Yoichiro Nambu

Ashrafi:

I read the things that Laurie Brown has written about you, and I’m particularly interested in starting with the Japanese education and how it is different from here. So for example, you come from a well-educated family, and you had one uncle who is an engineer.

Nambu:

Not necessarily. Do I have one uncle who is an engineer? I have one uncle who was a medical doctor.

Ashrafi:

There is a mention of someone who did work in radio, and you started playing with radio sets as a youth.

Nambu:

Oh, but I wouldn’t say he was an engineer. He died at a young age in his 20s, so I saw him only a few times. I don't know, my memory is very vague. I don’t think he ever went to a school. He was sort of dabbling in kind of amateur radio.

Ashrafi:

Your father was in the humanities rather than in the sciences or engineering.

Nambu:

Yes.

Ashrafi:

At what point did your interest become science and mathematics?

Nambu:

Oh yes, that’s a good question. Actually, my father ran away from home and went to Tokyo and got married there, and that’s where I was born. We had to go back to his hometown because of the great earthquake of 1923 when I was two years old. And that is where I grew up, in his hometown. And my father, of course as you said, studied English literature and wanted to be a writer. He never made it to be a writer, but he ended up as a high school teacher.

Ashrafi:

So you grew up in a family with lots of awareness of Western culture.

Nambu:

Yes, that’s right, that’s correct. I think in my childhood he gave me science books to read and magazines for kids, which I loved to do.

Ashrafi:

So he encouraged science?

Nambu:

I think so, yes. Because he believed that being a writer he had to know everything—all human activities, including science. But he never had any education in science.

Ashrafi:

And your early education included several languages?

Nambu:

By self-study only when I was of high school age. Of course English was taught in high school.

Ashrafi:

Standard for all the students?

Nambu:

Yes. But no conversations or anything like that, just reading.

Ashrafi:

And what kind of science or mathematics courses did you have early on, before college?

Nambu:

Not really, just regular science courses.

Ashrafi:

Laurie Brown mentioned something about you not being as happy with physics as with mathematics early on?

Nambu:

I do not agree with that statement. When I was in my childhood, before school age actually, I read those science books and magazines, mostly about animals and plants and stuff like that. My childhood hero at that time was Thomas Edison. So that’s the kind of thing that I acquired early on. But then in grade school—in those days grade school went only to sixth grade, and after that was high school, which was not compulsory. So compulsory education ended at sixth grade.

Ashrafi:

Were these magazines that you read published in Japan?

Nambu:

Yes, the regular mainstream magazines.

Ashrafi:

And these were in Japanese.

Nambu:

Oh yes of course, science for the kids or something like that.

Ashrafi:

And why Edison? Do you remember? What is it that attracted you to Edison?

Nambu:

Well, he was an inventor, and that was what attracted me, inventing things.

Ashrafi:

And then when you went to high school??

Nambu:

When I went to high school I did regular courses, chemistry, physics, natural history, what else? Not very much.

Ashrafi:

And so you knew early on that you were going to pursue science?

Nambu:

Not really, no.

Ashrafi:

So in high school you were still studying many things, and not yet sure.

Nambu:

Yes, that’s right, nothing really in particular. Of course I was more oriented towards science, yes.

Ashrafi:

And you did well?

Nambu:

Yes. And you mentioned this engineering uncle. I found some radio equipment rummaging through the uncle’s possessions, and that was when I was in grade school. So I built a crystal radio.

Ashrafi:

Before sixth grade?

Nambu:

That’s right. Oh, actually I recently wrote a brief article for the Trieste Institute—they are going to publish articles by various people about their childhoods, so I have a little one here. It is not published yet, so I don’t know whether I should show it to you, but maybe if you just keep it confidential I can make a copy of that for you.

Ashrafi:

Sure, yes. Thank you. So then you went to Tokyo. Why Tokyo?

Nambu:

Why Tokyo. Was a challenge! In those days the educational system was quite different from what it is now. Nowadays it is patterned after the American system. In those days it was more like the German system.

Ashrafi:

How do you mean? With gymnasium?

Nambu:

Yes, well it’s not exactly gymnasium, but there was a higher school which is equivalent to the college nowadays, which is separate from universities. So we called it higher school, not high school. It’s higher than high school. There were several, maybe a dozen or so, national higher schools in those days. And number one was in Tokyo. And it was the most difficult, challenging schools to get in. So maybe it was also encouraged by my father. It was a challenge to try it.

Ashrafi:

Your father encouraged you to try Tokyo?

Nambu:

Yes.

Ashrafi:

So there was a national exam?

Nambu:

No, no, it was not national exams. Just each school had its own exams. And fortunately I was able to get in.

Ashrafi:

I see. And did Tokyo at the time specialize in scientific or engineering?

Nambu:

No, not at all. No, nothing of that kind. So actually I got kind of early admission. A year ahead of schedule, I was able to get in, just barely, at the bottom of the rank.

Ashrafi:

This is in ’40? No.

Nambu:

’37, around there.

Ashrafi:

You went to the Army in ’42.

Nambu:

Yes. So that was after our graduation from the university, not higher school.

Ashrafi:

First there was grade school, then high school, then higher school in Tokyo?

Nambu:

Yes.

Ashrafi:

Oh, I see. And then Tokyo University. I see. So you took the exam. Now the exam you just described, that was the exam for higher school, or for university?

Nambu:

From high school to higher school.

Ashrafi:

So there you’ve had general courses, including science and mathematics.

Nambu:

Mathematics and humanities. Everything.

Ashrafi:

Do you remember what kind of science courses you had?

Nambu:

Well not much, really just routine: physics, chemistry, and mathematics of course.

Ashrafi:

For example, did you get calculus in higher school?

Nambu:

Yes of course.

Ashrafi:

Okay, so before University you had calculus?

Nambu:

Yes, that’s right.

Ashrafi:

And your family was living in Tokyo at the time?

Nambu:

No, they always stayed in my hometown.

Ashrafi:

I see. How long was the higher school?

Nambu:

Three years.

Ashrafi:

Three years, and then you went to Tokyo University. Now how was that process of going to Tokyo University?

Nambu:

We just take another examination. Going to another different school.

Ashrafi:

And why Tokyo University?

Nambu:

It was the most prestigious one of them. My memory is rather vague, but the three years of higher school was a very interesting life for me because it’s living in the dormitories. The students were separated into science oriented and humanities oriented.

Ashrafi:

Oh they were. This is at higher school?

Nambu:

Higher school.

Ashrafi:

Okay. So when you went in you hadn’t decided yet?

Nambu:

Well I applied for the science side. But living in the dormitories, of course all students mix together. The dormitory is not the kind that we know here. There they put maybe eight or so students in the same big room, and the bedroom is the same way with eight beds. So they are all mixed. In the first year, actually, the science and humanities students are all mixed together. So I had a very interesting time interacting with kids from all parts of the country.

Ashrafi:

In what way?

Nambu:

Well, you see, what we discussed was not science or anything like that; just what is life, for example. And popular novels, literature, and things like that. That’s what we talked about for most of the time.

Ashrafi:

And so this would be in the years leading to??

Nambu:

Let me see, what was the year? Do you have my vita there?

Ashrafi:

Yes I do. I have that you graduated from Tokyo University in ’42. So you must have f finished the higher school in ’39?

Nambu:

Actually ’40. The school year started in April. Because the War started when I was at the University, which was 1941, and I was in the second year and supposed to finish in the Spring of 1943, but because of the War that was cut short. I was in the University for two and a half years.

Ashrafi:

And the University is all male at this time?

Nambu:

All male, yes. Even high school was all male. So from high school on.

Ashrafi:

So girls only got to the age of sixth grade?

Nambu:

Girls went to a girls’ high school, and there were a few universities for women, but very few of them. I went into the University in 1940. I entered a higher school in 1937.

Ashrafi:

And was there much military training required in the University?

Nambu:

Yes, from high school on.

Ashrafi:

You went to University, you went to the science side of the University. There was some compulsory military.

Nambu:

Nothing when I was in the University. There was no such thing.

Ashrafi:

Oh, I see, higher school required military. So you didn’t have compulsory military training at University?

Nambu:

No.

Ashrafi:

So you went in with some physics and chemistry and calculus already. Do you remember what you studied in the two years you were at the University?

Nambu:

University?

Ashrafi:

Yes.

Nambu:

After calculus and things like that, just regular physics courses. Oh, I don’t remember. Just everything I think people take in that age. Physics and classical mechanics. You had physics courses in higher school already, which included classical mechanics and thermodynamics.

Ashrafi:

In higher school?

Nambu:

Yes. I really remember because I flunked it! [chuckles]

Ashrafi:

I guess Laurie Brown mentioned you didn’t like entropy.

Nambu:

Well I didn’t understand it. And then some experimental physics there. And then I went into the University’s courses: classical physics, including hydrodynamics and experimental physics, doing experiments; but also a course on experimental physics, the Theory of Experimental Physics.

Ashrafi:

The Theory of Experimental Physics. Which means what?

Nambu:

Data analysis.

Ashrafi:

I see. Did you have relativity?

Nambu:

No.

Ashrafi:

No relativity.

Nambu:

No, not at all. We had quantum mechanics at the University. And then nuclear physics, both theory and experiment. But no particle physics yet.

Ashrafi:

So you had quantum mechanics but not relativity, not even special relativity?

Nambu:

Special relativity, I think we had some of it, but not the gravitational side of it.

Ashrafi:

Do you remember what kinds of materials you used? Were these textbooks in Japanese?

Nambu:

Yes, and also just the teachers themselves made up the lecture notes. And there also were books available in those days, especially for students, including series of paperbacks on individual topics in physics. So those were not required things but we could read those if we wanted to. We could also buy those.

Ashrafi:

Do you remember who the teachers were on quantum mechanics?

Nambu:

Professor Masao Kotani, he’s a well known person in solid state physics, and I think he did the course on quantum mechanics, and somebody else too. The University of Tokyo was good in condensed matter physics, not in the particle side of it. That was the exclusive domain of the Kyoto School and Riken. Nishina was known for this Klein-Nishina formula, but he became an experimentalist after coming back from Copenhagen. He joined this laboratory called Riken. Riken was close to our university. During the last year of the University we were supposed to start reading on some specialized topics, choosing solid state or condensed matter, or whatever.

Ashrafi:

Is this the last year before you went to the Army?

Nambu:

Yes.

Ashrafi:

So this is your third year at University?

Nambu:

Yes. Of course, particle physics was not available, and even our professor did not encourage the group. He thought it was too difficult for us.

Ashrafi:

Did people distinguish between particle physics and nuclear physics at that time?

Nambu:

No, not yet. But nuclear physics was what you learned.

Ashrafi:

Where was Tomonaga?

Nambu:

Tomonaga was in a nearby University called Tsukuba right now and is located elsewhere, but in those days it was a different name. Then, it was called the University of Education. It was meant for training high school teachers.

Ashrafi:

And you were about to say about your special topics readings?

Nambu:

Yes. We wanted to study particle physics because of the fame of Yukawa who became very famous in those days. It was a most appealing or challenging topic. Four or five of us decided to study and get into particle physics. Of course, we were discouraged.

Ashrafi:

Who were the four or five?

Nambu:

One of them I can mention because he also became famous. He is Chushiro Hayashi. He went to Kyoto University, to the Yukawa Institute there, and he did great pioneering work on nuclear physics and cosmology. He’s internationally well known. He also got a national medal. I think he also got a Kyoto prize, which is a very prestigious international prize.

Ashrafi:

And the others didn’t stay in physics?

Nambu:

Some of them stayed in physics, but I don’t know what happened to them, actually.

Ashrafi:

So what did you end up doing for your special reading course?

Nambu:

Well, we started reading the “Review of the Modern Physics” article by Bethe, 1936. It’s generally referred to as Bethe’s Bible. It is a set of two articles written by him, Bacher, and also by Livingston. And we started reading just the first article under the guidance of Professor Kiichiro Ochiai. I think he went to study nuclear physics under Heisenberg in the 1930s. He was not particularly distinguished, but he did agree to take care of us. So we read Bethe, followed by I think a book, Heitler’s book Quantum Theory of Radiation, and some on statistical mechanics.

Ashrafi:

So was Heitler’s book in German or English?

Nambu:

Just English. And also I want to mention that in those days, because the war was on already, we could ignore the copyright laws. So an enterprising classmate of ours started a photocopying business and he made copies on demand for us. So he gave us those books on demand and sold the books to other universities.

Ashrafi:

Was it easy to get a hold of either RPM or??

Nambu:

Yes, I think so.

Ashrafi:

And how about Heitler’s book?

Nambu:

Oh, these were all available in the library.

Ashrafi:

And what was the third book you mentioned?

Nambu:

Fowler’s Statistical Mechanics.

Ashrafi:

So you did all of those in one year?

Nambu:

Yes.

Ashrafi:

And your preparation beforehand, you’d had enough quantum mechanics and enough statistical mechanics to be able to read those fairly advanced texts.

Nambu:

Yes, yes.

Ashrafi:

And did you make it through Heitler’s book?

Nambu:

I don’t remember that. Probably not all through. Fowler’s book was huge so I don’t think we read it all.

Ashrafi:

And then you were drafted into the Army.

Nambu:

Yes.

Ashrafi:

What was the status of your education? Did you get a degree?

Nambu:

Yes, I was supposed to get a degree at the Master’s level. There was also graduate school if we wanted to go there—nobody really went into that because it wasn’t required to get a job.

Ashrafi:

So, I missed at which you decided that physics was going to be your topic. But let me ask this question first. When you went into the science program at Tokyo University, did everyone who went to the science program take the same courses, the same program, or did you distinguish between chemistry, physics??

Nambu:

You applied to some specific department, physics, chemistry, mathematics, etc., and each department had its own program.

Ashrafi:

And when you say that graduate school was not required for a job, what kind of job could you expect with a degree?

Nambu:

A university job.

Ashrafi:

As an instructor?

Nambu:

Yes. Not a professor, not right away. But an instructor or an assistant.

Ashrafi:

And this would be teaching and research?

Nambu:

Yes.

Ashrafi:

At what point when you were in the science program at Tokyo University did you choose physics rather than math, for example?

Nambu:

That was when I applied for the university; you apply for a particular department, physics or chemistry or something like that.

Ashrafi:

So even though everyone in the science program follows the same program, you apply to different departments?

Nambu:

Yes, including medical school, too.

Ashrafi:

So at the end of higher school, you knew that you wanted to do physics and not math.

Nambu:

That’s right.

Ashrafi:

Was there some way that you made that decision?

Nambu:

Yes, that was a hard decision for me, because I had an interest in mathematics, and even in the humanities. But I don’t know how I decided or ended up in physics, but apparently I saw it as the most feasible for me.

Ashrafi:

In what way?

Nambu:

My ability; I did quite well in mathematics but did not want to devote my whole life to mathematics.

Ashrafi:

Because??

Nambu:

Because it is too abstract. And also this fame of Yukawa cannot be ignored. He was a national hero at that time.

Ashrafi:

And one of the things you describe was the prevalence of Marxist theory at the university.

Nambu:

Everybody was interested in Marxism. You mentioned that my interest was influenced by some physicist, like Taketani Sakata.

Ashrafi:

I was going to ask about that, but more in general about the milieu, the environment in the university. And some of the things Laurie Brown wrote was that some of the academics saw Marxism as a counterpart to the militarism that was prevalent.

Nambu:

We were not to be taught such things at the school, but we read them in the books.

Ashrafi:

And discussed them in the dormitories?

Nambu:

Yes, yes. I have to modify this statement: At the higher school, my roommates did not discuss political problems.

Ashrafi:

And did you see them then as a way of opposing the militarism, or was it just an idea to talk about?

Nambu:

Well, not really a way of opposing the militarism, I was not conscious of that. I might tell you that during the University a very interesting thing happened. One of our classmates was an underground communist. He was a very nice man, and he was the enterprising person who made photocopies.

Ashrafi:

So he was a communist and an entrepreneur.

Nambu:

Oh yes, very interesting. I made very good friends with him. He liked me, and he told me all about things that I did not know about. Another classmate who studied with me the same books that I mentioned, the one who wanted to do particle physics, he was the son of some high ranking naval officer working at the headquarters, I believe, in Tokyo. He knew all this secret news about the war situation. So for example, after some big naval battle in the Pacific, and Japan lost it, but the government would not tell us that we lost it or something. But he knew everything, so the next day he would tell us everything, like some aircraft carriers were lost. I didn’t know even the names of those carriers, their existence was secret. He was also a leftist. So I was surrounded by those kinds of people.

Ashrafi:

Do you mean you were surrounded by leftists?

Nambu:

Yes.

Ashrafi:

Was that true that they were mostly leftists?

Nambu:

Well, I was surrounded by at least two or three such people, including this communist guy who also told me about all the secrets, certain news that was going on.

Ashrafi:

What was your family’s reaction to picking a career in physics? Was that a good decision?

Nambu:

Oh yes, I think so. I don’t remember any objections.

Ashrafi:

So they didn’t, for example, say, “There aren’t many jobs, you should find something more profitable.”

Nambu:

No, he never said that. What he actually encouraged me to go into was any academic career.

Ashrafi:

And for your father it didn’t matter whether it was science or humanities?

Nambu:

I don’t think it mattered much, no.

Ashrafi:

Did your mother?

Nambu:

She wouldn’t say much about those things.

Ashrafi:

So you are now going into the Army, and you received your degree before going into the Army? Is that right?

Nambu:

Yes.

Ashrafi:

And you started doing radar research?

Nambu:

Not right away. In those days the university students could start kind of a special career in the Army or Navy leading up to becoming an officer in a short period of time. So it was sort of a program that was available. So every student tried to apply for that, and I flunked it the first time because of my health conditions. So I was assigned to become a regular soldier. The first time I was drafted into a regiment in Tokyo because I was born there and my family register was in Tokyo. I spent about a year there as a regular rank and file soldier. The special program to become an officer, I flunked that, but still being a university graduate I could become an officer more easily and I was sent to some kind of academy near Tokyo to become an officer in the Engineer Corps. And a second time, a year later when I was in the Army, I also applied to become a technical officer. That was the position I had applied for previously and flunked.

Ashrafi:

Was there education in the Engineering Corps?

Nambu:

A kind of training, basic training—digging holes and trenches. Actually my specialty in our company was to operate the outboard motor boat for landing.

Ashrafi:

So that’s what you did, you didn’t do any kind of mathematics or physics.

Nambu:

No, not at all.

Ashrafi:

So you applied a second time to become an officer, and this time you passed.

Nambu:

Yes.

Ashrafi:

And how did that change your condition?

Nambu:

Then I was assigned to an army radar laboratory. There were several specialized army laboratories, ten or so, and one of them was specialized in radar.

Ashrafi:

Was that in Tokyo as well?

Nambu:

Yes, near Tokyo. So I was assigned there and had a certain basic training for three months about electronics. Then I was appointed to that laboratory, but by that time the war was getting closer and closer to us, to Japan. We had to evacuate from Tokyo because air raids were going on. So part of the laboratory was evacuated to Osaka area, and I spent the last year of the war there engaged in this radar research.

Ashrafi:

Which means what?

Nambu:

Which means I was kind of a liaison officer between the Army and the universities and industry.

Ashrafi:

University in general, industry in general?

Nambu:

Yes. Osaka University was closest, and professors from Osaka were consultants for us. And they came regularly to our lab and we had discussion sessions and workshops and things like that. Also I went out to other universities and found out what they were doing in terms of war research and things like that. Also we went to companies, different industrial companies, including Matsushita and Sharp.

Ashrafi:

And what did you learn?

Nambu:

Oh, that was very, very interesting. I learned quite a bit in the lab. The head professor consultant from Osaka was by the name of Kenjiro Okabe, who was one of the early contributors to the development of the magnetron.

Ashrafi:

And what did you talk about, what did you do?

Nambu:

We talked about the design of wave guides, as far as I remember. Basically we were most concerned about that because our magnetrons were very inefficient and the power was small, so you did want to lose much power during transmission. So how to design wave guides for wavelength of 10 cm, let’s say. The magnetron available at that time was made by Toshiba. Our section of the lab, which moved to this Osaka area, was specializing in detection of submarines by radar. Of course, we could not do it, but that was our aim. So I was engaged in a lot of tests of the radar equipment. We mounted a dish antenna on top of a trailer, and inside the trailer there’s the magnetron and the power source and things like that. We are supposed to detect the submarine periscopes. Osaka is facing the inland sea of Japan, so we went to that seaside and set up this equipment, hired a fisherman to go out with a steel pipe put up on his boat, and we wanted to detect it at 300 meters, or something like that. We never succeeded in that.

Ashrafi:

So not only were you talking to people from industry and the universities, but you were also testing equipment?

Nambu:

Yes.

Ashrafi:

Was this equipment that you designed or built?

Nambu:

No, no, no, who designed it I don’t remember. But a company made it, I think. Of course we built some primitive parts of the equipment, but I never did it myself; some other people did it.

Ashrafi:

And was this the first exposure you’d had to research in industry?

Nambu:

That’s true, yes.

Ashrafi:

And did you notice any differences to what you had seen academia?

Nambu:

Well, that’s completely different, of course. It is like what happened in the Manhattan Project here. Those young university students went to Los Alamos and worked out the real program together with professors. So that was the kind of atmosphere at our laboratory in Osaka.

Ashrafi:

But what about in industry? Did you get much exposure to how it was done in industry in Japan?

Nambu:

No, it was just more or less superficial inspection and talking to people.

Ashrafi:

Were you ever tempted to work in research in industry?

Nambu:

No, I don’t think so.

Ashrafi:

One thing I forgot to ask: when you went to the Army, did all of the students from the university go to the Army?

Nambu:

Most of them, unless they were rejected, went to either Navy or Army. Now Navy is more difficult to get in—the standards are much higher.

Ashrafi:

So everybody went.

Nambu:

Everybody went.

Ashrafi:

So you were in the Army for three years, and after the first year you did radar research for two years?

Nambu:

Two years, yes.

Ashrafi:

Was there anything else in the Army that we should talk about? Maybe I can ask you this. You wrote one sentence in one of your recollections that the Army was not a waste of time, that it was a big influence for you professionally and personally. How do you mean?

Nambu:

First of all, it was hands-on research, essentially, that we were engaged in, as opposed to just going to lectures. Also mingling with the kinds of people coming from all walks of life. So not just university physics students, but coming from colleges or technical colleges. In the first of the Army, of course, I was just one of the rank and file soldiers, so all of these from broad classes of society also got together, and it was a very, very interesting sort of experience for me.

Ashrafi:

So what did you learn about hands-on research?

Nambu:

First, there is a ridiculous thing, but the first assignment I got when first I got into this lab was to see whether or not one can detect a submarine from an aircraft magnetically. One of the pieces of equipment or material I was given was a little piece of magnetic alloy: “Do something with it!” [laughs] I couldn’t imagine how we could detect a submarine, you know? But anyway, I did, and I think I went on a test flight. Of course my report was negative. But then moving to the other site we had frequent workshops with the professors from Osaka and Tokyo. Dr. Kotani, I already mentioned that he taught us quantum mechanics. He worked for both the Army and the Navy, I believe; Tomonaga was working for the Navy. At the Navy laboratory near Mt. Fuji, the two people worked out the theory of the magnetron, and it was very, very interesting. That was published after the war. I understand that Julian Schwinger also did the same thing. Also, Tomonaga, he never worked for the Army, but he developed the S-matrix theory of wave guides, which also Schwinger did. So at the workshops, there was a rumor going around that Tomonaga did that. The Army and Navy were almost completely separate.

Ashrafi:

And Tomonaga was with the Army?

Nambu:

With the Navy. So I learned something about Tomonaga’s theory, and even I was ordered to get a hold of the secret documents. So I studied those things, and learned the theory of the S-matrix for the first time.

Ashrafi:

In the context of wave guides.

Nambu:

Yes. Also I joined this workshop for solving the efficiency of transmission wave guides, so I also tried various calculations and things like that.

Ashrafi:

Were there other topics in these workshops?

Nambu:

All of the workshops mostly was about the transmission problem. That’s about it. Also testing of equipment and also some repairing of equipment, going out to the airfields. Also I remember one incident about the B-29, the bomber which came day and night. And one of them apparently dropped radar equipment in to the sea accidentally. This was scanning equipment, and it was picked up by the fishermen and brought to our lab. I think It went around from lab to lab, both Army and Navy. We dissected it and looked at the inside, and we marveled at how ingenious the Americans were. That was a radar using 3 centimeter wavelength generated by klystron which we could not produce yet. It was a special oscillator tube. I think it was made by Western Electric or something like that.

Ashrafi:

And did you figure out what it was and how it worked?

Nambu:

Yes, more or less but the amplifier section was so tiny and all were buried in epoxy. I marveled that the intermediate frequency part was so tiny I could not figure out what was inside.

Ashrafi:

I just wanted to ask you. You say you mixed of people of different class; this did not happen in the University?

Nambu:

No, not really to the same extent. At the University we had all gone through the higher education, but most people in the Army never had as much education.

Ashrafi:

To sixth grade was compulsory, but above sixth grade was it public and free, or private for a fee?

Nambu:

Both public and private schools were available, and I went to a public school, but its not free.

Ashrafi:

So was there a class distinction in the people who went to higher school and to university?

Nambu:

Well, not really. Of course I was from a small town and we didn’t have much of a class distinction. My father’s case, he went to a private university in Tokyo, so it was a bit of difference.

Ashrafi:

So that put you in the upper??

Nambu:

Yes, interns of social status and prestige.

Ashrafi:

When you read this Tomonaga paper about the S-matrix theory of wave guides, was that the first time you were aware of Tomonaga?

Nambu:

No, not the first time. Actually in my university years some of us wanted to do particle physics.

Ashrafi:

And by particle physics you mean nuclear physics.

Nambu:

No, no, not nuclear physics. Particle physics like by Yukawa and Tomonaga. And that was available only at Kyoto and Nishina’s laboratory at Riken near our university. Nishina had two cyclotrons there doing sort of particle physics. It was nuclear physics that would become particle physics. The discovery of mu mesons and things like that happened there. And Tomonaga was joining Nishina and had regular weekly seminars there in the laboratory. So some of us sneaked out of the University and went to hear the seminars, and that was my experience. That happened several times in the last year of my university.

Ashrafi:

Why do you say “sneaked out”?

Nambu:

It wasn’t really sneaking out, we went freely out of our own will.

Ashrafi:

And you heard Tomonaga or his associates speak?

Nambu:

Yes. Nishina and Tomonaga were always leading the seminars together, and I was impressed. We learned quite a lot by listening just to them about cosmic ray physics in the first place. And also I distinctly remember a couple of occasions where Tomonaga? usually Tomonaga tried to explain things very kindly and clearly to us, to the audience, and he read a letter from Shoichi Sakata, his close associate who was in Nagoya at that time, had moved there from Riken, about his theory of cosmic rays. For example, just a few months before I was drafted into the Army, the summer of 1942, Tomonaga read a letter from Sakata saying that the cosmic ray mesons and Yukawa’s particles are two different things. This is the so-called two meson theory. And he explained to us what that theory was, and I was very impressed.

Ashrafi:

And so the preparation you’d had was sufficient to understand.

Nambu:

Oh yes.

Ashrafi:

And this is why you’re reading Heitler and Bethe?

Nambu:

Yes, I think so.

Ashrafi:

And were you known to that group? Did you talk to them at all?

Nambu:

No, we never dared do that. We were in the back part of the room and we just listened.

Ashrafi:

And was it 5, 10, 15 people?

Nambu:

Maybe 20 or so. A group of Nishina and Tomonaga’s lab.

Ashrafi:

And did other people from other places come, or was it just you?

Nambu:

No I don’t think so; just us.

Ashrafi:

And they didn’t know who you were at this time.

Nambu:

I don’t think they knew.

Ashrafi:

And this was before you went to the Army.

Nambu:

Yes.

Ashrafi:

So in ‘45 you go back to the University of Tokyo. Now how did that happen?

Nambu:

Upon graduation, graduating students get assigned to some jobs.

Ashrafi:

Automatically?

Nambu:

Not automatically, but the professors arrange the things for the students. Fortunately I was retained as a kind of post-doc at Tokyo.

Ashrafi:

So who retained you?

Nambu:

I was given a notice, that was it.

Ashrafi:

This is before you went to the Army?

Nambu:

Yes. So I was supposed to be on leave for some time during the war. And after the war, because Japan lost the war, whether I could keep the job or not was not clear. But fortunately I was able to go back to Tokyo after the war.

Ashrafi:

And Tokyo—now things have changed.

Nambu:

Yes.

Ashrafi:

You mentioned several times the new democratizing feeling of the university. So what was different?

Nambu:

There was a kind of chaos at that time, really, because nobody called the shots. Everybody was busy just finding a way to live and eat. So even some of the professors lived in their own offices. And we had to scrounge for food—that was the main job for us.

Ashrafi:

And you were there for four years?

Nambu:

Yes, that’s right. I thought it was three, but over three years, maybe four.

Ashrafi:

So life was hard, but in the meantime, who else was there with you that you were talking to?

Nambu:

Oh, in Tokyo, my roommates, maybe a dozen or so people could work there. It was a big office or lab space or something like that. Many of them had just come back from the war. Not everybody had a regular job at the University, but they would come in and stay there to study. One of my closest friends was Ziro Koba. He had a desk space just across from me. He was a graduate student working for Tomonaga. Why that happened, because Tomonaga was never a professor at Tokyo, but somehow the last year of the war before I went back there, he was for a year a visiting professor at Tokyo University. So he started to take on some students, and Koba was one of them. At that time Tomonaga was working out his re-normalization theory, so Koba helped him. I watched him do the calculation, and slowly I learned what that was.

Ashrafi:

And did you have a research topic of your own?

Nambu:

No, not at all. I was just given a sort of job. Nobody took care of me, actually, because I was trying to work out particle physics things and there was no professor there to talk to. I don’t know what Professor Ochiai was doing, he was probably having a difficult time. I don’t know. I don’t think he was coming into office at all.

Ashrafi:

So you’ve described how difficult life was. How much of your time were you capable of committing to study or to research?

Nambu:

Well, that is very interesting. Almost all the time, except for going out and buying food or looking for food. Day and night, actually. There was another guy who lived in my room, and still another in the adjacent room and day and night we talked physics.

Ashrafi:

Who were they?

Nambu:

Giicti Iwata and Ko Aizu.

Ashrafi:

You were telling us about your office mates when you went back to Tokyo in 1946?

Nambu:

Yes. I talked about Koba. He later went to Copenhagen, and he’s best known for the Koba-Nielsen formula about string.

Ashrafi:

You were talking about the three people that you worked with all day and all night?

Nambu:

Three people, one was Giichi Iwata, and he was I think a lecturer or something or other, so he was senior to me. And he was the one who really first introduced me to modern physics.

Ashrafi:

What do you mean, “modern physics”?

Nambu:

Well, not really modern physics, I shouldn’t say. Particle theory.

Ashrafi:

Meaning?

Nambu:

Meaning things like higher wave equations of various kinds—higher spin and things like that. And he also introduced me to the Ising model. That became quite an industry at that time. Onsager theory got published during the wartime, and I think it reached Japan after the war, probably. And Mr. Kubo, he was one year senior to me in my class in the university, and he was kept as an assistant. He didn’t have to go to the Army fortunately because he was an important figure in the Physics Department, so he stayed there, and of course had a lot of good students under him. Those students were just next door to my office. But I did not really closely interact with him or his group, except that through Iwata I learned about the Ising model.

Ashrafi:

Was Iwata a student of Kubo?

Nambu:

I think he was older than Kubo, so a student of somebody else. He taught me all those things besides physics, like Latin, Greek. [laughs] He was a very erudite person. He even translated Lucretius’ poems from Latin into Japanese and published it. That happened before my eyes!

Ashrafi:

So you learned about higher spinwave functions. Was there a strong reaction to Onsaga’s solution as a counterexample to Landau theory? Or was it just interesting by itself?

Nambu:

Interesting by itself, yes.

Ashrafi:

Just the fact that he’d solved it exactly.

Nambu:

Yes.

Ashrafi:

Was there awareness of Landau theory?

Nambu:

I was not aware of that myself. I was fascinated by the mathematics side of the Onsager solution, and worked at my own way of solving it. That was my first work.

Ashrafi:

But not published.

Nambu:

Oh, it was published, yes. [Refers to papers] The first, number one?

Ashrafi:

“The Relativistic Formulation of Perturbation Theory.” There is an Ising, but it looks like it came later, if I recall correctly.

Nambu:

Yes, the eigenvalue problem or something like that?

Ashrafi:

“Eigenvalue Problems in Crystal Lattices,” published 1958.

Nambu:

Yes, because I did not publish it for two years. That was just a mathematics problem, so it wasn’t very interesting.

Ashrafi:

But you did it before your other work.

Nambu:

Yes, that’s right. When I first started work in Tokyo, that was my first work. I was at least happy that I was able to do this. Then right away there was the discovery of the pi meson and then a Lamb shift, so I switched my interest right away to that. That is why I did not publish this. But later, Kodi Husini, a professor at Osaka who was a graduate from Tokyo, he was a brilliant person, and he also worked out his own way of solving this Onsager problem. I went later to Osaka and I told him about my work, and he was very interested in my work too, so he encouraged me to publish, and that’s how I published it.

Ashrafi:

So you said there were three people you worked with day and night, and you mentioned Iwata.

Nambu:

There were only two people actually in the same room, Iwata and me, and two more in adjacent room.

Ashrafi:

And who were the others?

Nambu:

The one in the next room was Ko Aizu. That room housed mostly Kubo’s students, but I do not think Aizu was his student. In another room lived Seitaro Nakamura and his family. He was Yukawa’s student in Kyoto.

Ashrafi:

Well, maybe I should ask what you were talking about with them.

Nambu:

Talking about the latest happenings in physics, like discoveries and things like that. Including the Onsager solution for one thing. There was not much I learned from Aizu or Nakamura. But we talked, the four of us.

Ashrafi:

And when you started thinking about the Lamb shift, who were you talking to? What were you reading?

Nambu:

Ah, yes, let me try to recall. There was the Physical Review generally available, but only a few copies I think reached Tokyo. The guy called Mitsuo Taketani, who was one of the collaborators of Yukawa. On his own he made his name because he was a very articulate person and had kind of philosophical theories about doing physics or research.

Ashrafi:

Oh, this is Sakata and Taketani? Did you meet them first after the war, or did you meet them at University?

Nambu:

No, I met them first after the war.

Ashrafi:

And were they at Tokyo?

Nambu:

Sakata was at Nagoya University. Taketani was living in Tokyo at that time and he would come to visit us occasionally, to our office.

Ashrafi:

But he didn’t work at the University.

Nambu:

No, no. He was kind of an independent person. He may have had some position at Rikkyo University. And he had his friend, Seitaro Nakamura, who was living across the hall from my office, so he would visit him and he would come into our office too and chat. A very interesting person.

Ashrafi:

And Sakata?

Nambu:

Sakata never showed up here. He was in Nagoya, but I knew of his name and his theories.

Ashrafi:

So, these are the two people you associated with the dialectical materialism and fossil fuel science?

Nambu:

Yes.

Ashrafi:

And you learned about this while you were at Tokyo University?

Nambu:

Yes. I knew something about that because in my higher school days, I read Marx and Lenin and things like that.

Ashrafi:

And in your higher school days, did you read them as part of the education?

Nambu:

No, not at all.

Ashrafi:

So what was this philosophy of science?

Nambu:

Sakata’s theory or Taketani’s theory?

Ashrafi:

Either one. Are they the same?

Nambu:

They are more or less the same, because they are close associates and worked together.

Ashrafi:

Oh, they knew each other and worked together.

Nambu:

Oh, they were both Yukawa’s students and worked together on the meson theory with Yukawa. Sakata is the more famous and more talented a person. When Taketani was a student early on in the 1930s, he started out right away from theoretical views of his, about how physics develops. And that is now called Taketani’s “three stages” theory, namely that physics goes through three stages repeatedly. First a phenomenological stage where you discover something new in nature and you really don’t understand that, and you have to study that and get the data and find in the phenomenon some kind of regularity, some kind of law there. Then you try to explain that regularity in terms of some kind of hypothesis, in terms of some kind of particles or whatever. The first stage is describing the phenomenon in terms of a formula of a phenomenological nature. Then you have to try to find an explanation for the origin of the phenomenon in terms of some concrete objects. For example, you had conservation of mass in the 19th century, and regularity in the chemical reactions, initial sum of the mass equals the sum of the total final mass, which you explain in terms of some kind of elementary particles or units of mass. So that’s the kind of explanation that comes into the second stage. But that is not the final story and one has to really find the final more detailed or precise mathematical framework. So Faraday’s law had to work into the Maxwell theory, the Maxwell equations. Then, according to Taketani, that is not the end of physics, so eventually there will come up some new phenomenon which you cannot explain by the existing theory. So we have to start over again. That was Taketani’s three stage theory.

Ashrafi:

So part of the theory is about how knowledge develops, and another part of the theory is that it is never finished.

Nambu:

Right, right. So he applied this to the ongoing physics and particle physics going on at the time. Sakata also took that up. And he was also a leftist of some kind. He left a bad influence politically in the Japanese physics community as a result. Although he was himself a great physicist.

Ashrafi:

What do you mean, bad?

Nambu:

Dogmatic. Like Stalin, like what happened in Russia.

Ashrafi:

Where people who didn’t believe Sakata’s view were excluded?

Nambu:

Yes, he politicized physics in that way. And we cant talk about it more later on. But anyway, but the important thing that I learned from him was, for example, what stage are we in now?

Ashrafi:

So is this something that was commonly discussed among the people you worked with?

Nambu:

Yes.

Ashrafi:

So this was a topic of discussion, to determine in Taketani’s theory what stage are we in now. Was it written down?

Nambu:

Oh yes, he was a prolific writer and wrote a lot of books in Japanese.

Ashrafi:

So what stage did you decide you were in?

Nambu:

Well, in Taketani’s time the problem was that they did not know what the cosmic ray meson, the moon, was. They were in the first stage, the phenomenological stage, and they moved to the second stage when they explained it in terms of the two meson hypothesis. Then, during my time w hen I went back to the university, new particles called V particles or strange particles were discovered also in the cosmic rays. So we again had to work out and understand what they were to move to the second stage. For example, one of the problems was why those new particles had a long life, relatively speaking. With my colleagues, I was able to explain it by postulating associative production, which means that they have a new quantum number and are produced only in pairs. Once produced, each has a long life because it can decay only by violating the conservation of the quantum number. There was a consciousness, in my mind, of the three stages.

Ashrafi:

So did you use the theory to set research priorities?

Nambu:

Not really priorities, but I had this kind of thing in mind when I did research.

Ashrafi:

How did it affect your research?

Nambu:

Oh, both positively and negatively.

Ashrafi:

In what way?

Nambu:

For example, in 1957, I had a theory of this new particle, omega meson, as it’s called omega now. [Shuffle through papers] Ah yes, it’s on the bottom.

Ashrafi:

So “Possible existence of a heavy neutral meson”, in 1957?

Nambu:

Yes.

Ashrafi:

So you were saying how the Taketani theory affected your work.

Nambu:

The problem that I wanted to solve was that nuclear forces had to be saturated to form a stable nuclei. So there must be some kind of short range repulsive force. And then there was an additional problem of understanding why the electromagnetic form factor of a neutron was almost zero. So I wanted to solve them by postulating a new neutral particle and it’s now called omega meson. In those days, people were trying to solve this kind of problem, most of them, not in terms of a new particle or something like that, but in terms of existing meson theories. After Pi meson was discovered, people thought that the particle that mediates the strong interaction. There was a strong reluctance to pose that there are many elementary particles. So once it was stated that that was it, that was the end of the story. That was the kind of thinking that people had. On the other hand, Taketani and Sakata’s school did not hesitate to introduce any particle. Yukama maybe did it first, but Sakata went on farther.

Ashrafi:

And how does this relate to the Taketani theory?

Nambu:

Taketani is the one who did that kind of thing. According to the Taketani theory, the second stage is to try to understand the phenomenon in the terms of concrete objects.

Ashrafi:

I see. So that made it easier for you to think about new particles that would explain the theory?

Nambu:

Yes. Still I was reluctant to do so, I remember that. And also I had in mind that this particle should be another elementary particle. I never thought the meson would be just a bound state of quarks, for example. Once it’s an elementary particle, it should be rather stable. I didn’t understand why an elementary particle should be unstable by itself. So I tried to keep the mass of the new particle as low as possible so they would not decay into three pions, for example. So that’s one of the kinds of prejudice I had. And it turned out to have much higher mass than three pions.

Ashrafi:

And did you ever get more involved in Marxist theory?

Nambu:

No, not really. I was very disgusted by Lenin.

Ashrafi:

At what time?

Nambu:

Higher school.

Ashrafi:

Is there anything else we should say about the Taketani-Sakata philosophy? You mentioned it several times in your recollections, like you mention your materialism as opposed to Sudarchan’s principled approach. So with this materialist philosophy influence your whole work, your whole career?

Nambu:

Certainly during the ‘60s, yes. But in spite of that when I worked out the theory of spontaneous break down. It had nothing to do with that kind of thing.

Ashrafi:

Is it a theory you thought about much more when you were younger? Or when you were in Tokyo, the philosophy of Taketani?

Nambu:

Yes, in those days.

Ashrafi:

I guess I’m trying to understand how important it was in your estimation, to your work?

Nambu:

At least in my generation of physicists, this philosophy had a great influence on them.

Ashrafi:

But not Yukawa and Tomonaga.

Nambu:

Yukawa was sort of aloof. Of course both Sakata and Taketani both were his students. But he did not really embrace that kind of thing, really, with enthusiasm.

Ashrafi:

Did he dislike it?

Nambu:

It is difficult to say. But later on, in the later ‘60s, Sakata became more kind of radical in the political sense. He tried to spread his influence all over Japan. Yakawa was not that kind of radical. He was a very interesting person, but he was not a political activist. So essentially during the 1960s, the whole of Japan was divided into two halves. One formed that way out to the west under Sakata’s influence. But to the east his influence did not reach. Sakata himself was a great physicist, but his underlings were not; just blind believers in Sakata philosophy. But he wanted to appoint those underlings to various universities to spread his influence. For example, Yukawa once had a student who he placed at the university in Kyushu. Sakata worked secretly to undermine that appointment, and he succeeded and placed his own man there. I don’t know what Yukawa thought of that, I really don’ t know. And these two groups, west and east physicists, were not on speaking terms at the time. So I was supposed to be regarded as belonging to the east because I was from Tokyo. Moreover, I lived and worked in America, which they regarded as the enemy. So I was kind of an unwanted person.

Ashrafi:

So in the era of ’45 to ’49, this divide hadn’t arisen yet.

Nambu:

No.

Ashrafi:

But you knew of the Taketani-Sakata theory and it was already influential?

Nambu:

Yes.

Ashrafi:

And your first work was on the Ising model, but you switched quickly to the Lamb shift work. And you were watching the Tomonaga theory develop in front of you. So the other papers that you did in this period were “The Level Shift of the Anomalous Magnetic Moment,” and “Meson Theory and Quantization.” You did two papers on second configuration space and quantization.

Nambu:

Oh, that’s a kind of mathematical formalism—I was fascinated by the mathematical side of those, yes. That was not the way of the Yukawa school.

Ashrafi:

So basically you did one thing on the Ising model, then you started working on formal aspects of second quantization? Is that right?

Nambu:

Yes.

Ashrafi:

And this describes most of your time and energy between ’45 and ’49.

Nambu:

Yes, right.

Ashrafi:

Now how does it occur that you go to Osaka in ‘49?

Nambu:

I had a kind of a post-doc type job, and I was not sure what my future would be.

Ashrafi:

This is at Tokyo?

Nambu:

Tokyo. At that time we worked hard. Those people of my generation joined, organized a union within the university, so we worked hard on it to improve our status at the university. And as a result of which I was able to get an assistant job. An assistant is a sort of regular governmental position; post-doc type is not. So once you get this permanent job, you are very safe.

Ashrafi:

This is all at Tokyo?

Nambu:

Yes. But I am not sure you can get any promotion after that, you know, because the positions were scarce. But fortunately this new university system was instituted in 1949 or ‘50 or thereabouts by order of MacArthur. The system was reorganized, and also new universities opened up. For example, each prefecture (there are 40 or 50 so prefectures in Japan, like the states in this country), and each prefecture was supposed to have at least one national university. But also there were other universities that sprang up, like city universities and things like that. In Osaka, there was a university specialized in business school. The city of Osaka operated that university. It was promoted into a larger type university, which started to open up a school of science and engineering. So they started to recruit some people and upon the recommendation of Tomonaga, I got a job to go there.

Ashrafi:

Now how did Tomonaga know you?

Nambu:

Because I started working with Koba, and through Koba I eventually got to know Tomonaga, and I was invited to give a seminar at his university. That’s how I got closer to Tomonaga.

Ashrafi:

And this is your work on quantization?

Nambu:

No, about the level shift.

Ashrafi:

So you got to know him in?

Nambu:

I don’t know.

Ashrafi:

The paper was published in ’49.

Nambu:

Yes, so I think I really got to know him in ’47 or ’48. I joined his seminars.

Ashrafi:

Before we move on, were very involved in the union organizing at Tokyo University?

Nambu:

Myself, I was not really involved, but my classmates and some other senior people, did. After I went to the university, Osaka City University, I remember once I presided as a chairman of a union meeting.

Ashrafi:

So you attended union meetings. Did everyone attend union meetings?

Nambu:

No, I don’t think so.

Ashrafi:

You had an interest, then?

Nambu:

Well, I did not really have too much of an interest, but I really had to do something once in a while.

Ashrafi:

So you became an assistant at Tokyo, and you moved as an assistant to Osaka, with the same position.

Nambu:

No, not assistant. That’s an interesting story. I became a professor right away.

Ashrafi:

On Tomonaga’s recommendation?

Nambu:

Yes. There were four of us who went from Tokyo to Osaka City University. And four of us were all in Tokyo. I was the most senior person, and the next one was Satio Hayakawa. He worked under Tomonaga. And next was YoshioYamaguchi, who I don’t think was a student of Tomonaga, though maybe he was, but he studied at Tokyo. The last one was Kazuhiko Nishijima. I don’t think he was officially Tomonaga’s student, but he was in Tokyo anyway. So four of us w ho were close in Tomonaga’s circles were appointed to the new jobs. And because I was most senior, I became a professor. The next, Hayakawa, became an associate professor, and Yamaguchi became a lecturer, and Nishijima was an assistant. There was one more, Tadao Nakano who came from Osaka University to Osaka City University.

Ashrafi:

When you went from your first position at Tokyo to assistant, did your duties change? Did your responsibilities change?

Nambu:

My duties in Tokyo were almost nothing. Just to take care of students, to help them work out problems.

Ashrafi:

Like tutoring?

Nambu:

Yes, tutoring kind of thing at problem solving sessions.

Ashrafi:

And when you went to Osaka??

Nambu:

Because we started brand new, there were no students yet. Maybe there was one or two. So we didn’t have to do any formal courses. So it was kind of tutoring again.

Ashrafi:

Did you have to get involved in the administration of organizing a new department?

Nambu:

Only I had to attend faculty meetings made up of professors. So I had regular professor meetings.

Ashrafi:

So did your life change much from ’49 to ’52 when you were at Osaka? You didn’t have to do much teaching, there weren’t that many students, so were you??

Nambu:

About the same, it was a very light duty. In fact when I was at Tokyo I did more or less the same kind of things. Except that I was married at the time, but I left my wife you see, back in Osaka when I went to Tokyo after the war.

Ashrafi:

Sorry, when were you married?

Nambu:

I married right after the war, and she was left in Osaka. I left her in Osaka and went to Tokyo myself.

Ashrafi:

Oh you married in Osaka, I see.

Nambu:

So now I came back to Osaka, so I was with her.

Ashrafi:

Oh, is that the reason you wanted to go to Osaka? Did you ask for that position?

Nambu:

No, I didn’t ask. Somehow I was offered that job. But they knew that I was from Osaka and that I was married.

Ashrafi:

So you were back with your wife in Osaka, but now being married you don’t spend all the time in your office working. So things change a little bit.

Nambu:

A little bit. Except that still in the miserable conditions of that time, the physics department was opened in kind of a shack. They used a burned out concrete grade school building, and they remodeled it.

Ashrafi:

Your family lived in there?

Nambu:

No, not my family. We were living with her parents. The living conditions were really horrible, even at that time. But we didn’t have any duties to speak of.

Ashrafi:

So from ’49 to ’52 you’re still working on lots of things now. You’re working more on quantization and meson theory.

Nambu:

Yes, there’s a paper on that.

Ashrafi:

Well there’s one “Effect of C-meson field, an Anomalous Magnetic Moment of the Electron” with Koba and Tati?

Nambu:

Oh, these were papers I did in Tokyo. Koba actually moved to Osaka University at the same time. So we were close friends and neighbors.

Ashrafi:

Now, Kinoshita [?], when did you make Kinoshita’s acquaintance?

Nambu:

That was 1946. He was a student and also worked under Tomonaga at that time, and he had his desk in the same office.

Ashrafi:

So he was a Tokyo student working with Tomonaga at Riken.

Nambu:

Yes, I think so.

Ashrafi:

And this paper was published while you were at Osaka.

Nambu:

Yes.

Ashrafi:

But the work was done when you were in Tokyo?

Nambu:

I suppose so, yes.

Ashrafi:

So you have a series of papers with Kinoshita, but I see in 1951 you published a paper with Nishijima and Yamaguchi on V particles. So were you mostly working on strange particles at Osaka?

Nambu:

Yes. Not only that, but that was my main interest, because those are the new particles that came out.

Ashrafi:

So the three of you at Osaka worked on this paper. Was it a tight group?

Nambu:

Yes, very tight group.

Ashrafi:

And you were working on all the same or similar projects?

Nambu:

Yes, yes. And also I must say that Hayakawa, who became an associate professor under me, he went to America for a short period of time, during the summer of 1950 or so, to MIT. Worked under Bruno Rossi because his main interest was in cosmic ray physics. At first he was a theorist under Tomonaga but later switched to experimental physics, and then he did x-ray astronomy. He went to MIT, and he would send us all the news that he got there, including the stories about V particles. And we would think how to interpret the V particles. So we were vaguely aware of what was going on. But then we went ahead on our own to undertake that, understanding V particles in concrete terms, and we came up with a theory of V particles. Also, at the same time, a few other people in Tokyo and some other universities, young people our age, came up with ideas very similar to our theory of V particles. And also in this country, Abraham Pais had the same kind of a theory. So that was the first successful work that we did, when I became the boss of that group.

Ashrafi:

So you were the boss of that group. What does that mean? What did you do?

Nambu:

I was senior, I was kind of moderating the other people to do this kind of thing. For example, I got fascinated by that new plasma theory by Bohm and Pines. It’s a modern formulation of plasma oscillations. Plasma theory was first introduced by Langmuir in the 1920s. But the modern theory showed how to treat collective modes in a medium in general. I got fascinated by that theory that appeared in Physics Review one night in Osaka. Se we undertook a study of the plasmas, the Bohm-Pines theory. My interests continued after that in that direction, and when I came to the institute at Princeton, my project was to apply the theory, to understand, explain the saturation of nuclear forces. Kind of how to handle the many-body problems in general, and also to understand the origin of the spin-orbit forces in nuclear physics. I did not succeed in that, but I had a very keen interested in that kind of theory.

Ashrafi:

So your interest in Tomonaga theory, in field quantization, started when you were at Tokyo, and you had also seen the Ising model, and you brought those same interests to Osaka.

Nambu:

Yes, yes.

Ashrafi:

Now one difference is that you have more information from America while you were at Osaka. Now why the interest in Bohm-Pines? What fascinated you about that?

Nambu:

I don’t really know. I already had an interest in many-body problems when I was a student at Tokyo.

Ashrafi:

And was this because of the second quantization?

Nambu:

No, I don’t know; I don’t really remember why.

Ashrafi:

This is the first time in our conversation you’ve mentioned this topic.

Nambu:

I don’t know why I had an interest in many-body problems.

Ashrafi:

Was it perhaps someone you were talking with?

Nambu:

Because the Tokyo University was stronger in condensed matter physics, and Katani, Kubo and the people around then were doing it, and that’s why also I got interested in solving the nuclear force problem that was also a many-body problem, the nature of the potential between nucleons, for example. How do you derive a potential from the field theory, from Yukawa’s meson theory? And what is the correct form of the potential that includes relativistic effects. So I had a great interest in that sort of problem.

Ashrafi:

And was it common for people to think about both topics, high energy and low energy, or was it rare in your community?

Nambu:

Probably rare. In the first place, high-energy physics was not really much in Tokyo. Nuclear physics was around, but still nuclear physics was in its infancy. I also read the history in Japan that when quantum mechanics came out, people in Tokyo were very reluctant or indifferent to quantum theory. They were mainly interested in classical physics. On the other hand, Kyoto people like Yukawa, he was a student at the time, and his professors there were more progressive and took an interest in understanding quantum mechanics. So Tokyo University was kind of behind the times. And therefore, again, when the particle physics started, they didn’t have much interest in it.

Ashrafi:

But it was not common to think about condensed matter and field theory?

Nambu:

No, no, not at all.

Ashrafi:

Were you aware of any of the Russian literature?

Nambu:

Like what?

Ashrafi:

Maybe this is too early, I should ask in the ‘60s again. When did you become aware of Matsubara? A lot of Russians refer to Matsubara’s work later on in the ‘60s.

Nambu:

No, I met Matsubara, but I learned about his work a bit later.

Ashrafi:

I’ll ask that later when we come back to the ‘60s. So we were at Osaka, and you’re telling me you had a new research interest now in plasma theory. You’re in Osaka from ’49 to ’52, and you’re newly married, and you have two children in this period?

Nambu:

No I had only one. The second was born in Chicago. Right now we have only one. We lost the second one.

Ashrafi:

Is there something else about Osaka we should say? You’re now in a new position as the leader of a research group.

Nambu:

Yes. A couple of interesting things. One is that in those days there was not much interaction between the universities in Japan. Each had its own territory, let’s say. And it was not common to send a graduate from one university to another, especially between Tokyo and Kyoto—they were rivals! So naturally we thought that was a very lamentable situation, and we saw that we—by “we ” I mean the younger generation of people—to have more interaction among the universities and people. So we instituted a new system of visiting students, sort of itinerant students, let’s say. In the feudal days there were samurai who were unemployed and followed no particular lords so there was a name for them which we adopted for these students, and started exchanging them. When we moved from Tokyo to Osaka, we invited young students from Tokyo to come to us, to stay with us for a while, maybe for a couple of months or something. I think this kind of system just took root and still exists now. But anyway, what was interesting was the first arrival of Hironari Miazawa. He made his name by predicting the delta, so he’s one of the people who said that the large ?+ +b cross-section that Fermi discovered here in Chicago was due to a new particle, new resonance. Enrico Fermi did not think of a resonance. Se he was the one who predicted that. He was the first arrival to us from Tokyo. The next one was Koshiba. He got the Nobel prize two years ago for the work on neutrinos in his laboratory. Then some other people followed. At that time their living conditions were so miserable, so they stayed in our laboratories, sleeping on the sofa. That was a sort of odd but interesting interaction that we had. The other one was a kind of anecdote. At that time I cooked up a theory or found some kind of regularity in the masses of elementary particles that were known at that day, and said that this comes in some integer or half-integer multiples of 137. It was the kind of theory where there is no basis for it except just observation. I think actually when I came to this country, Oppenheimer got interested in that, and I think that’s one of the reasons he took an interest in me. That made a newspaper story in Osaka. And some reporter got wind of this and came to interview me. But I was at that time in a movie house seeing a movie. I left home early in the morning saying that I was going to my office, but on my way I stopped at the movie house. When the reporter came to see me, the other guys in our group called my home, and they were told that I had left home already. So they were wondering where I was. Yes, so that was the kind of easy life there at that time. For one thing, it was very hot in the summer and no air-conditioning was available in general, the only place to have air-conditioning was a movie house. It was also a good place to learn English by watching American movies, especially because we were not too used to English conversation. So we liked to stay there as long as possible.

Ashrafi:

But life was easier than it was in Tokyo?

Nambu:

Yes, it was easier, because I didn’t have to go looking for food.

Ashrafi:

So you’re beginning to become known now. Tomonaga knows you. Are you getting any reactions to your work?

Nambu:

At that time, oh, I think so, but I don’t really know to what extent. He was the one who recommended me to get the job in the first place, and I think I got attention from the Yukawa School people in Kyoto. At that time Yukawa was famous, and after getting the Nobel prize in ’48 or ’49 he became very famous, and Kyoto people built a new institute in his name, a theoretical institute. And some younger generation of people were called in to serve on an advisory committee or something like that. I don’t remember the name. But anyway, we got involved in the running of the institute. I was one of them.

Ashrafi:

So what other administrative duties did you have when you were in Osaka? One was that you were the leader of your own group; the second, you’re advisor to the new Kyoto Theoretical Institute.

Nambu:

I interacted with a cosmic ray group at Osaka. It was a distinguished group, because one of them was an early disciple of Nishina in Tokyo, his name was Seishi Kikuchi. He is famous for showing the diffraction patterns of electron beams after Davisson and Germet. He was appointed professor at Osaka University and he s tarted his own group of disciples, and one of them was a cosmic ray physicist by the name of Yuzuru Watase. He became the dean of the School of Science and Engineering, so he was my boss. And he had his own cosmic ray lab there, and the City University had also a high altitude cosmic ray lab in the mountain area. His group went there to do physics, and also we visited that group occasionally too. So we had a close interaction with his group.

Ashrafi:

So what did you do when you visited?

Nambu:

Oh, I didn’t do any research myself, but we talked to people, getting information, and discussing physics.

Ashrafi:

So you had fresh information from an experimental group. But the question was whether or not you were involved in any kind of administration.

Nambu:

No, I was not really involved.

Ashrafi:

Did you have a role in placing students or in determining who would get these trips?

Nambu:

No, there were not even students who finished yet.

Ashrafi:

And what did you do as an advisor to the new Kyoto Institute? What were your duties there?

Nambu:

I was there, I don’t know, for very short time period, because I came to America after that. So Hayakawa took my place and he moved to Kyoto.

Ashrafi:

Should we move on to Princeton?

Nambu:

Yes.

Ashrafi:

So how did it happen that you went to the Institute?

Nambu:

That was upon the recommendation of Tomonaga, I believe. Because after the war, Oppenheimer started to invite some people from Japan, and first Yukawa was invited, and then next was Tomonaga. And after that I guess it was Tomonaga or Yukawa who they recommended some younger people. So first after Tomonaga one of Tomonaga’s students from his university went there. And after that Kinoshita and I were chosen. That’s how that came about.

Ashrafi:

Did you know it was going to happen? Was it a surprise?

Nambu:

No, no, I did not.

Ashrafi:

So you just got a letter one day inviting you?

Nambu:

Yes, I suppose so. I still have the letter somewhere. I did not really expect that to happen although I was eager to go abroad, at least for a short period of time.

Ashrafi:

Were you looking for opportunities to go abroad?

Nambu:

Yes, we were all looking for opportunities at that time.

Ashrafi:

So it was known that you would like to go. Did Tomonaga and Yukawa know that you wanted to go?

Nambu:

Oh they knew it, probably they knew it.

Ashrafi:

You were telling us about going to the Institute.

Nambu:

As I recall, everybody really wanted to go abroad for a while, actually. Some kind of summer school was operated at MIT, and I wanted to spend some there, and I also applied for that as Hayakawa did, and he got the job. Well, actually he was working under Tomonaga on cosmic rays so Rossi had more interest in him. That was maybe part of the reason. So he went there and I had to stay home, but he communicated with us all the time. I was fortunate enough to go to Princeton after that. But then the other guys in my group, Yamaguchi came to America as a post-doc too, he came to the University of Illinois where Jeff Chew and Francis Low were. So they were very active in Illinois. Then Nishijima and Nakano discovered the law relating charge isospin and strangeness that came out after I moved to Princeton where I learned the same thing from Gell-Mann. So the three names got attached to the law. Because of that, Nishijima was invited to Heisenberg, Germany, and eventually from there he moved to America and was a professor at the University of Illinois for a while before he moved back to Japan. Nakano also spent a year at Princeton sometime later. So all the people eventually came out to America, at least for a limited period of time.

Ashrafi:

So in ’52 you go to Princeton, and when did you get the letter inviting you? Was it right before you went, or a year before you went?

Nambu:

Oh, maybe a half a year, or a year. I have my letter at home; I don’t think it’s here. Probably a year before.

Ashrafi:

So you take a temporary leave from Osaka and you go to Princeton, but actually there’s several people you meet on the way. There’s some Japanese physicists who reach you when you land on the west coast. Did you know??

Nambu:

Yes, this guy, Ryokichi Sagane, who met me at Berkeley, was my professor at Tokyo in nuclear physics. And he was working under Nishina on the cyclotron. And actually this guy called Sagane was one of the sons of Nagahoka. And I think he took a liking to me when I was a student at Tokyo, and I became rather close to him. He was actually sent by Nishina in the 1930s to work under Lawrence to learn the cyclotron technology.

Ashrafi:

In the 1930s. And he stayed?

Nambu:

Yes, stayed for quite a while, and Lawrence was very helpful, and he gave him the same design as his own cyclotron. He brought it back to Nishina and Nishina built the cyclotron. A couple of cyclotrons, actually.

Ashrafi:

So Sagana returned to Japan?

Nambu:

Yes, but after the war he was again Berkeley, spent a few years there, and I met him there. And he brought from Japan a kind of magnetic spectrometer to measure electron energies. It was invented or designed by another person in Tokyo. Also, one of my roommates in Tokyo, Iwata, who taught me various things, also helped the calculations for the guy.

Ashrafi:

Which guy?

Nambu:

The spectrometer was developed by, I think, Hideo Aoki and it was called SOS: Spiral Orbit Spectrometer. It had 360 degrees acceptance.

Ashrafi:

So were there more than one Japanese physicist in the United States that you were communicating with?

Nambu:

More than one, yes. So this guy Sagane was very kind, and he met me at Berkeley and introduced me to Lawrence and other people there. Also, there was another professor not in the Physics Department in Tokyo, I guess maybe it was the Engineering School of the University of Tokyo, by the name of Satosi Watanabe. He was a theorist who studied under DeBroglie and Heisenberg both. He was the sone of an aristocrat who served in the Imperial Court. He had a German wife, and she didn’t feel quite comfortable living in Japan after the war, so eventually both moved to America. And this guy Watanabe was a close friend of Taketani’s, although they had philosophies completely opposite. Anyway, they were very good friends. So I got to know both of them in Tokyo, and he was also kind to me, and when I was invited to Princeton, I think I had to get a written recommendation and I went to Watanabe, and he very kindly wrote a letter for me.

Ashrafi:

Where was Watanabe then?

Nambu:

Watanabe at that time was living in Tokyo. Then he moved to California after that, and he was teaching at the naval post-graduate school in Monterey, California. So I met him there. And maybe that’s a bit out of the point, but he later moved to the IBM laboratory at Poughkeepsie and after that, became a professor at the University of Hawaii, and then after that he moved back to Japan.

Ashrafi:

So in these two years, when you first arrived at Princeton, were there a network of Japanese scientists?

Nambu:

Network, yes, a very small number: Sagana, Watanabe. Other physicists, there weren’t any that I knew. Though my generation of people came here, around the same time.

Ashrafi:

But there was not a network of Japanese physicists that received...

Nambu:

Not of physicists, but I got to know some Japanese mathematicians at Princeton. One of them, the famous Kunihiko Kodaira, he was an associate professor at Princeton University. He was a bit senior to me at Tokyo by three or four years. He had studied both physics and mathematics and got the famous Field medal. So he was one of the mathematicians I got to know.

Ashrafi:

So when you got to Princeton, Dyson was there, and he’s teaching Feynman diagrams to everybody? Is that right?

Nambu:

I don’t know if he was teaching there. I mean he wasn’t [overlapping voices]

Ashrafi:

No, I mean informally.

Nambu:

Yes, yes. I first met him not in Princeton, maybe at Cornell.

Ashrafi:

When was that? Oh, he was on leave for a year.

Nambu:

Maybe. Maybe that’s why.

Ashrafi:

Is that right? Was Rohrlich there?

Nambu:

Rohrlich, no, not Rohrlich was— Let me see. I first met him, where was it? I remember he was in Iowa, but I distinctly remember meeting Dyson together with Kinoshita on Christmastime. So we stayed at his home, and he took us out to the mountains to get a Christmas tree.

Ashrafi:

Wow, where?

Nambu:

Near Cornell, at Ithaca. But so in Princeton there were Dyson, Frank Yang, and T.D. Lee. Einstein of course. And then Pais. Another member I remember was George Placzek. I have to add that Pauli was also there for a year.

Ashrafi:

But in some of your recollections it’s both positive and negative.

Nambu:

Both.

Ashrafi:

Can you tell me more? There’s some period where you don’t publish, from ’52 to ’55.

Nambu:

Yes. Actually I published one paper with Kinoshita. Well, maybe I took the wrong subject to study which was to understand the saturation properties of nuclear forces, and the origin of the spin orbit coupling, and they were two unsolved problems at that time, and it was because of my inherent interest in many-body physics. The paper I wrote with Kinoshita was a generalization of the Bohm-Pines theory which I intended to apply to these problems.

Ashrafi:

So tell me what the relationship is between these three fields. Can you tell me what the saturation problem, for example, is?

Nambu:

The saturation problem is that nuclear physics means the physics of the binding of the nuclei, but if you have only attractive forces, eventually they’ll collapse in. But the nuclear density is a constant that saturates at certain density. And this was an unsolved problem at that time, and I wanted to understand that in terms of the new theoretical treatment started by Bohm-Pines. And at the same time as this saturation problem, also the spin-orbit coupling was an important element of the nuclear shell model. Where did it come from? A force that is rather large and of opposite sign to that of the electrons in atomic physics. So I tried to understand them, and also that was to be solved in terms of the theoretical formulation, the precise formulation of the Yukawa meson theory. Eventually it was to be solved in terms of new particles. I tried very hard at it, and I got very, very frustrated, but I couldn’t make any progress.

Ashrafi:

So you were working on two separate problems?

Nambu:

No, the two were tied together in the nuclear physics program, not the particle physics. I should probably have considered following up on that V particle. Eventually it was solved by Gell-Mann and Nishijma as I have said. But I got really frustrated during the two years I was there. And also I didn’t quite like the atmosphere of Princeton. It was kind of a fierce competition.

Ashrafi:

Other people have said that.

Nambu:

Yes. Yes, I heard of the same story from other people, too.

Ashrafi:

But before you went, or after?

Nambu:

After.

Ashrafi:

So it was very different from the environment in Tomonaga’s seminar, for example?

Nambu:

Yes, he was a very relaxed person. And also when I moved to Osaka City, there was nobody to compete against.

Ashrafi:

So how did this competitiveness manifest itself? What was it that made you uncomfortable?

Nambu:

Basically I had a feeling that other people were much better than I. And besides, I was not able to make progress on my project, so that compounded it. I felt very inferior.

Ashrafi:

Can you describe to me what your life was like while you were at the IAS?

Nambu:

Yes, first the living conditions were like paradise compared to Japan. My wife and I and our little son, about two years old, came and joined me after one year. And she felt the same way that it was a kind of real paradise. Because it was a very small close-knit community, and living in the housing project, and there were several Japanese who would come together. There were two or three mathematicians and Kinoshita, and also the young guys from Europe, and we became very close. So as far as she was concerned, she was very happy. Because when I was in Japan, especially in Tokyo, well even after we moved to Osaka we did not have our own house to live in. So it felt like paradise. The same feeling was also expressed by Tomonaga earlier when he went there and he wrote us back. He said he was sort of exiled in paradise. Because he went alone there; he did not have a car, he did not know how to drive, and so he was sort of exiled at Princeton.

Ashrafi:

So who did you talk to when you were there?

Nambu:

I talked to a number of people, actually. A lot of the younger people I talked to, oh, half a dozen or more. C.N. Yang, T.D. Lee, Nicolas van Kampen, Robert Jastrow, Gunnar Källen, Walter Thirring, Boris Jacobson. Laurie Brown was also one of them. And van Kampen and Jastrow were my driving instructors.

Ashrafi:

So was there a particular way that your work changed because of these conversations? Was there something you learned? Did you learn new methods or new topics?

Nambu:

Not really in terms of new methods, but I think I had to adjust to the new kind of life; speaking English, for one thing. And of course the customs are different in this country than in Japan, so I had to learn those things. Also I was fascinated by meeting with famous names, not just in Princeton but meeting in other places. The Rochester Conferences started around that time, so I was fortunate enough to be one of the few who were invited. Oppenheimer took me and a few others with him to Rochester.

Ashrafi:

Did the new environment distract from your work, adapting to the new environment? So in Osaka and Tokyo you worked all the time, apparently. Was it the same in Princeton?

Nambu:

It was.

Ashrafi:

But not much progress this time.

Nambu:

Not much progress, no.

Ashrafi:

And the first year you went to Caltech in the summer to try some experimental work.

Nambu:

Yes. In Princeton, they paid the salary only for nine months, and in the summertime you were free to go anyplace. Oppenheimer kindly arranged for Kinoshita and me to go to Caltech with the money that was left by Yukawa because there was a limit to the amount he could receive. And so we did. And at first at that time I was actually concerned with the arrival of my wife and son in Los Angeles. So we stayed three months or so there and got to know people at Caltech. And also I tried to join an experimental group. I was declined, but at least I was able to do a phase shift analysis of the photo-pion production data and published a preprint. If I remember correctly, the results favored electric quadrupole as opposed to magnetic dipole, but the latter turned out to be the case later.

Ashrafi:

So were you seriously thinking about doing experimental work?

Nambu:

Oh, yeah, that was the influence again of Taketani. Because around that time there was no Japanese experimental physics to speak of, especially after the war due to the poor condition. But he encouraged us to learn experimental physics as much as possible, learn experiments. He didn’t say to do experiments ourselves. So that was in my mind.

Ashrafi:

He was quite an influence on you, apparently.

Nambu:

Yes, that’s right.

Ashrafi:

Were you still in communication with him?

Nambu:

He died a few years ago.

Ashrafi:

Oh no, I meant when you were in Princeton.

Nambu:

Oh. No, not at all.

Ashrafi:

But he’d already influenced you.

Nambu:

Yes.

Ashrafi:

Were you in much communication with your Japanese colleagues?

Nambu:

Yes, yes.

Ashrafi:

In the same way?

Nambu:

Yes. I would write a report to my group in Osaka about what I learned in America. I kept doing that.

Ashrafi:

And what did you write about, what were you learning?

Nambu:

Well, my impression of people, for example, and some news that I heard. For example, I learned of Murray Gell-Mann’s work on the Gell-Mann-Nishima law. And I was very excited, and right away I wrote back to Osaka people. Then Hayakawa had gone back to Osaka at that time, he wrote me back right away that Nishijima and Nakano were working with the same kind of ideas.

Ashrafi:

And then you go back for the second year to Princeton, and it’s not more productive than the first.

Nambu:

No.

Ashrafi:

And you still don’t find the atmosphere conducive?

Nambu:

No, the second year I think was especially depressing.

Ashrafi:

Because of the work?

Nambu:

Yes, because of the work. And fortunately I was saved by Goldberger to come to Chicago.

Ashrafi:

But first you went to Wisconsin?

Nambu:

Oh, that was just summertime. For three months. Robert Sachs, the chairman of the physics department invited me to come to his summer institute.

Ashrafi:

When did you learn you were coming to Chicago?

Nambu:

Well, actually it was during my second year of my stay at Princeton. I really did not want to go back to Osaka right away. Also, as I said it was a two-year leave, and I had promised them that I would come back. But I didn’t want to go back to the same miserable living conditions; that was my main problem. And I wanted some more work, because I was not able to do good work at Princeton maybe I should try some elsewhere.

Ashrafi:

Did your wife agree with the decision to try to stay?

Nambu:

Yes, of course. Particularly she was so happy in Princeton.

Ashrafi:

Did you ever have any difficulty as a Japanese person in these early years?

Nambu:

Oh yes, of course, in those days, from prejudice and things like this, yes, although not really explicitly, not at all. But certainly not among physicists. When we moved to Chicago we had a little difficulty finding an apartment. Well, nothing overt, but when I looked for an apartment, they claimed that there was no room. That happened a couple of times before I found one.

Ashrafi:

So you must’ve left a positive impression at Princeton despite your lack of productivity if Golberger invited you here. Do you know how that happened?

Nambu:

Yes, I don’t quite remember, but of course I met Golberger either at Princeton first, because naturally he would travel around, or I met him in conferences. When I first came to the States first I landed in San Francisco and went to Berkeley. Kinoshita and I took a train together across the continent, and our first stop after that was in Colorado, cosmic ray labs at Echo Lake and Mt. Evans lab because of our interest, or my interest anyway. Because of my work on V particles, I had some connection there. Then we stopped in Chicago. We wanted to visit Marcel Schein, the famous cosmic ray physicist. But he wasn’t there at the time, but anyway we visited his lab. And then we went on to Rochester to see Bob Marshak, he was also in cosmic theory. And then we stopped at Cornell, and then finally I came to Princeton. So I had already made acquaintances. When I was in Princeton, I got invited by David Pines because of my interest in Bohm-Pines’ theory.

Ashrafi:

Now how did he know of your interest?

Nambu:

I think we were in communication with each other already in Japan.

Ashrafi:

And where was he at the time?

Nambu:

The University of Illinois. He is still there.

Ashrafi:

He was already there?

Nambu:

Yes, he was already there. And he wanted me to come and give a talk about my theory. I had only one paper that I published in Princeton with Kinoshita.

Ashrafi:

This is on the electro-magnetic “Properties of Mesons.”

Nambu:

No, no, no.

Ashrafi:

Oh, ’50, sorry. “Collective Description of Many Particle Systems”?

Nambu:

That’s right, I think so.

Ashrafi:

So that’s published ’54. Okay, so you did it ’52 to ’54. So you talked about this with Pines.

Nambu:

Yes. I also met many other famous people. Bardeen, Pines, Fred Seitz, Nordsieck and a few other people.

Ashrafi:

Okay, and was Golberger there?

Nambu:

Golberger was in Chicago. I have not finished the story yet. So on the way I also stopped at Chicago again and met Gregor Wentzel. He was really kind, and he invited me a party at his house. And I think I met Goldberger there too. That is how it started, I think. And they liked me, apparently. That is how I was able to get invited to come to Chicago.

Ashrafi:

So after your official stay in Princeton ended, you stayed on. And you stayed at the IAS. Where did you stay?

Nambu:

Just after I ended my two years there, I moved to Chicago.

Ashrafi:

Oh, so did you do a search?

Nambu:

Oh I did a little bit of search, yes, for positions. Fortunately there was one possibility with the help of Abe Klein. He was a student of Schwinger and did Lamb shift calculations. He tried to find a job for me, and there was a possibility at Yale with Gregory Breit. Because of my interest in the nuclear force problem, my work on nuclear potentials, apparently he took an interest in me. But unfortunately he did not have the money to hire me. Then came the offer from Goldberger.

Ashrafi:

Okay, you just finished saying that one possibility was at Yale with Breit, but they didn’t have any money. And that came through Klein, that possibility at Yale?

Nambu:

I don’t remember. He went to Yale, Klein himself? I don’t know. No, Klein was my friend. We met in conferences. He tried to help me find a job. And I think probably he told me that there was a possibility at Yale, but unfortunately that did not materialize.

Ashrafi:

And was he inquiring on your behalf?

Nambu:

Yes, I think so. Probably I wrote a letter to Breit, and he answered that there was no money. But I am not positive.

Ashrafi:

Did he inquire at Chicago?

Nambu:

That I don’t know. Probably not. I have to add another story here. It was before the Chicago offer. At Princeton I made good friends with Boris Jacobson. He was on leave from the University of Washington. Once we took a long walk. He was in search of a project, and I suggested a problem for him to work out. Then one day he took me out again for another walk and s tarted to ask me if I was interested in a tenure position at Seattle. I asked back, “a ten year position?” He smiled and explained to me what tenure meant. I was not familiar with the American system, so I was not overly impressed. Then Oppy also urged me to go to Seattle. Obviously it was his idea. I believe the boss at Seattle was his student. I am sorry I have forgotten the name. But at that time I had an impression that Seattle was a remote corner of America, far from the centers of physics; I would be better off going back to Osaka. So I ended up declining it. Later when I visited Seattle, I learned that Boris had proposed to hire me even foregoing the possibility of his own promotion. I was very moved. He was promoted after all, but I am sorry he died rather young. I hope my memory is correct.

Ashrafi:

But one way or another, an offer came from Chicago and you came to Chicago.

Nambu:

Oh yes, that was my good luck. [Lunch Break]

Ashrafi:

Okay, we’re back from lunch. Would you mind putting on the tape your story of visiting Oppenheimer that you told me at lunch?

Nambu:

Oh yes. Visiting him is one of the stories I can tell you. When I arrived at Princeton, he held a party for the newcomers. I stayed there for two years. So at the first party, I remember Oppy introducing me to Cecile Morette-deWitt, because she was with a baby. I met several new people there. The second year there was a party, and by that time my family was there, so I took my wife with me. We went to this house, and I remember there was a huge Van Gogh, The Sunflower, one of the famous paintings that you could find in art books. It was there, and there was also a small Renoir, so I was totally impressed. My wife almost started to say, “Is it genuine?” or something, “Authentic?” [laughs] So I was really embarrassed and I kicked her shin. Of course he comes from a wealthy family; the Oppenheimer family was in the clothing business or something like that. Later I found that there was at Princeton, a department store called Oppenheimer’s. So he belonged to that line of people, no doubt that he was a very wealthy person. I understood that his family had a ranch in Los Alamos which he used to build his laboratories. That kind of thing I learned and remembered reading in Time magazine when I was in Japan. But anyway, Oppenheimer was a very sort of? Ah, I was scared of him, as I told you, to talk to him, to tell him about what I was doing there. I had to make an appointment three days in advance and I had to go through three checkpoints because at that time he had secret documents with him and an FBI agent was guarding them all the time. So I passed this guy and then two more secretaries in two different rooms, and finally I reached his office. And he seemed to be reading pre-prints all the time, and so he was conversant with any topic even though he did not understand or appreciate it in a deep sense. Superficially he seemed to know everything, so he could make comments about anything. I get in his office, and I started telling him what I would like to discuss with him. I search my words, and before I could open my mouth he says exactly what I was going to say, so that it really scared me off. After a discussion for a few minutes he just says, “That’s enough,” and shows me the door, and encourages me to keep on doing my work. That was it.

Ashrafi:

So altogether not a very friendly encouraging place.

Nambu:

No, not an encouraging place.

Ashrafi:

So you came to Chicago, but the summer before you came to Chicago you spent in Wisconsin?

Nambu:

Yes, before arriving in Chicago I spent three months in Madison at the University of Wisconsin. Robert Sachs, he passed away several years ago at Chicago, but he was the chairman there and he was organizing a summer institute every summer at that time. I was invited to spend the summer there, and it was a very nice experience, especially because you were with all the big names like Eugene Wigner. Wigner used to be at Wisconsin for a while before going to Princeton because he was not considered good enough for Princeton the first time. Then he did work on the Wigner crystal. That made him good enough and he got back to Princeton. I was also told that Gregory Breit was there once. There was a boat that he had left, which we would ride on Lake Mendota.

Ashrafi:

What was the topic of that summer institute?

Nambu:

Oh, just general high energy physics. Rochester conferences were on high energy physics, so I met there many younger people who also came to Madison summer institute. I kept on attending it three or four times after that.

Ashrafi:

So then you came to Chicago.

Nambu:

Then I came to Chicago.

Ashrafi:

And from your recollections that you’ve written elsewhere, it was a very different atmosphere.

Nambu:

Yes. It was very different, and I liked it right away—the atmosphere, not the city of Chicago—because it was a very close-knit type of institute and faculty. There were rather small numbers there at that time, so everybody was treated like a family member. I could talk to everybody freely, and every week on Thursday afternoon there was so-called institute seminar, I don't know what was it’s official name, but people spontaneously got together on the fourth floor, Room 480, and talked about anything you had on your mind. Fermi was naturally the leader, he was a master of that kind of thing, I was told, but I came too late to witness it because he died three months after my arrival. There were people like Maria Mayer and her husband Joe Mayer. Joe Mayer sort of served as the chairman of that session. But people usually called that a Quaker meeting, and everybody was encouraged to speak up. It was really fascinating because there were not only physicists but chemists and geologists and they talked about their own things.

Ashrafi:

So what was your position? You were research?

Nambu:

I was a research associate at that time on leave from Osaka.

Ashrafi:

And did you get any reaction from the Osaka people for not going back there?

Nambu:

Yes, but at the time a few years’ extension was considered a sort of natural thing.

Ashrafi:

And you continued the same line of research?

Nambu:

Yes, actually I switched fields more or less because I was depressed that I had not made any progress on the program in nuclear physics. But Golberger had started his dispersion theory, and so Chicago was the center of dispersion theory. It was started by a paper by Golberger and Murray Gell-Mann and Walter Thirring when they were all on the East coast.

Ashrafi:

So did you consciously decide to switch fields?

Nambu:

Yes, I got more interested in the mathematics of it.

Ashrafi:

But you got interested in it because it’s being done here?

Nambu:

No, it just happened that he was doing it here, and I was supposed to work under Golberger more or less, being a post-doc. I was fascinated by the mathematics of the dispersion theory. So I spent a few years studying it, and there was a post-doc also, Reinhard Oehme, a student of Heisenberg. He is still here. And Miazawa, I think I mentioned his name before in connection with the discovery of the delta resonance. Both Oehme and Miyazawa arrived just a year before me. We were all involved in this dispersion theory more or less.

Ashrafi:

And Kinoshita?

Nambu:

Kinoshita went from Princeton to Columbia as a post-doc and stayed for a few years and then he moved to Cornell.

Ashrafi:

And he stayed at Cornell.

Nambu:

Yes.

Ashrafi:

So if I look at from ’55, ’56, it’s Green’s function, renormalization, dispersion relations, lots of dispersion relations, at least until 1960.

Nambu:

Yes, I think so.

Ashrafi:

And here you were working with the other faculty?

Nambu:

Mainly with Golberger.

Ashrafi:

Where was Chew at that time?

Nambu:

Chew was in Illinois. Chew and Low both were at University of Illinois.

Ashrafi:

So after two years you become associate professor.

Nambu:

Yes.

Ashrafi:

Do you start teaching at that point?

Nambu:

Yes. The first course was Statistical Mechanics.

Ashrafi:

And did you teach undergraduate or graduate?

Nambu:

Graduate, all graduate courses.

Ashrafi:

And did you then teach the whole spectrum of courses?

Nambu:

Yes, more or less. We all rotated teaching assignments. So quantum mechanics, electrodynamics and nuclear physics. Particle physics, I don’t know if there was that course there at that time, many of the advanced courses I taught.

Ashrafi:

At what point did you start getting involved in graduate dissertations?

Nambu:

Right away when I became associate professor. Golberger at that time left Chicago to go to Princeton, so he left his students. I took some of his students to finish them up.

Ashrafi:

And you said you had a list of your students? We can get it later.

Nambu:

Yes, because it is in my computer.

Ashrafi:

You could email it to me.

Nambu:

Yes, I will. Speaking of students, this is someone I don’t know myself but he came from Korea. This is an Asian Pacific Physical Society. Do you know about this?

Ashrafi:

I do not, no. Association of Asian Pacific Physical Societies.

Nambu:

And there is an article written by this guy.

Ashrafi:

Oh! Wow.

Nambu:

He is still working on it, apparently.

Ashrafi:

Su-yung Chang, Academic Genealogy of European Physicists. Wow. From 1856 to at least 1950.

Nambu:

There is also a genealogy of American Physicists.

Ashrafi:

I see. Very nice. [Copy given.] So as soon as you arrived you started getting students to supervise, and we ’ll attach a list of students after that. So it looks like there’s one period from roughly ’54 to almost ’60 in which all of your work is about representations of Green’s functions and dispersion relations. And you worked with this group here. So what should we talk about that period? Now how new is this for you? What did you have to learn that you didn’t know?

Nambu:

That part I don’t remember. Well, that sort of mathematics, the theory of analytic functions, of course I knew more or less, but I learned it in more details. Dispersion theory was based on analyticity, unitarity and essentially the S-matrix theory that Heisenberg invented and wrote about it during the war time, but making use of analyticity specifically to analyze this, that was a new thing.

Ashrafi:

And were you talking to experimentalists very much?

Nambu:

Yes, of course. The cyclotron was just next to us, and I used to go down there to the pit and talk to the experimental physicists about the experiments that were going on.

Ashrafi:

But at this point you’re not doing anything related to many body physics. Is that right?

Nambu:

Not quite, because I still had this lingering interest, and I wanted to make use of that many body theory of Bohm-Pines, and that helped me in my work on superconductivity. So that was a very important part of it.

Ashrafi:

But in your first six years at Chicago, there’s no publications along that line.

Nambu:

No. Speculation about the new meson Omega to account for the saturation properties of nuclear forces and the form factors of the nucleon. Another thing is that, in connection with the dispension theory, I made some discoveries, like the anomalous threshold of a dispersion relation for a form factor. If you know the imaginary part of a scattering amplitude or a form factor, you can express the whole thing in terms of that imaginary part alone because of the analyticity. Suppose two particles can form a real intermediate state, not a virtual one. These states contribute to the imaginary part of a dispersion relation, or the absorptive part as they call it. But there are exceptions in which some other states also contribute to the imaginary part, not really states, but some extra contributions. They come in when the particles involved are weakly bound states. I made the discovery, but two other people also discovered it independently. One was Oehme, who was then at Princeton and the other was Robert Karplus at Berkeley who found it for scattering amplitudes. I also discovered a general parametric representation of the N-point Green functions by analyzing the Feymann diagrams. This was quoted by Landau in his paper on the Landau singularities. I was very pleased. In 1959 there was the first Rochester Conference held in Russia, in Kiev. I was invited and I met Landau. He was very kind to me, and after the conference I spent a few days in Moscow and visited Landau’s laboratory.

Ashrafi:

This is in ’59?

Nambu:

Yes, ’59.

Ashrafi:

So who else did you meet there other than Landau?

Nambu:

He introduced himself to me, he came up to me at the conference. So then I asked to visit his lab on the way back.

Ashrafi:

And who did you meet there?

Nambu:

Only Landau. Kapiza was also there, but it was kind of secret, off limits. So he was really apologetic about that. I also visited other institutes in Moscow, and met several people.

Ashrafi:

Any of the students?

Nambu:

Not there, but Gor’kov, I think I met him, not at the Institute but some other Institute. Fradkin I met in Kiev; he was from Kiev I think. If I remember right, I was told that he had fought against the Germans.

Ashrafi:

Do you remember what you discussed with either Landau or?

Nambu:

I don’t really remember. I only remember that he said that he had difficulty writing papers, only one page a day, or something like that. I also met Okun’ in Kiev. He gave me a set of small triangles made with Lucite, and said that they were for determining the presence or absence of anomalous thresholds for various reactions according to my paper. I still have them.

Ashrafi:

Where did you learn Feynman diagrams?

Nambu:

That was when I was in Tokyo. The Physical Review was available at that time.

Ashrafi:

You learned them before ’49?

Nambu:

Oh yes. I don’t know exactly when I started, but there was talk about the Lamb shift being calculated by Schwinger and Feynman, and we learned about Feynman’s fancy theory of diagrams. And Tomonaga was already there in ’47 or ’48, so he would write us back.

Ashrafi:

When you’re at Chicago, so this is a long period now, at least when you first arrived, are you still in pretty constant communication with you colleagues in Osaka?

Nambu:

Oh yes, sure.

Ashrafi:

And how did that continue?

Nambu:

Pretty long.

Ashrafi:

Did it stop at some point?

Nambu:

Tapered off, I think, because communication got much better in general. So we didn’t have to go through this kind of personal communication. Actually I remember when the J/Psi particle was discovered in ’74, I got the news out right away. That morning I cabled the people in Kyoto about the news. They were very much grateful and excited about that.

Ashrafi:

It looks like your first publication on superconductivity is in 1960. “Quasi-Particles in Gauge Invariance.” And you write in your reflections about seeing a talk by Schrieffer here?

Nambu:

Yes, same house.

Ashrafi:

And that was in ’58, and you thought about it for two years.

Nambu:

’57, I think.

Ashrafi:

It’s mentioned in Laurie Brown’s article in this “Progress and Theory of Physics” and other places as well.

Nambu:

I think the seminar was in ’57 before the publication of the BCS paper.

Ashrafi:

So this is now your return to many-body theory.

Nambu:

Yes. Of course, through that time I had already kept the interest in many-body problems or superconductivity or super fluidity.

Ashrafi:

Did you have a sense that there were people thinking about field theory and many-body theory and condensed matter physics?

Nambu:

I don’t think so. I really doubt it.

Ashrafi:

So it took you several years to think about Gauge invariance in the talk you heard from Schrieffer.

Nambu:

A couple years, yes. Of course I met Phil Anderson also by that time. In Princeton, I also had an interest in many-body problems and things of that sort.

Ashrafi:

But then you go back quickly to arial conservation, weak interactions, and more meson dispersion theory. Until Jona-Lasinio comes, it looks like.

Nambu:

Yes.

Ashrafi:

So this one paper was the one thing you did in many-body theory in gauge invariance, then you returned to your particle physics.

Nambu:

Yes.

Ashrafi:

And that particle physics for another year had nothing to do with many-body theory.

Nambu:

No.

Ashrafi:

And then how was it that Jona-Lasinio came?

Nambu:

Before that maybe I should mention this work.

Ashrafi:

I’m sorry?

Nambu:

This “problem of symmetry breaking,” I first reported my ideas at the Kiev conference in ’59 in a discussion session after a talk by Toushek. I don’t know if there’s anything written about it?

Ashrafi:

Yes, you mentioned it in this thing which you sent me for Butsuri. Here, “Reminisces of the Youthful Years of Particle Physics.” Is this published?

Nambu:

This one is not the published version. The published version is a bit shorter than that, and published in Japanese. So where does Jona-Lasinio come in, is that the question?

Ashrafi:

Well how did he come to Chicago, first of all?

Nambu:

Wentzel, Oehme, and myself were now on the faculty. Goldberger was not here anymore. The three of us tried to get post-docs every year. Oehme had a connection to Europe since he came from Germany; he is a student of Heisenberg, so he knew people around Europe. My colleague Peter Freund arrived from Vienna. He was a student of Walter Thirring. I knew Thirring from Princeton days. But Oehme brought him here as a post-doc. I think Jona-Lasinio came after him.

Ashrafi:

And he had training in field theory?

Nambu:

I think he was a phenomenologist before. After he arrived here, he switched to the more formal kind of theory. He has made important contributions to theoretical physics since then. There is a festschrift for him in Journal of Statistical Physics, published this year, and I contributed a paper to it. According to what he told me recently, Herbert Anderson was the director of EFI at that time. Herb was a graduate student at Columbia when Fermi arrived from Italy, and collaborated with him ever since. This Anderson spent some time in Rome and got to know Jona-Lasinio. Then in 1959 Herb and I traveled together to attend the Rochester Conference in Kiev, but we first stopped in Rome. I gave a talk there about my work on symmetry breaking, and apparently Jona-Lasinio became interested. He wanted to work with me. I agreed, so Herb invited him to come to Chicago.

Ashrafi:

Oh you brought him in?

Nambu:

I asked him to join me to work on this.

Ashrafi:

Why did you ask him?

Nambu:

I thought I needed help.

Ashrafi:

And why him?

Nambu:

Well he was the only post-doc who had arrived, and was eager to work with me, or perhaps he asked me for a problem to work on.

Ashrafi:

I see. So the result of that was these two papers in 1961, “A Dynamic Model of Elementary Particles Based on Analogy of Superconductivity”.

Ashrafi:

You were going to say about working together with Jona-Lasinio.

Nambu:

Yes. Before his arrival I think I was already working along this line, and I said that I had briefly made a remark at the Kiev Conference about it, then wrote a brief Physical Review letter in 1960, “Axial Currents Conservation in Weak Interactions.” That was a sort of summary of my basic results, how to apply this idea of basic symmetry breakdown to particle physics. And I think probably Jona-Lasinio arrived that year.

Ashrafi:

Did he know of this work?

Nambu:

No, not at all, except for the talk he gave in Rome. And at the time, I had really personal problems. I don’t want to talk too much about it, but my son was seriously ill. I was totally involved in this problem, so I needed some help. So I asked him to work with me, and in fact the second of my papers was written by him, by Jona-Lasinio. I just want to say that there were these Midwest theoretical physics conferences that rotated around the universities in the Midwest. It started out in St. Louis, George Washington University, the second one was in Iowa where Jauch and Rohrlich were and I attended that. At that time, I was still a post-doc, and Goldberger game me a ride to go to Iowa City. I remember that. The conferences rotated around, but, it never happened in Chicago because we were kind of lazy about doing such things [chuckles]. But that year, in ‘59, it was at Perdue University in Lafayette, Indiana. And I was supposed to report on my work, but I could not because of my problems. So I asked Jona-Lasinio to go there and he made the presentation there. This was the first time of officially announcing our results. Still, I have here the proceedings. For example, I remember that Wightman was there.

Ashrafi:

Yes, it’s in here as well, “Broken Symmetry.” And there’s a few questions at the end, I think one by Wightman. So did you get any reaction?

Nambu:

Not really much of a reaction. Because at the time, particle physicists’ interests were elsewhere. Like the Chew-Low’s bootstrap, thinks like that. That was the heyday of the Chew’s philosophy. So people didn’t take much interest in my work. Rather the solid-state people were more interested because the connection with BCS theory.

Ashrafi:

Who?

Nambu:

The faculty members who were here, for example, and those from Illinois, I think. But then I attended this Rochester Conference in Rochester the next year, 1960, and in 1962 in CERN. I made a first thorough report at the Rochester conference in Rochester in ’60. That made a big splash, I think.

Ashrafi:

How do you mean?

Nambu:

Because of the Heisenberg theory, Heisenberg’s unified theory which had some similarities to mine, people thought there must be something in it. But still, I don’t think the majority of particle physicists quite believed it or took it very seriously. Heisenberg gave a report on his theory at the CERN Conference, and after that, I visited his institute in Munich and stayed there for three days.

Ashrafi:

So, as I look at the list of publications here, then you’re back to meson theory.

Nambu:

Yes.

Ashrafi:

Well, there’s a mix now. Here you’re doing both electro, weak, weak interactions, pions, mesons, and then something about the energy gap in superconductors, and then magnetic field and phase transition in thin film superconductors. More about scattering and meson theory. And then chiral symmetry. So if I look now through say the mid-‘60s, I see a lot of stuff on mesons and scattering, but also things now about symmetry, broken symmetry, superconductivity, and gaps. So are these two separate fields of research for you?

Nambu:

[Looks at list] Not separate, but maybe in parallel. You see, take a paper like “Possible Sigma-Lambda System” with Shrauner. I don’t remember this paper. There is a paper with Sakurai.

Ashrafi:

Yes. J.J.?

Nambu:

Yes. He was here around that time from Cornell.

Ashrafi:

Oh, he was in Chicago.

Nambu:

Yes. He was a Ph.D. from Cornell in the late ‘50s, and his thesis was so remarkable. We were very much impressed, and we appointed him right away as assistant professor. He came out here and started up his own theory of vector meson dominance. So we worked together with him. I have a few papers written with him, too, on phenomological kind of analysis. And the other thing that happened was a paper on “Chirality Conservation Soft Pion Production”. That was just applying the concept of chiral symmetry breakdown and to specific problems to show that this works, and that was my air, that this was not an abstract theory but it could be applied to real problems. So I invented the name “soft-pion”. Later, I also applied the concept to nonleptonic weak decays. Basically the technique is what is known as chiral perturbation theory now. On the other hand, I also was interested in real superconductors because there were some problems with BCS theory when a magnetic field was applied to a thin film. If the magnetic field is perpendicular to the film, it will lead to vortex formation. If it is parallel to the field, the field penetrates into the film and the gap parameter changes as a result, and the question is how much does it change. And there were theories. Gregory Wentzel, our senior professor, worked out this theory, using his way of handling BCS theory, and got one answer. And I did mine also, and got a different answer, so there’s the problem of who was right or wrong, and there was some controversy. I thought clearly Wentzel’s theory was not correct. But in that connection, I worked on this magnetic field problem together with Sani Tuan. He is right now at the University of Hawaii, just retired, but he was a post-doc here. He’s from Taiwan originally. But anyway, he was educated in England. He was spending some time in Berkeley and was supposed to go back to London. But he had run into a visa problem so he got stranded in Chicago and stayed on here. So we worked on that program for a while, for a couple of years.

Ashrafi:

So you have two parallel problems. One is in low energy, one is in high energy, but you’re also looking, in general, at symmetry breaking in both.

Nambu:

Yes.

Ashrafi:

Now are you in contact with other people who are working in many-body and field theory methods?

Nambu:

That’s a good question, a fair question I think. Not really. Of course there are University of Illinois people I knew. Schrieffer came as an assistant professor and spent a year here, then went back to Illinois. So with Schrieffer I interacted very much.

Ashrafi:

When was he here? Do you remember when that was?

Nambu:

Probably 1960. I think he wrote his text book while in Chicago.

Ashrafi:

Did you have much interest in the Martin-Schwinger formulation?

Nambu:

Yes, I had some interest in that too. I knew about it, yeah. But not particularly interested in that.

Ashrafi:

And Baym and Kadanoff were at Illinois at some point in the early ‘60s?

Nambu:

I met both Baym and Kadanoff at Illinois, yes.

Ashrafi:

No collaboration.

Nambu:

Not much collaboration.

Ashrafi:

And what about the Russian groups? What about Patashinski [?] and Pokrovski [?] ?

Nambu:

No, I never met them. I don’t remember meeting them. I never interacted with them.

Ashrafi:

How about Matsubara [?]?

Nambu:

Matsubara I knew the name, only I don’t know exactly when, probably in the 1960s in connection with the Matsubara temperature and things like that. I thought it was very nice. But then later I met him of course in Kyoto. Actually I remember that in my Tokyo days, I contemplated using beta as an imaginary time.

Ashrafi:

What about Matsubara’s greens functions for low-energy physics?

Nambu:

No, I didn’t know about that. The only thing I can mention is that I brought a post-doc from Kyoto around that time by the name of Kazumi Maki. He is at USC in Los Angeles. He was a very quick person and wrote paper after p aper on superconductivity. He was here for a year, but I didn’t really quite interact with him; he worked along by himself.

Ashrafi:

So you didn’t have much interaction with these other people?

Nambu:

No, not really.

Ashrafi:

Then we start seeing work and strong interactions. You continue work in symmetry breaking, but now what shall we say, after ’64 or so.

Nambu:

You mean on the color problem?

Ashrafi:

Yes, when was Hahn here? Was that ’65?

Nambu:

The paper was in ’64. But Han was not in Chicago.

Ashrafi:

So up to this point, up until your work with Jona-Lasinio, we’ve described how you were motivated to do these different projects. And then you start pursuing your discovery of symmetry breaking, as well as continuing to work in mesons and superconductors. Now can you help me understand how your work is changing in the mid-60s?

Nambu:

Yes, that was because of SU3 , the discovery of the SU3 symmetry by Gell-Mann and Ne’eman. That happened in ‘62. Before then of course, there was that problem of phenomenologically how to describe symmetry in terms of concrete substances and particles.

Ashrafi:

Is this a Taketani model?

Nambu:

Taketani-Sakata thesis, I should say. Sakata took that up, and he proposed a Sakata model before the SU3. He took three fundamental constituents as proton, neutron and lambda particle, lambda hyperon. So that represented the basic quantum numbers. And he saw that in terms of those particles, the other particles are built up. In terms of symmetry, of course, that works all right, for the mesons but for the baryons he had trouble because there are lambda and sigma that have more or less the same maser. So that was superceded by the formal SU3 theory of Gell-Man and Ne’eman. But at the same time the Sakata group (it may not be Sakata himself, though maybe Sakata was involved), his disciples Ikeda, Ogawa and Ohnuki at the Nagoya worked out the same mathematical theory of SU3 in 1959. That is also on record in Prog. Theor. Phys. There is also a paper by my former colleague at Osaka, Yamaguchi, around the same time, in Prog. Theor. Phys. Suppl. So I got interested of course.

Ashrafi:

This is back from your days in Osaka?

Nambu:

Yes, that’s right. And so there was the SU3 theory. I had to learn the group theory to understand that. Most particle physicists had to do it around that time, because people had very little knowledge of group theory, especially the representation theory.

Ashrafi:

And here you start looking at broken symmetry and SU3, is that right? Broken SU cross SU3 cross?

Nambu:

Yes, that was a kind of thing that many people tried to do. So SU3, then they extended to SU6. Taking the idea from Wigner’s nuclear physics SU4 theory, the istopic spin SU(2) of proton and neutron and their SU(2) spin combined and you get to SU4—it’s a larger group. Similarly you combine SU3 and spin SU(2) you get SU2 cross the SU3 embedded in SU6. And that was the famous SU6 theory of Gürsey and Sakita and Wali. People also tried further extensions of the symmetry scheme.

Ashrafi:

And how are your duties in Chicago changing at this time? You’ve been a full professor since ’58?

Nambu:

Of course I had to teach courses. But teaching was very light compared to other universities because we had the quarter system and only taught one quarter out of three.

Ashrafi:

Is that because you are at the Institute?

Nambu:

Yes. But almost all belonged to one or the other of the institutes and even if you did not, everybody was treated equally as far as teaching was concerned.

Ashrafi:

Did you ever participate in the administration of the department?

Nambu:

That was later when I became Chairman of the Department in ’74 to ’76.

Ashrafi:

So what shall we say about your work from the mid-‘60s to—what’s a good bracket to use?

Nambu:

Well, let me talk about this color problem.

Ashrafi:

Oh, okay, ’64?

Nambu:

Yes, that was good stuff, yeah. The quark model of Gell-Mann and Zweig worked and also there came the Cabibbo theory on mixing of quarks. Although all the people had very little understanding of what really it meant at that time. But then I started to worry about this constructing of baryons and mesons out of the quarks. And Gell-Mann, in his paper, was very ambiguous; he said that the quarks may be mathematical symbols or maybe real particles. And because, as I just mentioned, I subscribed to the Taketani-Sakata philosophy. I wanted to see the quark model in terms of real particles. So I already believed quarks must be around, be a real object. But then I ran into the problem of statistics with quarks. Because you have to assume that quarks have to obey Bose statistics to construct a baryon representation. So quarks looked like a boson – just mathematical label of the representation. That was not acceptable to me. I had to believe that if the model works, quarks are real particles. So I thought about it for a while and finally hit upon this color degree of freedom. I did it slowly, gradually, because I first increased the degree of freedom from one to two, then two to three, and finally, I found that the theory looked very elegant and simple.

Ashrafi:

When you say slowly, how long were you working on this?

Nambu:

About a year or so, I think. Because before my work of color with Han, there was a paper by Greenberg about a year ahead of me. He said that quarks may obey para-statistics, para-fermions. I wasn’t really impressed by that paper, to tell you the truth, because I didn’t think that para-statistics was of much interest; just sort of a mathematical construct and not of real physical interest. Because it is just manipulating symbols and there is no real dynamical content in it. I thought I had to understand it in terms of real particles, and the possibility was to understand it in terms of the three color degrees of freedom. Then I sent a pre-print out of my ideas, and maybe a week or two later came back a paper from Han. He was a graduate student at Syracuse. And he improved upon my mathematics regarding group representation and it looked very nice, so I offered him to write a joint paper. So that is how it came about.

Ashrafi:

And what kind of reaction did you get?

Nambu:

That was again lukewarm, I think. It was not a real sort of interest of those people at the time who were involved in phenomenological analysis. They fit the data with the quark model assuming the usual representation. That was enough. So I don’t think there was much interest. But soon after that first paper with Han, I wrote another article which was meant to be in the Festschrift for Vici Weisskopf, “Systematics of Hadrons in Sub-nuclear Physics.” In that already I was? That if you really think of baryons or mesons made up of quarks interacting with an attractive force like gauge interactions, then you can understand why the baryons with three quarks and the mesons with a quark and an antiquark are very stable. Because the total color of the systems is zero, neutral. It is just like in atoms when an atom has a net charge, it is in an ionized state, but when it is totally neutral it is in its most stable state. So in terms of working out the theoretical representations, I was able to show that only those color neutral systems are the most stable states. So in terms of working out the theoretical representations, I was able to show that only those color neutral systems are the most stable states. I said that then it makes sense that there may be other colored states, but they will be much higher in mass. So I was very satisfied by that observation. But I went a little too far and said that quarks are real, according to the Sakata-Taketani philosophy, so they must be observable. But there are no fractional charges around, so they must be integer. I was able to show that I can also accommodate integer charges for the quarks. That is how the integer charged quarks came up.

Ashrafi:

And then from ’65 to let’s say ’70 you have a series of papers about non-leptonic decays?

Nambu:

Yes, this is just application of this spontaneous breakdown, the sort of soft pion problem.

Ashrafi:

But these are all in particle physics; there’s no many-body theory.

Nambu:

No.

Ashrafi:

And you’ve written elsewhere about what a tumultuous time the ‘60s were, of course for everybody, and I wonder if that had any affect on you here at Chicago.

Nambu:

What did you mean, really?

Ashrafi:

You’ve written in your reflections, I don’t remember which one now, about what a tumultuous time the ‘60s were, just in general with the Vietnam War.

Nambu:

Yes, right.

Ashrafi:

And I wonder if that affected your life or work here.

Nambu:

Yes, in some ways it affected my life.

Ashrafi:

Can we talk about that, or would you rather not?

Nambu:

I’d rather not. Except to say that I had a hard time with the Russian authorities when attending conferences in Russia, as well as with American authorities. Partly because of my fault in just ignoring formal registration and things like that. But also because I expressed my feelings about Vietnam on this campus. So it was a really difficult time for me for my personal life. Also, I was kind of frustrated because I didn’t quite get the recognition I had hoped for my theories. And then if I may continue, I thought that of this group theory was going to become a very hot thing to study, but I did not have enough knowledge about group theory, or representation theory. So I spent a year reading on it, and as an exercise, I tried to apply it to physics. At that time, a large number of hadron resonances were already known. It seemed that there were an infinite number of them which formed the so called Regge trajectories of higher and higher spins. I thought of representing all of them in a single wave equation in terms of an infinite-dimensional unitary representation of the Lorentz group. I called it infinite-component wave equation. I knew that people like Dirac had discussed it before. But I just tried a simple formula and found that it produced a spectrum which looked like that of the hydrogen atom. Basically the wave function is a re presentation of a dynamical group. A dynamical group explains the degeneracy structure of the spectrum, the so-called accidental degeneracy. I found that the bound state spectrum for the nonrelativistic hydrogen atom could also be expressed in this way. My friend Feza Gürsey told me that Majorana had done a similar thing just after the Dirac equation, but it had a very unnatural spectrum. The Dirac equation had the problem of negative energy states. Majorana did not like this and so he invented an equation which did not have negative energy states. This Majorana equation had its own troubles, but before his paper came out, the positron was discovered and so it was forgotten. Anyway, I rediscovered this kind of approach and applied it to hadrons.

Ashrafi:

“The Relativistic Groups and Infinite Component Fields?

Nambu:

Yes.

Ashrafi:

And what did you find when you applied it to hadrons?

Nambu:

The point is that there were many, many hadrons discovered which were on linearly rising Regge trajectories. My equation produced a spectrum which went up to a saturation point. In Majorana’s case the problem was that it went down with rising spin. It is easy to understand why this happens, but it is totally unphysical. Mine was slowly going up to a saturation point, like the hydrogen atom. Actually, I found that the real nonrelativistic hydron atom problem can be represented as an infinite component equation. Simultaneously, a couple of people also made this discovery. One was Asim Barut. He was Turkish and at the University of Colorado. The other was Chris Fronsdal at UCLA. Originally he was a seaman from Norway but jumped ship in New York and became a physicist. So I interacted with them and also with a guy by the name of T. Takabayashi at Nagoya. He was one year ahead of me at Tokyo but started to interact with Yukama at Kyoto. Yukama had a vision that the elementary particles had internal structure, and had proposed a kind of non local field theory. Takabayashi took that up and worked on it, and arrived at a mathematical formulation similar to the rest of us. We all interacted closely with each other for a year or so.

Ashrafi:

And in 1970 you get your U.S. Citizenship. What can we say about that?

Nambu:

Well, I had decided that I had to be part of the community—to be involved I had better get a citizenship. And also this is the part where I don’t really want to say, but because of the problems of the Vietnam days I had some personal problems, I had some danger staying as an alien here. And I asked my colleagues, Herb Anderson, partner of Fermi and Fred Zachariason who was the Dean to be my sponsors. So there was no problem getting citizenship.

Ashrafi:

Now what turned your attention to confinement other than everybody wanted to understand it? Was there something specific?

Nambu:

[laughs] Continuing on this infinite component equations. I worked on it for a year or two, and finally I had to give it up because it didn’t work. Because it ran into all sorts of problems with unitarity, non-locality causality and also the violation of TCP. All these problems came together. I gave a report at the Nobel symposium one year in Sweden, but I had to give it up. I wanted to forget about all these things. But then came out of nowhere the Veneziano model in 1967. The Veneziano model realized the linear Regge trajectories and the duality of scattering amplitudes in a simple formula. So I got fascinated by it in spite of my depressed feelings at the time. First of all, what physics lies behind it? It is a mysterious formula nobody really understands. You can write down the formula in various ways. I wanted to decompose the formula as an infinite sum of Breit-Wigner resonances to see how many of them are at each resonant energy, what their spins are, and if the residues are positive os that they are real physical states. When I started doing this, there was a postdoc, Paul Frampton, arriving from Oxford. So I got his assistance right away and we were more or less convinced that all Breit-Wigner poles were positive. We also found that the degeneracy of states goes up exponentially with energy in the asymptotic limit. This paper was published in the festschrift for Gregory Wentzel.

Ashrafi:

1970, “Asymptotic Behavior of Partial Widths in the Veneziano Amplitudes”?

Nambu:

It was in 1967. Wentzel retired in 1967 and went back to his wife’s place in Italy, Ancona by Lake Cumo. My colleague Peter Freund, our friend Charles Goebel at Madison, Wisconsin, and I solicited contributions and edited the book, which was published by the University of Chicago Press. Incidentally, it contains some interesting contributions, for example, Schwinger’s unpublished notes on strong coupling theory. After that I worked further on analyzing the structure of the Veneziano amplitudes. I started from the Koba-Nielsen representation of the beta function, and in the course of this analysis, I discovered that the resonances can be interpreted as the excitations of a string.

Ashrafi:

Mathematically.

Nambu:

Mathematically. So I introduced the string in my paper. A similar conclusion was reached by a couple of other people too. But they didn’t use the name string. Sergio Fubini is one, an Italian particle physicist, and he was also post-doc back with us in the ‘50s. I worked with him too. The other one was Korkut Bardakci at Berkeley. My work on the string was presented in a conference in Detroit at Wayne University in 1968.

Ashrafi:

“Quark Model and the Factorization of Veneziano Model”.

Nambu:

This was recorded in ’68 and published in ’69, I believe. Then after that I kept working on that, but still I ran into all sorts of problems to represent the real physics. I had assumed there were some extra dimensions in space, formally speaking, mathematically. Like six dimensions at least. And I hadn’t thought of this Kaluza-Klein theory at that time yet. I knew about it. I didn’t quite like it; I didn’t know what to make of it. But even so, even with that, I thought the theory not satisfactory. And finally in the ‘70s people were discovering the problems with the hadronic string theory and abandoned it, until the superstring theory came around.

Ashrafi:

Nonetheless, this period looks like a very productive one for you.

Nambu:

Yes, I must say so. Also, I must say at that time I was in a depressed, kind of depressed state because of the lack of recognition, and I was sort of stuck in the string theory and not making much headway. But in 1970, I remember there was a Rochester conference in Kiev to which I was invited, so I wanted to attend it. Now, I’d gotten my citizenship in ’70. I got a relief from my problem —I had some sort of immigration problem, but it was solved by then so I was able to go to Kiev. At the same time I got an invitation from the Copenhagen people for a summer institute or something, so I wanted to attend that too, to give a talk on my theory. It was in the summer of 1970 before going to Europe, I wanted to deposit my family in California with my friends. So we drove out from Chicago, and unfortunately on the way we had an accident on the road in the Salt Lake Desert. Actually the whole cooling system ruptured and the engine overheated and was destroyed. So we had to stay three days in the desert to fix it, and managed to get to California. But by then I had missed a plane connection, so I gave up going there and came back to Chicago. But in the meantime I had sent my manuscript to Copenhagen, hoping that it would come out eventually at the proceedings, which it did not.

Ashrafi:

This is “Use of Regulator Fields”?

Nambu:

No, it was unpublished actually, but so it must be there. Duality, number 78. Duality and hydrodynamics. This is the paper in which I introduced the two-dimensional surface action.

Ashrafi:

Well at what point do non-Abelian gauge theories?

Nambu:

I mentioned it just briefly in passing in this paper with Han, that I suppose the interaction, color interaction is described by a gauge theory.

Ashrafi:

This is ’65?

Nambu:

Yes. Color gauge theory and so on and so forth, without knowing whether does it really will work or not. Because at that time yet there’s no precise formulation of gauge theory. No confining properties are known yet. It was just a word, as far as I was concerned. But I worked with the gross features in the next paper in the Weisshopf Festschrift. I have already told you about it.

Ashrafi:

And then you say in ’74 you become chair of the department?

Nambu:

Yes, I think ’74-’76, for three years.

Ashrafi:

And that must have affected your work.

Nambu:

Yes, it was very hard on me.

Ashrafi:

What can we say about that time?

Nambu:

I was very much involved with the appointment problems in the department. Plus the fact that I was getting old enough to start having various health problems at the same time, like high blood pressure, gout, and also herpes, that virus infection which is very painful. But I also managed to do some work. Looking at the list of publications, I notice that there was the question of whether the newly discovered J/Psi particle was an excitation of a new flavor or that of color according to my integer quark model with no confinement. On the other hand, I had this string model. I knew that it can confine quarks and antiquarks because of the strings that join them. So I was in a quandary. Which theory should I prefer? I tried both. There are papers I wrote with Han again to save the colored quarks, and other papers I wrote about confinement by strings viewed in analogy with Abrikosov flux tubes.

Ashrafi: 

So at this point you’d been at Chicago for a good 16 years, by ’76, and it must have changed a lot while you were there, or did it? Did it change much in the time you were here? 

Nambu:

Yoichiro Nambu discusses the decline in the quality of physics students in the 1960s.

Yes, that is an interesting question. All the people were getting older, though not quite died away yet. I was getting to be one of the senior members. And I must say that the quality of the people, starting from Fermi’s days, was getting lower. The quality of students was also low, during the 60s in particular. That was a problem with me, how to train and use these students. In the ‘60s people did mostly phenomenology. The students were given just phenomenological problems, basically data analyses. That was all they did. These people have completely disappeared since then because they could not catch up with the revolution in particle theory that occurred in the ‘70s, like asymptotic freedom, supersymmetry, topological excitations, new flavors, Kobayashi-Maskawa theory, emergence of the Standard Model ... Unfortunately I myself started to lag behind because of my chairmanship. But I also started to get recognition. So in the ‘70s I was more or less involved in all sorts of administration and other things. Then the ‘80s were a really bad time for me because of my family problems; my parents died and my son died. It was a horrible time for me actually.

Ashrafi:

I’m sorry to hear that. Did you in your time here ever consider returning to Japan?

Nambu:

Yes, that was always on our minds all the time, but you see, this had happened to all the people who are immigrants. If your kid grew up older than 10 or 12, then they had better not go back because of the problem with education, because they cannot adapt to the new culture and system well. So most people did go back to their own countries before that period. I really adapted to here, but I just said when I was working on symmetry breakdown, my son became very seriously ill. At that time we were thinking of going home, because our son was getting around that age at that time and I had an offer, too. If we missed that time of course, we would not. Unfortunately with my son’s problem we decided to stay on.

Ashrafi:

You also mentioned during lunch that you’ve had many offers to go places other than Chicago. Did you ever consider going someplace else?

Nambu:

Yes, sometimes, like Stanford which was quite attractive, for one thing. Actually, I got an offer twice from them. Other places, I don’t know, maybe a dozen or so. I was not very serious about that. The East Coast I didn’t quite like. No, Stanford was the only one that was quite attractive. But in the end we decided not.

Ashrafi:

You said you liked the Midwest of the United States. Did I understand you correctly at lunch that it reminded you of the farm regions of Japan?

Nambu:

Because the people of the Midwest are more comfortable to live with because they are honest in a naïve kind of way, and unprejudiced compared to the people in the West or the East Coasts. People in the East Coast are too sophisticated. On the West Coast there are too many oriental populations there, and more ethnic prejudices. I don’t know if you realize that my wife taught at a community college just outside of Chicago.

Ashrafi:

I completely neglected to ask you about your wife, about whether she comes from a scientific background.

Nambu:

Oh, no, no not at all! I met her in Osaka, and Osaka is a merchant city. Learning is not prized at all. So her background is not?she comes from a family of coal broker. But they had not come from Osaka but from another part of the countryside. But anyway, she has no real scientific interest; she is more interested in the arts. And she taught at the community college in the suburbs of Chicago in the fashion design department. She was chairman of that department for a while. So when she started to teach at the college in the early ‘70s, the local people, just outside of Chicago, she was the first oriental they had met. Those kids were young little girls and a few boys, many of them had not even come to Chicago yet here because the parents were very strict: “Don’t go to that city of evil! Sin city.” Very naïve, extremely naïve people. So that’s the kind of atmosphere I found in general here.

Ashrafi:

Well, I’ve crossed out all the questions which I had written. We’ve covered a huge amount of time. Is there something else that we’ve left out that we should talk about?

Nambu:

Until the ‘70s? Yes, maybe that there was a community of physicists from Japan when I came here. There were very few older people, then our generation of followed. When I arrived here there were a few people already of the post-doc kind. Mr. Miyazawa, who had worked out this delta resonance idea; and also a few others, half a dozen or so. Some of them I knew from Japan, and they formed a small kind of community of Japanese physicists, mostly physicists. We interacted closely with each other. But eventually they all disappeared or dispersed. Many of them went back to Japan or maybe to other parts of America. Some of them are dead by now, unfortunately. There are other people in other parts, other universities, and mostly they are dead or had gone back to Japan, and may be also dead too there. So right now we have very few people that I know. There are young guys, not many of them, from Japan.

Ashrafi:

Now, they can perfectly well stay in Japan.

Nambu:

Yes, but even in Japan of course people of my generation are dying out fast. Our relatives and friends are dying. So there are only very few people even there.

Ashrafi:

So if we go back now, if we start say the last work you mentioned was in ’77, you start getting some awards, some recognition. The J. Robert Oppenheimer prize at the University of Miami in ’76; the Order of Culture in Japan in ’78; and then a lot more during the ‘80s and the ‘90s. So you’re beginning to get recognition now for your work. So there are two things to talk about: the prizes that you were winning, and also the work you did in the ‘80s.

Nambu:

Yes, there is some work I did in the ‘80s. Still I like one of them. Of course it is kind of forgotten by now, a little bit, but there was still some hope in it. Namely the nature of the Higgs field. That is a paper in the late ‘80s, ’89?

Ashrafi:

So here you did some formal work on strings and on quarks, topological things?

Nambu:

Yes.

Ashrafi:

Should we say anything about those first before we jump to ’89?

Nambu:

Yes, that was the outburst of the new gauge theories, and the topological nature of the gauge theories was a hot topic in those days. Like monopoles and instantons. Okay, I’ll say one thing about confinement and the relationship to gauge theory and the string. I hit up on this string interpretation of the Veneziano model, and immediately I knew that that could confine the quarks, because quarks attached to the ends of the string and can not separate. On the other hand, if you work out the mathematics, it did not quite work out well. Sooner or later people found out that you needed 26 dimensions, something like that. And in the meantime, there emerged a new gauge t theory of color which was very nice in explaining the possibility of quark confinement. That is the usual quantum field theory, and my string theory is not quantum field theory but a more general one which also has various problems. Some of them are theoretical so far, they were found already when I worked out this infinite component wave equation. So I was in a sort of quandary, in the following sense. I knew that strings can confine quarks. On the other hand, I had also my pet theory of integral charged colored quarks, so the quarks were free to come out. But anyway, it explained the stability of color-neutral particles, hadrons.

Ashrafi:

What year are you talking now?

Nambu:

In the early ‘70s. So I was in a quandary of which theory I should really side with. And I knew that string theory had mathematical problems. So probably it would not quite work out. Many decided to abandon string theory. I think it was around 1973. There was a summer institute at Aspen, and string theorists of the day got together. And more or less around the time people realized that we had to give up the hadronic string theory.

Ashrafi:

Were you at that meeting?

Nambu:

Yes. I met most of the string theorists of the day there. And of course John Schwartz was there too. Super-string was discovered by Green and Schwartz in the early ‘80s or thereabouts. ’80 or ’81. And before then whole new discoveries came out, like the discovery of J/Psi which was a shock to many of us. And super-symmetry got born then.

Ashrafi:

You were saying super-string theory was discovered??

Nambu:

Early 1980s, I think 1980 or ‘81 or thereabouts. I am not sure of the exact date. Before then in the ‘70s there were discoveries of J/Psi and new flavor, charm, then the upsilon, the new flavor.

Ashrafi:

Why was the J/Psi a shock?

Nambu:

Oh, first visibly it was a shock because it was such a huge peak, peak at such high energies — out of scale, you know — and why that should be such a narrow resonance. And of course then the question of what is the nature of this resonance? There were speculations at the time dating back to the early ‘60s, that there may be a new quark flavor by several people including the Sakata group. So we were aware of that possibility, and Sakata had said the number of the elementary particle may be infinite. They didn’t care how many there are. So he was not afraid to introduce such quarks. It was inferred by the Cabibbo theory that there must be a partner of the strange quark, the flavors must come in pairs, up and down, and straight and charm, and even further to the next generation. And I really liked the theory of Kobayashi Maskawa, phenomenological theory around that time, 1973 or thereabouts, saying that — The CP violation had been discovered a long time ago in the ‘60s, and what they said was that if we introduce the third generation, at least six quarks, not four, then you could accommodate the CP violating phase. They explained that phenomologically. So really nice things, I really liked it. I was impressed. And just they come from the Sakata group school. They practice what Sakata said. They are not afraid to approach anything new. So I was very impressed by that in 1973. Then came also the super-symmetry which I was not impressed because although it was a very nice mathematical idea, nature didn’t seem to have any sign of super-symmetry. So what’s the use of that? But it was challenging; mathematically a challenging subject, and very difficult to master, actually. But also the gauge theory about SU3 color, there are all the problems of so-called instantons and monopoles and other possibilities. So if your theory predicted the existence of such object, then it would have to be taken seriously. And they were trying to find monopoles, for example, and they failed actually. But that was the atmosphere of that time. I must say, I used to say that my favorite sort of theory of physicists is that there are three modes of physicists, theoretical physicists, their operating style. One is the Einstein mode; the other one is the Yukawa mode; and the third is Dirac mode. And the meaning of those things is that Yukawa mode is a bottom up kind of approach, starting from phenomenological facts. There is the nuclear force, and you explain it in terms of some particle. Yukama school has no compunction in introducing any new particle if necessary without asking questions about its origin. The Einstein mode is just the opposite. It is a top down approach. You start from some fundamental principle, like general convariance, and build a theory to explain known phenomena like gravity. The gauge theory or the gauge principle belongs to that approach. The third one is the Dirac mode. This is more drastic than the Einstein mode. Essentially it is the attitude to pursue theories that are esthetically and mathematically beautiful. Dirac introduced magnetic charges, or monopoles, in addition to electric charges in order to make the theory symmetric between electric and magnetic fields. In his paper he said that this theory is mathematically so beautiful that the nature had better adopt it, or something to that effect. In doing so he also invented the concept of fiber bundle independently of mathematicians. I would say that this mode showed up in the ‘7 0s in theories like supersymmetry, supergravity, and superstring. It is still thriving today.

Ashrafi:

Not very much like the Taketani philosophy.

Nambu:

No, not very much of that kind of idea. I met later with Taketani in Japan. In the ‘60s I was told that the Taketani/Sakata group looked at me and all Americans as a sort of enemy. But Taketani changed his mind and he was very kind to me later, in the 1980s.

Ashrafi:

So you mentioned this paper in ’89?

Nambu:

Yes. That was only a pre-print, I think, or the one proceeding a Polish meeting.

Ashrafi:

BCS Mechanism, Quasi-Super-Symmetry, Fermion Mass, 11th Warsaw Symposium On Elementary Particle Physics, New Theories, and Physics.

Nambu:

Oh yes, that’s it.

Ashrafi:

You said you particularly liked that paper.

Nambu:

Yes, I had health problems and also family problems around all the time in the ‘80s. But I thought of this idea that the Higgs boson may be composite. By then of course the top quark was assumed to exist—not really discovered yet, but people took it for granted, and it must be very heavy. And according to symmetry breakdown kind of idea, the heavier the mass of that fermion, the larger the coupling constant, the Yukawa coupling. So the top quark has a large mass, and— How does it go?? I may not have said it exactly correctly, but the point is that if you build a bound state of top quark and anti-top and make it a kind of Higgs boson, then you can understand the nature of the Higgs boson without introducing it in an ad hoc way. And we could even compute the mass of the Higgs boson, given the top quark mass. And that was my idea. And I did not realize its importance really at that time because I was not quite familiar with what was going on at that time in physics because of my involvement with the family problems and things like that, but I made a speech in Poland t this time and there were some errors and I think it was rather incomplete. But then after a few months, maybe a year or so, the people at the Fermi Lab, Chris Hill and Bill Bardeen called me, and they thought quite something of it, and also other people were getting excited about it. And in fact Bardeen and Hill worked out more detail and computed the Higgs boson mass. Of course this kind of idea still has a problem; all the Higgs boson theories have problems in accounting for the mass spectrum of the quarks and leptons. These are just ad hoc parameters. My idea has the same problem. But anyway, I don’t have to assume any new fundamental particles. So they worked at that time and then decided that it really didn’t work because the mass of the Higgs boson came too high, a little bit too high. Not exactly much too high, but compared to the mass inferred from experiment indirectly.

Ashrafi:

You mean the mass of the TT bar?

Nambu:

TT bar, yes. So they abandoned it, but I still have some hope that the theory will come back someday. Maybe in connection with super-symmetry.

Ashrafi:

Then shortly thereafter in ’91 you retired.

Nambu:

Yes, yes.

Ashrafi:

Do you want to say anything about since that time?

Nambu:

Yes. Also at the time my health problems got worse, in the ‘90s. In ’94 I got a stroke. I recovered from that fortunately, but I still have this other problem, the high blood pressure and other things. But I retired and became more free—I had more free time, and so decided to spend part of the time in Japan. And it is comfortable to work there because I still have a lot of friends there. These are the past post-docs here or other friends, and many of the post-docs I had here, maybe half a dozen or so, became quite established in Japan. And one of them became the director of the KEK.

Ashrafi:

So where in Japan do you go?

Nambu:

My home base is in near Osaka. It is a suburb of Osaka, but the Osaka University Campus is in the same town.

Ashrafi:

Not the City University of Osaka.

Nambu:

Not the City University, no. I have no connection with that except that I know a few people there. But I have my friends from the old days who are professors at Osaka. I can sneak into their group, even though I do not have a formal appointment, and I get office space and things like that, and attend the seminars or give seminars myself. I go also to a laboratory there called the Research Center for Nuclear Physics. I have friends there, so I go there and enjoy talking to the experimental and theoretical physicists. There have been some new discoveries there recently. Tokyo is my old home university. I go also to Tokyo because I have friends and past post-docs there too. And also Kyoto is not far from Osaka; it takes about one hour by train. For example, last fall, last December was the 50th anniversary of the Yakawa Institute, so I was asked to give a memorial lecture.