Bob Sugar

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ORAL HISTORIES
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Credit: Bob Sugar

Interviewed by
David Zierler
Location
Video conference
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Interview of Robert Sugar by David Zierler on May 13, 2020,Niels Bohr Library & Archives, American Institute of Physics,College Park, MD USA,www.aip.org/history-programs/niels-bohr-library/oral-histories/44887

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Abstract

In this interview, David Zierler, Oral Historian for AIP, interviews Robert Sugar, emeritus professor and research professor of physics at UC Santa Barbara. Sugar recounts his childhood in New York and Ohio, and he describes his developing interest in physics in high school. He discusses his undergraduate education at Harvard, his early decision to focus on theory and his decision to go to Princeton for his Ph.D. Sugar describes his longtime collaboration and friendship with his graduate advisor Dick Blankenbecler, and his graduate research on phase shifts that appeared in scattering amplitudes. He discusses his postdoctoral research at Columbia, and his decision to accept a faculty position at UCSB. Sugar describes his contributions in building up the physics department into a major center of research, and he discusses his interest in Regge theory and the behavior in in the angular momentum plane. He discusses the development of the Kavli Institute and his growing interest in lattice gauge theory and describes its relationship to QCD. Sugar describes his collaborative work on MILC and explains how computational power has consistently lagged behind his theoretical interests. He explains how the priorities of the DOE and the NSF with regard to supporting physics has changed over the decades, and at the end of the interview, he discusses his long-term collaboration with Fermilab and his contributions as a mentor to young physicists.

Transcript

Zierler:

This is David Zierler, oral historian for the American Institute of Physics. It is May 13th, 2020. It’s my pleasure to be here with Professor Robert Sugar. Bob, thank you so much for being with me today.

Sugar:

It’s a pleasure, David.

Zierler:

OK, so to get started, please tell me your title and institutional affiliation.

Sugar:

Well, now I guess I'm a professor emeritus, or research professor, at the University of California Santa Barbara.

Zierler:

What does the designation “research professor” mean?

Sugar:

Well, it means that I can still do research. I can have grants. I don’t teach, but I spend my time doing research. And the university is kind enough to provide me with an office.

Zierler:

Very nice, very nice. OK, great. So let’s take it right back to the beginning. Tell me about your birthplace and family background.

Sugar:

OK. Well, I was actually born in Chicago, Illinois, but that was a bit of an anomaly. My parents and their families mainly lived in Cleveland, Ohio. My father was a metallurgical engineer who specialized in aluminum. And in the Second World, we moved to New Jersey, where he was running an aluminum foundry, which obviously was important for the war effort. And then we moved when I was in elementary school to New Rochelle, New York, where we lived until I was in tenth grade. At the end of tenth grade, our family moved back to Cleveland, and I spent my last two years at high school in Cleveland, Ohio. To be exact, in Shaker Heights, Ohio. And that’s where I went to my last two years of high school.

Zierler:

Now, what was your father’s educational background?

Sugar:

My father went to Case Institute of Technology which is now a part of Case Western Reserve, but at that time was an engineering school. And I guess he got a bachelor of science degree there.

Zierler:

Did he consider himself more of a scientist or an engineer?

Sugar:

I think he considered himself more of an engineer.

Zierler:

Now, in terms of your own developing interests in science, when did you start to distinguish yourself in the math and sciences? During high school? Earlier?

Sugar:

Well, I think it was in high school. I found it fascinating that there were a few laws of physics which could explain the physical phenomena we observe, and there were a few objects which were basic building blocks of matter. This sounded very interesting, very exciting. And it was reinforced when—I guess I was a high school senior—when I took a year long course in physics. There was a fantastic physics teacher named Wayne French, and he really inspired me to become a physicist. My father was quite supportive. He was happy that I [laugh] became a physicist, no question, but he didn't push me in any direction. And I wouldn't say Mr. French pushed me, but he inspired me.

Zierler:

Now, did you know you wanted to study physics when you were thinking about what schools to apply to out of high school?

Sugar:

Yes, I did. If you had asked me, when I was a senior in high school, what was I going to study, I would have told you right then I was going to study physics.

Zierler:

And was Princeton physics—that was the tops, as far as you were concerned?

Sugar:

Well, yes, but if we back up—so I was an undergraduate at Harvard.

Zierler:

Oh, I'm sorry, I read that—[laugh]. I read that upside down. [laugh]

Sugar:

[laugh] OK. But yes, I went to Harvard, because I thought that was just the best school. And then when I was at Harvard, the question was where would I go to graduate school, because there was no question in my mind when I was at Harvard that I wanted to go to graduate school and get a PhD and do research in physics.

Zierler:

Let’s stay on Harvard for a little bit. I'm curious about your impressions when you got to Harvard, the courses that were most intriguing to you, and some of the professors on the faculty that you grew close with.

Sugar:

I was not ahead of myself as many were. I just took the regular physics sequence, until my senior year, when I first of all took a course from Edward Purcell on basically I would say the need for quantum theory, the need to go beyond classical physics. It wasn’t the advanced course in quantum mechanics that Schwinger taught. I wasn’t ready for that. But it was a really interesting course. And Purcell was, again, an inspiring teacher. And when it was time to choose a graduate school, I was admitted to Princeton, and I was admitted to Harvard, and I forget if I applied to any other schools. I must have. And I went to Purcell and said, “What would be your advice?” And he said, “Well, we’d love to have you stay at Harvard, but it’s probably better if you go to Princeton, because you'll meet new, different people, and that’s always good. And you say you want to study particle physics, and there’s just no better place to do that than Princeton.” And so it sounded like very good advice. I think it was very good advice. And so I went off to Princeton.

Zierler:

Now, was there a senior thesis at Harvard?

Sugar:

No, there wasn’t. At Harvard, I was just taking courses.

Zierler:

Did you do any lab work during the summers or any other relevant internships?

Sugar:

During the summers—I think it was two summers—I worked actually in a nuclear physics lab. I had decided way before that that I was not cut out to be an experimentalist.

Zierler:

[laugh]

Sugar:

So I had thought that I was going to be a theorist, and my work in the lab tended to confirm that. [laugh] And then when I got to Princeton, they had just inaugurated a requirement that theorists must either work in the lab or do a project such as building a piece of equipment for the senior lab, for the undergraduate lab. And so I had to do that. And fortunately, one of my friends, Tom McIlrath was on his way to becoming a really outstanding experimentalist, so the two of us worked together. Working with him was terrific. It was not just fun, but he really knew what he was doing when I didn't know.

Zierler:

Now, I'm curious, when Purcell said that Princeton is the best place to be for particle physics, do you think he had in mind—was he thinking about specific people, or was he thinking about the overall emphasis, or the laboratories at Princeton? What do you think he was thinking about?

Sugar:

Well, I had already told him that I wanted to do theory. He himself was an experimentalist who won the Nobel Prize. I think he really meant the overall excellence of the department. And of course he knew that they had some very outstanding particle physicists. So it was a combination of those things, I believe. I don’t remember the details of our discussions.

Zierler:

And as an undergraduate, what was it about particle physics that was so interesting to you?

Sugar:

Well, it was that it was fundamental, that this was where the basic laws of physics, I thought, were coming from. And I wasn’t broadly educated in physics at the time. So, I didn't think about astrophysics, or condensed matter physics. What I knew about was that particle physics was just at the foundation to everything. So not terribly well informed, but—

Zierler:

[laugh] Well, it certainly worked out.

Sugar:

It all worked out.

Zierler:

In terms of you setting yourself up at Princeton, what was the process there like in terms of getting an advisor? Did you do that from the beginning? Did you sort of think a little bit about who you wanted to work with? Were you approached? How did that play out?

Sugar:

OK, well, I was thinking, as I was there, that I would of course have to choose an advisor, or [laugh] maybe persuade someone to take me on. But at Princeton, typically you took courses for two years, then you took a qualifying exam. And at that point, you would start research, and at that point you really needed to have an advisor. So I didn't until near towards the end of my second year.

Zierler:

So for the first two years, it was mostly course work.

Sugar:

That’s right.

Zierler:

And in terms of the course work, was it largely general, or did you focus your courses in particle physics?

Sugar:

Well, there were general courses, partly the first-year courses. It was quantum mechanics and electricity and magnetism, et cetera. But again, there were focused courses—I remember taking a course in particle physics from Sam Treiman, which was great. So, it was both. And there were courses in field theory, which were critical.

Zierler:

And so what was the process for getting connected to an advisor?

Sugar:

Well, I think at the time, you could walk in and ask someone [laugh] if they would take you on. And some of the people were very busy and already had a number of students and were not ready to take on additional ones. It was suggested to me that a very young professor in particle physics, Dick Blankenbecler, was really good, and he was not overrun with students, and I might talk to him. So I did, and he agreed to take me on as his student, which was one of the great things that happened to me. We worked together a lot and were just very, very good friends. I've known him for 55 years or so, something like that.

Zierler:

Had Richard been at Princeton for a while by the time you got connected with him?

Sugar:

No. I don’t know off the top of my head exactly when he arrived, but it was only a few years.

Zierler:

And what were some of the projects that he was working on during your time together?

Sugar:

Well, he was working on things like dispersion relations and particle scattering amplitudes and things which were quite topical. Also I think he was already at that time working on Regge poles.

Zierler:

And how did you go about developing a dissertation topic?

Sugar:

Well, it was interesting. So I knew it was the dispersion relation approach and S-matrix theories that were things that most of the senior high-energy theorists were working on. Goldberger, Treiman, Blankenbecler. And that’s what I sort of expected to work on. But Dick said, “Well, it would really be interesting to be able to calculate some quantities accurately.” And someone came by to give a colloquium on how to get upper and lower bounds on phase shifts that appeared in scattering amplitudes. Dick suggested that I take a look at that. And I developed some general ways of doing it, and then he said, “Well, how about applying it to a specific problem which has something to do with experiment, like the scattering of an electron off a hydrogen atom?” It’s a three-body problem.

Zierler:

When he said apply it to a specific problem, what do you think he was getting after, there?

Sugar:

He wanted to be sure I understood that when you are doing research in physics, it should be applied to real physics, not some completely abstract thing. So he really wanted me to end up with results. He wanted me to end up with results that could be tested experimentally.

Zierler:

Bob, that’s interesting. So is that to say that his concern—there was a legitimate concern that you could really do a dissertation that was entirely abstract, that was entirely disconnected from the physical world?

Sugar:

He didn't want me to do that. [laugh] .

Zierler:

[laugh] But that’s to say that such a dissertation could be done.

Sugar:

I guess.

Zierler:

[laugh]

Sugar:

But not with him as the thesis advisor!

Zierler:

[laugh] Right. And do you think that was simply his concern about the way that he wanted to develop you as a physicist? Or that he just thought generally that just physics should not be done like that?

Sugar:

No, he really wanted to teach me, and he did. [laugh] I don’t know. He was a terrific teacher. I mean, I remember we had these sessions where I would just be in his office, and there was a blackboard, and we were writing equations and discussing what it meant and what we were doing.

Zierler:

So of course this begs the question, how did your dissertation connect to the real physical world?

Sugar:

Well, [laugh] it did, because if you scatter a low-energy positron off a hydrogen atom, there’s a phase shift and that determines the low-energy cross-section. And so what I was supposed to do was calculate that phase shift and do it by having upper and lower bounds on what the phase shift was. Which I finally did.

Zierler:

To the extent that you thought about such things at the time, how did you understand your research fitting into the larger world of particle physics?

Sugar:

Well, that was interesting. I didn't think that—obviously, the scattering of a positron off[ a hydrogen atom was what the field of high-energy physics was looking at. But what it was doing was teaching me how to go about addressing problems, and hopefully developing techniques that might lead to some calculations in particle physics. It did, in a sense. It sort of naturally led me to be thinking about, OK, if you want to consider, say, scattering, say, two-particle scattering process of relativistic particles, you would like to write down equations for this which would guarantee that the scattering amplitude satisfied two-particle unitarity and didn't have any extraneous stuff in them. And I eventually did. This was of course much closer to what was being done in particle physics. Dick and I used those to study pi-pi scattering and the properties of the rho meson. The funny part was that 20 years later, 25 years later—I'm not sure—I have a nephew who is a chemist, and he said to me one day, “Are you the Sugar of the Blankenbecler-Sugar equation?”

Zierler:

[laugh]

Sugar:

I said, “What? What is that?” [laugh]

Zierler:

You must be!

Sugar:

I said, “Uh, must be, because both Blankenbecler and Sugar are very unusual names. So it must be.” And he said, “Oh, this is very, very widely used to study scattering in atomic physics.” He said, “You have hundreds and hundreds of citations for this paper!” [laugh]

Zierler:

And you had no idea?

Sugar:

I had absolutely no idea— [laugh]

Zierler:

[laugh]

Sugar:

—that this was the case. When we first did this work, there was minor interest, I guess I would say, but not a whole lot. And then to find out [laugh] that lots of people were interested [laugh] in this, just in a different part of physics. So I always thought that was amusing.

Zierler:

Who else was on your thesis committee?

Sugar:

Well, I remember Val Fitch was on my thesis committee, because—now, I don’t remember what the question was, but he pinned me to the blackboard [laugh] with an experimental question. And I think Sam Treiman was the other person on the committee. I'm not 100% sure, to tell you the truth. My last semester at Princeton, Dick went off on sabbatical to Cambridge, England, and left me in Sam Treiman’s care. Which was nice, because it allowed me to meet a different person and see how he did things.

Zierler:

Now, you defended in, what was it, the spring of ’64?

Sugar:

That’s correct.

Zierler:

And then what were you thinking about for your next move? What kinds of programs and institutions were you looking at?

Sugar:

Well, I was hoping to get a postdoc, at someplace where there was interest in high-energy physics. And there was a mix-up because while Dick was off in Cambridge, I got a letter from Leonard Schiff, who I thought was offering me a postdoc position at Stanford. And I wrote him a letter, which I thought was accepting that position.

Zierler:

[laugh]

Sugar:

But when Dick got back, he said—he was very surprised to hear [laugh] this, and I guess he talked to Schiff, and no, I [laugh] hadn’t been offered a position—

Zierler:

What was it that Schiff was writing you about, if not that?

Sugar:

I think he was trying to say, “Maybe you're interested in the job.” Not that he was offering it. Anyway, there wasn’t a job, or the job had been filled, or something. So Dick said, “Well, look, let me call around. Where would you think you would like to be?” And I embarrassed myself by saying, “Well, there is—I'm very much involved with a young woman who works in New York City, and so all things being equal, I’d like to be in New York.” And then as soon as I said that, I thought, “Ooh, I've disgraced myself. He'll think I'm not interested in physics.” But it turned out that there was a position at Columbia. That’s how I went there. I guess Dick had talked to some people there, particularly Mike Nauenberg, who was the person at Columbia at the time closest to the things I was interested in.

And yes, I married Joan, who is the woman who made me want to stay in New York. And Dick, he was just tremendously kind to her. I mean, again, we've been friends now for 55 years or something. And so he was fantastic. She was suddenly introduced to this world of physics, which she didn't know anything about, and didn't know any of the people. And he was just able to make her feel relaxed, and they became great friends. So I went to Columbia in the Fall of ’64, and the first thing I did was go to look for Mike Nauenberg and introduce myself. And he was busy packing all his books for his move to Santa Cruz! [laugh] So, not quite what I expected. But I had a good time at Columbia.

Zierler:

Now, was it a one-year postdoc that you renewed, or it was a two-year program?

Sugar:

It was a two-year visit. It was a two-year position.

Zierler:

I'm curious—when you were starting to go on the market for tenure-line positions, what was your sense of what the market was like in those days?

Sugar:

Yeah, well, I misjudged. In fact, I thought the market was good, and I was hopeful of a good position. So I was offered the position at Santa Barbara, and I was also offered a postdoc at SLAC. And of course, SLAC was much more prestigious, but it was a temporary position, whereas the Santa Barbara position was tenure track. And so I was not quite sure what to do, and I went down to Princeton—I of course talked to Dick, but I talked to some of the other senior people at Princeton. And the thing that I remembered most was that Murph Goldberger said to me, “Doesn't matter where you go now! You're going to move three or four times before you really settle down. So go where you think you'll do the best physics for the next few years.” So he was as wrong as I was.

Zierler:

[laugh] What were you impressions of Santa Barbara in those years? Clearly there was this overall mission to build up the program, right?

Sugar:

Right. Yes. Of course Santa Barbara is a beautiful place. At the time, Ray Sawyer was already there, and I had known Ray from a summer session at Wisconsin. Wisconsin in those days would invite a few people to come in the summer to do physics, and such. And so I had met Ray. And Jose Fulco was there. And I knew that the plan was to hire two more senior people, as well as me, and as it turned out, Jim Hartle. So it had the looks of being a very rapidly developing place.

Zierler:

Was your sense that it was developing across the board, or were there particular areas in physics that were being more emphasized than others?

Sugar:

Well, I had the impression that they wanted to build a broad department like the other UC physics departments, but it was clear that particle physics was going to be an important part of that. So I finally, maybe just in part because I tend to be a cautious person and this sounded more secure, took the position at Santa Barbara. And I think had I taken the SLAC position, I probably would have had a great deal of difficulty, because that's just when the market was falling out of jobs in physics, primarily because of the Vietnam War. So I was very fortunate.

Zierler:

Who did you see as the driving force behind building up the physics program? Was it the department chair more than anyone else?

Sugar:

No. Well, the fortunate thing was that there were several senior people, and not that senior, if you considered their ages, who provided leadership in building the department. Among the theorists, Ray Sawyer and Doug Scalapino were clearly the senior leaders. Now, when I came, Dick Blankenbecler also moved to Santa Barbara. He hadn’t told me he was even considering it, because he didn't want to influence my decision, when he didn't know what he was going to do. But he did come, for a couple of years, but then left and went to SLAC. But the people then who stayed in Santa Barbara were terrific.

And what I had meant to say and got a little sidetracked was that one of the great things was, yes, Doug and Ray were the leaders, but they really involved the younger people like me and Jim Hartle in the decision-making process within the theory group. And then within the department as a whole, there were some senior experimentalists like Vince Jaccarino and David Caldwell. The department really early on developed a tradition of being quite democratic and involving people, the young people as well as the more senior people, in the development. And that’s one of the reasons I think the department did so well over the years.

Zierler:

Now, did you see a pretty solid trajectory in terms of your own research when you got to Santa Barbara? Were you looking to continue what you were doing at Columbia? Or were you looking for new avenues of inquiry, new research projects?

Sugar:

I was looking for new research projects. Actually, I had started a new project just before—well, towards the end of my stay at Columbia. There was S-matrix theory. We didn't know what the theory really was, but we thought we could learn a lot just by using unitary or probability conservation and analyticity, how scattering amplitudes behave as a function of energy, or momentum transfer. Most of the early work had been involved to two-particle scattering processes.

I had started working on a project with Mort Rubin, who was another student of Dick’s, and George Tiktopoulos, who was a postdoc at Princeton. We started to study the analytic properties of three-particle scattering amplitudes, which are more complicated. And this turned out to be a longer project than we had first anticipated, and there were three long papers on it, which I thought were pretty nice.

But I also then became really interested in Regge theory, which told you behavior in the angular momentum plane and determined the high-energy behavior of scattering amplitudes. And so I had a bunch of things that I was interested in. It was a concern of mine whether I was going to be able to think of problems that would not just be interesting to me, but be interesting to other physicists. And I thought that the work with Mort and George was an interesting project, as was the later work on Reggeon field theory. These projects calmed my fears that I wouldn't be able to think of interesting problems to do. That was a concern at the beginning.

Zierler:

Now, at what point did you start thinking about what would become the Kavli Institute? When did you start thinking about that?

Sugar:

That was around 1975. As you probably know, the Institute was really the idea of Boris Kayser, who was the program director for theoretical physics at the NSF at the time.

Zierler:

And were you in direct contact with him, or you were just aware of his interests?

Sugar:

Actually, he spoke to Ray Sawyer about it. I guess that happened in Washington, I don’t quite remember. But I do remember that Ray had seen Boris and spoken to him, and came back and talked to Doug and me and Jim Hartle. And the request from Boris was that if we didn't like the idea, we should say that. If we liked the idea, we should write to him and tell him how we thought such an institute could be organized. So we did that and then were very pleased to see that the NSF had a call for proposals, which were not inconsistent at all with what we had been thinking about.

Zierler:

But even from its conception, the Kavli Institute was a very unique kind of place, right?

Sugar:

Oh, absolutely. And controversial, at the beginning.

Zierler:

Oh, how so?

Sugar:

Well, there were people who thought that this was not how theoretical physics should be funded—

Zierler:

I see.

Sugar:

In particular there were people who didn't think that the NSF’s money should be spent in that way. They preferred the traditional approach of funding individual investigator grants, and argued the more money that you spent on an institute, the less money there might be for individual investigator grants.

Zierler:

So what was your way of countering that line of thinking?

Sugar:

Well, it wasn’t clear that the money for individual investigator grants would go down. One hoped that there would be an increase in funding, total. And in any event, the basic idea of the Institute, which is that there are ever-changing problems, many of which crossed the traditional lines of the subfields of theoretical physics, could best be addressed in this way, because if there was a new exciting problem which maybe needed intense work for a few years, it was hard for a physics department, which is hiring people mostly for the tenure track, to keep changing directions.

And that was actually Kayser’s basic idea—that you wanted to address what we would call interdisciplinary problems, ones that cut across the subfields of physics. Or, from physics to chemistry, or physics to math or materials science or whatever. That with those sorts of problems, you would want changing sets of people working on them. And that's why an Institute based on visitors was thought by some of—by us, by Kayser, and some others—to be a good idea.

And then there were those people who, as I said, thought that that’s not what you want to do. So it was controversial. And the nice part was that most of the people who had opposed it, came around after seeing the Institute operate for the first few years. The original grant was for five years, and by the end of the five years, when we were applying for renewal, it wasn’t nearly so controversial. It was supported by many in the theoretical physics community.

Zierler:

Given the scope and just how—what’s the right word?—broadly conceived the Institute was, I would think that this would be the kind of place that might be more suited to a bigger program. So what was it about Santa Barbara, do you think, that made this work so well?

Sugar:

Well, there were several things. One is that we recognized at the very beginning, maybe more so than some of the other competitors, that this must be a truly national institute, not one controlled by a single physics department. There were, by the way, a number of sites competing to be the location of the Institute. There were a set of finalists, For example, Caltech was one of the finalists. The leaders of that proposal were Murray Gell-Mann, Kip Thorne, and—Murray Gell Mann.

Zierler:

Oh, so this was a zero-sum game? It was one place that got this, to the exclusion of the others?

Sugar:

That was the understanding—that if you broke the money up into several pots, you wouldn't have enough money anywhere to do what one hoped. But on the other hand—OK, I'm sorry. I lost my train of thought. But what I wanted to say was one of our advantages, I think, is we took very seriously the idea that this was going to be a national institute. And if it’s a national institute, what areas are the institute going to cover each year? Well, a national institute is not going to have four guys in Santa Barbara making all those decisions. So the very first thing after Ray came back from talking to Boris, was we sat down in his office and had a meeting, to draw up a list of people for the Institute’s National Advisory Board. And it would be those people, along with the director, who would make these decisions, decide on the scientific directions and so on.

Zierler:

I mean, was this like a David and Goliath kind of proposition? Did you think you had a chance when you heard about Caltech?

Sugar:

Well, yes. And you see, Boris, when he thought about it, said, yeah, he’d rather have Santa Barbara, because it wasn’t going to be a national institute if it were at Caltech; it would be a Caltech institute.

Zierler:

Meaning that Caltech would just sort of suck out the air from the entire thing just for itself.

Sugar:

Yes, they would use most of the money. And in fact, I don’t mind saying this out loud, because just a few months ago, there was an 80th birthday celebration for Jim Hartle, and Kip Thorne gave one of the talks. Kip himself said that in retrospect he was glad that Caltech hadn’t won, that Santa Barbara had, because that’s exactly what would have happened if it were at Caltech!

Zierler:

[laugh] Bob, I wonder if also part of the equation was that because it was baked into the concept from the beginning about visitors, that Santa Barbara is just such an awfully nice place to go for a little while. That must have been part of the equation.

Sugar:

Well, we certainly—if you read the original proposal, you will see [laugh] that that point is mentioned. [laugh] And that, yes, of course, it’s a nice place for visitors. What we didn't mention [laugh] was that it was no easy thing to get housing for visitors in Santa Barbara. Santa Barbara is a—it’s a resort place, and people—it’s just hard to get temporary housing. We had to work very hard at it. We had a staff member whose entire job was to get appropriate housing for visitors as they came. And there were typically at the beginning 30 people in residence at any one time, and now there are more. Now, however, that problem has completely disappeared, because Charlie Munger donated—I forget how many million dollars it was—to build a residence for people coming to the Institute.

Zierler:

With NSF, did they provide the seed money, or was this a long-term commitment?

Sugar:

Well, the NSF was very worried [laugh] because it was controversial, as I had mentioned. And they wanted to be clear that they were not making a long-term commitment. So much so that we originally wanted to call it the National Institute for Theoretical Physics, and they would not let us use the word “national” because that’s in National Science Foundation, and it implies a permanency that they were not willing to go with. So yeah, they were worried. They made a five-year commitment, and they made it clear that it was an experiment, and that there was no commitment to go beyond the five years. Now, by the time we got to the fourth year, it was pretty clearly very successful. We wrote another proposal and there was a review committee and so on.

But then you asked about funding, the seed money. At the beginning, the NSF provided the money, and oversaw the budget. The first budget was a million dollars. As time has gone by, responsibilities have shifted. There’s a director’s position and at the beginning, there were three permanent members. The permanent members—let’s see, the director was paid for by UCSB. And the permanent members, I think at the beginning, they were split. We couldn't afford to pay them off the one-million-dollar grant. But gradually, the university accepted more and more of the responsibility for the permanent members. Then everything else at the beginning was paid for by the grant, the NSF grant. But as time went by, the university contribution increased, and funds were obtained from elsewhere, but the NSF remained the largest funder—but now there’s even an endowment. There’s Kohn Hall, the main building, and then there’s Munger Hall, the residence. And they are increasingly paid from other sources.

Zierler:

I'm curious, to the extent you were aware of things from your vantage point in Santa Barbara, what was UCLA and Berkeley—what were they thinking about this? Is Santa Barbara sort of viewed as a brash upstart with the Kavli Institute? Were they supportive that at least it was on the West Coast? How did those things work within the UC system?

Sugar:

Well, UC Santa Cruz had a proposal, which wasn’t all that different than ours, although we had—they didn't have permanent members. They had a position for a director.

Zierler:

So it’s redwoods versus ocean is the two choices.

Sugar:

Right. I think an advantage we had was the four of us, who Kayser kept calling the Gang of Four, actually had a track record of working across subfield boundaries with each other. [laugh] So we thought we had—and it was one of the things we said, was that we had some real experience in the types of physics we envisioned the Institute doing. More so, for example, than Santa Cruz. There was a proposal from University of Illinois at Urbana, which of course has a very excellent and broad physics department. And then there was one from the New York area, which I believe involved Columbia and Cornell and Yale and a few others. So not chopped liver, by any means. [laugh] So it was a significant competition.

Zierler:

Maybe it’s a bit of a chicken and an egg problem, but I'm curious, around this time that you start getting interested, are you interested in lattice gauge theory as a result of the Kavli Institute being up and running, or did you develop that interest and you thought that the Kavli Institute would be a great place to work on this?

Sugar:

Well, actually there were two things for me that happened around 1980. One of them was the high-temperature superconductors, and that was very exciting. And Doug Scalapino was very involved and became one of the leaders in that field. And we talked about it, and the thinking was that the Hubbard model was likely to be a pretty good model for this, and we wanted to really understand what it predicted. And so Doug and I started to work on this and developed algorithms for doing numerical simulations of the Hubbard model. Not easy, because the basic particles are of course fermions, and simulating fermions is very hard because of the minus signs and such. So now you said, would we have worked on the Hubbard model if the Institute hadn’t been there? I think we would have.

Zierler:

It was certainly a great place to work on these things, though.

Sugar:

It was a great place, and there were some really outstanding young people, who became involved. And so I don’t think it would have gone nearly as well!

Zierler:

Bob, how well developed was quantum chromodynamics at this point, in 1980?

Sugar:

OK, yeah, well, let’s go back to that. Because that was the other thing that happened, at least to me, in 1980. OK, quantum chromodynamics I think followed directly from the discovery of asymptotic freedom on the one hand by Gross and Wilczek and Politzer, and that led to the theory. Then shortly after QCD was invented, Ken Wilson came along, showed how to put it on the lattice, and certainly had the idea of doing simulations, or doing numerical calculations, I should say.

Now, this is going to partly answer your question. Wilson had one approach to numerical calculations of QCD which was clearly going to require a tremendous amount of calculational power. Mike Creutz came to Santa Barbara to give a talk at the Institute and waved around a pack of IBM cards saying, “Here’s how you solve QCD.” And he and Claudio Rebbi had the idea of doing the Monte Carlo simulations. And that seemed very interesting to me.

And again, there were some really outstanding young people—Doug Toussaint, Tom DeGrand, Steve Gottlieb—who were interested, and we started working together. And again, I think it would have been pretty hard to do this without the Institute, which had brought these really terrific young people to Santa Barbara. So it turned out that it was fantastic for my career, even though my original participation was because I just thought this idea of the Institute was great and I wanted to help build it.

Zierler:

Just so that I understand this, what is the application of lattice gauge theory to quantum chromodynamics? Does it further QCD? What’s the relationship?

Sugar:

So you have a theory, QCD, which is defined in a four-dimensional space-time. And that’s hard to solve—really hard [laugh]. And what happens when you formulate it on the lattice is it’s the same theory, but you introduce a finite lattice spacing. And then you can calculate at least some quantities. Then you want to take the limit to zero lattice spacing, and that will give you the results for the full theory. Now, it’s better than that because you do know how various quantities will behave as a function of lattice spacing for small lattice spacing. And therefore you're not doing this blind. And that’s important. There was a point a number of years later when we were trying to get the Department of Energy to support the field of lattice gauge theory, both with computing power and funds, and we went to see Ray Orbach, who was the head of the Office of Science at the time. And Ray had this picture from condensed matter that, “Well, OK, you do it at one lattice spacing; then you might want to do another lattice spacing. You'll never get finished!” Which isn’t quite correct

Zierler:

What did he mean by that? Why would you never get finished? Because the calculations can just keep going on and on and on?

Sugar:

Yeah. I mean, every time you go to smaller lattice spacing, you need more computer power, and you won’t know when you're finished.

Zierler:

[laugh] Right.

Sugar:

Fortunately, we (Norman Christ and me) had taken along to this meeting—T.D. Lee and Frank Wilczek. And when we got to this point, Frank just gave this beautiful explanation of how asymptotic freedom for the continuum theory translated into very important knowledge for the lattice theory. I think it was crucial. But Frank was always very interested in and supportive of lattice gauge theory. Anyway, yeah, so both of those things happened in 1980. And there was a lot of fruitful work. There was the work on high-temperature superconductors, the Hubbard model and related models, and then the work on QCD or lattice gauge theory.

Zierler:

Bob, where does lattice gauge theory fit in with the more fundamental questions in physics? How does it help us understand the biggest questions about how the universe works?

Sugar:

Well, one of the questions which I think my own work is headed toward, but lots of other people’s too, is where does the standard model break down? Or does it? I mean, it’s quite amazing.

Zierler:

So that’s an open question—where does the standard model break down, or does it at all?

Sugar:

Yes, it’s almost—it’s inconceivable that it doesn't break down.

Zierler:

Why? Why is it inconceivable that it doesn't break down?

Sugar:

Because—well, first, if you just look at all the numbers and parameters that are involved, it’s not aesthetically pleasing. But it’s also true that with the Higgs fields in the problem, they're scalar fields and the theory is not really renormalizable. So the standard model is undoubtedly a—I'm grasping for the right words here—it’s an effective field theory; it’s not a really fundamental theory. And it can’t be, because of the scalar Higgs fields in the theory. But maybe more importantly it is the presence of all these parameters. So I think virtually everybody you go and talk to will tell you that this can’t be the end. Nevertheless, every time we test it, the standard model passes in flying colors.

So what’s going on? Well, one of the things you can do, and one of the things that certainly our group and many lattice gauge theorists are doing is to look to see where it might break down, where there might be a contradiction. And among those things is how the quarks couple to the weak interactions. There’s a set of parameters which are called the CKM matrix elements, which can be determined by a combination of experiment and a lattice calculation. And the question is, are there some places where there are tensions between different calculations of the CKM matrix elements.. So the idea is that you can calculate these CKM matrix elements, and do it in different ways, with different experiments, and different lattice calculations, and you can look for contradictions. And so that’s one way to go. There are also people who just look at other theories. But that’s really hard, because every theory requires a tremendous amount of calculation.

Zierler:

Now when you say you look for contradictions, is that to say that if you find a contradiction, there’s a problem with the theory?

Sugar:

Absolutely.

Zierler:

And the more fundamental question there is, it has to be a problem with the theory, because there’s no such thing as a contradiction in nature.

Sugar:

Well, that’s true.

Zierler:

So how do you resolve that? If there are contradictions in the theory and you say it passes with flying colors, how do you square that circle?

Sugar:

So what does it mean, “it passes with flying colors”? You can make a measurement of some decay rate, and the standard model tells you that that’s equal to some stuff with factors like two-pi and such, that you know about. And then there’s something like a leptonic decay constant or a semi leptonic form factor, things you could calculate on the lattice, times one of these CKM matrix elements. So if we calculate with great accuracy, say, a leptonic decay constant, and the experimentalists measure the full decay rate, , then that determines the CKM matrix element. But if we then go back and do a different process, we'll have a different leptonic decay constant but the same CKM matrix element, and the things better come out the same. And they do.

And some of these calculations are now getting very accurate. For example, our group and the lattice group at Fermi Lab, working together have calculated leptonic decays constants and quark masses to a fraction of a percent. You have to understand—I've been working on this area for 20, 24 years, and we started out—you were very happy if you got a 30 to 40% accuracy calculations, and now we're getting fraction of a percent results. Admittedly this is for some of the easier problems; not for everything, yet. But what it says is that it has become a very well developed field, where you can really learn a lot about QCD.

Zierler:

Now, is it M-I-L-C, or is it MILC? How do you say that?

Sugar:

MILC..

Zierler:

And what is the collaboration? Who are the main collaborators in MILC?

Sugar:

Well, first, just to finish answering your question, MILC, if you ask senior collaborators, they'll say it stands for MIMD Lattice Calculations. OK? So that’s why the final letter is a C instead of a K. On the other hand, I used to bore my wife over dinner talking about this, and my daughters decided that MILC stood for milking the government out of it all of its supercomputer time.

Zierler:

[laugh]

Sugar:

Anyway, when MILC started—there was me and Doug Toussaint, Steve Gottlieb, Claude Bernard, Tom DeGrand, Urs Heller, and Carleton DeTar. So those are the senior members. Now, Tom decided to pull out a number of years ago. So, he is not there any more. On the other hand, we have in recent years been working with people at Fermilab. So a lot of the papers that you'll see will not just say MILC Collaboration, but they’ll say Fermilab-MILC. And there, we have Paul Mackenzie, Andreas Kronfeld, Aida El-Khadra, and I'm probably leaving out a couple of the Fermilab people. So it has become a fairly large group.

Zierler:

Is Kavli the home of the collaboration?

Sugar:

No, no. MILC has nothing to do with Kavli, except it got inspired by the Institute we got inspired and maybe started on our way because of Kavli, but it’s a separate operation. The Institute could not support one group in one field over one period of time. That would be contrary to its charter, and it would not be the right way to use the Institute’s money. We did, in early years, hold summer meetings in Santa Barbara. But of late, there’s a summer meeting in Salt Lake City, where Carleton is, and a winter meeting in Tucson, where Doug Toussaint is, when Santa Barbara just became too expensive for our meetings.

Zierler:

Now I'm curious if you could talk a little bit about, what was the impact of supercomputing on your work? Did you rely on supercomputing a great deal to conduct this research?

Sugar:

Yes, although to say—well, back at the beginning, Doug Scalapino and I got a grant from the NSF to buy an array processor, which was an interesting machine. At the time the fastest Cray was a Cray-1, and for lattice calculations the array processor had about the same speed. And of course it was much less expensive. However, as time went on we used the array processor mostly for lattice gauge theory, but we also did use it for a couple of condensed matter problems. My one foray into assembly language programming [laugh], where I was instructed by Doug Toussaint, was in a condensed matter problem.

But then we switched. The array processor became outmoded, and we switched to supercomputers, and they provided the computing power. Although more recently—what, ten years ago or something—within the field; it wasn’t just us—the idea that you could build computer with just everyday components, the processors that would be in your laptop, and very fast interconnects, and put those together, and you would get very cost-effective machines.

Zierler:

I'm always interested at the interplay between advances in computing technology and the research. So for your career, what was playing catch-up with what? Were you relying on the computational power to achieve a certain level before you were able to go to the next step? Or was the computing power always ahead of you, and it was always available and ready to do what you needed it to do?

Sugar:

The first. We were always straining to have enough computer power. We never have enough computer power.

Zierler:

You mean to this day? You still don’t have enough computer power?

Sugar:

To this day. To this day. Orbach was right in that [laugh] respect. No matter how much computer power we have, we would always come back and ask for more. But one of the things at least that I was most pleased about was that at some point, we said, “Well, we have to get organized here.” The DOE was—and this was around 1990—wait a minute, is that right?—around 2000—decided to have an initiative in supercomputing. And our friends at the DOE, in the Office of High-Energy Physics, who were very supportive of lattice gauge theory—in fact one of them, Jeff Mandula, is himself a lattice gauge theorist—invited some of us to Washington to have a meeting to see how we would prepare for this initiative.

So we formed a committee, and for one some reason or another, I was asked to chair the committee and be the spokesperson for the group. And our idea was that we would learn how to take advantage of this initiative and get more computing power and funding for the field as a whole. Because it was made clear that what we did had to be for the whole field, which was only right. And so we worked on that. This initiative fell through. But we decided to keep on working.

Zierler:

Why do you think it fell through? What happened?

Sugar:

As I think often happens, just like the formation of the Institute for Theoretical Physics, there are competing desires, competing proposals. In this case, I think it just lost out to its competitors. But within a year—one to two years—the DOE came back and said, “We're going to resurrect—” They didn't say, “We're going to resurrect it”—“We have a new idea”—which sounded pretty much like the old idea!

Zierler:

Who were your main contacts in DOE? Was it the Office of Science mostly?

Sugar:

Yeah, it was the Office of Science. And in particular, within the Office of Sciences, there’s an office, as you know I'm sure—a high-energy physics office, and nuclear physics. And it was those two offices that were our contacts, and we talked to them.

Zierler:

So what was their idea?

Sugar:

Well—oh, and I shouldn't leave out ASCR, the Office of Advance Scientific Computing Research. And our ideas didn't mesh. ASCR’s idea was that they would be given a lot of money to buy some supercomputers, and then make them available for all of the different scientific offices. Our idea, which we had already started to initiate, was that we would make machines specially constructed for QCD, and this would be much more cost effective, and that was the way for us to go.

Well, there were two types of those machines. Norman Christ at Columbia is the originator of one series of specially designed machines. And for the other, our friends at Fermilab were interested in building clusters out of everyday components that would be very cost-effective. So we pursued both of these directions, and we were fortunate to get the DOE to fund them. And for a number of years, we worked in this mode. And to this day, we still have clusters that at Fermilab and at Jefferson Lab and at Brookhaven, that are dedicated to the field. But more and more, we're using the big supercomputers that ASCR and the NSF run.

But it was very good, very educational. Of course, working with this many people with different ideas, is not so easy, but it did in fact work out. One of the things that made it a little easier was we had basically all the lattice gauge theorists in the U.S. And we weren’t telling groups what to work on. We were saying, “There’s computer power available. A resource available. There is money to support people to help us with the software, which turns out to be a big thing.” So it has worked out amazingly well.

I was the chair of the executive committee for the first ten years, which was basically 2000 to 2010, and then Paul Mackenzie at Fermilab was chair from I guess 2010 to 2019. And now Andreas Kronfeld, Fermilab, is doing this. It’s a huge amount of work to keep this going. But we do have a fairly democratic system, both for choosing directions and for yearly proposals for computer time, and we have to distribute that fairly, and also—not just fairly, but to make the field go forward.

Zierler:

So in terms of the directions that the field goes in, from your vantage point as chair of the executive committee two generations ago to today, how have those directions changed over the decades?

Sugar:

There have been some basic directions that haven't changed. I mentioned the calculations having to do with coupling of quarks to the weak interactions, and how that then affects decay processes. And that remains one of the big directions in the field. There are other people who are exploring other theories beyond the standard model. And there’s more of that now than when we started, for sure. There’s high-temperature QCD, which is important for the heavy ion collisions.

Zierler:

Interesting.

Sugar:

And then there’s nuclear physics, low-temperature nuclear physics. And I think that that has grown in importance and they have become more and more adept at doing those calculations.

Zierler:

Bob, I want to come back to something you said earlier, which was intriguing, and that’s even today the supercomputing lags behind what you needed to do. Obviously, supercomputing today is unbelievably powerful. How is it still not up to snuff in terms of what you needed to accomplish?

Sugar:

Well, OK, I don’t think it’s fair to say it’s just computing power. The systems we're trying to simulate are huge. The largest lattice which we're working on right now is 144 cubed by 288. That’s the number of lattice points. And you're manipulating files which are tens of gigabytes. But as the lattice spacing gets smaller, you need to have bigger and bigger lattices, more and more lattice points. But the basic calculation, which is to determine the propagator of a quark through the current gluon field that your simulation is working on takes more and more computing power. This calculation involves inverting a huge matrix—144 cubed by 288 in that one example I gave you—and the matrix becomes increasingly ill conditioned as the lattice spacing decreases, and as the quark mass decreases. So as the quark mass gets smaller and smaller, you can do more accurate calculations as we knew, but you need more and more computing power.

And in fact, we have only in recent years gotten to the point where we can perform simulations with the masses of the up and down quarks, which are the two lightest ones, at their physical values. It used to be that you had to do calculations with the up and down quark masses larger than their physical values, and then extrapolate to the physical masses. Well, you lose a lot of accuracy when you do that. So we worked very hard and the computer designers worked very hard, and we're now doing calculations at the physical quark masses. But it has created another problem, namely among the most important quantities in the weak interaction calculations are the bottom quarks. Now, the bottom quark is really heavy! And what has to fit on the lattice is the lattice spacing times the mass of the bottom quark. And unless the lattice spacing is small enough so that that product is less than one, you are going to have all sorts of finite lattice spacing effects, which will affect the accuracy of the calculation. So we still haven't reached nirvana, because the bottom quark mass is too heavy. But we're just learning how to deal with that.

Zierler:

Can you conceive of a time when the computational power will be enough to satisfy your needs?

Sugar:

Oh, sure.

Zierler:

What might be a timeframe for that?

Sugar:

I don’t know.

Zierler:

I mean, I'm sure you've been following—computational power increases exponentially, right?

Sugar:

Well, sure. And our ambitions—

Zierler:

[laugh]

Sugar:

—increase exponentially. No, we're getting there. I mean, the DOE is always pushing forward. There’s this exascale initiative, which we're part of, which is going to give us a very big boost. But again, these are four-dimensional lattices, so you want to halve the lattice spacing—you're increasing the problem by two to the fourth for volume effects alone. It takes a lot of computing power to put you up a step. But as I said, there are some quantities that are now being calculated to a fraction of a percent precision, which is awfully encouraging.

Zierler:

Bob, now that I think we've taken your work substantively up to the present day in terms of the narrative, I want to now ask you some questions that are sort of broadly retrospective, over the course of your career. And the first one is your assessment of—I mean, you've been involved with science and government policy for so many decades. And I'm curious—a very broadly conceived question—how has that relationship changed over the years? What are the kinds of things that the NSF and the DOE have emphasized, and how has that changed in the many decades that you've been involved with these projects?

Sugar:

Well, good question. [laugh] Let’s see. [pause] I mean, one of the things that I think is very good is that they have—there has been some real flexibility in the system. They have been willing to try new things. And just the examples that have directly affected me, like the Institute, USQCD, the lattice gauge theory groups—there was a time when they couldn't have—I don’t think they would have happened. But there is some real flexibility in the system, and you have some people who are willing and able to take initiatives, like Boris Kayser and Jeff Mandula. There are also of course people in the system who are much more rigid. But the system will support innovation, and that’s tremendously important, I think. So that’s one. I perceive that as a change, but maybe it’s not. Maybe it was my lack of awareness in earlier times. And of course, it goes up and down as things get tighter or looser with the funding. You can’t expect these agencies to take a lot of risks in very tight times.

Zierler:

My next question is about your overall relationship in terms of collaborations with the national laboratories. Do you view it essentially as like a yin and yang relationship, where you need things that only they can do, and they need things that only you can do in an academic research environment?

Sugar:

I don’t quite see it that way. As I mentioned, we have a long collaboration now with Fermilab, which has been very fruitful, I think, for both groups. We wouldn't have been able to do some of the things we're doing certainly without our Fermilab co-workers—and in the case of USQCD, it’s not just Fermilab, but Fermilab, Brookhaven, and Jefferson Lab. Without the labs, we would have had to structure USQCD in a very different way, and it probably would not have been nearly as fruitful. So yes, there’s an example. The Kavli Institute doesn't depend too much on the labs, although we do certainly have people come and visit from the labs, just like they come and visit from universities.

Zierler:

I'm curious, Bob, how closely you followed the narrative of the rise and the fall of the SSC, from ’89 to ’93. When that was first being proposed, was this personally exciting to you? Was it potentially going to offer things that were going to allow you to take your research in new directions?

Sugar:

Well, of course, had it been built [laugh], I guess it certainly would have. Although I must say that I thought at the time the amount of money people were asking for just seemed to be too much. I didn't think that that could be pulled off, and wondered whether it would have been better going for something smaller. Now, I was not involved in that in any close way, so I didn't know—I didn't have the right to an opinion. I would say I was worried about it. There are limits to how much you can ask for. I had seen that come up in some lattice gauge theory initiatives, and there were people who wanted to ask for amounts which would have certainly been great for the field if one could have gotten them, but it seemed to me were counterproductive, because you're asking for so much that you couldn't possibly get funded, and then that hurt your credibility.

Zierler:

To bring the story forward, I wonder, given that in some ways CERN picked up what the SSC would have done, I'm curious if you’ve had any collaborations in CERN. If they've advanced your research.

Sugar:

No, I haven't. Is that right? Well, two things. I certainly had a collaboration with Alan White, who was a young, outstanding theoretical physicist at CERN. He was at CERN when I first met him, and I really enjoyed that. At the same time, we got John Cardy to come to Santa Barbara from CERN as a postdoc. I was working on Reggeon field theory, and so was John , who was just a young postdoc at the time. He left Santa Barbara and went to CERN as a CERN Fellow. And then after a couple years, he came back as an assistant professor. And that was one of the great things that happened to Santa Barbara. He is just fantastic. He’s won the Dirac Prize and the Boltzmann Medal, and just played a leading role in both high-energy and condensed matter. physics. And on top of that, he is a fantastic teacher. [laugh] So yeah, CERN did something great for us [laugh] there.

Zierler:

Bob, one topic we haven't really touched yet is on your career as a teacher and a mentor to graduate students. So first on the teaching side, for undergraduate courses, what have been your favorite courses to teach undergraduates?

Sugar:

Well, there was a period of a few years where I taught introductory physics for physics majors and engineers, and such. And I enjoyed teaching that. There were some really good students in those courses. But most of my teaching has actually been in graduate courses.

Zierler:

And does Kavli have a teaching infrastructure itself, or all the teaching is done within the physics department?

Sugar:

No, it’s all done within the physics department. Kavli, from time to time, has had summer schools, but they have not been UCSB summer schools, they are Kavli summer schools. It’s different. A number of them have been in biophysics. And my understanding, even though I know nothing about that field, but I've been told, that those have worked out very well.

Zierler:

In terms of your work as a mentor to graduate students, obviously you can’t name everybody—I don’t want to put you on the spot—but who have been some of your most successful graduate student or postdoc collaborators?

Sugar:

OK, let me see. Well, I just mentioned John Cardy. He’s probably—any objective person would say he was my most successful postdoc, although the truth is, he was more my mentor than I his mentor. He was just terrific. Richard Scalettar who worked on some of these high-temperature superconductor calculations is now a professor at UC Davis, and was terrific. He was a joint student of Scalapino and mine. That was great. There was Steve White, who was really Scalapino’s postdoc, but I worked with him a lot while he was here. I thought very highly of him. Doug Toussaint came here as a postdoc. He got his PhD from Princeton and came here. And he’s fantastic. He’s one of the leaders of the field of lattice gauge theory, and he’s also a really nice guy. [laugh]

But then there were other extremely good people like Steve Gottlieb, and Urs Heller. Urs was a postdoc here. Steve was actually not a postdoc here, but he was a good friend of Toussaint, and Toussaint had started working with him, and I worked with him for years. And so those are the young people who come first to mind. As you say, I can’t possibly name them all.

Zierler:

No, no, no, you can’t name them all. I am curious—given the fact that you've been sort of part of the overall expansion and excellence of the Department of Physics at Santa Barbara, if over the years, really starting with the building and growth mode that they were in, that you were part of in the 1960s, has Santa Barbara really been able to attract top graduate students?

Sugar:

It is now. Now, it’s interesting—of course, after we got going [laugh] in the seventies and the eighties and so on, we were certainly able to attract top faculty, and get many great people. As the faculty got better and better, we were able to attract better and better postdocs, and then better and better graduate students..

Zierler:

And where did Kavli play into all of this? Was it always part of the equation for people making these decisions?

Sugar:

Well, I'm sure it was. It wasn’t that they were being—well, there were postdocs at Kavli, but there were also postdocs in the department. So it wasn’t just one or the other. But certainly having the Institute here made this an attractive place, a really attractive place, for postdocs. Because they could come to Santa Barbara and, in two years or three years here, interact with all of the best people in physics. Name almost any field, and Kavli would have a program in it. We tried to make it not matter, whether your office was at the Institute or in the physics department, and where your paycheck came from. So yeah, I think that for postdocs, this became a very attractive place. And we saw the difference in the institutions we were competing with for postdocs., people who were at the top of our list. They started to be Princeton and Harvard and Caltech. And of course not every one of them came, but just the quality of people who were seriously considering it seemed very good. The quality of the graduate students, improved more slowly, which is completely naturally.

Zierler:

There’s going to be a lag behind the professors, you're saying.

Sugar:

There’s going to be a lag. The graduate students lagged behind the postdocs, and the postdocs lagged behind the professors. Nevertheless, I think we now are getting very good graduate students. But certainly that took longer.

Zierler:

Bob, I think I want to ask, for the last part of our discussion, I want to ask you some sort of broadly introspective questions about the development of the field over the course of your career. And the first one is, looking back on the questions that you were looking for answers, way back from your dissertation and fast-forwarding all the way to today—and you can either answer personally or as a representative of your field—what are some of the things that were very poorly understood or not understood at all in the early 1960s that are really understood very well now?

Sugar:

I think the strong interactions are a prime example, and it’s one that I've been interested in working on. We didn't understand in the sixties—well, QCD didn't exist, and so we didn't know what the theory was, and we were wandering around trying to compute things and see what was important without really having a theory to base it on. And whereas today, there’s theory of the strong interactions, and you can calculate a lot of things in that theory, and you can use it as a probe now to test other parts of the standard model. So it has come a long way.

Zierler:

And to flip that question on its head, what are things that were unknown or mysterious in the 1960s that remain unknown and mysterious?

Sugar:

I was going to say, why does the standard model work so well? But of course the standard model didn't exist [laugh] in the 1960s. So how could it—[laugh] but I mean, I think you get the point.

Zierler:

What is the state of the standard model today? You've been paying attention to it so closely for so long. Where is it now?

Sugar:

As I said, it works amazingly well. There are plenty of things we don’t understand. Why do neutrinos have mass? What’s the Higgs field doing? So some of these are pretty old questions which we still don’t have answers to.

Zierler:

And what do you think it will take to get answers to these questions? Is it more about waiting for the technology? Is it a stroke of genius? Is it more grinding out the equations and the lab work? How do you see these things working together to advance discovery in the future?

Sugar:

I think first of all the most likely to advance the field is more experimental information. I guess that’s always true. And that will come. So the CERN machine is certainly a key, and one hopes that there will be something beyond it, but [laugh] we're talking big money here. But I think that’s it. I think some of these calculations that we and other theorists are doing may shed some light on where things are going wrong, but it’s not likely to just by some stroke of lightning, it’s “Ha! Now we understand it.” Probably not. So, again, experiment is probably the thing. But theorists have a role to play here, certainly. I don’t want to undercut it.

Zierler:

Bob, I think for my last question, I want to ask you something that’s forward-oriented, looking toward the future. And that is, either in terms of your own ongoing work or the work of the field, where it’s headed next, what are you most excited about? What are you most interested in seeing in terms of development, in terms of avenues of inquiry, in terms of possibilities for discovery, looking ahead?

Sugar:

[pause] Well, again, I think I am being a little repetitious here, but no, I would really like to see these questions about the weak and strong interactions. I’d like to understand of course what dark matter and dark energy are all about. Those aren’t things that I worked on, but it’s obvious [laugh] that they're extremely important. And it may very well be that we learn more about astrophysics through gravity wave detectors, too. So those are really big things.

Zierler:

And I guess a more concentrated way of asking that question is if a graduate student came to you and they were strong in all areas and they were interested and bright in every which way, and they asked you, “What should I work on? What field do you see most exciting, most fortuitous for a career?”—what might you recommend?

Sugar:

Well, I'm not sure. Gravity is an obvious one. I'm a little disillusioned with string theory, which—obviously if we can make progress, it would be very important, but it seems to me that we've—not me; others smarter than me, who have been working on this for a long time, have not made as much progress as one might have hoped. In the long run, string theory may cast a lot of light on physics, but it doesn't seem to be happening quickly, so I don’t know if that’s the right thing for a graduate student to start working on.

Zierler:

Well, Bob, it has been an absolute pleasure talking with you today. I want to thank you for your time.

Sugar:

Not at all, David. I enjoyed it a lot.

Zierler:

Wonderful, wonderful.