars Brink, who I had been collaborating with, could not go to Aspen that summer when they did their work. By that time, I had given up on string theory. I was told, "If you continue to do string theory, you're not going to get a job." That's another thing. But yeah, I knew almost instantly what they were doing, although I didn't understand it at first because they were looking at anomalies in these theories and found semi-unique answers. That was a very big deal.
Tell me about your initial impressions when you arrived at Fermilab.
It was like a summer camp. I learned later on that the reason Bob Wilson ran it that way is because when he had gotten into Los Alamos as a young guy, the camp in Los Alamos. Fermilab (NAL at the time) was in a village called Weston, which had been bought by the Department of Energy. In that village, there was a little two-bedroom house. In it, there was theoretical physics, another was beam physics. And I remember an anecdote. I arrived a bit late because I was late leaving Trieste, and what happened is, I decided to focus on physics. First, to go and ask some experimentalists. So my friend, Lou Clavelli, with whom I collaborated, was also a post-doc at Fermilab. There were five of us, no senior person, so we were completely isolated. That was good and bad. The good part, I'll tell you later.
So what happened is, we go see the experimentalists. There was a house that said experiment. So we go in there, and there are a bunch of guys. And I remember, there was a big map of something on the table. They were looking at it. And I said, "What are you guys doing?" And they said, "Oh, we are designing the sewer lines for the laboratory." And that was exactly what was happening. Everybody was put to work by Bob Wilson without any boundaries. Bob Wilson did not want doors around the theory group. He wanted everybody to mingle. And that was the atmosphere. We got to be good friends later on, but at the beginning, it wasn't so easy. He was quite a dictator. But he was a builder, and he had an artistic sense to him. So he was a nontrivial guy. But yeah, Fermilab was like going to summer camp.
What were some of the major research projects that you were involved in during your time there?
Well, the major research project was, at first, trying to do some Veneziano model stuff. And while in Trieste, Sugawara and I had worked out something, the triple-Regge vertex. But in the meantime, somebody else (Sciuto) had published a much more elegant way of getting it. And therefore, we decided not to publish. But that was good because I'd gotten used to many of these things. And so, Lou and I started working on some aspects of generalized Veneziano amplitudes. And we did some really good work together. But the big breakthrough for me in my whole career was what I did there because that's where I invented the supersymmetry business and the Dirac equation. And that came out of that work.
When did you first come across Dirac? Was this as a graduate student or at Fermilab?
Neither. I came across Dirac at Newark College of Engineering. I was working in the library, reshelving books, and a former student at NCE, who was a graduate student at Penn, was there. This was his spring break. And I said, "Jeff, how are you doing?" etc., because we had met a few times. And he said, "Well, I'm reading this book on quantum mechanics." And he said the name Dirac. And I opened it, and I didn't recognize anything. Absolutely nothing. And I went out very depressed, I remember that. That's the first time I saw the name Dirac, which is kind of interesting. And after that, the appreciation of Dirac is not easy. Once you appreciate it, it's obvious. But before you appreciate it, it's a maze.
Tell me about the intellectual process from Dirac to the invention of superstring theory.
So I told you, in my earlier ways of looking at things, I always liked equations. And in fact, there was an equation I liked very much, which is called the Majorana equation, which was like a Dirac equation, but what's known as an infinite component wave equation. And I studied it, but it was not as good. But then, I learned the Dirac equation, at the same time. And the Dirac equation was a lot better. A lot of things around the Dirac equation, I tried to learn. But the structure was unbelievably beautiful, as usual, once you understand it. So in string theory, we started looking at amplitudes. You have an amplitude, and what happens is, you have an intermediate state for the amplitude. Two guys come. They coalesce into one thing, and then they come out, and that's two things into two things. The thing in between there is a propagator factor, which is 1 over P-squared minus M-squared. P is the momentum squared minus M the mass-squared. And that's the structure that the Veneziano amplitude was actually pointing to. Except the P-squared was a generalization of the P-squared for one particle, and the mass-squared was a complicated mass operator. But it had the structure 1 over P-squared minus M-squared. So I recognized there was simplicity in all that stuff, and I went to Aspen. So the summer of 1970…
I'm sorry, when you say simplicity, what do you mean exactly? What was simple?
Because I recognized it. P-squared minus M-squared is an equation of motion. P-squared = M-squared is an equation of motion. It tells you the momentum-squared is equal to the mass-squared.
Of course, it begs the question, if it was so simple, why had nobody thought of this before?
I think it's because some people had laid down the work for it, but they were still thinking in terms of amplitudes. I was thinking in terms of equations. That's what I learned. When you look at old Dover Books in the 1960s, none were talking about amplitudes. So this is the way. And so, it's a question of timing. So I look at it, and I said, "Jeez, it looks like there's a momentum to whatever the hell this is," which is a generalization of momentum, and then there's a mass. "And so, it looks like a point particle. Except the P is more complicated. I call it the dual atom. It's a name that didn't stick. I didn't know about string theory at the time. So what happened is that, "Oh my goodness. This looks like a generalization of a point particle," which I learned in mechanics. A particle and the position X with momentum P moving along and doing its thing. And then, I go to Aspen. Bob Wilson said to everybody, "All theorists must go to Aspen." Maybe he wanted to get rid of theorists, I don't know. But I did not want to go. But Aspen was a paradise because you went there in a very beautiful setting.
And what year is this?
Summer of 1970. And I said, "Well, I should pursue this analogy." So I set up the particle [inaudible] momentum, etc. And in Aspen, I listened to a lot of music and played a lot of volleyball. And that was more or less what I remember of Aspen, except I was thinking. I was thinking completely outside the norms of the time. And then, at the end, I said, "Maybe I should try to do the same thing for the Dirac equation." Because the P-squared = M-squared is derived from the Dirac equation. It's not fundamental. The Dirac equation is fundamental. And so, that fall, that's what I did. I generalized the Dirac equation to the string, therefore as a result of that, the fermions were added to the string. Although, I did not do it. And there are many reasons I didn't do it, but several things happened. Hired in '69. In the fall of '70, we are told that we have to look for a job. Bob Wilson had said it would be a three-year job, but then he changed his mind, he said two-year job.
So right away, we do this. And at the same time, this very same week, I also get a rejection letter from physics letters about the work on the point particle and the analogy in what will be known as string theory. And then, I became unfocused because I knew that getting a job was very difficult, and that probably, I wasn't going to get a job because nobody was paying attention to this way of looking at things. And that was that. So I focused on the wrong things. I focused on adding electromagnetic interactions, and that was the wrong thing to do. And the people who eventually did it was Neveu and Schwarz.
So coming back from Trieste, we are going on a ship, on the France. The France was a very beautiful ship, and neither my wife nor I like to fly particularly. And we were there, and I brought with me a paper by Fubini and Veneziano on the oscillator formalism for Veneziano amplitudes. And it's a five-day thing. And there was a reading room, and I brought the paper, and I started working on it. And then, I go back to my cabin to get some postcards, and then I would write some postcards.
So I go back to the reading room, and what do I see? A paper by Fubini and Veneziano. And it's the same paper that I was reading. I said, "Jeez, I didn't know I'd forgotten it." There's nobody around. I open it, and there are annotations on the paper. And I never wrote annotations on the paper. So that was clearly somebody else. And in walks this guy called André Neveu, who was on his way to Princeton to join Joël Scherk. So that was it. So we became friends. And when Joël Scherk and André Neveu did their beautiful work on one-loop renormalization of the Veneziano amplitude, I invited them to Fermilab. Because one of the advantages of being a junior member when there were no senior members is, you could do a lot of things that you would not have been able to do otherwise. And then, when I wrote the paper on fermions, I sent André a copy of it. In those days, you sent out preprints, and that's how they got to know about this work very early on.
How did the opportunity at Yale come about?
Well, that's another instance of serendipity. Very weird. So as I said, I'm looking for a job, and of course, there are no jobs. Nobody's paying any attention.
No jobs generally?
No jobs generally because I think that was the end of the Sputnik era, and basically, there were no jobs. Everything froze within the space of a few years.
So this is really unrelated to your interest in string theory, it's just true for physics across the board?
Yeah. Veneziano amplitude was still a very, very important concern. What happened, the rise of the standard model is, basically, what got a lot of people--Coleman said that with the rise of this, "Now, we can take all our Lagrangian models out of a desk drawer and forget about all this S-matrix stupidity." [laugh] So I go to look for a job. As usual, nothing. And I've always been very, very nervous about getting a job because I was never getting jobs. Later on, I did, but at that time, no. So Lou Clavelli and I go to the New York meeting. In those days, the New York meeting was very much for particle physics, very much what the March meeting is for the condensed matter community. It's a gathering every year where all kinds of important talks are given. And in those days, this is what it was.
So we go to the New York meeting, and I used to call it a slave market because people were looking at the teeth and the strength of the post-docs. It was very depressing, but very necessary. I go there, and of course, nothing. And then, Lou Clavelli and I were sharing a room, and Lou said, "I'm going to New Haven tomorrow. Why don't you come with me?" I said, "Why are you going to New Haven?" He was a post-doc at Yale. He had been at Chicago before, a student of Nambu. And then, he married this local girl Estelle. He said, "Why don't you come with me?" I said, "OK, thank you." So I go there, and of course, he introduces me to the physics department. And this was on a Friday. We arrived there on Thursday night. And there, I meet Dick Slansky, who became my close friend. He's long gone, now, but he said, "Why don't you give us a talk?" "Fantastic." So I gave a talk, and it was on the work of generalizing the Dirac equation to strings. Nobody's asking me anything. That night, we go back to Illinois. On Monday afternoon, I get a phone call from Charlie Sommerfield.
Poor Charlie died a few weeks ago. He was in Florida because his wife is a big researcher in taste, and she has an appointment here. I didn't even know of Charlie's existence, but he says, "We want to offer you a job." That's the Monday after I gave a talk. And he said, "We don't have very much job to offer, but we have an instructorship for one year, which might actually become an assistant professorship, but we don't know." And I said, "Wow." So I call my wife, and my wife is long-suffering because at the time, she had a job as an electrical engineer. She was a working electrical engineer, of course, before children. And so, I call her up, and I said, "Yale, Yale. It's a big reputation." And they had put me on their waiting list. So what happened is, I called Charlie about two hours later, and I said, "I accept." Just like that. I did not know anything. I didn't know the process. I was so pleased, I accepted. And that's how I got to Yale. So it was total serendipity.
Did you take on new work at Yale? Or you continued what you were already doing?
I continued. I wrote a very important paper, with my student Michael Kalb, this thing about using the string picture to understand the geometry of things. But at that time, I was also told that if I wanted to stay and get tenure anywhere, I had to do no more string theory. I was told that explicitly.
You weren't convincing the right people.
Well, in America, at that time, there were very few people who were doing the very formal aspects of string theory. John Schwarz. David Gross, yes and no. Both David Gross and John Schwarz had been graduate students at Berkeley under Chew. So they had been injected the virus before. And they're also very good. Of course, David Gross had gotten completely away from that. He's talked about asymptotic freedom, etc. He went in a very good direction. But John Schwarz stayed in the Veneziano model, especially after what I told them.
They wrote the Neveu-Schwarz model using the same idea that I had for the fermions, except they used it for bosons. I don't know, that's something I don't want to talk about, but I'm still not very happy.
To the extent that you can talk about it, what are you not happy about?
So I sent them this paper about the fermions, which contained anti- commuting objects. And anti-commuting algebras, which, basically, were now understood to be the beginning of supersymmetric things, etc. That was the first example. And so, I hear nothing. The next thing I hear is a paper by Neveu and Schwarz, not for fermions, but purely for bosons, but also using the same kind of algebra that I'd introduced, and no reference to my work. A week later, there was another paper, and I was referenced, but at the very end of the references. And this one had fermions in it.
This was unfair to you.
Oh, I thought so. Very much so. And I think John Schwarz is the one who did it. And I've known John Schwarz for a long time. He's a complicated person. He has a complicated personality. So later on, he tried to basically take full credit for these things. André Neveu never did that. As far as I know, André probably did not even look at the references.
Now, for your own career prospects, I know you were told to abandon string theory if you ever wanted a job, but you were promoted at Yale.
So what happened is, they were keeping a job for Howard Georgi. Howard Georgi was a student of Charlie Sommerfield, and the year he graduated was the year I got to Yale. And they secretly wanted to promote him and keep him at Yale. But then, Howard went to Harvard and did beautiful things, so he became untouchable. And therefore, they offered me an assistant professorship. That's what happened. So when I was told not to work on string theory, at that time, there were Mandelstam, Neveu, Fubini, Veneziano. Those were the named people who were working on string theory in the United States. After 't Hooft and Veltman got on the scene and showed renormalizability of the model, everybody was working on other things. So Fubini and Veneziano went back to Europe. Even though they were at MIT, they were doing fine, but nobody paid any attention to it.
The herd instinct was to go after one thing, just like right now, when you look at the archive and the younger people, you see they all want to understand what dark matter is. Even though they cannot say anything intelligent about it because unfortunately, we don't have many clues, save for its existence. If you write a paper on that, people will say it's interesting. But I think it has always been like that in any country, anywhere. There's always a herd instinct on things to work on. The stuff that the establishment things is important. And then, three years later--so for people who are established, it's no big deal. But for the people who are out of phase with hiring, that becomes very bad. Europe is better that way. People tend to have more stability and time to do research. But the US has always been instant gratification. But that's the way it is. Which is good and bad. It goes in different directions.
Speaking of Howard Georgi at Harvard, were you paying attention to grand unification during these years?
At first, yes. At the beginning, I paid attention to Weinberg's model. I went to string theory meetings, talking about the Weinberg model. Because in the old Veneziano model, there was a tachyon, a particle of negative mass squared. Well, in the theory of leptons, there is one, which triggers spontaneous breaking. So I mentioned that to people. It was not the right time. Now, in 1974, there was a big conference in London for the high energy community, and Feza Gürsey was the big person at Yale, a rather remarkable mathematical physicist. He came back, and he said to me, "Salam has gone crazy. He thinks the proton can decay." What Salam (and Pati) had done is basically to think of lepton as a fourth color. So they're the ones who really got the ball rolling. But that was the first time I'd heard of it.
But at that time, I worked with Feza, and Pierre Sikivie was a graduate student of Feza at that time. So we worked together. We even produced the E6 model. After SU(5), SO(10), there is E6, which actually was resuscitated from a different point of view by the string theory people. But we were looking after geometric structures and all kinds of stuff. But anyway, there it was. So those were my bifurcations. And so, at the end of the Yale years, clearly, theorists at Yale did not get tenure. This has changed, but back then, they did not. And so, the question, again, was looking for a job. And what Yale had at that time for assistant professors who were ending their years there, you could go for a one-year fellowship. Yale would pay a one-year fellowship, no teaching, and you could go anywhere you want. I don't know if it exists anymore, but it was really good. So I go to Los Alamos for half a year, and then Caltech for another half year.
What did you do at Los Alamos?
Well, Dick Slansky had just joined. He had been preceding me at Yale. He was an assistant professor as well. But then, he couldn't get a job at Yale, so he became a staff member at Los Alamos, where a theory group was being set up by Pete Carruthers from Cornell. And he was a good friend. We'd become very good friends. So I went there. And this is where I met Gell-Mann. Because Gell-Mann was coming back and forth to Los Alamos for various things, and I started interacting with him.
What was Gell-Mann interested in when you first connected with him?
Grand unified theories. Gell-Mann was very interested in that. So my interactions with Gell-Mann were kind of weird. When I was in graduate school at Syracuse, there was this big experiment called the Omega-Minus Experiment. And the Omega-Minus Experiment was done at Brookhaven. And there was a man called Nick Samios, who was the head of the experiment, but there was another man called Jack Leitner. Well, Jack Leitner was a professor at Syracuse University. And he died of a heart attack at a very early age. He clearly was a man who was driven beyond his ability to be driven, at least physically. And I took a course from him. It was a wonderful course. And he humbled me in a very nice way, which I remember.
So there was a memorial for Jack Leitner, and Murray Gell-Mann came. And that's where I first met Murray Gell-Mann. He doesn't remember it, but then again, I didn't expect him to remember it. But the second time, he came to Yale because his daughter was entering Yale as a freshman. And he and Feza were good friends. And so, there was a dinner organized by Suha Gursey. And there was Gell-Mann, and he bored the hell out of everybody because at the dinner was another person, a psychologist. And when Murray learned that she was a psychologist, he proceeded to show her that he knew more about psychology than she did. Unfortunately, that is a very negative aspect of Gell-Mann's incredible talents but total social ineptitude.
Meaning, he thought he had the intellectual capacity to do everything better than everyone else?
Correct. And for many things, he was right. But for other things, he was completely off.
Now, were Slansky and Gell-Mann already working together by the time you met Gell-Mann?
Well, they were beginning to work because of grand unification.
And Slansky was also interested in grand unification?
Oh, definitely. So we knew Georgi-Glashow, we knew of Georgi and Fritzsch and Minkowski for SO(10), we knew all of that. But Gürsey had been looking at octonions, which are these rather weird, non-associative systems, which produce unique structures, and therefore, uniqueness to a theoretical physicist is harder to resist. So they were studying this, and that leads to the study of what's now known as exceptional groups. And these exceptional groups, E6 is one of them, but G2 is another one, etc. And those groups, by the way, came up in string theory much later on. And what happened is, the language for this group looked very complicated. But a very convenient language was the language of octonions. And that was a language most physicists were not familiar with. But Feza Gürsey kept on going.
And this led to the question, how do you describe these groups? And in the process, we learned that there was a Russian guy many years ago called Dynkin, who made his fame in statistical mathematics. But he had, basically, found a way of labeling representation of these groups. And it was very, very useful. So when I met Gell-Mann and Slansky at Los Alamos, and they were looking at these groups that Gürsey, Sikivie, and I had been looking at, they were using antiquated methods. Methods that were pretty awkward. They were applying, but they would be very difficult. And I said, "Well, why don't you learn about Dynkin?"
So Slansky knew nothing about Dynkin. I knew a little bit about Dynkin, enough to get by, and Murray said right away, "Oh, I knew Dynkin." And yes, they had overlapped at the Institute of Advanced Study. But later on, I learned when Murray said, "I knew Dynkin," that means he knew nothing about Dynkin's description of groups. Because Murray always said something that he knew. "Oh, I knew Dynkin," etc. So it was a Tuesday. And Murray and Dick asked me, "Why don't you give us a beginning course in Dynkin?" So there I am in front of them, and I do that. And then, on Friday, we were supposed to meet again. So on Friday, we meet again, and suddenly, I feel completely left out because both of them were in competition to learn everything there was to be learned about Dynkin.
Why competition and not partnership?
Because that was their nature. Murray was competing continuously. I have stories about him that way, which are unbelievable. So this is how I got to know Murray, about the breakthrough with Murray. Murray was not very impressed with me for reasons that were during the Yale days. Maybe I'll tell you about that, but not now. And suddenly, Murray said, "Well, what about this?" And I said, "No, you cannot do it." And when you told Murray that he could not do something, his face would crinkle. He would start thinking very hard, which meant all his muscles would relax. If you ever saw Itzhak Perlman in his heyday, when he was playing, suddenly, it looks like his face was kind of flowing. I think he was at an intense level of concentration where control of the muscles, except for the fingers, was totally unnecessary. And Murray was like that. And he said, "What?" And I explained it to him, and after that, Murray listened to me a little.
What exactly was it that you explained to him?
It was a trivial thing. He thought something was real, and I showed him it was complex. Some trivial stuff. But Murray had not focused on that.
But as you say, he had preconceived notions about you going all the way back to Yale.
We have to get going soon, but this is interesting. So in those days, I was doing string theory still. This was 1973. And I was doing what is known as string field theory. And I was doing that quite early. And Murray said to me, "Oh, that's interesting. I'm doing that, too." Now, there's no published work by Murray on anything like that. He said, "Why don't you come to Caltech and give us a talk?" The amount of trepidation, talking in front of Gell-Mann and Feynman. I'd met Feynman. That's another story. And so, I go into Caltech. The day I'm at Caltech, Murray comes in and says, "I'm sorry, but Ken Wilson is here, and he has some exciting news to tell us about coming from the East Coast. I wonder if you would be good enough to postpone your seminar by one hour." I said, "Of course." So I go there, and there's Ken. We had known each other from our Fermilab days. We had stayed quite good friends over a long period of time. And what happened is, what Ken was bringing to Caltech was the news of asymptotic freedom.
Why would it have been Ken to bring this news?
Because it was so new, I think. I don't know why it was Ken who brought it. And so, what is fascinating is that there's both Feynman and Gell-Mann, and I watched them, and they're both desperately trying to understand. And of course, they get it very quickly. And then, they start asking lots of questions, like machine gun. Both of them. The rest of us are like the guy in the trenches. The artillery's going this way. And Ken Wilson is the recipient of this. At some point, Ken Wilson gets very annoyed with Murray. And for Ken to be annoyed is very amazing. So Ken stomps his leg and says, "Murray, let me finish." I'd never seen Ken so annoyed. So Feynman leaves at the end of the talk, completely exhausted. Gell-Mann stays. And then, I give my talk. And my talk was disastrous.
You're saying because of how drained everyone was.
Well, maybe. But then, John Schwarz later on told me that Gell-Mann told him, "Oh, I thought you said he was good." So I remember those things because I don't forget many things, as you may realize. So there it was. At that time, Ken Wilson told something for historians of science. You will like this. Ken and I have dinner together at the FMU, the faculty club. More familiar in “Beverly Hills Cops”, I think. And Ken says, "I finally have more citations than my father. His father was E. Bright Wilson. He was living under the shadow of his father.
[End Session 1]
[Begin Session 2]
OK, this is David Zierler, Oral Historian for the American Institute of Physics. It is April 15, 2021. I'm delighted to be back with Professor Pierre Ramond. Pierre, good to see you again.
Let's get right back into it. The last thing we were talking about is when Ken Wilson finally achieved more citations than his father. What were the circumstances at this point? Where were you interacting with Ken?
I met him when I was in graduate school. He was at Cornell, I was at Syracuse, and he came to give a colloquium. And of all the colloquia that I heard during graduate school, that one impressed me the most. And later on, when I was at Fermilab, I invited him there to give a colloquium, and we hit it off very well. We never collaborated or anything like that, but we enjoyed each other's company. When I was at Syracuse, I forgot to mention, I went to Cornell a few times when I was in graduate school. One time was for Hans Bethe's retirement. Now, Hans Bethe retired 1966 or '67, I'm not sure. And of course, he lived a very long life.
And so, I went there, and I was driving from Syracuse, and I was late. And there was hardly any room in the auditorium. But there was room in the first row, so I sat there. A few minutes later, a guy with a red mustache comes in and sits in the first row, too, because he was late. He was an "older guy", and I think the man who was talking was Freeman Dyson, if I remember correctly. And he was talking about how to set up different types of life (living organisms) and stuff like that. And then, the guy next to me starts mumbling, and he said, "This is bullshit." So there I was, a second-year grad student, not knowing what to say. And this was a senior guy. I didn't recognize him at all. And he had a big red mustache. And then, he kept on going, mumbling to himself. "I don't believe this." And I got progressively more and more annoyed because I desperately wanted to understand what the hell was being mentioned, and I was being prevented. And I was kind of getting enough nerve to tell him to shut up, nicely. And I was saved by the bell.
Marshak was the master of ceremonies. "Thank you very much, Professor Dyson. And now, let me introduce to you our next speaker, Professor Feynman." And the big guy with the red mustache gets up and starts giving a talk. And I said, "My God, I was about to tell Feynman to shut up. [laugh] Phew." I had a cold sweat. And then, I told that story to various people, and they said, "That's not true. It could not have been Feynman because he did not have a red mustache." But then, I went back, and yes, he did have a red mustache for a year or two. He grew a mustache, and it was red. And so, that was my first meeting with Feynman, although he later on told me he had no recollection of this. But it was a close call.
Who were some of the key people you collaborated with at Syracuse on the faculty?
Well, I didn't collaborate with anybody, except my advisor. My first advisor was George Sudarshan, and he left me with a particular problems, which was very complicated. And I didn't get anywhere. But then, he had left to go to India on sabbatical, and I was left on my own. It was a very mathematical problem, so it was not particularly enticing. And then, when he came back, I told him I wasn't making any progress. "Oh, yeah, it's OK. It's already been solved." "All right. I did not know that." I read lots of books and learned lots of stuff, but that was it. Now, the one person I collaborated with was my advisor, Balachandran. And that was the only person. One of my experiences was with a general relativist called Josh Goldberg. I remember, this was on the landing of the staircase on the old physics building. And he was teaching general relativity because that's what he did. And I was getting very confused.
And then, he asked me the following question. "Pierre, what's a vector?" I remembered that one. And I said, "A vector is just three things, something in the X direction, Y direction, Z direction," and that's it. He said, "No, that's not what I'm looking for." And so, he let me think about it, and I gave him other answers and didn't get anywhere. And I said, "What is it?" He said, "Something that transforms itself under rotation has a vector. And that's what differentiates a vector." That was a revelation for me. Because up to that point, it was just something you put an arrow on top of, and you didn't think about it much. But yet, he gave me the punchline, and I'll remember that forever because it was a mini epiphany in a certain sense, that you can't unlock things by the way they transform. It's very interesting.
But I never collaborated with Josh. When I left you last time, we went on to the Lou Witten 100th birthday, and we saw him, and he looks amazing, and his mind is tremendously sharp. And Josh Goldberg, Lou Witten, and Stanley Deser are, I think, the only three survivors of the very important meeting on general relativity at Chapel Hill. And in those days, the government was giving money to for science through the Office of Naval Research. Josh Goldberg had worked for the ONR and was kind of the conduit in trying to do this thing. That was a very famous meeting because after the discovery of gravitational waves, Barry Barish told me about this meeting. I kind of knew about it but had never focused on it. And Barry told me that that was the meeting that really set gravitational waves on a firm foundation.
What specifically happened there?
Well, what happened there was, up to that point, the solution of Einstein's equation for gravitational waves, people knew it existed, and people had been looking at it for a long time, but everybody was mixed up because there were lots of singularities. And then, in those days, not even Einstein knew those things. There were different types of singularities. There are singularities that are due to the core unit system you use. For example, in spherical coordinates, the origin is a singularity because at that point, you don't know which direction you're in. Whereas in X, Y, Z, you can say, "Well, X is 0," but it still leaves the other ones. So he said that at that conference, a man called Pirani basically presented the gravitational wave solution in terms of the Riemann tensor, but the Riemann tensor is a covariant quantity of the transformation.
So its formulation did not depend on the coordinate system. And the singularities disappeared. And it was at that meeting that people suddenly realized–and Einstein, who had just died a year before, I think was still mixed up about whether or not there were gravitational waves. Because there was this question of singularities. And at that meeting, Dick Feynman was there, and Feynman asked Pirani the following question. "Do these solutions carry energy?" "Yes," said Pirani. And Feynman said, "Well, there must be a way to detect it." And at the meeting, he devised an experiment to detect gravitational waves as, basically, causing a stress on some material. It was called the sticky ball thing, like a Velcro type thing. It's a famous thing. But that was it. Anyway, we're digressing. But as you can see, I like history. I think it's very important. When I was at Yale, one person who I talked to a lot was Martin Klein.
History. Everything. Dick Slansky and I took a course from him on the history of statistical mechanics. Martin was fantastic.
Have you ever found that your broadened perspective on the history of physics has influenced your science?
In what ways?
Well, a few weeks ago, I gave a Zoom colloquium. And one of my things was Mark Twain's thing about history. It doesn't repeat itself, but it rhymes. And I think it's very important to look at history to see how, in a given period in time, human beings reacted in a particular way. And you find that if there are similar circumstances, human beings will react more or less in the same way, even though the details are completely different. So right now we have a model in elementary particle physics called the standard model, which is about 50 years old.
It's showing its age, too.
Well, a little bit. But maybe not. These new effects are not really quite there yet.
So the muon wobbling at Fermilab, you're not too excited yet?
I am excited. Let me put it this way. In the standard model, the fact that the neutrinos have masses, which I played a role in, means that there are extra degrees of freedom in the model that we don't know anything about. But the standard model can accommodate these things as add-ons without putting in question the basic principles. So if you've got this G-2 experiment, maybe there are new particles. I hope supersymmetrical particles, that are basically causing an effect, which is larger for the muon than it is for the electron. Or else, it could be a new force.
If you believe the G-2, there's something new, which is a four-standard-deviation effect, and you really have to start taking it seriously. But of course, for the last 30 years, people have been saying that. It's not a new thing. That if you measure G-2 with a certain accuracy, you have a way in this fantastic probe as to whether or not there are new particles. But right now, it's the age of public relations. So what happens is, it amps it up. At the same time, experiments are very expensive and need to be funded. Therefore, the more publicity there is about an experiment, the better the chances of funding.
But doesn't it cut both ways? The more attention an experiment gets that does not produce new physics, the bigger the embarrassment, perhaps?
Indeed. In fact, that's what happens in the standard model. Everybody thought that there would be supersymmetric particles of masses commensurate with the Higgs mass.
It could be true yet, we just don't have experiments operating of that high of an energy.
Yeah, but it was supposed to solve the so-called hierarchy problem. Basically, the mass of the Higgs is an anomaly because it gets renormalized very much. Everything in the standard model is like electrodynamics. The cutoff is very far away from the experiment at energies much, much higher. So it's an effective theory. There was a Landau pole in electrodynamics that gave rise to this. Because the charge of the electron is going up, and up, and up until you get out of perturbation theory.
Back to administration, what were the circumstances of you leaving Syracuse and joining the faculty at Florida?
It's a random walk, right? So the first thing was to, basically, get a job at Fermilab NAL as, really, a last resort. I was among the people who maybe should've gotten a job, but there was not enough room because there was not enough money. That was my first post-doc. We were hired for three years, and then I explained to you what happened. At the end of the first year, they told us to look for a job, then I went to Yale. So at Yale, I was first, an instructor, then an assistant professor. And then, I got a fellowship from Yale to be away for a year and do some research. But as I said, the chance of getting a tenured position at Yale in those days was basically zero. There are famous tales about that.
So what happened was, I went first to Los Alamos in this sabbatical, where I met my friend Dick Slansky, who had just moved. By the way, the name of the person that was forming a group there was Carruthers. It was a fantastic group. And Gell-Mann was visiting, and that's how I got to Gell-Mann. Then, the second semester, I get to Caltech. And of course, I completely fell in love with California, and Caltech, in particular. Caltech is a very small, unbelievably rich place, not only in terms of money, but in terms of intellect. It was just spectacular. Yale was good, but this was a different level. My office was next to Gell-Mann and three offices from Feynman on the same floor. And I got to know both of them. I got to work with Gell-Mann a lot. I never worked with Feynman, but we were talking.
So it was a different experience. And Murray had no faculty jobs to offer, so I met John Schwarz there, who had been rescued by Murray from Princeton because Princeton gives tenure to two people. John Schwarz and Abarbanel were bypassed. Gross and Callan were kept by Princeton, and they're both extremely good physicists today with well-known names. John was given a soft money position by Gell-Mann. So when I was at Caltech, all of a sudden, things are clicking with Gell-Mann. We're just working away. And suddenly, Steve Frautschi says, "Pierre, you have a minute?" And he goes to the blackboard, and he writes down $18,000. I said, "What is this?" He said, "That's the amount of money we're willing to give you if you stay at Caltech." And as with Yale, I immediately said, "Yes." And I basically said to Yale, "Goodbye. You're not going to give me tenure anyway."
What year was this that $18,000 was a lot of money?
That was a lot of money. It was 1975, '76. Maybe it was $14,000. But it was much more than what I was making at Yale. Yale was always cheap. There was a history at Yale going back to J. Willard Gibbs, because he wasn't paid for a long time by Yale, and Yale didn't think they had to pay scientists. So he offers me a Millikan fellowship. So I'm a Millikan fellow. And then, after the three years of the fellowship, he offers me some of his soft money. Because Murray was the king of the mountain, and he had all kinds of money. But by that time, my first two daughters had been born while I was at Yale, and the third one was born in California. And the financial aspect of doing theoretical physics with three daughters and a wife who stopped doing electrical engineering became very acute. We basically had no money. We were living paycheck to paycheck.
So at some point, some people at Florida asked me to do some advising. The usual thing. I was too young to understand, but, "Can you give me some advice on who you think would be a good person?" And I gave some advice. But then, the person who hired me was extremely persistent. And at some point, my colleague, Rick Field, was working with Feynman. Rick was also the brother of Sally Field, the actress. So Rick and I used to plan tennis together. He was good, I was learning. Because what you do in California, you play tennis. Certainly, not on the East Coast. And we didn't think we were going anywhere. We were both on soft money. And I was getting pretty antsy about getting a tenure position somewhere. So Florida pursued us. And Florida was not a presence university in my field. Anything south of the Mason Dixon Line, I did not know about, except for the neutrino because it was discovered in the south. But at some point, Rick and I said, "Maybe we should explore this."
So we did. And then, it turned out they wanted to really start a physics department on the broader basis. They had people in different areas, but nobody in particle physics. And suddenly, it becomes kind of obvious, "Maybe we should ask ourselves how to get a group going." And then, Charles Thorn, who was at MIT, who was the golden boy of string theory at the time, a student of Mandelstam, was there. And all three of us decided, "Maybe we should do something like this as a group." Now, both Feynman and Gell-Mann, we told them, "We don't want to leave Caltech. Can you do something for us?" And we said to Murray, "If we do something, we also have to get John Schwarz in." Schwarz stayed in string theory all his life. I was going back and forth, but mostly away from it. So the Caltech faculty was asked if they could give three tenured positions to the three of us. And there was a new tenured position in the theory group. Politzer, who had just been hired a year or two before, was opposed to it for both John Schwarz and me. And Feynman was fighting for Rick Field. But I think it came to the faculty as a whole, and it was rejected.
So basically, we said goodbye. John stayed at Caltech. And then, in 1984, when, he did this marvelous work with Mike, all of a sudden, University of Chicago offers him a job, and he's ready to go there. But of course, Caltech said, "No, no, no, no, we're keeping you." So we go to Florida. And in Florida, we had some hires to make. The first and best hire I ever made was somebody called Pierre Sikivie. I met him at Yale when he was a graduate student, and we collaborated on two papers. And then, he went to different post-docs. And at some point, I had invited him to Caltech to give a talk, and he gave a wonderful talk. And he did extremely well, very nice. So I'd been impressed with him, but I was even more impressed when I saw it. And so, my first hire was Pierre Sikivie.
And you got there in 1980?
And where was the department at that point? Did you consider it a strong department?
No. It was not. What happened is, the department had been decimated by lack of funding. There was a condensed matter experimental group there, which was doing Helium3 and discovered a new phase in a magnetic field. In fact, It did very well, the experimental group. In theory, there was a man whose career had been in fluid dynamics, and he later got interested in particle physics. His name was Arthur Broyles and he was the one who brought us to UF. He worked at the Rand Corporation when he got to be very good friends with Teller and Wigner, of all people. But for us, there wasn't anything in our field. And there were a few theorists here and there, and there was something called the “quantum theory project”, which was physical chemistry, which had been headed by Slater. Slater was at MIT, but in the winter, he went to Florida to head this group. And that was a very well-known group. But it was a bunch of physicists and chemists working at the border between physics and chemistry. Nothing wrong with that, but it was not our thing. Francis Low, who was at MIT, famous physicist and collaborator of Gell-Mann in his early days, wrote down a map of how to make a better department. He said, "The first thing to do is to hire a group of theorists because they're cheaper, and if it works, people will congregate around them."
Theorists are cheaper because they come with a pen and pad, not a big, expensive laboratory.
That's right. And so, that was a no-risk thing. And you can get a first-class group to come in. And this is what happened. And later there's a letter from Steve Weinberg. Somebody was asking him advice on how to form a group. He said, "Look to Florida. This is how to do it." But then, the year after, some condensed matter experimentalists came. And the department now is completely different from what it used to be. For a state university, it's a very good physics department. It will never make it to the level of the private universities, but it's good, and it has played a role in various things, especially in the Higgs discovery and gravitational waves. They set up the way to detect gravitational waves from coalescing black holes. Remember, coalescing black holes was not the thing that they were looking for. They were basically looking for neutron stars forming in the field of a black hole, but they could never see it because it looked very unlikely. And yet, this is what was detected.
So at Florida, unfortunately, what I felt was that we could survive as a group because we could always hire good post-docs. And if we had enough faculty people, we could attract them. But where I was completely off was attracting first-rate graduate students. There are not that many graduate students in theoretical physics, anyway. And the first-rate graduate students go to the private universities. And a few state universities, like Michigan and Berkeley. And now, of course, a lot of state university systems in California are very good. But that's California. It's basically 100 years ahead of its time compared to some other states.
We might put the University of Washington in that group as well.
That is true. Not so much in particle physics, but in gravitational physics, for sure. It has a fantastically good nuclear physics group, for example. Definitely. Berkeley has maintained its stature, but that, of course, is because of the system in California, where politicians cannot meddle with the funding of state universities too much. So the path was just that way. Then, in Florida, the graduate students that were coming in were good, but not of that caliber. One of my best graduate students is in the National Academy. Jeff Harvey, who's a string theorist, was a student of mine at Caltech. And he's first-rate. But this is the way things are. So I miscalculated from that point of view. I thought after maybe five years, it would get better. But it turns out, it's more like a diffusion process than anything else. It's very slow.
Let's talk about the so-called string revolution of 1984. What was your involvement in the years leading up to that?
Well, I quit string theory back in 1974.
On the basis that QCD effectively killed it at that point?
No, on the basis that I wouldn't get a job.
So you were still a believer, but you were a realist in terms of your career.
Yeah. As I said, my first daughter was born in '72, my second was born in '74, and then when I was in California, my third daughter was born in '77. So with that comes responsibilities. My parents had been traveling all over the world, and I was left behind. That kind of forms your attitude about children. It's a human thing. So in a certain sense, I had to look after them. And the uncertainty that comes with not having money is not good for research. It's not good for anything. Because you worry too much about these things. It depends on your personality. So for example, John Schwarz, the reason he's still at Caltech is, he was not married. He had no responsibilities whatsoever except that. If he had been married with young children at that time, his attitude may have changed. And my friends in France, Joël Scherk, André Neveu, by the time they were admitted to the École Normale, they basically had tenure. So they didn't have to worry. So they were free to look after anything they wanted.
So this is to say that in the early 80s, when you had gotten to Florida, you were out of the string theory business for the time being.
I was, except Charles Thorn was not. He was full-blown in string theory. I was out of it, and I made some bad jokes about it because I said, "You guys are in higher-number dimensions. I'm in the right number." And then, I learned later on that some people got offended by this because I was looking like a turncoat. I'd been one of the founders of the thing, and then I kind of renege on it. If I'd gone back to Europe, it would've been different. But by that time, I had my wife and three children. And indeed, two of my children have PhDs, one in microbiology, one in physics, and the third one's an architect. So it worked out. You could start them in life without being burdened by obligations to repay this or repay that. And going to Florida was an essential aspect of it. Because by the time the third girl was an undergraduate at Cal, as an out- of-state student, we had to pay full tuition. So one went to Bryn Mawr, the second went to Duke, the third went to Cal. By the time the third one finished, we basically were about to borrow money. But they got out of it scot-free. So that was important for us. You make those choices in life, and that's it.
Did the revolution compel you to get back in?
Yeah, but it was too late. It was too fast. So by 1983, I was asked to organize a Les Houches summer school in particle theory. I still thought that string theory was very important, and I booked my friend Lars Brink, basically, to give a set of lectures on string theory. I still felt that was very important. I did not know it was going to go where it went. But I thought it was a very important thing. Once you have done string theory, you cannot forget. It's Odysseus with the sirens. You have to be chained to the mast. And then, 1984 comes, but the school is in 1985. So then, I look up what happened ten years earlier, 1975. And I see the names Ed Witten and Chiara Nappi. "A-ha." So I thought to myself, "This is where they met, and they got married." So I went to Ed, and I said, "Ed, you must come to the 1985 to give a set of lectures." He was all booked with speakers, but he could give lectures in the evening.
And so, he and Chiara came for two weeks and gave lectures on string theory from the horse's mouth. And of course, the students appreciated it very much. In 1984, I didn't quite understand what was happening, except I knew the exceptional groups E6, E7, E8, where we're part of it, and that, I knew very well. The rest, I did not know, and the construction looked very strange. But I didn't doubt at all that it was correct. The question was, was it relevant for nature? And by 1985, these people had worked out a lot of things that looked a heck of a lot like nature. Except the details didn't match. But everybody believed that the details would be fitted in.
What details did not match?
Well, the questions of trying to understand what singles out–you had to depend on a particular compactification, you had a particular way to go between ten dimensions and four. These guys had found these Calabi-Yau manifolds. And if you had these manifolds, you were obtaining a chiral group, like E6. So the contact with the real world was this E6 exceptional group. Which is the group that Gürsey, Sikivie, and I had worked out much earlier.
Because once you go below E6, you are in SO(10). Once you go in SO(10), you are in SU(5). After that, you're going to the electroweak model, the standard model. There's a mathematical progression, which is very clear. So there was no doubt in my mind that that was it. But then, they start looking at the details. "How can we make E6 fit into the world that we know?" And there are many, many parameters. It gets very dirty. And yet, there's no guidance from the string theory.
So the gauge structure of string theory seems to match the gauge structure of the world as we know it. But it offers absolutely nothing in terms of the masses of the particles, the breaking of the symmetries. In other words, it was hoped that the theory was so good and would tell you exactly what to do. And at some point, some people in 1985, my friend, Lars Brink, basically, at one time told me, "We don't need to experiment anymore." I remind him of that whenever I meet him. Because the feeling was that they'd found it. That was it. And it may still be true. But there are ingredients missing. And yet, ever since that time, string theory has become more and more mathematical in trying to fit those details and trying to find figures of merit that will single out what we observe. But the background is there. So I think it's impossible not to think of string theory. And with the event of supersymmetry, string theory becomes incredibly powerful.
But it's powerful in the mathematical sense. The great genius of that time is basically Ed Witten, and Ed Witten got the Fields Medal in mathematics. He's incredibly brilliant, but nevertheless, it has gone into a mathematical sense. But now, there are analogues. People are studying black holes, black hole solutions in that context, trying to understand the black holes of statistical mechanics type origin. And there's this work at Harvard by Vafa and Strominger. So all these things feel right. But the details have to match. One physical prediction is important.
Were people in the mid-1980s during this exciting moment talking about the testability of string theory? Were those concerns and optimism present at that point, that string theory would be testable?
How did they think it would be testable?
Well, the way the testing was going was, people, with the event of supersymmetry, generalized the standard model to supersymmetry. Supersymmetry is a symmetry more general than the symmetry of Einstein, of special relativity. There is a generalization of special relativity where some parameters are Grassmann numbers, which are very strange things. But mathematically, it enables you to do an enormous amount of things. And you asked, "Does the standard model fit if you supersymmetrize it?" And it does. However, it predicts all kinds of new particles. So there's a quark, and there's a squark, which has the same quantum number and charges as the quark, but rather than being a fermion, it's a boson. To the photon, which is a boson, there is a photino, which is a fermion. In other words, it's a one-to-one correspondence.
And then, people found that the mass of the Higgs could be suppressed to the electroweak scale because you're assuming that the cutoff is at the Planck scale, some scale where gravity is supposed to become quantum mechanical, and nobody understands it, but there is that scale. And so, it looked like it was going to be useful. And when the LHC was built at CERN, everybody believed that there would be a discovery of supersymmetric particles. That would not have said it was superstring, but boy, it was getting there. Because the superstring theories, of course, have supersymmetry. But it was indirect. However, the big surprise of the last few years is that the Higgs is there, and a very interesting mass.
So you find the mass of the Higgs interesting? Meaning that it's not perhaps what it was predicted to be?
Well, we did not know what it was going to be. But we knew roughly where it had to be. It could not be too heavy because if it were, the weak interaction would be too weak. There are a lot of consequences. For example, the mass of the W boson, which mediates beta decay, gives you the strength of beta decay. And if it is very heavy, then the strength of beta decay would be even weaker than it is. Because the strength had been measured a long time ago. How often does a particular particle decay? That gives you the strength of beta decay. And so, everybody was waiting with bated breath for such a thing, and it didn't come up. So the big mystery of the last five years is that the supersymmetric particles did not come up within reach of CERN. It could still be there, but they're more massive. And a weaker link to explaining this gauge hierarchy problem, which means that the Higgs mass is low compared to the cutoff of the theory–the natural cutoff of the standard model is very large because all the funny things happen logarithmically far, far away, at much higher energies when there is a cutoff, like a “Landau pole”.
Let's go back to quantum electrodynamics. So quantum electrodynamics is just a quantum mechanical way of setting up field theory for the photon in interaction with electrons. It's written by Dirac. And then, it was found that there were infinities when you computed the corrections. That was back in the 1930s. That was a big problem of the 1930s. How come there were infinities? Well, the Dirac approach to this was that it means it's the wrong theory. Because the theory of the world has to be free of infinities. Now, some people say, "Wait a minute. Maybe there's something going on." When Tomonaga, Schwinger, and Feynman devised what is now known as QED, they found that you can absorb those infinities at the price of introducing a cutoff somewhere at a completely different scale. In other words, when you have an integral, and you take it between A and B, if B becomes infinitely large, it blows up. But if B somehow has a given cutoff at that point, that's where the cutoff, whatever B is, lies.
So what actually happens is, for example, the charge of the electron depends on the scale at which it is measured. When people talked about alpha is 1/137, that is basically the value at the mass of the electron. But at CERN, it has increased a great deal. When you measure the electric charge at CERN, which is a few hundred TeV right now, and that's called the Debye effect, all the coupling constants, they all change the scale. And that is well-known. The problem is, when you follow the charge of the electron, and you go to the ultraviolet, that means higher and higher energy, and you follow these equations of what's known as the renormalization group, you have to renormalize the value as you change the scale. That curve starts blowing up. Once the charge becomes too large, you cannot use perturbation theory anymore. But if, nevertheless, you continue it, it blows up, and that's called the Landau pole. Lev Landau noticed this, and said, "Well, that means that quantum field theory is no good."
But then, people said, "Well, wait a minute. Maybe it's not good, but it's a damn good effective theory. It works very well for what we measured." So nowadays, the point of view is that all these quantum field theories–except for the asymptotic freedom one, because the asymptotic freedom one, the charge goes down as you go to the ultraviolet rather than going up. Because that means that at shorter and shorter distances, the strength of interactions between quarks gets weaker and weaker, not stronger and stronger. And that means we can do perturbation theory there, but in all the other theories, it went the other way. So they all said, "Forget about it." And then, people said, "Well, how can we forget about it? It's such a beautiful theory." Well, it's an effective theory, it's not a fundamental theory. So quantum field theory has an actual cutoff somewhere, and everybody believes that that cutoff has to do with quantum gravity.
What is the distinction between effective and fundamental theories?
The distinction is that an effective theory is valid for a certain range of parameters. In other words, it's like an approximation. When you take any complicated anything, and then you cannot solve it, but in a certain range, it simplifies, and you can follow what's going on. Well, that's an effective thing as long as you don't ask too many questions. You ask only questions limited by a certain range. After a while, it breaks down, and then it doesn't mean anything. So that's what is meant by effective. When I was a kid, the thing about quantum field theory was the notion of renormalizability. Which effectively means that all the bad parts of it can be relegated to the future in terms of detectability. Sweeping it under the carpet, so to speak. And that was the approach of Feynman, Tomonaga, and Schwinger, who basically felt that yeah, maybe Dirac is right, but it's a very good theory. It works very well." And therefore, as long as we don't push it too far, it's going to give us good results.
So that's what is meant by an effective theory. And now, we're up with the standard model. The only thing that we have in the standard model for sure is the fact that the masses of neutrinos are very small. And the mechanism that Gell-Mann, Slansky, and I invented, called the Seesaw Mechanism. So a neutrino accompanies an electron. Now, for a long time, people thought that neutrino had no mass. Nowadays, we know it has a mass. But it's still much, much smaller than the mass of its electron. And the question is, why? Well, this is where the suppression enters in terms of the mass scale. So you have a mass scale for the natural cutoff of the effective theory, and you have a mass scale for, say, the mass of the proton. Or the mass of a W boson. That ratio is very small, mass of W boson versus the Planck mass, which is 10 to the 16 GeV, or 10 to the -16 in length units.
So what happens is, you have a suppression mechanism, and this is what we proposed a long time ago at Caltech, that there was this thing. It was also proposed at the same time by a guy called Yanagida in Japan. Murray didn't want to publish it. So Slansky and I wanted to publish it. Murray said, "That's a stupid little matrix. Why should it work?" And he sat on it. I didn't know how Murray was before the Nobel Prize, but after it, he was so terrified of being wrong that he was paralyzed. That happens to some great men. Because they don't want to be remembered for being wrong. Like today, you have these idiots who talk about Einstein was wrong in the cosmological constant, etc. That's absurd. That's a revolution of the idiots, as far as I'm concerned. Nobody's perfect. And a little bit of imperfection is not bad sometimes. Once you have such an overwhelming genius. So this is an indication that, perhaps, this enormous scale differs. The scale which occurs in the grand unified theory, basically, comes up in the suppression of neutrino masses. And that is what we advocated quite a long time ago.
This was an example of my other life into physics in four dimensions. So right now, the field is in a state of stasis. We've got this beautiful standard model theory, and it gives you all kinds of ways of looking at things. It opens new intellectual pathways. But none of them have been vindicated. That's why G-2 is so interesting. Because at the fourth standard deviation, it's not yet discovery mode, which is five standard deviation. But still, it's pretty close. And then, LHCb, which is the CERN experiment, also seems to indicate that there's a difference between electrons and muons. They compared decay modes into electrons versus decay modes into muons. And the lore should be that the muon is 200 times heavier than the electron- otherwise there is no difference. Their result seems to imply that there is more to the difference, but remember that it is only a three-sigma effect, so it may be true or maybe not. As I become older, I get more and more conservative.
For the last part of our talk today, let's discuss your term as president for the Aspen Center for Physics.
Well, I went to Aspen in 1970, as I mentioned before. Bob Wilson said, "All theorists must go to Aspen." Because in 1967, I think, he went to Aspen together with a lot of friends to produce a study to this future accelerator. So the summer study was done in Aspen. And he had a whole wooden building built just to house that community while they were spending their time in Aspen. And the reason was that physicists like beautiful parts of the world, and Aspen certainly is that. By that time, Murray Gell-Mann, who was the king of kings, spent time there. And people who wanted to know what Gell-Mann was thinking went to Aspen. It's difficult to overstate the overwhelming influence of Gell-Mann on the field for a period of 10 to 20 years. I wrote an obituary for Gell-Mann almost two years ago, and so I reread a lot of his papers, and it's a phenomenal thing, somebody with such incredible insight and genius to be such an idiot in terms of everyday life. [laugh] But that's the way it goes.
So I go to Aspen with the group at Fermilab, which was then called National Accelerator Laboratory. And I spent a few weeks there. And I absolutely loved it. And this is what got me started thinking about the point particle model, coming out of these amplitudes. And then, at the end of my stay there, I was thinking about generalizing to the Dirac equation. So in 1970, I go there, and I didn't go there again for quite a few years. In 1974, there was a famous workshop on string theory organized by John Schwarz. But I didn't go because this was the summer my second daughter was born. And under threat of death, I could not go. My wife was quite adamant that she had her hands full with the first daughter. But in 1975, I'm part, now, of the Caltech group. And the Caltech group goes to Aspen.
So I go to Aspen, and after a year or two, I'm asked to become the secretary of the Center. The secretary was a one-year position by a physicist to decide with a group who is accepted and who isn't. So it's some sort of gatekeeper. And then, Fred Zachariasen, who was a professor at Caltech, is the one who called me up, and he said, "Would you be interested?" And I said, "Well, yeah. I liked it a lot when I was there." He said, "OK. You're going to be secretary next year." So I am. I will not recount to you all the vagaries that happened. But I was hooked. And then, for every other year, maybe sometimes every year, we went to Aspen. And for several years, I did nothing but physics there. I didn't even know about the internal organization, etc. all I had done was one year duty of being a secretary there. But then, at some point, somebody said, "Would you like to be treasurer?" I said, "No." That was my first reaction. But it was Aspen.
And then, some of my friends, people that I'd become friends with in Aspen, were very persuasive, and I became treasurer at the same time Appelquist became president. Well, more or less the same time. And then, after that, I became president of the Aspen Center for Physics. And this was at the time when we were building up Aspen. There's a new building, etc. And there was a man called Stranahan, better known, now, perhaps for Stranahan Whiskey. But his family was the owner of the Champion spark plugs many, many years ago. If you like cars, you will know them.
So one thing led to another, and I became part of the fixture of Aspen. Did a lot of work for Aspen. And then, of course, the children became extremely enamored with Aspen. And there are many children of physicists who became very famous in music because, remember, there's the Aspen Music School, which is Julliard going to the Rocky Mountains every year, more or less. And so, it's a bit like string theory. Once you go to Aspen, you cannot get Aspen out of your life. It's a very special place. But it is a very fragile place. Because we depend on NSF support, since the rent is very expensive. As you can imagine, real estate in Aspen has become more and more expensive. So it's a very fragile environment. We have this bunch of theoretical physicists with basically no money of their own. We have friends with mega money, but friends with mega money doesn't mean very much. We only got a lot of money from those people when we brought Stephen Hawking to Aspen. When he came, they came out of the woodwork. [inaudible] Stephen was very helpful in fundraising for us. But now, we're on our own. But every year, except last year, the best young theorists in the world come to Aspen and spend about two or three weeks on a workshop. It's just fantastic.
And for me, as an old guy, when I go back there, I can learn about a new field just by listening to these talks. There used to be a time when I knew most of what was going on in my field. Now, I only know a certain percentage. So Aspen has been a big part of my life. I'm going there this summer for two weeks. I'm looking forward to it.
And it's definitely maintained its cachet over the years?
The best people in the world go there before they're known. There are workshops there, which have been fantastically influential. And now, of course, it has gone into biology. Gravitational waves, of course. It has morphed into different places. So in particle physics, Gell-Mann was there, but then Philip Anderson was there in condensed matter, the great guru of the condensed matter theory field. It was and is an intellectual center. The only thing is, it's an intellectual center for a few weeks in your particular area. But that's important because you get together with people.
And then, of course, people take those ideas back with them to their home institutions.
Oh, yeah, there's a definite correlation for the year after. In other words, somebody has gone a particular summer, then you go and look at what happens six months afterwards. And this was true in my case. There are all kinds of connections that one makes, some of them knowingly, some not knowingly, which you're exploiting. Because the mind works in a funny way. You have a store of information that comes in. You don't necessarily process it all in an evident fashion, but it's there. And sometimes, it rings a bell, and then things happen. So I'm a firm believer in this.
That's a great place to pause for today. We'll pick it up for next time.
[End Session 1]
[Begin Session 2]
OK, this is David Zierler, Oral Historian for the American Institute of Physics. It is April 22, 2021. I'm delighted to be back with Pierre Ramond. Pierre, it's great to see you. Thanks again for joining me.
My pleasure. By the way, are you working for the American Institute of Physics?
I am proudly working for the American Institute of Physics, where I direct the oral history program.
I see, you're the big boss. OK.
Hardly, hardly. We ended last time talking about your tenure at Aspen. Let's head back to Florida and talk a little bit about some of your service work at Florida. Let's start with the faculty senate position. When did you get involved in faculty senate issues?
That's a very good question. I don't know. I have a sense of duty, which is very strange, and I always regret doing it. I've done that with Aspen and at the University of Florida. I've also been head of the Division of Particles and Fields in the American Physical Society. I'm always thinking back to my father, who was a very gifted man, but he had a terrible flaw. He thought he could be a very good businessman. And he was absolutely horrible at it. He lost interest, etc. And so, I felt maybe this came from him, but also felt that I had an obligation to the community to do something, to go outside. And I did it, but I don't think I was ever very good at it. I'm much better at physics than I am at dealing with people. It's a kind of skill I do not have. There are people who are actually very good at that.
My friend, Appelquist, who you interviewed, has this ability to compartmentalize his physics with his dealing with people. And that's quite remarkable. I have a colleague like this in Florida called Mitselmakher who also has this ability. I'm very envious. I certainly do not have it. So I got involved in the faculty senate because the University of Florida was not, I thought, a very good university overall. It was trying to become one. And I thought that I should be able to help a little bit. I'd been at Yale and Caltech, although at neither place was I really active in anything like that. But the one thing I realized is that when you're at these first-rate places, a lot of things are handed to you. You get visitors coming. And they're delighted to come to Yale or to Caltech.
Let's take Caltech as an example. So you have lots of very smart people coming in, and you never isolate. You always get the latest. At Florida, it's quite different because you have to create your own environment. For example, University of Florida was always very good in sports. And whenever I've dealt with people from the athletic association, they've been tremendously competent and sure of themselves. Which is good. But in the intellectual environment of the established universities, you get into this, and they are given to you. So you don't have to work for it, you just become part of it. So when you go to a place like Florida, which I did not realize at the time, of course, fundamentally, you have to create the environment. And so, that comes with time. You cannot just do it right way.
And funding, of course. Budgetary support.
You need budgetary support, and you need long term support. For example, particle physics, especially theoretical physics in general, is a very fragile endeavor. You have to keep with it for a long, long time before you get anything. Sometimes, you might not get anything. Maybe only the training of a substantial workforce. But in a society that wants immediate results, which is the American society, it's not so easy to let them know, "Give me ten years, and I'll do this and that." It simply doesn't work that way. So I thought I would be involved in all these things and bring in a certain sense of proportions. But frankly, I did it out of a sense of duty. But somehow, in retrospect, I felt that I should've been doing better just concentrating on physics. Which is what I know how to do relatively well.
So it's a question of skill. But I do have that sense of duty. There was an undergraduate who was organizing a list of teaching assistants who had complaints and were not understood by students. The usual thing, bullying. And of course, there are underlying things like racism and exceptionalism. "We're better than them," etc. And I was walking by, going to lunch with a bunch of people, and there's this guy being interviewed by television. And I listened to it, and this guy said to the TV, "I've compiled a list, but I cannot show it to you." At that point, I blew up completely. I went out of my mind. I said, "You know, this is what totalitarian regimes do. They always have a list of things they don't like, but they can never show it to you until the next morning, they show up at your door." And this was a reflexive thing. But I started going after this guy. So I have that side of me, but as I said, I'm better off doing physics.
Well, as an observer, given what you were interested in 15, 16 years ago for Florida writ large, how well has the university adapted and responded to the ideas that you had then?
I think by osmosis, it has. But not directly. The culture is very different. Changing a culture is a generational issue. Very difficult. University of Florida is beginning to be known in science. In ecology, it was always very high up. But in physics, not so. They have a few people. But still, not so. And now, they're getting recognition. So several of my colleagues are getting into the National Academy mostly other fields. But that's fine. So they're getting some sort of a national recognition. And the tuition is very cheap. And so, they're ranking very high.
In academia, there is this thing, US News and World Reports, which rates everybody. And all the administrations of all the universities that I know of, except the very top ones, care about this to show to the legislature that they're doing well. And Florida is doing very well. But the more important thing, which takes time, is the intellectual aspect. By us going to Florida, we opened the gates to many other positions. And little by little, some extraordinary people joined us. And they're making a big difference. There's this Russian guy I was mentioning to you. He's Lithuanian, but he was in the Soviet Union. And he's an experimentalist. But he set up a high energy experimental group at the University of Florida.
And by the way, the way it was set up, my colleague, Rick Field, brought in his sister to have lunch with the president of the university so as to get money to really start the experimental group. Not bad. That's pretty good. But it worked. But this guy set up a group. And when they discovered the Higgs boson at CERN, it was one of the groups that was very important because they were looking for signals in lepton sectors. And then, these same experimentalists worked with GEM, which was headed by Barry Barish. Mitselmakher had been hired because he'd been known at CERN as an experimentalist. He came to the US, got hired, and he and Barish became good friends. And so, when the SSC went kaput, Guenakh came to Florida. Barry wanted Guenakh to come to LIGO. But Guenakh didn't want to go. But Guenakh organized a bunch of people at Florida to work on LIGO. Therefore, some of the group were condensed matter experimentalists, and some were laser physicists, and they were actually building hardware for LIGO. So basically, after Caltech and MIT, Florida is one of those institutions that was extremely well -represented. It was not one of the founding institutions, but nevertheless, it was a very important one. So little by little, the department is getting more and more visibility. But that's a diffusion process. The real thing is when somebody gets a huge prize, meaning lots of money. There are prizes around, like, for example, this Milner Prize, millions of dollars. That's real money. Nobel Prize is just prestige, no money. But it's very interesting. So I think we got the department going. Not by ourselves, just by being there. But then, eventually, there were lots of good people who came in different fields. Not only in particle physics. So that works.
The greatest recognition I ever got from the University of Florida was in the mid-90s, when I was nominated as teacher of the year. And I got it. And so, the athletic association calls me up and says, "Go to the stadium. We want to recognize you." "All right, fine." I'm a ham, so I'm very happy. So this guy who said, "Go to the sideline” and gives me a pass. I never realized football players were that big. And then, at halftime, I'm in the middle, and they give me a team uniform for the year 1996. And I put it on in front of everybody. I got more recognition that way than anything else. People said, "Oh, I saw you." But the amusing thing was, it was 1996. And so, the number on the jersey was 96, which is typically a number for a lineman. So I looked minuscule in comparison. So that was funny. But Florida is an upcoming state university to the extent that the state legislature will allow it to become any better.
Another service question. You were chair of the Division of Particles and Fields at the APS the year that the Higgs was announced. I wonder what that was like for you.
We were, at the time, preparing like mad for one of these “Snowmass Meetings”. I only served for one year, and my successor to DPF, Jon Rosner, did the bulk of the work. And if you want continuity, you really have to get the people before you and after you together with a common message. So we were preparing for these “Snowmass meetings”.
Snowmass meetings had taken place typically in Aspen for many years. But its purpose is to make the case to the government why they should fund particle physics. And there was a crisis in the field because when the SSC was canceled, that was a tremendous shock. And the psychology of the shock was, the previous generation of people were young during the war. And therefore, they had government service. They worked for the government. The governments instantly understood the value because people are working on radar, for example, the Manhattan Project, etc.And so, these people cashed in with having complete faith in the scientific establishment. Because the political arm in those days, I am told, was very much ruled by chairmen of various committees. And if you had the trust of these chairmen committees, who were always reelected, especially in the Senate, then you could name your ticket.
So Bob Wilson had to testify in front of the committees to say, "Give us money. This is very, very important." So he gets into the building, and he has to wait because somebody was speaking. And it was a closed-door meeting, so this person was probably speaking for his own thing. So he waits and waits. And suddenly, the door opens, and he sees Admiral Rickover storm out of the place. "Oh, boy." So there was a little recess. Rickover leaves. I don't even know if Bob knew him. But during the recess, one of the Senators came over and said, "Bob, let me tell you something. I know you're going to ask us for money. We're going to tell you we don't have the money. And then, you're going to insist, and we're going to tell you no. And then, eventually, you will get so mad that you will basically storm out of the room. But my advice to you, when you stomp out of the room, don't go to the door on the right because that door leads to the projection room." And this is what Rickover did. [laugh] So Rickover probably had to go back to the room sheepishly, after going to just a closed room, and go around. So this was a little anecdote of those days.
And we had a man at Florida called Harold Hanson, who was the chief of staff for the science committee for many, many physicists. Used to be chair at the University of Texas at Austin. And he said that after Watergate, the big disaster came because they lowered the power of committee chairs. And as a result of that, the scientific community was very much at the mercy of the newer types of people.
What were your feelings more generally when the Higgs was announced?
It was wonderful. From my point of view, the standard model was not complete. Everything pointed to the Higgs being there. And Fermilab had semi-positive signals. And then, of course, CERN blew it out of the water, except CERN blew up before they blew it out of the water. They had a little accident at CERN. That was very, very bad. But it had to be there. But it is a relatively new mass. It's not a surprising mass. Except for theorists, it is surprising because the mass of a scalar particle should be renormalized like mad by quantum effects. And it's not protected by any symmetry. So quantum effects, whatever they are usually, sometimes has a partial amnesty from the effect of quantum fluctuation. So you allow just a little bit, just like, for example, G-2. With G-2, the effect is nicely controlled and experimentally verified.
So one thought, "A-ha, supersymmetry particles are around the corner." And that was fantastic. And everybody thought so. Because it had been pointed out. Several of us actually pointed it out. I never wrote my suggestions, but I pointed out that if you had a supersymmetry, you could protect the scalar particle from the fluctuations, and therefore, they would be small. I said, "Well, maybe it's true," but there were no supersymmetric particles found. And the big thing about 2015, 2016 when CERN started running again, there was tremendous expectation because they had more luminosity, but nothing happened. And that was a tremendous downer. And to this day, I don't think anybody understands why the Higgs has such a low mass.
What is your hunch?
I wish I had one. I have no doubt that supersymmetric particles–when I say supersymmetric particles are not there, what I meant is, supersymmetric particles whose mass could have explained this taming of the what's known as the hierarchy problem could contain those fluctuations. But I don't know what to expect. I think that everybody in the community that I know of and respect doesn't know what the hell is going on. The cosmological constant, for example, which everybody said was zero because what else could it be? Well, it ain't zero. The whole thing is accelerating. And so, nobody really understands the role of the vacuum. In the standard model, you have this phenomena of spontaneous breaking, where there is an order parameter. The Higgs is a signal that there was an order parameter. And that's it. So the whole picture fits, except the suppression mechanism, which allows the Higgs to be light. Nobody knows. So I don't have any idea at the moment. It's probably a combination of things. There's no simple answer to it at the moment.
How would you characterize the overall approach to what's happened at the LHC post-Higgs? Would you say it's a disappointment? Is it patience? Is it impatience? Are people elated by the progress that's been made since 2012? What's your read on the field?
Oh, the field is in a depressed state. Because remember, this is a field that exists on discoveries, which are not too far apart from one another. For example, whenever there was a technological improvement, an improvement in detectors and stuff like that, and tremendous computing power at the same time, which did not exist and enables you to analyze extremely rare events, something new was coming up, something new turned up. I have a poster from the 1990s or so from the American Physical Society, and it gives you the standard model. The Higgs is not there. But the Higgs is part and parcel of the standard model. It's there. People right now are measuring everything they can, but yet, there's no real explanation. So there's just an extra parameter, which should be small compared to the actual cutoff, but we don't know. And the cruelty of this is that all the couplings of the standard model–the couplings change with scale. The Debye effect in solid state. When you're at CERN energies, the mass of the Z boson, for example, all the couplings of the standard model are perturbative. What does that mean to a theorist? It means, "Fantastic. We can do perturbation theory because that's the only thing we know how to do." And if we can do perturbation theory, that enables you to go and extrapolate to shorter and shorter distances. Well, we thought there were supersymmetric particles not far away from the reach of CERN. And now, we don't know.
Many people thought there would be more strong coupling theories. Appelquist liked that at some scale. But at the end of the day, we don't know. And we're completely at the mercy of the theorists. All the beautiful theoretical ideas, which started with Pati and Salam, the idea that the lepton is the fourth color, and therefore, you could have something from lepton to quarks, because of asymptotic freedom, you could say all these things are beautiful, wonderful, marvelous. But nothing. So my attitude right now is that this will be a new insight, and it's very difficult to think of a new insight when you know too much.
If you had to guess, would supersymmetry be resolved if the SSC went through?
Yes. I spent a month at the SSC at some point, just the summer before it was canceled. And before that, I had visited the SSC because I was on various committees, etc. And it was in that warehouse in Dallas. When I first visited it, it looked like a corporate thing. Felt like I was walking into Bank of America. Everybody had ties. The secretaries were pretty. Everything looked fantastic. The audio/visual was working, whatever it was at that time. And that reminded me of my years as a kid, when I went to NAL Fermilab, Bob Wilson. Nothing was working. People were setting up everything. The secretaries, I'm afraid were not hired for their looks, they were hired for their abilities. It was a completely different thing. However, by the summer before, when I spent a month there, it was changing. Fewer people had ties. It was much more of a working organization. People were actually doing physics.
So it was a real shame that it got onto the radar of politics. And then, of course, the particle community was so used to getting its way that, basically, they did not enlist the help of other groups in science. They actually upset a lot of other groups in science, especially the condensed matter physicists. Because what happened was, they said, "Oh, we invented this, we invented that." And the condensed matter physicists said, "Wait a minute, what about superconductivity? What about all these things?" Because they observed quantum mechanics at work in real systems, and the devices they used and the structures they discovered, Phil Anderson especially, who was very upset about those things, are turning up in nature in the fundamental stuff, but then the particle physicists took over. So it was a real mess.
I've always read history, and I continue reading history, but what I notice very much is that the people who make progress when they're young, some of them are born with abilities the rest of us do not have, but at the same time, they have an instinct for simplicity. Especially, in physics. And they're not put off by the complexity of what's in front of them, and they start analyzing things in a simple way. And of course, even though it's a century later, we're still living in the shadow of Einstein, exploiting whatever the hell he was doing. So we live in his shadow. It's like a kid living in the shadow of a famous father.
I'd like to give you a belated congratulations for your receipt of the Dirac Medal in 2020. And I'd like to ask you, first, if you see any particular meaning in what Dirac's contributions were and to what you have done over the course of your career.
Well, for me, that medal was very special. I've gotten other recognitions, but this one was very special because of the name Dirac.
I thought you might feel that way.
Absolutely. So let me backtrack. There's a lecture by Dirac from the 1930s, where he talks about beauty and simplicity in nature. I think I mentioned it to you. But it's well-worth reading. I have my physics haiku. Einststein’s E is equal to MC-squared is a haiku paper. It's just as beautiful as Mozart and the like. To me, Dirac was fantastic. The first time I met Dirac was in Trieste at ICTP in Dr. Salam's place. And I asked Dirac, "Have you ever considered octonions?" Octonions are these funny numbers that many people have been obsessed with, myself included. And he said yes. And having gotten the nerve to talk to him, I did not know how to follow it up. So I only met him a few years later. After that, I told people, "When you ask Dirac something, he will answer you, but that's it. He'll say, 'Yes,' and then he's waiting for the next thing."
So Dirac, to me, was a God. One of the great gods of physics. The simplicity of his monopole paper, for example, the elegance and simplicity of thought was just remarkable. Einstein was similar but different. But there was always this beauty to it. So my work was basically applying Dirac's equation to the string. And following Dirac's structure, I found myself with these funny algebras, these supersymmetric things which generated these supersymmetries. I did not work that out, but I knew they were generating some sort of symmetry. And so, what I felt was that I was like a shepherd, tending my sheep on Mount Olympus, and I meet a God. And then, for a little while, I was able to follow and even go a little bit further than Dirac, but only for a little while because I'm no Dirac. Just for a little while. And to me, that was amazing. And I'll tell you a weird anecdote because I'm a very strange person. In my days, you wrote notes with no computer or anything.
So when I did my work on the fermion, it was time to write a manuscript to give to a secretary. And I was so much in awe of what I'd found because I realized it was very important that, basically, I had offered my wife a very beautiful Parker pen set, which she never used. And therefore, I use it. And so, I used that particular Parker pen, rather elegant, to write that paper. Because I thought this was an inspiration from the gods. It sounds stupid, but it's true. I haven't felt that way since. But there was this thing that somehow, there was Dirac pushing me in that direction. And all kinds of good things were happening. And they did. My last interaction with Dirac was two years before his death. He was at Florida State, and I was at University of Florida. I went to Florida State to give a colloquium, and Dirac was in the audience. And I knew that he was sleeping all the time, etc. I don't remember the title of my colloquium, but I remember the substance, which was, "Is there any reason to look at physics in higher dimensions?" Because string theory was going in higher dimensions.
And so, why should we look at more than three space dimension? So I go and talk to him, and I ask the first question. "Professor Dirac, do you see any virtue in going into higher dimension?" And he says, "No." So I'm totally deflated. But then, by that time, I'd gotten more nerve. And I said, "But do you think there's no virtue in this, really?" Then, he said, "There's an exception. If it leads you to more beautiful mathematics." I said, "Oh, good." I was relieved. Then, I asked, "Professor Dirac, would you like to come to Florida to give us a talk on anything you want? We'll bring a chauffeur for you, whatever you want to do." And he says, "No, I have nothing to say." And I said, "Well, if Dirac says he has nothing to say"–and then, a very sad thing happened. He started talking almost verbatim about what he had said about quantum field theory: “All my life, I have been told that if it is infinite, you do not neglect it.” The question about renormalizability. And somehow, that great, great man had never gotten over the fact of the renormalization program. Because he was convinced that the theory was not consistent. And he's right. But for the times, that was not the approach. And he went on and said, "My life has been a failure." So second encounter by a God on Mount Olympus, and I'm tending my sheep, and the God comes over and starts telling me how his life has been a failure. [laugh] It's very sad.
Puts some things in perspective, doesn't it?
Yes, it certainly does. And I started to tell him about this N = 4 supersymmetric theory, which has no ultraviolet infinities. And this was a time when, basically, people had looked at singularities in one and two loops in perturbation theory, and they didn't find any divergence. So it had not been set in stone, but it was clearly going in that direction.
None of it was my work, but I tried to tell him about it. But he never answered. And then, two years later, he was dead. And to tell you how close I was, although he didn't know I was that close to him, when he died in Tallahassee two years later, my colleague, Tom Curtright and I went to his funeral. And it was a pitiful funeral because there were very few people there. Of course, his sister and wife were there. And it was a very small ceremony and burial. So maybe ten years later, I'm having lunch with Monica Dirac, one of his daughters, and she's bitching to me about the fact that her father is not getting any recognition because the mother had tried to sell Dirac's handwritten manuscript, and she wasn't getting anywhere. And at that time, I told her to go to AIP and give it to them. But then, she said, "Einstein's manuscript got all the money." And so, that was so sad. So Monica starts bitching on and on, "My father doesn't get enough recognition." So I got very exasperated, and I said, "Monica, maybe he doesn't, but how many people have their equation on the floor of Westminster Abbey?" That stopped the discussion completely.
Maybe the idea was, she was drawing a distinction between reverence within the community and then name recognition in the broader public eye.
Yeah. Einstein was a public figure. Dirac was not at all. So for me, this Dirac medal was really a big deal. And it still is, except I haven't gotten it because of the pandemic. We cannot go and pick it up. And also, I'm in very good company. My friends, Neveu and Virasoro, who I knew a little bit, who never wrote an algebra, but, basically, he was at Wisconsin when he did that work, and he tried very hard to change it because it didn't look like strong interactions. To me, the Dirac medal was big, big, big.
Now that we're right up to the present, I'd like to ask, for the last part of our talk, a few broadly retrospective questions about your career, and then we'll end looking to the future. So first, and this is an impossibly speculative question, but a fun one nonetheless, knowing what you know now, 50 years since you started thinking about those things, how would you have initiated superstring theory differently? In other words, what do you know now that you didn't know that, which might've influenced how and when superstring theory came about?
Well, there were indicators of supersymmetry. But like all indicators of supersymmetry, or anything, you never pay attention to them. So this isn't superstring, this is just supersymmetry. In 1939, Wigner wrote a paper on the representations of the Poincare group, which we talked about. And he attacked it mathematically on the suggestion of his brother-in-law (Dirac), actually. But what happened is, in it, there were two representations. There were the usual ones that we're familiar with, which are identified with particles, either particles that move with the speed of light or particles that have mass and do nothing, but then, there were two more. And they were weird. Only two. And they were infinite dimensional representations, whereby when you made a boost, a Lorentz boost, you change the helicity.
Now, when you have a regular particle, like a photon, you can boost it all you want. It still has the same helicity. So how did you change the helicity? Well, there were two types of representation. One, when the helicity was going to half odd integers, plus or minus one-half, plus or minus three-halves, plus or minutes five-halves, etc., and the second one, when it went zero plus or minus one, plus or minus two, etc, and those representations are in the mathematical literature in Wigner's paper. They're there. And those, of course, are supersymmetric partners of one another. But in graduate school, I read that paper. I read it the way a graduate student reads. And it was there, but since there was no evidence in nature of these representations, nobody paid any attention to it. But if somebody had been looking at this, my goodness, somebody would've found it at some point. There was an interesting symmetry between them. Because in a supersymmetric thing, if you have a particle of helicity lambda, you get another particle of helicity lambda plus one-half. But only one value of lambda, one value of helicity at a time.
So this was the pattern. Now, Dirac could've done it. But I think he had enough on his plate. Because again, I think what happened with Dirac is a spectacular thing. In the early 1930s, he set up quantum field theory just like that. He did the monopole solution. And then, he came across this infinity problem in quantum electrodynamics. And then, he could not go beyond. He wrote a very nice paper in the 1940s. That paper is called the light-cone paper. The frontline, we are doing dynamics. How do you use dynamics from the point of view of a particle that's moving with the speed of light? So its only degrees of freedom are transverse because otherwise the Lorentz-Fitzgerald contraction does not allow you to do anything. You're just too busy moving with the speed of light. And he did that.
And now, of course, that's a very, very famous thing. He wrote some beautiful notes on quantum mechanics for constrained systems when he was visiting at Yeshiva. He did what great men do. But he never went back to the front, and he could've been in the front of the establishment for the next ten years. But he met these infinities, and that's all he was thinking about. And in a certain sense, I wondered what the equivalent was for Einstein.
That leads me to my next question. From your perspective, Einstein's misgivings regarding quantum mechanics, what has aged well and not aged well?
Well, I think the EPR Paradox stuff is kind of a hoax. You just have to be careful. When you do quantum mechanics, people say that words have meanings. Well, my God, every word is a measurement, and you have to tell a path of measurements, how you go from A to B. And when you look at a classical system, when you go from A to B, you don't pay attention to such things. You just think of what A was, what B was, and boom, there's a path to it. But it's much more than a path. By the way, Dirac did the path integral, too. In fact, in my book on quantum field theory, which I'm very proud of, I mentioned that to Dirac, and I went to Feynman, and I said, "I hope you're not getting mad at me for not giving you that much credit for this." And he said, "You absolutely are right." But he said, "Dirac didn't know how to use it, but I used it." And all he did was cancel infinity from the top numerator and denominator. And then, to use Feynman's thing, "Damn the torpedoes." Boom, and then he went.
So I think he was a great man. And I go back even to Newton at that point about the theory of light. Light being a particle or a wave. That was a concern. And it was forgotten for a long time. Until the advent of the photoelectric effect and stuff like that. And it became a wave. It was a wave. Everybody knew it was a wave. The 19th century was wave, wave, wave, wave, wave. But then, if you look at Einstein's paper on the photoelectric effect, he looks at that very carefully, and I don't think he was influenced by Planck, although I don't know. Because he said he was bothered by the lack of symmetry between particles and waves. He didn't understand why. He said he understood that the whole wave picture came in a particular approximation. But there's this beautiful paper in this issue of The Natural Philosophy. This is number two, and here, there is mark inclines on quantum. It's beautiful. So going back to Newton, he was upset about this, and I think that fundamentally, this great, great physicist knows that there's something that doesn't fit right. They don't quite know what it is.
So I think Einstein's thing is the same. It's not fitting right. Einstein never had any doubt that you could calculate stuff, but there was something that didn't feel right. And it may take quite a while. My hope is that the cosmological constant is a great hope for mankind. Because the next genius will calculate it. Now, as a historian, my analogy is Brownian motion. So Brownian motion was a fact found by a biologist, Mr. Brown, in 1820-something. But in 1905, Smoluchowski and Einstein, basically independently, calculate it using a statistical point of view. And in the Brownian case, there were measurements had been made. There was this French guy, Perrin, who had gotten more accurate measurements, and Einstein wanted to know about that measurement, how to explain it. So he does. But in the process, in order to explain that stuff, he finds a very large number, which happens to be Avogadro's number.
And so, immediately after that, the whole community changed. Because it gave him an idea of what the underlying theory of matter was. Whereas before, they were all complaining. So I think that somehow, the cosmological constant is one of those numbers where, basically, it will have an eventual explanation, but only at the expense of changing our notion of space time. Certainly space. And that somehow, somewhere, I wish I knew, there will be an explanation of that. And it's too easy to think it's like statistical mechanics redux. It's not. So that's a fundamental thing to look at. Descartes thought of the vacuum as full of vortices. For Newton, there was no vacuum. There was nothing. In quantum physics, we know the vacuum is full of fluctuations, full of stuff. So I think we're all converging to the notion that we don't know anything about what the vacuum is. And the Higgs mass is an example of that. The cosmological constant is another example of that.
The Higgs mass is a small number compared to the Planck scale. And all of these things are theory of what will be the new paradigm for what we call the vacuum or flat space time. That's where the answer will be. I wish I would know how to attack it. I don't know how to attack it. When Voltaire was on his deathbed, a priest was summoned. And he said, "Do you renounce the devil?" And Voltaire said, "No, now is not the time to make new enemies." Isn't that wonderful?
I have two more questions for you. One more retrospective, and one that looks to the future. As you well know, the broader physics community puts a special onus on string theory and string theorists to demonstrate that their work should now or soon be testable. From your vantage point, where is the patience worthwhile that string theory will be testable, and where is the testability of string theory already demonstrated in the here and now?
Well, I don't see any direct test. So what does it give you? A lot of people have been thinking there could be a lot of theories in extra dimensions. Whether that's string theory or not, I don't know, because Kaluza and Klein, a long time ago, were thinking one extra space dimension, and you can have electromagnetism, all these things. So the test will come not so much through string theory, I think, as much as through some field theories, with some characteristics. For example, if I find a bunch of supersymmetry at some level, and of course, the easiest way is to find these particles, and then see how they decay, that will not tell you it's string theory. It will just give to people some moral support for the fact that we're going towards that. There's another experiment, which is proton decay.
We haven't spoken about proton decay or neutrinos. Neutrinos are the one thing that we have in our hand where things have yet to be explained. And so, that is an insufficiency of the standard model. The amount of CP violation is going to be measured, the actual hierarchy of neutrino mass is going to be settled, all of that within five to ten years. And then, the proton decay. That is a game changer because we all believe that the proton should decay at some level because we need to generate the asymmetry between matter and antimatter. All our theories seem to believe that originally, the universe was matter, antimatter symmetric. And therefore, something happened on the way to the present. And so, we know that in the standard model, even if you have another violation you put in by hand, on some level, there's not enough to explain the observed asymmetry in the universe. There is still the hope of doing it through leptons. And the reason is, that comes through the breaking of lepton number, which then induces baryon number breaking. Because the combination B-L is conserved in your standard model, they are kind of linked together.
So once you break that symmetry, you don't know whether it's B or L, baryon or lepton. And so, that's what you get. And in the search for neutrinos, more and more things, was that you put a lot of matter away from noise, completely monitored, and in those days, those were called proton decay detectors. You just wait, and you have these billions and millions of protons, and you wait for one of them to decay, and you should see a burst of energy. That did not happen. However, what you did see, you did see neutrinos from the 1997 supernova. And then, what happened is, "Oh my goodness, we're going to change into neutrinos." So now, the whole industry, and the Japanese are at the head of this, they're still making a big amount of this Hyper K, which is an enormous amount of matter, and they will improve the limits under scrutiny with photo tubes all around. They will eventually give you a better limit on proton decay, but maybe they'll give you proton decay.
Now, if proton decay is observed, then you know that the past of grand unification is probably right, but it doesn't go and tell you its superstrings. In 1985, a year after Green-Schwarz, what people did, it was like an edict from the mountain. This is the theory that comes out. And everything was supposed to come out from the wash of strings. So you got E6, etc., but it didn't tell you any more than that. So it was not in a position to write down a particular number and compare it to an experiment. So all the things we need right now, I think, are just tests on the standard model. But the only thing that looks very strange is the cosmological constant again. Where the hell is it coming from? At the conceptual level, one has the Hawking path, that means the interaction between a classical construct, such as a black hole, which is real, and quantum mechanics–we haven't seen Hawking radiation, but it makes perfect sense after the fact. But this has to do with a conceptual thing.
So people have been trying to solve the so-called information problem. What happens to information once it goes into a black hole? And then, they've tried to explain it, and there is no explanation because at the end of the day, nobody knows what the hell is going on inside a black hole. So you have to make a hypothesis at some point or the other. But there is no real way. And so, there is a piece of the universe that is forbidden to us to access at the moment. And all we know is its effect on the environment, but we don't know what else is going on. Black holes are very much in the news, but remember, when they interviewed Kip Thorne soon after the announcement, he said he was disappointed. And the reason was because he expected to see a deviation from general relativity. Now, some people thought that was a disingenuous comment, but I think it was true theorist stuff. You're elated by the fact that these things happen, but on the other hand, you would like to see some chink in the armor of Einstein's theory. So this is the difference.
It's a good question. But I don't know how to answer it. I don't know how the pundits answer it. So they were answering it in 1985 by saying, "Oh, we can calculate everything for you. And then, you can calculate everything in terms of more parameters than you calculate." So you have consistency checks. Well, everything looks right. There doesn't seem to be any obstruction to go further. But the paths–especially the idea of supersymmetry look right now in terms of breaking.
One thing that is very interesting, which I don't understand, in condensed matter, people have discovered–so the Landau theory of spontaneous breaking needs to have an order parameter. You have an order parameter, the famous example, the Cooper pairs, are an order parameter. But there are also apparently phase transitions, which do not have an order parameter. Having to do with topology and stuff like that. Those things must play a role. Except I don't know what the hell it is. So I'm sorry to say, with all these things, it's hard to see the road ahead right now. But it would be good for particle physics if this G-2 experiment, for example–the public relations is a bit nauseating, but I understand, nowadays, you have to do it because you have to get more money to run better experiments, get more computing power, and everything else. I understand that. But at the same time, it's an important hint. But we don't quite know what kind of a hint it is. Because people have been working on the possibility for 50 years, really, that this is a crucial experiment to make, and therefore you basically should pursue it. But then, there are millions of scenarios that would give you a deviation. And so, it's difficult right now. But Rome was not built in a day to say the least.
Last question. Looking to the future, there are so many things, as you've indicated, that we don't understand now, but that there's some hope or cause for optimism that we'll crack the code at some point in the future. For you personally, however long you want to remain active and think about these things, what are you most curious about? What do you hope to understand about the universe in the next timeframe of your choice, whatever you feel like is reasonable? What are you most curious about?
This is also a good question. I'm not sure I know how to answer. There are sociological expectations. Evidence for any new particle beyond the standard model at the moment would do a lot of good. Whether it's a game changer is a different story. Everybody thinks those things are going to be game changers. We never spoke about dark matter. Dark matter, again, is something we know nothing about, except indirectly. It's an important thing.
What I always think about, what I would like to know, is this. The cosmology, the beginning of the universe, the nuclear synthesis of the elements, blah, blah, blah, and you go a few billion years later, and this is what you've got. The question is, are we really so sure about the initial conditions under which we operate? There are some discrepancies for the age of the universe. Experimental ones, apparently.
So there are ways of measuring it using data from the present universe, extrapolating backwards. And then, you have those from the cosmic background radiation, and they're supposed to be matching. And apparently, there is no match. Except I'm not sure I know what that is. Secondly, what about black holes and elementary particles? Is there an analogy between those? What is the genesis of dark matter in the supersymmetric view of things? There's one particle that survives and is stable, and that is dark matter. And there are numerical accidents. But again, the search for such a particle depositing energy on a bunch of detectors has not gotten anywhere. There is the axion. With due respect to my colleague, I feel that the axion does not tell me very much. It tells me there's just a global symmetry that is being broken spontaneously. And that explains everything, maybe. That would be very disappointing. But it could be that way.
When people talk about dark matter as being an important problem, well, I live in Florida. At least part of the year. We have children in Boulder, so we have a house in Boulder. So we'll go there soon. But because you live in Florida, do you think that silicon is the most important element? Because God knows we've got lots of silicon in Florida. So we don't know. We have no idea. That's why I called the standard model a cruel model. Because it's perturbative. It enabled us to go towards the beginning, shorter and shorter distances, way ahead of experiment. However, if proton decay occurs, it will tell us something because there will be some mediator for proton decay whose mass is huge. And you will know, depending on the couplings of the proton, the various channels. I know the main thing, but there will be different channels, partial width, and all that stuff. And anyway, it will tell you about how the world looked from the point of view of that big, big guy, how it couples to the various particles. I think proton decay is a game changer.
As for string theory, I don't know. Some people hope that some guy will have a very clever– string theory. What is missing a figure of merit. In 1985, people thought it would be easy to find a figure of merit in terms of the vacuum is populated by an infinite number of possibilities. And that's when they talk about parallel universes, etc. I have a 14-year-old granddaughter, who heard a Brian Greene talk. And Brian Greene is exceeding himself in speculation. But he's a very good speaker. Very persuasive. And he was talking about how to observe the universe. And I asked my granddaughter, "If we can observe it, isn't it our universe? It's not an extra universe. Because if you look at it from the point of the quantum mechanics of unitarity, and the unitarity tells you that if you get a new set of phenomena, you just increase your Hilbert space to account for this. So a lot of words go, but it is very nice.
A few days ago, Charles Thorn's wife, Mary Furman, sent me a cartoon with two cats. The two cats are talking to one another. And in front of them, there's a box with which to carry the cat to the vet or something. So one cat says to the other, "Oh, I feel good with this because when I get in it, I get home." Because of being at the vet. And the other cat says, "Is this what a wormhole is?" [laugh] I thought that was cute. Anyway, this is neither here nor there. But your question is a good one. I don't see it directly, except by somebody solving an important problem.
Well, we'll just have to wait and find out.
We have to wait and find out after lots of money and experimentation. Right now, we have to find out whether there's enough CP violation. Well, there are two experiments that are in front of us. One immediately in front. One is finding out the CP violation, the time reversal invariance in a neutrino mixing. Because we've got a big mystery on our hands there. Because we have two large angles and a small angle. Large angles, from my chemistry days, are faces of crystals. The second one is neutrinoless double beta decay. Neutrinoless double beta decay would tell me that lepton number is violated, and that some things are their own antiparticles and everything else. And that is very important. Because that gives you a way of generating baryon asymmetry because you're breaking total lepton number. That's what we would say.
So the experiment for the CP violation is going to happen probably in five to ten years. The neutrinoless double beta decay is going to be, I think, probably 20 years, unless there are some technological advances. So I don't know. On the other hand, we have CERN, this enormous machine, with improved detectors, improved computer reach, computing power, and everything. So maybe. But I'm very depressed because the fact is, at least the standard model, this beautiful thing, seems to be right, and just like after Newton, whatever people analyzed, they could analyze it in terms of Newton's laws. They did not have to change the paradigm. What changed the paradigm was a new set of experiments, and the voltaic cell. Because you could study electricity without getting killed. And then, blah, blah, blah. So that's why I'm thinking about all these things. So we're continuing the Einstein theory. And the insight he provided and his doubts, you should always take these people seriously. And this bullshit about people talking about Einstein's greatest mistake makes me mad. You don't play with the gods that way. But the little people like to play with the gods that way.
But the fact is, yeah, there's something weird with quantum mechanics. Feynman said he doesn't understand it. Gell-Mann and Hartle talking about all these measurements, whenever you make a measurement, the universe bifurcates it, all that stuff. Yeah, it's true, so what? The question is, what is the experimental proof of all that? How do you see this? It's mathematically satisfying that you have to look at the history, the Everett interpretation. But what are the experimental consequences? If you don't have experimental consequences, that's not physics. So that's very hard. But this is way beyond my pay scale. All my work in string theory was always started from simple things. I've done lots of calculations, which I can do, and you write papers, and do things like that, but say you have a feeling that you're missing the basic stuff. Because you should develop partial Alzheimer's. The tremendous amount of baggage that you have accumulated in your life in terms of knowledge that you think to be really true, but actually is not hinders you a great deal.
And so, I wish I could recover this kind of thing. But the mind is not quite the same. It takes longer to concentrate. It's not a big discovery. So to me, I think the cosmological constant is right there for a genius to understand. And what she will do, she will calculate the number by assuming a structure of what we call space that is so outrageous that nobody believed it. But by calculating this number, just like the analogue of the Brownian motion, she could duplicate that number. Then, people would believe.
Well, we'll have to see.
Pierre, it's been so fun spending this time with you. I'm so glad we were able to do this. Thank you so much.
Well, thank you so much.