Physics of Scale Activities

Wilson interview
 

Interview with Kenneth G. Wilson, 6 July 2002

Interview recorded in Gray, Maine.
Interview conducted by PoS collaborators: Babak Ashrafi, Karl Hall, and Sam Schweber.
Edited by A. Martínez and S. S. Schweber.

KGW

    I've come to realize that one of the most important dates in all of history is the date when people started making videotapes. And that will vie with the date that Gutenberg invented printing.

PoS

    Or very close to it. While we were coming down in the car, I was thinking that it would be really helpful to us if you could go back to your days as a graduate student. I think we know something about the background for your undergraduate days. I think it would be helpful to go back to Caltech and have you tell us about learning physics and, in particular, learning quantum field theory, renormalization and all those things at Caltech, beyond what you said in your Nobel lecture.

KGW

    I came to Caltech in 1956, and what I didn't realize was that for all practical purposes, I had already completed a Ph.D. Working with Arnold Arons specifically during junior and senior year. I did a project, I wrote it up. It was never really published, but it could have been. I spent a year taking courses at the same time that I - just for kicks - worked in the nuclear physics laboratory on an experiment which was supposed to reproduce parity violations, but never succeeded.

PoS

    Were you already learning some many-body theory at that stage?

KGW

    No, I didn't learn any many-body theory. It's just that I had done all the work of a thesis and I was clearly self-propelled then. I took courses, but it was boring.

PoS

    You did nuclear physics at Harvard or at Caltech?

KGW

    No, at Caltech. This was after I'm finished with Harvard, I'm at Caltech. And so the first year, I'm taking courses like the quantum field theory course. I can't remember. I had taken the chemist's quantum mechanics course at Harvard, so I think I was taking quantum field theory first year, but I can't guarantee that.

PoS

    And just to go back, when you said you essentially had done old thesis work already when you came to Caltech, can you say specifically what is it that you had done?

KGW

    I did a theoretical study of calculating propagation of sound in an ocean that had both a layer at the top of both constant temperature and sound velocity and then a thermocline underneath, which means a variable sound velocity. That meant there was a shadow zone because sound rays would come up to the surface, the rays would reflect and then go down again in the surface zone, they were caught because the rays were straight. There was a special ray that would come up, just graze the surface zone and then head down; and there was a shadow zone beyond this special ray. I worked out the theory of how the sound penetrated into that shadow zone. Arnold Arons, who was supervising, didn't know the mathematics that I was looking at, but he was, in a sense, probably a better supervisor than anybody I had at Caltech. So, once at Caltech, I did an experimental project in my first year, basically for fun.

PoS

    And this was with?

KGW

    Willie Fowler and people like that... I forget who.

PoS

    Tell us about your courses.

KGW

    I was just taking courses, and of course, at some point, in the period that was either the first year or the second year, I took the quantum field theory course.

PoS

    With [Richard] Feynman or [Murray] Gell-Mann?

KGW

    No, it was neither of them. It might have been [Robert] Christy, I'm not sure. I also became friendly with Jon Mathews. He and I would go on hikes and talk. Gell-Mann and Feynman were the big cheeses, but I spent very little time actually with Gell-Mann, and with Feynman. The third year I was there, Gell-Mann was off in Europe. Gell-Mann had urged me to come, too, but I wasn't ready for that. And so during the third year, there was a seminar that was run by Feynman, and that was very interesting. Feynman read my thesis because Gell-Mann was still away.

PoS

    This was all the time when Feynman and Gell-Mann were doing weak interactions.

KGW

    That's right.

PoS

    And how far did the quantum field theory course go? I mean, if it was Christy, did it included renormalization and all of these things?

KGW

    Oh, yes, at the heart of it, it was just QED-type renormalization. One of the texts that I certainly studied at the time was [N. N.] Bogoliubov and [D. V.] Shirkov. I think there was some other texts that we had, but I forget what it was.

PoS

    Bogoliubov and Shirkov didn't appear in English until 1959. So does that fit with what you're talking about?

KGW

    Oh, so it could well be that I read that afterwards.

PoS

    Berestetskii: does that ring a bell?

KGW

    You mean Akhiezer and Berestetskii? I remember...

PoS

    It wasn't so widely available because it wasn't officially published. It was simply translated by the AEC or something like that.

PoS

    Right, right, it was widely circulated.

KGW

    Well, there's no question that the field theory course I took in either in 1956 or 1957 or 1957/1958....

PoS

    Did it get as far as something like Gell-Mann/Low or Bogoliubov/Shirkov -style renormalization theory?

KGW

    No. That part I read on my own, I'm pretty sure.

PoS

    Well, it could be that you saw the Bogoliubov and Shirkov article in Nuovo Cimento.

KGW

    I know I came away with that book, so I'm sure there was another book that we were using. And I know I reacted very negatively to the book, too. It was so ad hoc, I couldn't stomach it.

PoS

    Field theory in general or renormalization theory?

KGW

    The renormalization procedure.

PoS

    Do you recall at what point you became familiar with the renormalization group, say, Gell-Mann/Low?

KGW

    Sometime toward the end of my second year, I started working with Gell-Mann. I went to Gell-Mann and he gave me a problem to work on and suggested I start working with fixed source theory of K-particles, where he wanted me to do things involving strong and weak interactions. And it's when I read about fixed source theory that I began to learn about renormalization group and realized it could be applied to fixed source theory, and I don't know whether there were papers that I read about renormalization group and fixed source theory, or I worked it out for myself, but in playing around with this, sort of trying to learn what was going on, I discovered that there were great simplifications that took place when you took the fixed source equation and took them to high energies, and when you did a leading log approximation. In the end, I discovered that those equations, simplified at the high energies -- you could get exact solutions. That was part of my thesis. And that was the initial thing that sparked my interest in the renormalization group. I remember when I presented my thesis to a seminar, and this was when Feynman was there, but not Gell-Mann. I went through all this exciting mathematics and toward the end, someone said, "Yes, that's fine, but what good is it?" I remember Feynman's answer as "Don't look a gift horse in the mouth!"

PoS

    So you come away from Caltech having really worked hard on renormalization group methods and the thesis is essentially what gets published early?

KGW

    No, the thesis was never published. I don't remember if I actually ever published the exact solutions of the fixed source theory.

PoS

    So at that time, who else did you know who was looking at issues with renormalization groups?

KGW

    No one. There was the work coming out of Russia. I mean the papers of Bogoliubov and Shirkov. I don't know when they stopped publishing on renormalization theory. I don't think they did anything through the 1960s as far as I know.

PoS

    I think Shirkov was off doing strong interactions.

PoS

    And so you feel pretty isolated in terms of people not understanding you or knowing what you did on your thesis when you talk about it. You come back to Harvard afterwards.

KGW

    Yes, I come back to Harvard, and at that point, I picked up with S-matrix theory and I tried to work with Mandelstam's bootstrap approximation and I tried to program a numerical solution. I tried to use the MIT computer and that went exactly no place, because I could look at the output only once a day. And you can't do computing on that basis.

PoS

    Your interest in computing and the relevance of computing and all of these things comes from where?

KGW

    That gets started in graduate school. Jon Mathews was the one who took me over to the Jet Propulsion Lab... It had some kind of machine which ran on paper tape. I think it was some kind of Burroughs machine. He showed me how to use it and I did simple programming things with it. I forget whether I was actually able to do anything useful or not, but I certainly got interested. So I was fascinated with computers starting from that point.

PoS

    And the philosophy which stems from saying that unless you can get numbers out... stems from where?

KGW

    All through my undergraduate days, I was fascinated with the question of how you approximate mathematical equations in order to solve them.

PoS

    And when you say you were fascinated, what stimulated you to think that way?

KGW

    Well, the strength I had, starting much earlier, was in mathematics. I learned calculus from a book that was given to me when I was in the eighth grade (in ninth grade we were in England for a year). There's no question that I had learned the essence of what calculus was all about before I went to England. I wasn't able to do very much... I went to two years of prep school after ninth grade and I wasn't able to do very much then because there wasn't anyone around to work with.

PoS

    But the fascination of approximation... Somehow, you were willing to consider approximate solutions. And perhaps that was the best one could do.

KGW

    That's right. That certainly built up as I went through the math courses as an undergraduate. And, of course, it was strengthened by the work I did with Arnold Arons. Here there was a need to actually do a problem and get approximations. And I remember early in graduate school, one of the things that happened at the end of the first year of graduate school, I had signed up to spend a summer working at Los Alamos on plasma physics. I was going to see what that was like. And then the whole Los Alamos group was going to go to this big international meeting and so I quick-switched to go to General Atomic and worked with Marshall Rosenbluth instead. So I spent a summer working on plasma physics and I think it was at that point that I got fascinated by the guiding center approximation for the motion of particles in almost constant magnetic fields. I remember working a lot on trying to understand -- you first have to study that circular motion and then you have to extract from that a set of equations for the motion of the center and the whole concept of that kind of approximation. So whenever something involving approximation would come up, I would always sort of keep working on it.

PoS

    And at this point, this was all on paper, or were you using computers?

KGW

    This was all on paper. I did do a dogwork project for Arnold Arons on the osmotic pressure of sea water. I don't know if we had a desk calculator at that point or not.

PoS

    What kind of exposure did you have to statistical mechanics at Caltech?

KGW

    I had to pass a thermodynamics course, which I did by never going to lectures, just reading [Enrico] Fermi's book and taking exams. But I don't think I had to learn anything more formal than that.

PoS

    When Gell-Mann handed you the problem of the three-dimensional Ising model...

KGW

    I didn't do anything with it.

PoS

    Did you look at it? Did you research it?

KGW

    No. I think that was my going into his office and asking what he was working on, and he wrote down the Ising model and told me it would be nice if I could solve it.

PoS

    Do you remember BCS being discussed when it comes out in 1957/1958?

KGW

    Feynman got interested in that stuff shortly after it came out, but I didn't keep track of that myself.

PoS

    Feynman was giving a set of lectures at Hughes Aircraft at that stage, things which involved the polaron, BCS, all of these things.

KGW

    I didn't pay any attention to that.

PoS

    You didn't look at the notes or anything like that.

KGW

    Right.

PoS

    So you went to Harvard as a Junior Fellow and you were still looking at problems of quantum field theory at that time?

KGW

    Once I started working with Gell-Mann, I was solely in quantum field theory until I come back to the Ising model in 1965.

PoS

    That includes S-matrix work?

KGW

    Yes. What happened, from the time I go to Harvard, the big project I tried to do was work on S-matrix theory. But then I had to figure out something to do because I kept having to wait for the turnaround on these programs, so a couple of things happened. I got interested in the strong coupling approximations, fixed source theory and what had happened there. Gell-Mann had talked about it in a set of lectures that he gave, which I attended. I suspect what must have happened is that I must have taken the field theory course the first year and then there was sort of a topical course given by Gell-Mann the second year and I was listening to Gell-Mann's lectures and not understanding a lot of what Gell-Mann said, but in figuring that I wasn't going to understand it I supposed it was just Gell-Mann. Then I come to Harvard and I become curious about strong coupling because there's a person named Helmut Jahn visiting Brandeis as a postdoc and it quickly became frustrating to me that Helmut Jahn understood this and Gell-Mann had lectured about it (the strong coupling approximation), and if Helmut Jahn could understand it, I knew I could. But I couldn't read the papers. I mean, I had the papers in front of me, I read them, and they didn't make any sense. And finally I realized I had to reinvent the approximation for myself and as soon as I sat down and said, "How would I approximate this?" it then turned out not to be very difficult. But I did have to stop trying to read the paper and work it out.

PoS

    Would you happen to have those lectures?

KGW

    Gell-Mann's lectures? No. I don't know that there were any lecture notes. I just know he lectured on them.

PoS

    Who were you working with or talking to while you were working at Harvard?

KGW

    There was hardly anybody at Harvard. So what I used to do was go down and eat lunch with people at MIT: Francis Low, Ken Johnson and those people. And that was very interesting. That set me up for what got me going in early 1963/1964. Partly it was looking at the work of Johnson and Marshall Baker and trying to figure out why I didn't agree with it.

PoS

    The canonical history of high-energy physics or quantum field theory is that starting in the early 1960s, quantum field theory goes into disrepute... Did you have that sense that you, being committed to quantum field theory, were in the minority and you were a little bit outside the fold?

KGW

    I knew I was outside the fold, and I didn't care. I had just come to one of these presuppositions that Gerald Holton talks about. I had come to the presupposition that S-matrix theory was going no place, that field theory was the only way to go, so I decided I was going to work on field theory. That was my rule; I was going to work on field theory and do the best I could, but that was what I was going to work on.

PoS

    Do you recall what people like Low or Johnson or maybe Gell-Mann made of the direction that you picked? Was this an issue of discussions for your lunches at MIT?

KGW

    Not as far as I know. Because remember, when I'm at MIT, what's happening is I'm working on the strip approximation, I didn't really discuss that with anybody. It was numerical work so there was nothing to discuss. I had just come back from CERN where I had worked on another thing altogether and that was the multiple production processes and very simple models of multiple production. And there's an article on that that I published in Acta Physica Austriaca which was a set of winter school lecture notes I gave on that, and there was one or two papers with [D. Amati] and [A. Stanghellini] from my period at CERN. I started working on the strong coupling theory, but I didn't publish anything on that until I got to Cornell. The only other thing that happened was a conjecture by [Freeman] Dyson that I got fascinated by. So I'm sort of all over the map. I felt isolated at Harvard. There's no question, but I found people to talk to at MIT, but it was more for lunchtime conversation than "Can you help me with this problem."

PoS

    Did you ever tell Francis [Low] about the work you had done for your thesis? Did he understand what you were doing, given in part that it was on renormalization group methods?

KGW

    Francis and I talked, but I have no recollection of whether we ever talked about the renormalization group per se.

PoS

    Or your thesis in particular. And starting in the early 1960s, which was when you were at Harvard, Paul Martin is there.

KGW

    But I don't think we ever talked. I don't remember ever talking with him. I was doing high-energy physics at that point -- that was where I saw myself. So I didn't talk to people about solid state matters.

PoS

    It's not so much solid state as all the technology that Schwinger and Martin had developed for many-body problems.

KGW

    No, I wasn't interested.

PoS

    So by the time you come to Cornell, people don't really know what you're working on. I mean on the surface, there are many things that you're doing, but deep down, there's a commitment to try to explore how far can you go with quantum field theory.

KGW

    The people at Cornell had more of an interest to know what I was doing than people at Harvard, because they were going to have to make a decision... Of course one of the things that happened was, as you may or may not be aware, is that they gave me tenure after only two years and with no publication record. In fact, there was one or two papers on the publications list when I was taken for tenure and Francis Low complained that I should have made sure there was none. Just to prove that it was possible.

PoS

    Before then, when you were working on the work of Ken Johnson, and you developed an expansion technique... Can you talk a little about that? What was the issue you were addressing and how you came up with this technique?

KGW

    There were several papers by Johnson and Baker, related in some way to the high-energy behavior in momentum space of quantum electrodynamics.

PoS

    Finiteness or divergence of the Z-factor...

KGW

    Something like that. I was skeptical, but that just gave me an excuse to work on the things I was working on anyway, which was just trying to understand high-energy behavior of momentum space. I'd also worked on a conjecture of [T. D.] Lee and somebody else which was on weak interactions, which involve renormalizability and high energy behavior. So I just started working on the high-energy behavior of Feynman graphs in momentum space... Things got more and more complicated. I have no recollection of what it was that triggered my thoughts of just freely transforming back everything into position space, in which case, things became much more transparent and that became the basis of the paper that I published.

PoS

    You said you heard some lecture by Klaus Hepp, and the lesson you took from that was that you should work in position space. Do you remember anything about how that went?

KGW

    I remember the locality requirements had to be stated in position space. These commutators that have to vanish outside the light cone. This was in the Nobel lecture?

PoS

    Yes.
    PoS
    So, it implies that you had followed all the things that were being done by people doing renormalization theory...

KGW

    I didn't follow it in detail. I knew that they were working in position space. It didn't mean that I had worked through the formalisms that they developed...

PoS

    When you had looked at Bogoliubov's method of doing renormalization and things like that.

KGW

    Well, I knew the renormalization group and the concepts that the axiomatic field theorists were working on.

PoS

    So you write this preprint, stating the rules for your expansion and then the referee suggested you look at the Thirring model. So what's the significance of that exchange?

KGW

    The significance is that when I set up the rules, I just used perturbation theory so I was using canonical dimension for the field operators and allowing logarithmic corrections because that was what was coming out from the perturbation theory. But then I looked at the Thirring model and discovered that the dimensions are not canonical in the Thirring model. I mean, the dimensions of operators changed depending on the strength of the interaction. And I concluded that I was going to have to completely rework the ideas so as to allow for non-canonical dimensions.

PoS

    Were you aware that the referee was Arthur Wightman?

KGW

    No.

PoS

    Are you aware of it now?

KGW

    I never found out who it was.

PoS

    Did he just point you in the new direction or did he just show you that what you were doing was wrong?

KGW

    You should have received a copy of the referee's report. The thing that was important for me was that it said: “have you considered the exactly soluble Thirring model?” Which I had not, so I had to go look at it.

PoS

    And then when you considered it, you realized that you left out the possibility that the dimensions could change, and did you have an idea of how to pursue this possibility? Or did it just stop you cold?

KGW

    It stopped me from publishing that paper. What could I do? I mean I had the Thirring model. You can solve it. But I didn't know what does this mean for field theory if it's not the Thirring model. So here's this huge blank. So then I spent a long time just trying to figure out how do I get more understanding about high-energy behavior given that it could do that. The perturbative approach doesn't work. So that sets me off thinking about a computational approach to go beyond perturbation theory. And I particularly get interested in the question if I had a computer big enough, how would I do this computation. That became sort of a guiding point to drive me to how to think about the problem. How can I convert this from a problem of infinite number of degrees of freedom, which you can't deal with anyhow, to a problem which is finite even if it was so large that you would have to have an astronomical size computer. I just wanted to convert it from an infinite number of degrees of freedom to a finite number.

PoS

    So the computer comes in by raising the question of how you program it in such a way that you can try to get answers.

KGW

    That's right.

PoS

    I'm dying to ask you just what happens next? If you try to formulate the question in a way that you can put in a computer, how far did you get? Did you try it? Were you talking to other people about this?

KGW

    There was nobody to talk to. At that point, I'm constantly going around in circles except...

PoS

    You come back to the fixed source scalar model at that stage?

KGW

    I continue to work on the fixed source theory. I sort of had several balls in the air. One of them was to keep coming back to the fixed source theory and there you have publications from time to time. First, reducing it to a very simple model that you can solve and then...

PoS

    1967...

KGW

    Something like that.

PoS

    It's actually starting to peel away degrees of freedom.

KGW

    You're right. This is when I start making models involving solving and eliminating degrees of freedom, and it culminates in the work that I did in 1969 when I was at SLAC, but talking to nobody about it, in which I took momentum slice models and provided as best I could a rigorous proof that it would converge despite generating effective Hamiltonian of an infinite numbers of couplings. So there's a long sixty-page paper on that proof.

PoS

    When you do that, you're aware that there in fact is a length scale which allows you to get approximate expansion. In other words, cutoff dependence is relative to some length scale that you have within the problem.

KGW

    Well, remember what I did there was I did this momentum slice procedure where there was a big separation of energy from one slice to the next. And then I was able to do the approximation of expanding in that energy ratio. Then, what I had done by 1969 or 1970 was a proof as rigorous as I could make it, although I'm not trained in rigorous mathematics, that the process would converge and even though the successive effective Hamiltonians generated by the process had infinite numbers of couplings, that didn't matter -- there was a convergence. You could prove a convergent expansion if you had the whole thing large enough. And I wanted to have that assurance that I wasn't just landing myself in the soup by just imagining these Hamiltonians with infinite number of couplings. That extends later to the treatment of the Kondo problem where I was able to get rid of the artificial gaps between momentum slices and still do a numerical calculation that was feasible. And I kept trying to think about how do you set up a field theory so that I could do the momentum slices. But that didn't get me very far. Then, as I was playing with this stuff, I began to start learning about the critical phenomenon.

PoS

    We're now talking 1966 or thereabouts... 1967

KGW

    Well, the first thing I do was attend a seminar by Ben Widom when he's introducing his version of the scaling. And that was 1964/1965 or something like that... It's before I go out to Aspen and start studying the solution of the solution of the 2 dimensional Ising model as formulated by Dan [Daniel] Mattis, [Eliot] Lieb, and Ted [Theodore] Schultz.

PoS

    Essentially, very shortly after you come to Cornell. Can we just take one step back? I'm just trying to understand the linkages in your investigations. You worked in 1965 on momentum slices and this all in the context of the fixed source theory?

KGW

    Yes.

PoS

    And you said, "This work was a real breakthrough for me and for the first time, I found a natural basis for renormalization group analysis."

KGW

    Right.

PoS

    Can you explain that?

KGW

    What drove me nuts was that in the Gell-Mann/Low framework, or as Bogoliubov/Shirkov did it, you had to start with a complete solution of the theory (obtained through perturbation theory). Then you go back, and you work through the renormalization group procedure. But I needed to get away from perturbation theory. I needed to find some way to handle the problem so that I could use the renormalization group as a way of solving the problem instead of a way of analyzing the perturbative solution. When I replaced the complete range of momenta by discrete and well-separated momentum slices, that gave me a parameter to expand in, which I could then use to actually get a solution in which each renormalization group step deals with a finite and feasible problem. (namely, the ratio of energies from successive slices)

PoS

    Can you say a word about how scales or length come into that?

KGW

    The way scales come into it is that for each slice, you have a different energy scale. If one inserts large gaps between the slices then the energy scales are different by enough so that the ratio of the energy scales becomes an expansion parameter. I mean the essence of the renormalization problem is that you have these different energy scales and at the extreme they're very far apart and you want to be able to expand. But of course, you're prevented in real life by not having a high ratio of energies between the adjacent scale. But by making the artificial momentum slice models, with big gaps in energy between successive slices, I made sure that every energy scale is separated from every other energy scale by a large factor. Then the whole problem became solvable even in the limit when you have an infinite set of scales. So suddenly, in that approximation, I now had what I wanted. I could solve the problem with an infinite number of degrees of freedom in terms of reducing it to a sequence of problems, each with a manageable number of degrees of freedom. But even with momentum slices, there are still an infinite number of degrees of freedom in each momentum slice. So I needed to conduct a formal analysis to assure myself that I wasn't still in the soup because of the infinite number of degrees of freedom in each momentum slice. And so I worked very hard to make sure that there were no problems in the momentum slice model that I wasn't aware of.

PoS

    You alluded to the similarity of your work to a conjecture by Dyson.

KGW

    Yes.

PoS

    What was that?

KGW

    Dyson developed a way of taking a field theory, putting in it a dividing line between the low momentum part and the high momentum part, and doing the perturbation theory on the high momentum part before the low momentum part. I was, in the end, able to develop more sophisticated versions of that as one way of setting up the renormalization group. But he did not carry that to the point of getting to the renormalization group concepts that Gell-Mann and Low had...

PoS

    But his conjecture was.... or maybe I misunderstood...

KGW

    There were conjectures of Dyson, but I forget...

PoS

    I think Dyson wrote a paper in Proceedings of the Royal Society where he outlines this notion that renormalizations are high energy effects that reparametrize the coupling constants in the theory and made analogies with fluctuations and considered the smoothing out of the low energy physics when you had intergrated out the high energy fluctuations at short distances. I believe the conjecture of Dyson that you give a proof of is a mathematical one that he uses in some other thing, not necessarily in that problem.

KGW

    The conjecture I studied at Harvard was about random energy levels, which is really separate from anything else.

PoS

    Can we take an interlude now before we move to Cornell? We've been asking you questions about the techniques and the conceptual development around renormalization groups and high energy limits. What if we were to ask you about your history in using computers to solve problems. So if we start with your work after graduating from Harvard, when you had access to a Burroughs computer. Could we just ask you to go back and tell a different story along a different trajectory, which is how do you learn to be more sophisticated and try things with computing?

KGW

    Well, I first started working with computers at Caltech. And Jon Mathews certainly introduced me to the Burroughs Machine that was there and I learned to program it. I'm pretty sure I did some of the work in calculating expansions for the fixed source theory with that computer. By looking at the numbers, I learned that I was getting expansions and I could recognize the analytic form of the expansion from the actual numbers that were being printed out.

PoS

    And you're talking mostly to physicists as you learned how to do this?

KGW

    It's just Jon Mathews who was interested in computers. When I went to Harvard, I'm not sure whether there was anybody I talked to about computers.

PoS

    Did your father use computers? Did you know of his models for getting infrared spectra? Did things like that play a role in your thinking?

KGW

    What I remember from discussions with my father was that he used get very wrought up about computational quantum chemists. Garbage in, garbage out. That set me up to spend some time at Ohio State studying quantum chemistry. I had done a little bit towards the end of my stay at Cornell, but took it more seriously while I was at Ohio State. And so then I had to find out from my father who were the good people. And he knew them, he had a list of them.

PoS

    And who did he say were the good people?

KGW

    There was [Isiah] Shavit. There was Ernie Davidson, John Pople from Carnegie Mellon. What's interesting about this is that later when I became interested in the history of physics and [Thomas S.] Kuhn's book, one of the characteristics of the pre-paradigm phase he discusses, and there really are pre-paradigm phases --you know, people don't want to admit that--is that everybody is arguing with each other and somebody comes in from outside and tries to figure out what's going on, like my father interacting with the quantum chemists, they learn who the good people are. And yet, they won't admit that there are good people, unless you ask them, otherwise they are more interested in complaining about the poor quality of the research by others in the field. I found the same thing with Arnold Arons who knew the people in education research and as soon as I asked him, he would tell me who the good people were too. In that case, I discovered he didn't know all the good people. And I didn't go back and check the names to make sure I got all the good people from my father, but he certainly gave me a good start.

PoS

    And the criterion for being good? I mean what makes a person good?

KGW

    These are the people who are smart, take serious problems to work on...

PoS

    The generative quality comes in?

KGW

    For instance, consider quantum chemistry for a moment. What I found was that the people who did the important work worked on algorithms. They improved the algorithms for solving quantum chemistry problems on computers. They couldn't do the calculations they wanted to do, so they worked on algorithms. And it was the algorithmic work that was absolutely essential. When the computers got better, and they could do serious things, it was the work on algorithms that made the difference and the people that my father knew made contributions to serious algorithm developments. At the same time, there was just a lot of stuff published where people were running programs and they were paying no attention to whether they worked or didn't work, and claiming all sorts of fancy things.

PoS

    So the interaction with your father on that score is important.

KGW

    Well, it's not important for the renormalization, but it's important from the point of view of what I'm doing now. And I think it's important, in the large sense, for what you're trying to do. I mean a larger sense than just the physics of scales, though even in the physics of scales, what I gather you're learning is this phenomena of the physicist adjusting their standards to the difficulty of the problem.

Continue reading part II of the interview.