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Interview of Raman Sundrum by David Zierler on September 22, 2020,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Interview with Raman Sundrum, distinguished university professor of physics at the University of Maryland. Sundrum recounts his childhood in India, Maryland, and Australia and he describes his life as the child of an international economist with the UN and the World Bank, and a pediatrician. He describes his undergraduate experience at Sydney University where he majored in physics and where he learned that his abilities were in theory. Sundrum discusses his time as a graduate student at Yale, where he was accepted to the math department, and he explains how he immediately shifted over to physics. He explains his initial difficulty settling on a research focus under the direction of Laurence Krauss before he developed a relationship with Mark Soldate and settled on thesis research on particle theory beyond the Standard Model. Sundrum discusses his postdoctoral work at Berkeley, where he spent time at the Lawrence Berkeley Laboratory. He describes being recruited by Howard Georgi to do postdoctoral work at Harvard, and he explains how he collaborated with Lisa Randall and how the Randall-Sundrum papers originated. Sundrum describes the impact of this collaboration on research in supersymmetry, and he explains the events leading to his tenure at Johns Hopkins. He explains how his research focus shifted to cosmology and he discusses his decision to switch to a faculty position at Maryland, where he became director of the Center for Fundamental Physics. At the end of the interview Sundrum explains his longstanding fascination with metaphysical ideas, and he reflects on the importance of developing intellectual maturity over the course of one’s career.
OK. This is David Zierler, oral historian for the American Institute of Physics. It is September 22nd, 2020. I’m so happy to be here with Professor Raman Sundrum. Raman, thank you so much for joining me today.
Thank you, my pleasure.
OK. So, to start, would you please tell me your title and institutional affiliation?
I’m a distinguished university professor of physics at the University of Maryland at College Park.
And when were you named to the John Toll chair?
Also as soon as I was hired. So, I think I entered as a John Toll chair shared with Jim Gates, and then a year later, got the distinguished university professorship.
Now, what is the connection with—to John Toll?
So, John Toll was a—was actually a physicist, a physics professor at the University of Maryland, but really the person that brought it up from a, you know, minor department to a, you know, top-ranked department by a major expansion in its early years. And so, this chair is named after him, and it’s a great honor to have that chair—to occupy that chair at this moment.
Well, Raman, let’s take it all the way back to the beginning. Let’s start first with your parents. Tell me a little bit about them, and where they’re from.
So, both my—you know, my heritage is Tamilian, the South Indian part—one of the South Indian states. And, but both my parents at different points in their lives, my—were raised in what was then Burma—Myanmar now. I’m a relatively young child of my parents. So, they actually grew up in pre-World War II and World War II Burma.
And what were the circumstance of their families getting to Burma?
Yeah, so, indeed, you have to remember that is the era of the British Empire, including India, including Burma. And so, in a sense, they were part of the—you know—the educated Indians that were important in, you know, probably on average more educated Indians than there were educated Burmese, and so there were many opportunities for lawyers and, you know, all sorts of professionals in Burma. And so, I think they were part of that set of people that had gone there for various opportunities. But it was very formative, especially in my father’s case. I think the culture was very formative, on top of their Indian culture because, of course, it wasn’t like they assimilated completely in those days especially. There would’ve been an Indian presence there, keeping its own customs and so on, but also having friends and so on who would’ve been the native Burmese.
How long did they spend in Burma?
So, decades [laugh] in a—like, my father I think was there—he was born there. And, in other words, his, you know, parents had moved there at some point. So, he had really spent all his time there except for some education in England and the US at postgrad level, and really was there until the military takeover in the ’60s when essentially he became a kind of—not refugee in the—you know—a well-educated refugee who had opportunities, but, still, somebody who wanted and had [laugh] to get away because he couldn’t stand the military government that came in. My mom I think was there off and on for a shorter total time, but again from her childhood spent a lot of time in Burma. They spoke fluent Burmese. That was their secret code language when the kids would—
—[laugh] when we, who didn’t speak much Burmese or any Burmese, had birthdays coming and things like that—
And what was your language growing up, your first language?
So, it really is English. There were efforts made by my mother especially to try and get Tamil into us. And I actually lived in what was then Madras, now Chennai, for three years between ages 6 and 9. So, I had more of a formal education in Tamil, but was never very—and still am not very good at it, but can sort of get by at, you know, street-level conversation.
And what were your parents’ professions?
My father was an economist, and mostly a development economist, so interested certainly in India, Indonesia, so countries in the South East and Pacific Rim. And my mother was a pediatrician.
And where did you grow up? Where did you spend most of your childhood?
So, I actually—you know, once my father left Burma, he ended up—because he was a stateless person. Fortunately, that meant he could be part of various international organizations. So, he was originally part of the UN, and then he was in the World Bank. And I was—so when I was born in Chennai, or Madras at the time, but very soon after was brought to Bangkok when I was zero years old as a—when he was in the UN. And then when he joined the World Bank, again, pretty much by the time I was 1 at most, we were here where I am right now in Bethesda—Bethesda, Maryland, in the outskirts of Washington, D.C., because of the World Bank connection. And so, I kind of grew up not far from where I am right now, you know, maybe a five-minute drive, until I was aged 6, and then we went back to India for three years. Then—and then we moved to Australia where my father had a job as an economist in the Australian National University doing research on development economics. He did not—I think he wanted to leave the World Bank. Something in its political and bureaucratic nature even at that time was bothering him. He was probably more of an academic than he was a creature of the World Bank.
And you spent the rest of your childhood in Australia?
And then I spent the rest of my childhood in Australia till grad school, when I came back to the US.
And what is your citizenship, or how many passports have you had over the course of your life?
Actually, it was pretty simple in that I just had my Indian citizenship from birth until I got—and I did get Australian permanent residency, but then just maintained my Indian citizenship. When I came to the US, it took me a little bit by surprise, but because I’d been doing my PhD for a couple of years, the Australian government revoked the permanent residency. So, you know, we begged and pleaded, and there was no way out. But that left me with my Indian citizenship, and but with mostly my plans to stay in the west and certainly most likely in America. So, it was kind of a tricky thing because I had to make sure I was on the right set of visas, working towards a Green Card, and ultimately got one in the nick of time. All these things sort of happened in the nick of time.
And I guess if there’s such a thing as a globalized accent of the British Empire, you would have it?
You know, I’m guessing that must be true. Of course, you—I hear what I, you know, imagine in my mind’s eye, which is I think of it as accentless. When I hear myself on recordings, as I increasingly do as I’m looking through my Zoom lectures and stuff like that for classes, yeah, it’s got some sort of clipped Anglo side to the American accent. So, it’s definitely a mix. I don’t think I picked up too much of the Australian—at least my Australian friends don’t recognize anything there. But something—something—took the edge off the completely American—
—accent, which I started with.
And you grew up in the suburbs of Sydney?
No, I actually grew—because my dad was in the Australian National University in Canberra, I grew up in Canberra, which is really a much more suburban, no big—you know—big inner-city kind of aspect to it, and a much smaller city. Much more—I think they literally called it a garden city. So, it was quite a different experience than Sydney. I went to university in Sydney, but I was mostly just growing up in Canberra.
Raman, growing up, what kind of cultural traditions did your family follow, given how sort of cosmopolitan and internationalized they were?
In a sense, quite traditionally Indian in that we—my mom would celebrate like the standard religious holidays of Diwali, things like that, would cook Indian food most days. There was a mix because they would sometimes cook Burmese food. And we often had a lot of friends—family friends—a lot of them were Indian background, and at a time when there was less—certainly in Canberra—there was much less immigration. So, it’s literally from India. So, you literally knew—of the hundred Indian families in Canberra, you knew all of them, and you would see them periodically and so on. So, my parents’ social life was mostly Indian but with a number of westerners of various types too. And I think we of course had our school friends, and we had some friends through our parents who were, you know, the children of Indian friends of theirs. And they kept to, you know, a lot of the little religious holidays. My mother kept to what aspects of her Hindu religion fit with her being in a different country. And I think with occasional contacts with Burmese people, that was mostly the cultural background. But it was very—my father listened to, you know, classical South Indian music all the time. And so, in that sense, we were Indian kids, and mostly assimilated to the Australian way of life as well, you know, barbecues and all that. [laugh]
And what kind of schools did you go to growing up?
We went to a—I went to public schools until I finished eighth grade. And I think I would’ve continued on that way, the way my sisters had, except I was not doing well by the—by my—well, by the standards set by my older sisters. And so, my parents were shopping around for a school with a higher reputation than the public school I was at and chanced on a Catholic school which was doing very well, and sort of moved me into that, against my wishes, but I moved. And it kind of worked out for me. I—you know—I had—you know, in terms of anything that ultimately came of me, I had an absolutely first-rate, top-notch math teacher. And the other teachers were good, but I did—they did give me this by shifting schools.
When did you start to get interested in science? Was this from an early age?
In a sense, no, no. You know, I see it even with my kids. That is, there’s what you are interested in, and what you would like to think you’re interested in.
I would like to say at the time that I was interested [laugh] in science. But I really had no interest in science. I was able to follow what was going on in school and so on. But I don’t think I had any interest in science. I was much more in a fantasy world of wanting to—you know, I would like to have been like a military officer.
That was much more the romance of the way I was thinking. And any of the bad sides of that were certainly not entertained by my teenaged self. But I liked the excitement of, you know, what I was perceiving [laugh] as war—the strategy, the mildly intellectual side to it, the heroic nature of it. So, I was much more in that—you know, that was what interested me. That’s what I read about. I read about military history and so on. But I was not sitting around reading Scientific American. I was doing my schoolwork and doing it pretty well, but that’s about it.
So, when you were thinking about colleges, you were not thinking about physics programs specifically in high school?
I was, again—again, you know, that’s why I think this is such a bad example for anybody listening to [laugh]—there was—you know, I was not a popular kid. And I was doubly damned by being, you know, brown in a country which was quite white, and where the culture was—you know—on a daily basis made it clear that you were not—I think the words they use is tolerance as opposed to [laugh], you know, celebration. So, in a way, as a little bit of a misfit, and by my own personality, you know, a misfit, I did sort of—I was proud that I was doing well in school. And it was constantly chaffing that I wasn’t doing as well—I mean, I wasn’t that good at it, but I was—again, in my mind’s eye, I wanted to be. So, in that sense, I was looking at the smartest kids in the school, and thinking, you know, if I could just sort of look at them, I could pull myself mentally towards their, you know, abilities. And, indeed, the smartest kid in the school was thinking of doing physics, and ultimately did math, but, anyway, was thinking of doing physics. And so, I thought that’s it. So, again, it’s not what I was interested in but what I wanted to be interested in. And so, I said, oh, well, if he’s doing it, then I’m just—I’m going to go do physics. And that’s sort of where I was going, except that I come from a clan—especially on my mother’s side—I come from literally a clan of doctors. My mother was a doctor, both my sisters are now doctors, all my cousins were doctors, and so on. So, there was this idea that I was thinking vaguely that physics might be something to do, but I was basically working towards becoming—getting into med school, which was an undergraduate degree in Australia, at least at that time. And so, I did. And it was really the last few days before you had to decide like to go to college, you know, and then what subject? Are you going to go into medical school, or are you going to go into a Bachelor of Science thing? And it was literally the last few days where I was all set to go to medical school, but then something kicked in. Again, I can’t even explain because it wasn’t—you know—it wasn’t very voluntary or deliberate that I couldn’t do it. And so, I quickly told my mom, who was quite disappointed, you know, that I’m not going to medical school, and I’m switching to this—you know—I’m going to Sydney University, and I’m going to do science.
And in the Australian system, you have to make this decision right away? The concept of a general education, and then declaring a major later on, that’s not how it works there?
You know, maybe nowadays, it’s picked up a little bit of the American style to some extent—probably to a lot—to a greater extent. But, at the time, absolutely not. It was very much the classic English style where you—everything is decided super early basically straight out of high school. So, that was a kind of momentous decision, except I think my memory is I didn’t make it. It just sort of happened in my head, and something dragged me off into science. So, that’s how I ended up sort of in physics. If you want, at best, you could say something unconscious in me or subconscious in me took me there. Otherwise, I’d be quite a happy physician at this time.
[laugh] And were your interests or talents in math—did that sort of naturally lead you to theory, even early on?
Yes. Again—again—pure ego was sort of pushing me to think that I had to be a theoretical physicist like an Einstein and so on. But then the second thing that pushed me was I was absolutely—you know, we had a lot of lab courses, thankfully [laugh], at University of Sydney, and many hours had to be spent there, and I was terrible at it. I was terrible at it, and so terrible that my eczema at the time got worse out of the sheer stress of it, and once while in the lab, I like fainted [laugh] from some infection I had picked up by scratching my leg out of pure stress. So, it quickly became evident that, you know—
—lab was not for me. And nothing in lab class ever worked. Nothing ever worked that I tried—I tried to get these things to work, but nothing ever came out the way it was supposed to in the lab. So, I think that sealed it and, yeah, it was probably the mathematical strength that therefore at least allowed me to continue with that idea of being a theorist. However, I do distinctly remember a—one of the lecturers in Sydney when I said, you know, I was thinking about being a theoretical physicist—and remember, I wasn’t a stellar physics student during college. Even my GRE scores to get into the US were actually quite pathetic. But when I said, “You know, I’m thinking of being a theoretical physicist,” he said, “You know, I really don’t think you should”—
— “become a theoretical physicist.” [laugh]
“I think that would not suit you.”
And now I can see that having heard the advice, it just washed right over me. It’s like somebody in totally denial. It was good advice in a sense. I can see the evidence that was being presented to this guy and—but it had no impact. I was not at that age able to think realistically what are my odds of success or does it even make sense? Do you even like the subject? It was still this idea that it was just this is the cool thing that smart people should do. [laugh]
Did you have a senior thesis?
I did. And at that point, let’s say that what the truly transformative moment was in my—what’s your junior year in American language—my third year. You see, the other thing was a deep interest of mine growing up was mythology. It again had the kind of romance of the storytelling and the heroes and all of that. But I used to read the mythologies from all the different countries—Chinese, you know, the Norse mythology, Greek mythology, Hindu mythology—and other than the heroics, which is—you know—it’s like you’re reading Lord of the Rings, except even better in some se…I mean, Lord of the Rings is borrowing from mythology. Other than that, there was another deep part which is it actually talked about something like, you know, the beginning of the world, right. Each religion or mythology had its own origin story. And this was somehow mind-blowing that somebody could even write a story like with that—which I perceived as depth, and probably it is, you know, just that even though it’s a story. So, something about that was in my personality that was blown away by the fact that they could have the origin story. Now, nothing like that showed up in physics in my education in University of Sydney, which was a stronghold of plasma physics—great subject but just not what I do. So, I was not exposed to anything that resonated with this sort of epic nature of my interests from childhood, until I was asked to write an essay in some sort of physics survey class, starting with some Scientific American articles, and then going up from there, but just in a topic that had nothing to do with any subclass that I was taking, right, just looking at research kind of thing. And by chance, I came across the subject of the mathematical physics subject called “fiber bundles,” which is kind of the mathematical language in which the—now I can tell you—the laws of nature are written. At the time, I had absolutely no concept that there was such a subject, and that it had this beautiful geometric side to it that—most people would know that there’s a kind of geometry of curved spacetime associated with general relativity. But that in fact all the forces of nature have a geometric structure was—is probably less known, and it certainly wasn’t known to me at the time. But in the course of just reading about it at the Scientific American or Nature level of discussion, I saw that, wait, this is something that is, first of all, as epic as the ancient epics, [laugh] OK, as the mythology. It was like daring to talk about something so fundamental like the entire universe in one shot. But not only was it that, it was saying that, you know, in a dirty, rotten world with dirty, rotten plasma physics—the way I thought about it then. I’m sure it’s a beautiful subject, but full of complicated effects, and I was not up for it. But here was something which was deep, in a certain sense simple—simple in an elegant way—and very, very beautiful. So, I think that’s when I said, “Oh, first, what subject is that?” [laugh] And then I asked around, and people said, “Oh, that’s called particle physics.”
And I had never heard of particle physics. And this is the third year of undergrad. So, at only this point did I have any sense of mission, like, oh, something that resonates even from my childhood personality is finally picked up in anything I’m studying.
But more particle physics than cosmology?
Indeed, at the time, it was more particle physics than cosmology. It was not about—in my understanding at the time—it was not about the beginning of the universe. That was just not being discussed in anything I was reading. But rather the deeper structure of everything that we’re made of, if you want, the dance of the universe and its smallest elements. Later, like even now, I found the connection to cosmology and, indeed, probably most of my papers write this—you know—this year and that last year are cosmological papers. But, at the time, it was really just what I’ll call the beautiful dance of particle physics and quantum mechanics. So, that’s when I tried to figure out, you know, how do I start doing that, and discovered that it really wasn’t pursued at my university in the physics department. But that’s where I discovered that the math department, while they were not claiming to be physicists, you could do a senior thesis on the mathematics of fiber bundles and so on and take that route as a math major. So, I actually stopped—in my last year, I just was a math major…I was—I did what’s called an honours year in the English system. And so, I got a First-Class Honours in math—in pure math, with my thesis—senior thesis—being on the mathematics of fiber bundles. Yeah. So, in fact, I then applied to the US for graduate school. As I said, I was so mediocre a physics student that I didn’t get into any physics program in the US. But I did get into the Yale math program because I was a much better mathematician than I was a physicist.
Raman, why go to the United States to begin with? Why not stay in Australia?
Oh, yeah, you see, I’m a very impractical person, mostly guided by some romantic ideas that make no sense. And one of those [laugh]—
—was I loved growing up here in the US till age 6, and it was a hard fall to go to India. Of course, in hindsight, I would say, well, that’s wonderful. It’s just—it’s so eye-opening to end up in India. But, at the time, I didn’t view it that way. I thought, like, you know, when I was in the US I had my Halloween—
—parties. I had television. And I end up in India in the 19…you know, in the 1970s where it’s no—there’s no such thing as television. It’s not like it’s black and white TV. There’s no TV. It’s much poorer. If you go to India today, you’ll see, you know, there’s great poverty, yeah. It was much poorer then. [laugh] And there were people with disease, terrible diseases everywhere you go. It’s a—it was a—well, for me, it was a frightening place, and I felt like a fish out of water. But, instead, I had internalized this idea that, oh, America, everything was great when I was in America. And even when I moved to Australia, where of course it was mostly an American-type lifestyle, the fact that I felt like I was an outsider—I kept feeling like, you know, they don’t want me, and I don’t want them—was there. But, again, I just had this sense that I was happy in America once. And there was some homing instinct to say, I’ll just come up with some rationale why I have to go. And I think I came up with one, which was that particle physics is pursued in America at an extremely high level. It is pursued in Australia, but with, you know, the resources of that one small country at a much smaller scale. In fact, many people that work in Australia in particle physics have trained in the US. So, I had a perfectly good reason why I needed to come back to the US. And it was all—and it was therefore through my college years I was thinking like, you know, quite apart from what I wanted to do, I thought I need to come back to the US [laugh] for ulterior purposes.
Raman, did you view from the beginning your admission to the math department as a backdoor entrée to the physics department?
Yes, I was cold-blooded, and my math professors in Sydney were cold-blooded on my behalf, saying, look—I couldn’t believe it from the Australian system. But they kept telling me the American system is very flexible, and that, you know, go lay your cards out on the table, and they’ll—you know—things will be possible. And so that’s what I did. In the first week at Yale, I went to the director of graduate studies in the math department, and I said, “You know, I really came here to do physics. And so would that be OK with you?” And he was a very laid-back gentleman, and so he said, “Sure, you know, if you want to do physics, then there’s no point us keeping you here in the math department.” But, of course, they have to agree to let you in. And the director of graduate studies in the physics department at Yale said, “You know, looking at your grades, and how well you did in physics, if you had directly applied to us, we would not have let you in. But the fact that you got into the math department probably says you’re OK, so we’ll let you into the physics department.” And so that’s how I switched over in that first week.
Oh, you wasted no time?
No time, yeah, no, it was completely cold-blooded. Oddly enough, ironically, I later discovered that, you know, a lot of the kind of physics that I was—that was going on at Yale Physics at the time ultimately stood me in extremely good stead. But it did not directly feed this appetite for the very beautiful kind of mathematical physics that I thought I was after. So, I, again, felt a little frustrated. But ironically, it turns out that—and I didn’t know when I switched—that a lot of the mathematicians, the topflight mathematicians in the Yale math department were doing exactly the kind of stuff that I thought was what I wanted to be doing. But I only discovered that several [laugh] years into my physics PhD. So, if I’d actually just stayed put in math, and found out what they actually did in the math department, I would’ve been closer to what I was telling myself [laugh] I wanted. Anyway, it worked out OK but, yeah, I did switch very quickly. And then I also expressed, you know, my desire to be a theoretical physicist to the director of graduate studies. He again warned me. He said, “Very few people are accepted into theory.” Later within that same month, I had lunch with some older students in physics. And one of the theory students said to me in a very matter-of-fact way, “Yes, Raman, everybody wants to be in theory, but nobody gets to.”
[laugh] But, once again, none of this really penetrated my skull. It didn’t bother me. It just—I didn’t take it in.
Raman, given, you know, that you really didn’t think much or know much about particle physics until you were in your third year, I wonder when you got to Yale, what other blind spots may there have been in your undergraduate education that were only apparent to you when you got to New Haven?
What I realized was because I had spent so much time in that last year in undergrad doing math that physics was not really that in my bloodstream. You know, the problem with physics—and if you ask any student, they’ll tell you the same thing—compared to math, it’s just not as well—it’s not unambiguous. And every—especially an imaginative person like person, whenever posed a problem, you’ll always say, “Well, it could—maybe it means this, but maybe it really means this,” because everything is said in words, and so you’re trying to guess—not even answer the question. You’re trying to figure out what the question is in the first place. How do you formulate it mathematically? So, half the art of the physicist—maybe I would say more than half the art of being a physicist is formulating the problem with precision and mathematically, given all the relevant and irrelevant variables and real-life interest of the subject. But boiling it down is incredibly hard. And that art was not very deeply in me—in fact, not really. It was not second nature, and I did not consider it a beautiful art. I considered it a pain in the neck. I wanted—I thrived more on the less ambiguous nature of pure mathematics. So, when I hit grad school at Yale, and I was doing graduate courses and so on, it was again a kind of nightmare. I was doing problems in electromagnetism, and I really suffered. I remember having a friend who had done his undergrad in Caltech and was suitably brilliant. And I would be like, “Did you manage to get this problem out?” with desperation. And he would say, “Yeah, yeah, it was—you know, I did it.” And I’d say, “Gosh, it’s killing me.” And he would say, “Oh, Raman, come on, relax. It’s OK.” And I would be very, very stressed out by the entire experience. Again, my eczema was flaring up. You know, now it hardly causes me any trouble. But that’s one of the virtues of tenure. But, at the time, it was incredibly stressful to see that I wasn’t that good a physics student. None of the—the art of doing it, and living with the ambiguity, and making the right guesses, was not drilled in. But I was also at that time taking quantum field theory, which is the heart of particle physics as far as the subject is concerned. And that always felt more natural, you know. There was something about the subject that I currently do which made sense to me. And because it actually underlies all the other subjects, ultimately the way I’ve learned the so-called easier subjects of physics is—I was just joking to some people the other day that I learned the so-called hardest subject, which came naturally to me, quantum field theory. And from that vantage, I could look at all the other subjects, and say, “Oh, now I understand.” Right. When I—so, for me, I’m a first-principles guy. It’s part of how the universe began in the Norse mythology, or any of these things. It’s like I need to go back to Adam and Eve to figure these things out.
Otherwise, I can’t get to what’s happening, you know, in 1800. I really have to start—my mental process has to always start from Adam and Eve. And similarly in my learning of physics, I had to go to sort of the absolute heights of—you know—where everything is first principles, and then sort of work my way down to practical subjects, like electromagnetism or thermodynamics. So, it was very hard going, and I was seriously thinking of quitting at that point.
And when did you connect with Lawrence Krauss?
I think probably my second year, I was casting around for advisors. I had been admitted ultimately—and to my surprise, in a sense, because I didn’t think I was doing that well. I was admitted to the theory group, one of I think three students of that year. And but the trouble was finding an advisor. There was—sort of Tom Appelquist was the sort of obvious theory head, if you want, that everybody would go for, but was already taking students. And so, I didn’t really know what anybody did. But Lawrence was open to taking a student. And so, I said, “Sure, I’ll do that.”
He was pretty young at this point when you became his student.
Yeah, he was a young assistant professor. I couldn’t tell. I mean, I didn’t know any of these things. I—you know—I was young enough that everybody looks old.
[laugh] Oddly enough, even though I’m old, when I look at everybody, they look old anyway.
My mental age is back there. But, so, I was just going through the ranks of the prof…and there weren’t that many to choose from. So, you know, there was a professor who I thought was really crash hot and—but was quite elderly at the time. And I asked him and, you know, I think he was gently suggesting, “Don’t come to me.” But, anyway, Lawrence said, “Yes.” I had no idea what he worked on, but that was good enough for me, you know. I just needed an advisor. I needed something to do. As it happened, there was something in me that is very fussy. And if something did not strike me as very fundamental, then I didn’t want to do it. And Lawrence was working in cosmo…Lawrence is a cosmologist, and so he’s working in cosmology on problems that, at the time, I thought, “I don’t understand the problem, but I know it’s boring.” And so, now, I wouldn’t say that now about the questions. But, at the time, that’s what I thought, and so I refused to do any of it. And so actually we’ve never written a paper together. [laugh] So, he gave me the official cover of having an advisor in that sense. But he tried his best to try and find me, you know—he actually did take me to visit Frank Wilczek when I was a student—
—trying to say, you know—because they were buddies, and so he’s like, “Come on, you know, can you do something with this young guy?” And Frank told me some—you know—what some ideas that he was having at the time, and so on.
And Frank was where at this point? At the institute?
I think he was still in Boston. We saw him when he was at the Center for Astrophysics. Now, I don’t know what his other affiliations were at the time. He was not yet at the institute. But he did have some position at the Center for Astrophysics. And I remember we sort of, you know, went out with the family, and just, you know, had fried chicken, or something like that. It was very informal. But, in the process, he was telling me some sort of ideas, which I now—like, I remember what it was about. But I look back and think, oh, that would’ve been a good thing to work on—you know—that was fertile stuff. At the time, I thought, you know, I can’t quite penetrate it. And we—he was in Boston. We were in, you know, New Haven. So, there just wasn’t enough overlap to get excited. But I already knew who Frank Wilczek was because, as an undergrad, when I knew what I wanted to do, I had done a vacation scholarship, a summer scholarship at the Australian National University, and actually written a paper on anyons, which is the discovery or invention of Frank Wilczek. So, I knew who he was, and I was excited by meeting him. He was not a Nobel Prize winner or anything like that at the time. But he was an exciting physicist and—but I just—I was not long enough in his company to make a connection. So, I was struggling for a while trying to figure out, you know, what to do. As a condensed matter theorist—theory professor at Yale told me when I was struggling, and even had come to him, and said, “You know, maybe I should do condensed matter theory or something,” because nothing clicked in terms of what I want to do [laugh], he sort of summarized it. And he said, “All dressed up, and no place to go, huh?”
And that’s the way I felt, like, look, I’ve learned all these subjects, but there’s nothing I—you know—that grabs me though.
And Krauss couldn’t simply have given you a problem that was related to what he was doing at the time?
Yeah, he could’ve and probably tried. But, as I said, I was the stubborn one, and, if it didn’t sound exciting to me, then I was not going to do it. And so, I didn’t. You know, there’s a joke among cosmologists—it’s not quite true anymore, but at the time it was perhaps true—that in cosmology, the data was such that if you could basically multiply and not make a factor of two mistake, then you were in business, right. So, with that being the mindset—now, of course, the subject is interesting even with poor data. It’s much more interesting nowadays with even rich data. But the idea of making quick estimates, which I now prize, right, but at the time, I’m like, “Look, I’ve got fiber bundles here. I’ve got all of this high-tech stuff that I’ve learned. And you’re asking me to multiply this by this, and get this?” And so, I was just not interested. Nowadays, I’m almost like the reverse. If I can multiply two numbers, and say something profound, I get a bigger kick out of the fact that it’s done in a low-tech way—
—than a high-tech way. [laugh] But, at the time, I wanted it to be, you know, high-tech. And so, I’m sure Lawrence tried. Nothing worked. And, in a sense, he had the grace to just leave me alone, to just say, “OK, fine.” And I—
And he didn’t give up on you either.
He didn’t really give up on me. I remember coming to him one day, and saying, “You know, I’m depressed.” I’m not clinically depressed but I’m like—
“This is terrible. This is really terrible. It really sucks. I don’t have any problems. It’s terrible.” And he said something that stuck with me, which was, “Oh, so you’re really, really down, right?” And he said, “That’s perfect. That means you’re almost at the level where you could do something.”
[laugh] So, in a sense, that was good advice, that you didn’t have to panic over the sense—the very fact that everything was conspiring against you was not necessarily such a terrible thing. And that, you know, a—like many great artists and scientists, you can be really down, and that might actually bring out your creativity in some way. So, that was a strange thing to hear, but I remember it after all these years. So, he did—yeah, he wasn’t pressing me one way or the other. And, ultimately, there was another assistant professor Mark Soldate there, who was a very—he was literally part of our gang. He was so non-authoritative that we didn’t even—we thought of him like a postdoc or something. And so, we would have lunch together, and we’d just be friends. And chatting one day, I was complaining to him and saying, “You know, nobody’s giving me a problem, and it’s all their fault, and I’ve got nothing to do, and I’m wasting my time here, and I’m already in my whatever fourth year of a PhD.” And so, then he’s—in his very quiet way, he said, “So, have you asked anybody else for a problem?” And then I was like, “Ah, no, I haven’t asked anybody, but they haven’t given it either.” And so, he said, “Maybe you should just ask people for a problem.” So, then, suddenly, I looked at him with different eyes, because I just thought of him as a buddy who has lunch with us, and chats with us. So, I said, “What about you, you know? You’re a professor.”
“You have a problem?” And he said, “I have a couple of problems I could run by you.” And, in fact, it’s—that was how I ultimately got a problem to work on, and, as a result, I’ve got my Ph.D. Otherwise, it would’ve been the end. [laugh] But it was through this guy. And so, he was unofficially my advisor. He suggested that Lawrence as perhaps a higher reputation would be better as just the official advisor, and so we kept it that way, yeah.
And so, what was the problem, and what was your plan of attack?
Yeah, so, actually, there were two great paradigms that had been vying—actually, they’re still the great paradigms for particle physics beyond the Standard Model. One was supersymmetry, which is an extension of relativistic spacetime. And the other was the idea that some of the particles that we find most enigmatic, now we would call it the Higgs boson, but in the day—in those days, we’d at least just—we didn’t know about the Higgs boson experimentally, but we’d call it the Higgs mechanism. That some of the particles that we think of as elementary are secretly composites. They’re made of something else. So, these were the two grand paradigms—and, in some sense, still are. And Mark Soldate, basically said, “Look, I’ve got a little thinking I’m doing on this one, and a little thinking I’m doing on this one.” And so, he ran them by me, and I chose at random, and ended up in the composite paradigm, which was a fateful choice because it turned out that the sexy subject was the supersymmetry part. And that for the next decade or more was where all the jobs were. So, I kind of took the path less traveled there. And in that, the tricky thing is when you say that something is many—you know—a particle that you think is a particle is secretly made of many smaller particles glued together tightly is how do you have theoretical control? How do you understand, you know? It’s easy to understand a single planet flying through interstellar space. It’s harder to think of a solar system with all the complicated motions and so on. So, the thing is how do you have theoretical control? And I—so, he gave me a problem in which there was a variant of a theory of this type with compositeness. And we were trying to figure out just like experimentally what kind of things could you see? And so as I was looking at—so, here, I actually made, you know, a tiny little discovery, but it was an honest one, which was that in looking at the lightest particles, which are the easiest ones to see for humans that would be there in theories of this sort if some of the particles in the Standard Model were secretly composite, then I was looking at how these exotic particles, the ones beyond the Standard Model, would interact with each other. And I found out that it was stronger than had previously been thought. The standard way of guesstimating—hard to calculate because the theory’s tricky to calculate in—but the standard way of guesstimating was sort of wrong. And I introduced a—you know—a variant of that where we got it right. And I presented it to Mark Soldate, my de facto advisor, if you like, and he thought it was good, and helped me sharpen it up, and we wrote—basically wrote a paper, you know, along those lines, and saying why it made a difference to experiments. And then so we had a couple of papers following from this. So, it wasn’t quite what I really thought I was here to do, but it did get me—you know, and then there was some sort of I think incorrect thing that I did by myself. But put together, this was my thesis. And it’s a funny thing because it wasn’t—it’s not really an earth-shattering thesis by any stretch of the imagination. But because it belonged to this lesser club, just at least by the numbers, non-supersymmetry, the people who were interested in that subject were scattered all over the country. And, by chance, some were in Berkeley, which is a very good place to do a postdoc. And so, they had enough interest to look around for where they could get a postdoc—a graduate student who would come as a postdoc, doing this kind of work. And I belonged to that small club, and so it must’ve been my year or something where I got to go to Berkeley. But yeah—
Raman, before we get to that point, the obvious question here is, you know, when you’re talking to people like Lawrence Krauss and Frank Wilczek, and they’re not exciting your imagination to take on a problem that they’re suggesting, right, and then to go back to your early interests about, you know, these primordial mythological origin stories, right, what connects for this—what would become this dissertation topic that you jump into with both feet? What is it about this topic that really clicked for you that didn’t before?
Yeah. I think it was simple desperation. [laugh]
One, it was unlike sort of the—again, my caricature of what Lawrence was doing—I don’t think it is actually what he was doing. But my caricature to myself at the time was very simple: multiply this, multiply that. There was a—you know, I think I can frame it like this. There are some activities like chess which is a very, very deep game, but the rules are very simple. There are other enterprises like medicine, which you could also say has a great depth to it. In fact, it even has a practical side to it. But if you’re a student learning it, there’s just lots and lots of facts. And some of them you do not have the time to question, and take back to first principles, like, OK, there’s the theory of evolution, blah, blah, blah, blah, blah. And now this is how you treat the common cold, you know. Maybe there are some things like that. But most things, you just have to learn what works, and move on. My impression of cosmology—and, you know, there’s some truth to this—but my impression of cosmology at the time was that it was more like medicine. That, yes, there’s lots of things that are of interest to people, and I don’t blame them for finding it interesting. But I can’t remember that much stuff. I need simple rules with deep consequences. That’s who I am. And that’s true, by the way, [laugh] that is who I am. The problems that I worked on that ultimately were in my thesis were not earth-shattering. They were not what I thought I got into the subject for. But they did have one feature. They were based in quantum field theory. And quantum field theory, the core subject, is like chess. It has very simple but profound rules, and the set of consequences is rich. And so, I found it more my home rather than having to remember 1,000 experimental facts that come in at random times like going to med school. There was not that satisfaction that I understood it from first principles. The stuff I was doing that ended up in my thesis, it did have that virtue that it followed from first principles without having to rely in many ways on data and half-born theories. So, I think that’s—you know, the word “desperation” is still true in the sense that it wasn’t even that I didn’t want to do other things; I felt like I couldn’t do other things. And it’s still true. Some of the work I do does require other talents than the ones I possess. And I can only do them sometimes because I collaborate with people who have those talents. I have a very limited [laugh], you know, aperture in which I can see things. I’m lucky that it happens to be in directions that other people can’t see things [laugh] so that I can actually form good collaborations.
How involved did Lawrence remain as you proceeded to completion of the dissertation?
Mostly just periodic chatting to say, you know, “How are things going?” But there were a couple of papers that he suggested to me might be up my alley. One came up in an advanced class he taught, and the paper was pretty technical and specific, the “background field method.” The other was by the (late) famous theorist Joe Polchinski on his reworking of the one of the central tools of quantum field theory, the “Renormalization Group.” This paper Lawrence suggested to me, and, in particular, just the introduction of this paper, had a profound impact on my thinking, because it was not just technical, it presented a kind of satellite view of a tough subject which made it seem simple. And it introduced in that satellite view a related central tool, “effective field theory.” In a way, these tools permeate all my subsequent work and my way of thinking through hard problems. So, while Lawrence did not constantly talk physics with me, he introduced me to some peak insights. When I used to meet him after I graduated, he would keep reminding me in a joking way that he was the one that put me onto Polchinski’s paper and the importance of effective field theory, and my successes followed from that. You see, effective field theory tackles a recurring question also found in everyday life: life is full of details and information, and we are always challenged to figure out what subset of the information is highly relevant and what is irrelevant. Otherwise, we will not see the forest for the trees. And often in life we don’t! Effective field theory is the subtle art and science of doing this at the juncture of relativity and quantum mechanics. So, I would say this was one way Lawrence profoundly influenced me even though we did not work together.
But did Krauss remain your advisor, at least formally?
Yeah, yeah, he was formally my advisor, so that is in fact my PhD advisor. But he wasn’t really giving intellectual input beyond those couple of papers he put me onto. Yeah, we didn’t really—we didn’t talk physics so much on a daily or weekly basis. It was more like, you know, “Are things going OK?” and stuff like that, punctuated infrequently by one of these big suggestions, like “read Polchinski,” which would then blow me away. For a strange person like me, this may have been just what the doctor ordered.
Yeah. And who else was on your committee?
So, Tom Appelquist, and then there was a very—there’s some—there’s a condensed matter theory professor by the name of Shankar. It’s an R. Shankar. I forget. The R—it might’ve been Ramamurti Shankar. But, anyway, in the South Indian tradition, he gets one name, and that’s Shankar. It’s like my last name, Sundrum, is actually my father’s first name. So, I, in that sense, only get one name. So, I think these were the ones I remember, these four. Maybe there was another professor, but I forget who it would’ve been. So, Shankar was—even though I did not work with him, I interacted with him a lot. He was, again, somebody who uses quantum field theory in condensed matter physics, and he was an incredibly clear thinker, brilliant, and with a fantastic sense of humor. And so, the combin…and I took his advanced classes in, you know, statistical field theory and so on, and even TA’d for him. So, he had a huge influence on how I thought about field theory and its connections to things like condensed matter physics. And again, he reintroduced me to effective field theory from the condensed matter physics viewpoint. So, that was one of the big highlights of being at Yale was that, you know, I got an education in part through him. So, he would’ve been at least that fourth person in that room during the thesis defense, which was not very exacting. I think people were happy to let me out.
[laugh] How did the opportunity at Berkeley come together for you?
Well, as I said, I belonged to this smaller club of people who worked on what was called technicolor at the time, but basically in layman’s terms the idea that some particles that we see are actually secretly composite, tightly bound so it’s hard to see—to break them up and see that they’re composite. And that this was the way to understand some mysteries of the Standard Model. So, that technicolor club was strewn around the country, the path—the paradigm taken less seriously overall, and yet there were people at Berkeley who were interested in it. I was one of the relatively, you know, few students at top places coming out in that subject. And somewhere, the people at Yale—and I don’t know what conversations they were having, but I get the clear sense that they thought I was reasonably smart, even if not much had come of it. And so, they must have written a reasonably favorable letter, and Berkeley must have—you know, I think I was maybe their second-round offer or something like that. And so, they were having a hard time getting who they wanted, and so they ended up with me. And so, in that sense, I chanced into Berkeley. Now, Berkeley at the time—maybe it’s still so, but actually much more so pre-internet age. You know, you have to remember that this is actually just exciting in its own sense, that you can’t imagine the difference between the latest papers—
—the latest ideas in any subject not being available to you through the internet because there is no World Wide Web. And so, all the—you better be at the top place if you want to hear the top ideas quickly. And whereas now, you know, you can be at a second-rate place and do first-rate research because you have access to the minds of geniuses. They post their paper, you read it, right. But, in those days, it really mattered where you were holed up, right. And so, Berkeley was one of the— I was actually very lucky to go there. I suffer from this psychological problem—even when I got to Yale—which was that I despise any place that’ll have me.
And so, when I got to Yale math department—which, you know, I later learned is somewhere in the top-10 math departments, you know, in the country or on the planet. But at the time, I was like, oh, no, you know, this is terrible because—
—and just look at all my fellow students. I was—like, there were 20 students in the math class—incoming math class. Seventeen of them were from overseas. And I was like, gosh, no decent American is bothering—
—to go to this second-rate place, right. So, even when I got to Berkeley, I had the same impression. They took me, so it really can’t be that great. And I only later realized I was super lucky in where I ended up because it was the place that again and again had made many great careers.
Yeah, and how much of that was going to Berkeley, and how much of it was Stanley Mandelstam for you?
So, again, you know, I have an odd relationship to all my formal, you know, mentors and advisors. Stanley Mandelstam was paying me, but I had essentially zero contact with him, except slowly discovering the stature of the guy [laugh] which I barely knew at the time. But as I kept spending time there, I realized, wow, this guy is amazing. But he had sort of wandered off, I think, into more string theoretic interests and formal interests, and he was past the height of his powers. And so, I essentially never saw him. And I would spend time on the hill of Lawrence Berkeley Laboratory next to the campus, and he would spend all his time down on campus, so I really never saw him. And the other people who were interested in technicolor, I really, again, didn’t find them doing anything that I found interesting for me to jump into.
But your postdoc was at the lab or in the physics department?
I was paid by the physics department, but the two groups sort of just combined informally. So, I actually had an office in the lab, and hardly ever went down to campus, except for fun—except for fun. But I spent all the time up on the lab. And, again, the stars aligned in that I was given one of the absolutely best offices on the lab overlooking the San Francisco Bay. So, I literally had many days—every—but, you know, it was a drought. Every day was beautiful sunshine. And I would just joke about it. I’d say, “Oh, another beautiful day in California. What to do? What to do?”
And every day, there would be a stunning sunset from my hilltop perch. And on many of these days, the later Nobel Prizewinner, George Smoot of cosmology fame, would walk into my office, not to talk to me, just to look at the sunset. And then he would say—he didn’t even know my name. I mean, it was—he would just look at me and say, “You know, this office is far too good for you.”
Like, “You don’t deserve this office.”
And then he’d walk out. [laugh] And then he’d walk out again.
So, of course, with an office like that—and, you know, when I left there, like, the wolves came for my office. But basically, I spent all my time up there. That’s where all the young people were. In the end, I never worked with any professors at Berkeley. Hopefully, you’re seeing some pattern here of dysfunction. But I did meet truly influential people my own age who taught me the things that normally I think a professor would’ve taught.
Like who? Who was in that cohort with you?
Yeah, so, for example, Markus Luty, who had been a Chicago grad student, overlapped with me there. He was also in this club of people thinking about the compositeness paradigm. And from him, I learned something that you could only learn in person, which is I had this—like any normal human—I had this sense that, look, you’re trying to do research on a frontier subject. Now, if it’s not what you’ve already been taught to do, then to catch up to the frontier will take you many lifetimes because all the geniuses have pushed you up to that point. How can you ever go beyond that? And so don’t even bother trying. So, I would never even think to try doing anything other than what I had been taught to do, right. And in many places full of mediocre people, that’s what people do. They do what is close to what they did the day before, what they’ve been taught. They can never go completely somewhere new because they can never believe that they are capable of it. So, this guy shows up, and immediately as he’s talk…first, he’s talking to me, you know. It’s like I’m—he’s not avoiding me. [laugh] He’s like interested in talking to me. But as he’s talking, he’s like—as something comes up, there’s something to learn. Like, we don’t know anything about it. He would just go. And three days later, he had read up the relevant literature, and he was basically at the frontier. And it made no sense to me. It made no sense that a human could catch up to all the geniuses that fast. Of course, when the geniuses have laid a trail for you, now we know it’s possible. But there’s a certain way of catch…it’s not the way that a student does it in a laborious step-by-step-by-step. It’s done by a little bit of reading with an intelligent mind that makes guesses [laugh] and then jumps to another one and confirms some of those guesses. So, it is the process of the—of high intelligence that moves at lightning speed. But I had never seen anybody exhibit that skill, right. I’d talked to people who were professors at Yale, but they’d been doing it for years. So, I never had to see somebody go from zero to 100 miles an hour and do it again and again and again. And he showed me it could be done. And, you know, it’s not like I consciously thought that. I just thought it’s not—I didn’t think. I saw him doing it, so I could do it, you know. Just like a mother chimpanzee teaches the baby chimpanzee to use a stick or something, there’s no conscious thought about trying to learn from that person. I think that was probably one of the biggest things in just kickstarting being creative. It was just the thought that, oh, I can do it, right. I was also lucky to have Riccardo Rattazzi, who is now a professor at EPFL in Switzerland. He is, in my view and the view of many people—you know, one of the very top people in my field, I’d say. Maybe the top theoretical physicist in Europe in my field, but in an understated way, so only some people are aware of that. He doesn’t come with all the fanfare, but I believe he’s in that absolute top class. At the time, he was just this Italian postdoc on Italian money, spending time at Berkeley. And, in a sense, none of us recognized his abilities. I mean, we were obviously talking physics to him and he was obviously very good. We saw he had done lots and lots of things. But, in hindsight, to have made his friendship and acquaintance at Berkeley was like an unforeseen piece of good luck, because I have learned so much from him over the decades, even up till very recently, again and again, because, in my view, he’s a mind-boggling genius. But, at the time, we used to make fun of him, Markus and I, because we would make fun of him as sort of the lesser among the three of us—
[laugh] who was always claiming he had done great things. But, surely, he’s just some Italian guy from Italy on—you know—not even Berkeley is paying him. Why would he be that good? It made no sense, so we just assumed he was, you know, not that bright.
This suggests that you’re not really interacting substantively with your cohort.
No, we’re interacting substantively, but we’re not constantly carefully grading. Like, we’re seeing that we’re having this big—you know—we’re having conservations with him. He makes sense. Everything makes sense. But Markus and I were a little—in some sense—a little closer to each other. So, you know, it’s a funny thing. You don’t realize what riches you’re—like, even I didn’t even appreciate Markus at the time. I didn’t appreciate that Markus was having a profound effect on me. It just was taken for granted, you know. Everything is taken for granted at that point. Only looking back can I say, wow, if I had to hole up with two people as postdocs at the time, what a pair, right. [laugh] So, in that sense, they made my career, in many ways.
Yeah. So, this idea of going from zero to 100, which you had never really experienced among your peers before, right, what did that do in terms of changing up the kinds of questions you were asking and that you wanted to pursue?
Yeah. So, Markus and I really started to follow a procedure, which I now even recommend to my students and so on. But we didn’t do it as a policy. We did it unconsciously. But I can say exactly what it was. We would have—all the best seminars would come to Berkeley, right. And they would talk on many different topics. And we would go into the seminar, and often we didn’t have the background to follow it. And at the end of the seminar, we would sort of converse with each other. And I think it boiled down to sort of three steps, which I keep telling my students to do themselves, which is we are two smart guys, but ignorant as hell. [laugh] We’ve gone through the seminar. We try to figure out (1) what was the problem. (2) What was the magic that allowed the solution? And the third question, which is vital, once you’ve lost your respect for people older than you and better than you, is (3) were they right? You know, so many times before you ask the third question, you get tied in knots because you’re listening to something. They’re obviously there giving the talk. They’re much more brilliant than you. And you can go around thinking there’s something wrong with me because it doesn’t make sense. [laugh] But once you realize, no, they could be wrong, or they could be wrongheaded—and it’s such a hard subject. Many times, they’re very smart and, yeah, they are wrongheaded too, right. So, once you have these three questions, we would discuss it with ourselves. And each time we did, what could’ve been like listening to Greek, you know, in the seminar, like just—we would always guess. We didn’t know the answer to these three questions. Like, what was the nature of the problem? What was the nature of the solution that cracked it where others could not? And was it actually right? [laugh] We don’t know the answers. You guessed. And by guessing and talking to the other guy, the other guy would say, “Well, look, that guess can’t be right because blah, blah, blah, blah.” And then you’d come back and shoot back. So, this idea of debating in a friendly way, but debating and guessing became a cycle that I now tell my students. I occasionally pause in the middle of a lecture, and tell people, “You know, I don’t even care about teaching you anything”—
— “because it’s all just knowledge. Who cares, right? The only thing is how to be intelligent.” And I will sometimes say, “You want to know how to be intelligent? Because I didn’t read it. I just found that I tripped on it. “This is the way. Many people are intelligent, but they don’t know why. But I found it. So, I can tell you.” And then I’ll say, “Look, it’s not worth it. You’re not actually interested. Let’s go back to some knowledge.” But occasionally, I will tell them the secret. And I say, “It’s just these three steps. But you have to be religious about it. (1) You’ve got to guess. (2) You’ve got to let the guess be tasted. There’s something where you’re just letting it sink in. “And then (3) you have to kill, criticize, cut down ruthlessly. And then everything’s in tatters again. And then you go back and guess again.” And I say, “These are the three Hindu gods: the creator, the preserver or the lover, and the destroyer. And you have to go in this circle again and again. And when it’s second nature to do that, then you’re intelligent.” And I’ll even point out that all the pathologies are when you have, say, one of these skills but not the others, or you have two of them, and not the others. And you can see how a person behaves when they don’t have the full set. So, this sort of thing I feel I only picked it up from that Berkeley time. I didn’t really have it completely down. But it was set in motion from talking to Markus, and just seeing how he operated. And so, I think we were—Markus and I were constantly thinking of problems in this way, and so we wrote some papers together from this way of operating, even going into new subjects that we didn’t know much about. But we—but also, I was doing my own thing. I was able to have my own ideas and pursued them single-handedly. But I had more of a sense of how to do it, and, when I didn’t know something, how to learn it because of this influx of daring from Markus.
What did you want to do next? Were you thinking about academic jobs at this point, or did you realize that another postdoc was the best move for you?
I think I was not interested in a faculty position. And, in fact, I think—
Not interested or not ready?
I was not ready. I mean, I ultimately thought I needed to be a faculty member somewhere, but I was not ready. In a way, I liked being a postdoc, which, you know, a lot of people don’t. A lot of people are too—I mean, they’d like it if they knew the future. [laugh] But they’re too anxious to get onto their—to land their faculty job. I was not in that mindset at all. Again, in a kind of a denial sense, I didn’t keep track of the danger of not landing a job, so much so as I was getting towards the end of my postdoc at Berkeley, I got a call from Howard Georgi, offering me a postdoc at Harvard. And within minutes, I got another call from one of the UCs saying, you know, “Would you apply for our faculty job?” So, they at least showed enough interest to ask me. And, instantly, I didn’t even do what I now tell everybody to do, you know. Like, if it’s a big decision, just say, “OK, thank you. That’s really exciting. Can I think about it and get back to you?” even if you think you know the answer. So, I think as soon as that UC call came in, like as soon as the question was asked, “Would you apply?” I said, “No, I’m good, thank you. I’m planning to go to Harvard for a postdoc.”
Now, how much of that was just the fact that Howard Georgi reached out to you, that was a big deal to you?
Yeah, that was a really big deal to me. He was a giant—is a giant—of the field. And it was beyond—you know, I went through Berkeley sort of thinking I was a bit of an outcast there. That was again my own mental mindset. I didn’t work with any of the professors. Not necessar…again, that may have been because I never chose to work on what they were working on, and that was my call. But, in my mind, it was because I was not good enough to work with any of the professors, so I had to hang out with these “mere” postdocs.
Raman, I wonder by reputation if you appreciated even sort of instinctively Georgi’s reputation as a mentor? I mean, what a phenomenal mentor to students he was. And if this was something that—?
I did not know that.
I did not know that until much later. But I had read his—you know—his—he has—I might even have it here. He has a book on—yeah, I do. He has a—in fact, I’ll just show you the size of it because that’s what—you know, particle physics is a tough subject. The books are pretty fat.
Howard Georgi wrote a tiny book this thin. [Sundrum holds up the book demonstrating how short it is.]
And it’s very conversational in many ways, right. And, yet this is like a poem to physics—not prose. But it is one of the—it’s just an introduction to particle physics for people who know some quantum field theory. And it’s one of the deepest, deepest books on the subject, precisely because it has this poetic quality. And he’s picked intros, and in the entire thing, his personality is coming out, and his tastes are coming out, and what he thinks is— “Well, I’m not wasting time on that. But here, let’s focus on this.” It’s done in a conversational way, and I already knew that. I—so, of course, I knew mostly, you know, reputation. And I probably knew much less than I should’ve known, so. But I did know he was at Harvard—so that at least I knew—and this book. So, yeah, he was an absolute giant in my eyes. I had no idea, except for this book itself, whether he was somebody who was a good mentor or not. That was absolutely unclear to me, except that the book—you know, this is probably the easiest way for me to have learned some of the great ideas. So, no, I did not know any aspect of his ability to train people.
And what was his connection to you? How did you get on his radar?
Yeah, it was—you know—it was a strange thing. I think there were these mega conferences—well, there still are. But, anyway, pre-COVID [laugh], and pre-World Wide Web—again, that is a tsunami in terms of changing academia. But, prior to that, there were these big workshops where you would send your postdocs to give—in some parallel session—give a 20-minute talk and so on. And I was notoriously unwilling to go to these things, and always had to be pushed. So, you know, there was a beautiful workshop in the French Alps once, and I didn’t want to go, and my seniors had to sort of push me—no, the professors had to say, “You know, you really should go.” And, similarly, there was this one in Texas where, again, I didn’t want to go, and was told, “Look, it’s really good for you. Please go.” And I find these very depressing because there’s so many talks going on, and I’m only interested in a fraction of them, and then I feel guilty. But I did give my 20-minute talk, and he happened to be in the audience, and he asked a couple of questions. I can only assume, since we had no other contact, that that made some impression on him. And he belonged to this club. [laugh] He belonged to both clubs: the supersymmetry club, which he had in some—in many ways pioneered, as far as putting the Standard Model and supersymmetry together; and to the so-called technicolor club or compositeness club, which he’d also done major pioneering work in. So, my talk somehow must’ve resonated with him, and my references must have been good, I suppose. I’m not even quite sure who would’ve written letters for me at that time because I hadn’t worked with anybody. But, anyway, that must’ve led him to pull me into Harvard. Having said which, once at Harvard, once again, we almost never interacted [laugh] and we wrote no papers together. Story of my life.
[laugh] What were you working on at Harvard? What were some of your new projects?
So, some of them were still in this compositeness vein. But another body of work that took a lot of my time, done with my fellow postdoc Pilar Hernandez, was about solving a conceptual problem with putting certain types of thorny theories, “chiral gauge theories,” on discretized spacetimes suitable for computer simulation.
And you have been in this, Raman, for a while. How had the field changed since your initial interest at Yale? What were some of the advances in the compositeness subfield?
Since till today, or do you mean—
No, I mean up till Harvard, as you were continuing work on this.
Yeah, so it was moving very slowly. You see, the trouble was that it makes sense that progress was slow. For example, protons are made of quarks and gluons. So, there’s precedent for the idea that things that are first seen to be elementary particles, fundamental particles, are later seen to be just something made out of something else even more fundamental. The trouble is that the mathematics of controlling such a theory are very, very difficult. And so, the possibility was always there, but how to write theories of this sort, know what they say and do, and know what experimental predictions they give was a paralyzing problem. Exactly the kind of thing that somebody like me would want to go into, but most sensible people would steer away. Supersymmetry was much more calculable, and so progress was being made in rapid strides. Whereas in this subject, it was paralysis where people who claimed great strides, I often felt, were later found to not be right in the head, you know, where everything [laugh]—there was very little that could be said. So, things were moving relatively slowly. Now, as it happens, through the back door—you know, by the end of the 1990s when the Randall-Sundrum papers came out, that turned out to be the back door to this subject, which made it easy to model. The breakthrough was, you know, coming from this—if I interpret it in modern language—the AdS/CFT correspondence. This was the magical breakthrough that allowed it to work. The Randall-Sundrum papers were written in ignorance of that result, but in—if you want to say why did—why were they such powerful theories? It’s because of this powerful piece of magic under the hood. But until the end of the 1990s, this subject of compositeness was, you know, sputtering away in various ways. But there was no decisive breakthrough. There was no decisive realistic model. That only came—that picture only came after Randall-Sundrum geometrized it in a quite different way than the sort of brute-force attempts that we were making for most of the 1990s. If you want, the progress was therefore being made in terms of instinct in that, by battering our heads in the brute-force way, we were getting some instinct for what a breakthrough would be, in a way.
And when did you first meet Lisa?
So actually again, in this strange twist, this French Alps workshop, which I literally had to be forced to go to, was where we met. I had seen her at an earlier workshop because she was one of the very, very few women in the subject. And so, I’d seen her sort of [laugh] across the hall or something. But we had never met at that point. But at the workshop in France, she saw me give a talk on technicolor on this subject of compositeness. She herself is a Georgi protégé, was knowledgeable about it, working on it, interested in it. And so, she saw my talk, and she said, “You know, maybe—so here’s an experimental process that is being measured at this time—maybe we could work out what technicolor predicts for it”—so she came to me and said, “Maybe we could work”—this is 1993. “Maybe we could work out some of the consequences for this.” And she already, you know, had a reputation as one of the top young people. So, of course, I said, “Sure, yeah, whatever.” I think the same day, I think she said, “You know”—so, again, I had just learned to ski at this workshop, I should say. It was the first time I’d been on skis. But she also said, “You know, there’s this sort of paraskiing thing that they’re doing here in the French Alps. Wondering if, you know, you’d like to join? Would you like to go try that?” So, again, sort of in this daze, I said, “Yeah, sure, sure. Yeah, whatever.” And then one of my Canadian friends, who’s also a particle physicist, later after Lisa had gone, pulled me aside and said, “You know, she’s like a real athlete, and she knows what she’s doing—”
—and he continued, “But I just want you to know this is not America. There are no lawyers here. They don’t care whether you die paraskiing.”
“And you’ve never done this, right.” [laugh]
This was basically my roommate at this workshop. And so, he said, “I think you need to think again.” [laugh]
And so, for the rest of the workshop, I carefully avoided directly contacting Lisa. But we did work on the paper, once we got back to the States, we wrote our paper. So, we jokingly since our—you know—our famous two papers are called RS1 and RS2. We sometimes call this RS minus1 (I forget who came up with this joke name). It’s this thing done long before the other RS1,2 collaborations. But that’s where I first met her, and that’s where—so even this unlikely workshop that I kind of would normally have avoided going to, that’s where I met Lisa, which only made it easier for us to recognize each other and work together, you know, seven years, six years later.
Raman, this idea of the relatively narrow aperture that you have that complements, you know, collaborations with others, how did that work in terms of your collaboration with Lisa? What were the things that you were able to see? What were the things that she was able to see? And how did that come together for this remarkable work together?
Yeah, that is actually very to the point in the sense that prior to working with Lisa, I was working on the idea of—so this idea that extra dimensions could be experimentally relevant was percolating back up in the 1990s with some developments in string theory, and the idea of branes as higher dimensional objects in string theory. And I was working on these extra-dimensional theories just by myself, and thinking, you know, there’s something realistic that can be done. And, again, my own stubborn thing was I was noticing that you could write realistic theories with extra dimensions where the extra dimensions could be quite large, and therefore potentially visible. But I had to keep asking myself, but why would that be? Like, who would care? What would be the plot? And I was—by 1993—I was obsessed with one problem, which was the cosmological constant problem. It was the perfect mix of true scientific mystery combined with true egotism because I knew it was the top unsolved problem, [laugh] OK. So, by 1993, this idea of why the—ultimately—why is the universe long-lived—long-lived and “flat” enough to even support us—was sort of the driving question. It was the question sometimes called vacuum energy in this—in particle physics. Why is the vacuum energy consistent with the long life and flat geometry of the universe? And I was obsessed by it, and it was just the standard place that crackpots go to die because it was so hard, nobody could make any progress. And, in my mind, everything else I worked on was just to pay the bills, right. So, they all were interesting, and I’d work on this then. What I didn’t realize was that every time I hit my head against this problem, the cosmological constant problem, I was trying different attacks. And each time, I was learning something that actually then, even though I failed to solve the big problem, was paying the bills on everything else. So, it was sort of working. The final attack came by saying it’s all about extra dimensions. Extra dimensions are the way, you know. Basically, the cosmological constant problem was the vacuum energy is too big. And in Einstein’s theory, big energy means spacetime is too curved—too curved for us to live in. But if there are extra dimensions, then maybe the curvature could be “offloaded” into the extra-dimensional dumpster. And so that was my plan, and I was working on it heroically. This was, if you want, at the time my narrow focus. The rules were very, very tight—just like the perfect game of chess—very, very tight and very, very deep. And I was just marching forward, trying to do this one problem. Just as I was doing that, the thunder was stolen away in the sense that Arkani-Hamed et al. wrote their paper on large extra dimensions, but applied to the so-called hierarchy problem, which is a major problem in particle physics—but, by my ultra-high standards, nothing to be thought about. It was all about the cosmological constant problem for me. And so, it was killing me that they put out their paper. And I was like, look, oh, no, I know how to do all of this stuff, but they’ve written it just—you know, their application is just the hierarchy problem. And I have been totally stuck and obsessed with this, you know, ponderously more difficult problem. But then I wrote a couple of papers just as follow-ups to theirs, saying, “Look, here’s how to do what you’re trying to do. But here’s a few more equations to go with it, and make it, you know, solid.” Lisa saw those papers, and said, “Raman, we should work on extra dimensions, and maybe extra dimensions of supersymmetry.” So that’s how we started working together again, after several years break. But the narrow focus I came with is I had a pretty, at the time, probably absolutely world-class knowledge of extra dimensions, and the equations governing them in general relativity in terms of realistic model-building. But I had the sense that it was all or nothing. Either I was going to solve the insoluble problem, or die trying, and that was it. Lisa brought sanity [laugh]—
—which is to say, “Look, there—let’s just play around with these equations, see what things are fertile, what moves might open up. Like, let’s combine it with supersymmetry, see, well, you know, does that do something interesting?” There were just other things to try. So, when we started working together, it was me sort of like, OK, I will not keep talking about the cosmological constant problem. But we were working just seeing what came up. We were seeing a few ideas in the string literature and so on. And it was a fantastic collaboration because neither of us knew exactly where we were going, but we were exactly on the same wavelength as to the sort of level of rigor of thinking and the philosophy/approach of effective field theory, that I picked up from Krauss and Shankar at Yale and Lisa from the Georgi “school of thought.” When is it good to do the simplest example first? When is it good to bow in front of the string theorists, and when is it time to say, “To hell with them. We’re going our own path. We have a different aesthetic”? So, I think that sort of—you know, my narrow focus has many times missed things because it’s too—it’s got its sense—its standard of success, and it sees nothing else. Again, from her, I really—the aperture broadened, and forever more broadened. There are some killer instincts that she has, and I’d like to think they infected me, and permanently—permanently—that I was not able to go back to a completely narrow aperture in looking at physics. You know, I used to vaguely—I used to have some contempt for people who were in the absolute mainstream. Since I knew I couldn’t be in the mainstream, [laugh] I at least wanted to feel vaguely superior to them in my own backwater by saying, “Well, they’re in the mainstream.” But from her, I learned, yes, there’s a reason the mainstream is the mainstream. There’s a lot of interesting things going on there. There’s—it’s the most promising direction. And, in a sense, I got a sort of lightning tour of all of these considerations, including this thing that I’d had contempt for—again, not explicitly, but somewhere in the back of my head for a long time. It’s called experiment.
Of course, the entire subject is just built on experiment, right. So, it is insane to think that experiments don’t matter, or that you don’t want to talk to the experimentalists, or you don’t have anything to say to them, and just “leave me out of it.” But what I clearly saw in her was this is somebody who really talked to experimentalists, thinks about experiments, was constantly ticking away about when there would be an experimental association with whatever you’re working on. And this led to—you know—we actually had real fights where she would say—and I would say, “Look, the paper has to go out.” And she would be saying, “No, look, we’re sitting on an experimentally fascinating problem here, which has a kind of behavior that no—you know—we’ve never seen anybody else talk about. We have to work it out.” And I was like, “How can we—look, it’s trivial. It’s just experiment. Throw it out. Let somebody else deal with it.” So, she kind of introduced that idea of sort of due diligence on the experimental front. And that really, again, was a—you know—it was very late in my career, shall we say, learning that experiments actually matter, and that the fun of theoretical physics is ultimately finding these connections where experiment can come in, rather than sort of this insane, you know, “I’m just doing my own thing, and I talk to nobody” vision. So, I think that is her wider—she already came with a very wide aperture. And it’s so much faster when you’re working with somebody to just osmose rather than taking years to figure these things out yourself. So, I kind of got a crash course in almost all of mainstream Beyond Standard Model concerns by just hanging out with her.
And, Raman, when you talk about the mainstream, I mean, this is all pretty esoteric stuff at this point. So, in your mind, what’s mainstream and what’s sort of out of the bounds of mainstream in terms of your involvement here?
Yeah, so in particle physics—so particle physics is already not mainstream in terms of our culture. But in the subject of particle physics, which I inhabited, a lot of the progress in the ’90s was working out the theory of supersymmetric—the Supersymmetric Standard Model. Supersymmetry combined with the Standard Model and its experimental ramifications in cosmology, in particle physics, collider predictions, low-energy experiment predictions, all these things, this was very much the mainstream, and so I had a fixation that I don’t work on supersymmetry because everybody else is doing it, so let them do it. I’ll do something that nobody else is doing. So, you know, my working with Lisa, the first overture from her was, “You’ve just written some very nice papers on extra dimensions. How about we try combining it with supersymmetry?” And so that was already an invitation to combine my wacko direction with the mainstream of particle physics research. Again, even that might not have won me over, except I had just had a good talking-to by Markus Luty, who was still—you know, we’re all in the same circles—who had just told me, you know, because I had not got a faculty job now—having passed up earlier overtures [laugh], had not got a faculty job for many years—was basically saying—I was on my fourth postdoc—no, third postdoc—was saying, you know, “You should work on supersymmetry. And it might be good for your career.” And somehow careerist thinking was not in me, but something resonated when Lisa said similar things about supersymmetry and extra dimensions being a good place to go hunting. And I was—and so when Lisa said, “You should work on extra dimensions and supersymmetry,” I think with those two people saying it, I was willing to at least try. But Lisa and I did find one of the very exciting variations on supersymmetry and supergravity as our first paper together after the “-1” paper. It’s called “anomaly-mediated supersymmetry breaking,” not an “RS” paper. But we in fact did find something very exciting in this game of supersymmetry and extra dimensions. So, that’s what I mean by the mainstream that, in some sense, I was occupying corners of the subject where normally you’d say, “Look, no progress can be”—in fact, I think somewhere in those years as I was struggling for a job when I was at a workshop with Frank Wilczek, he let it be known through somebody we both knew, saying, “You know, I don’t think he should keep working on that stuff.”
“I don’t think it’s helping.” [laugh]
[laugh] And, Raman, did this work connect you at all with Jim Gates even before you got to Maryland?
It did a little bit. Oddly enough, Jim Gates belonged to a small gang of people who studied gravity in supersymmetry. And there was a—you know, again, the rules of the game were simple enough in the fundamental physics way of thinking about physics. They were simple enough. You’re—but you’re combining two simple ideas, two classic ideas: gravity and supersymmetry. And the trouble is the chess game that ensued by putting these two together was incredibly thorny—incredibly thorny—and totally forbidding. Like, it’s the kind of thing that I would lose all patience with, and therefore never entered into. But when Lisa and I started looking at supersymmetry and extra dimensions, and just following our nose, and seeing what resonated, and doing the simplest examples, in fact, we had the one inside track that the string theorists didn’t have. We did the simplest examples as opposed to the most complicated examples. And, yet, even the simplest examples, this combination of supersymmetry and gravity was still a nightmare. And then two UMD connections: One, I just happened to chance—again, I had come across this in the course of trying to solve the cosmological constant problem—a book by my current colleague, Rabindra Mohapatra, on particle physics. And his book on particle physics, a little thicker than this one by Georgi, but it had little examples of tricks on many different fronts. And one of them was a short chapter on supergravity where he made it actually look easy. And the methods that he was quoting, like he was reviewing in his textbook, some of them were developed by Jim Gates and others. OK. So, I learned these tricks from the Mohapatra book, and that’s what I brought with me to Lisa, and said, “You know, there’s a simple way to think about supergravity.” And then we keep looking at these enormous pages and volumes of algebra that everybody else was using, and she would even ask me, like, “Look, it can’t be—you know, you’re telling me it’s this simple. But we have to be able to reproduce all that garbage over there.” And we would occasionally check, and we’d be amazed. Yeah, there’s a simple way of getting the things that we want. Somewhere in all those vast volumes, the things that actually matter to us are condensed in a simple way in these tricks that I was reading in Mohapatra’s book that ultimately came from a certain approach to supergravity that Jim Gates was also one of the pioneers of. So, indeed, I knew of both these people at UMD. And it was absolutely central to our being able to say something I think totally, totally new and important in supergravity that is, again, now of relevance to realistic models of particle physics precisely because we had a simple way of thinking about something that normally is totally treacherous. Yeah, so I do have that little overlap with the UMD gang, even at that point. They did not know it, but I did.
In what ways did your collaboration with Lisa sort of clarify your next moves?
You know, the things—the—all the—the major two outputs of my work with Lisa in that second round in the 19…in the late ’90s were the supersymmetry work with her, supersymmetry and extra dimensions, and then non-supersymmetry, no supersymmetry but the Randall-Sundrum papers. Both gave a new—new paradigms for how to embed particle physics, and how to go beyond the current situation. And each of them gave new classes of experimental observables, which, finally, it had hit my head is where the action is. So, I entered the 2000s, (a), with a faculty position, but with the idea to try and also push the consequences of these two things. These are two paradigms, but all the details are still up for grabs. They’re all the variants and so on. So, really, it was working these out, and cementing them, that took up a lot of effort. I had, again, collaborations with Markus Luty on the supersymmetry side, and had a variety of collaborations with postdocs and, you know, many, many people over the next decade really putting the Randall-Sundrum picture on a firm footing, one which was attractive, predictive, lots of—on both fronts—lots of, you know, things that have then influenced experimental searches, and so on. A lot of collaborations with my then postdoc, and now UMD faculty colleague, Kaustubh Agashe. So, I would say it had a—you know, that it’s really had a profound—the work with Lisa has had a profound effect. And not only that—this is probably true for many people in quite different fields—that as you learn and develop some deep set of tricks, and they’ve gone very deep into your head, you start seeing their application in very different settings. It’s not just a simple extension of what comes next. You start seeing new ways in which problems that seemed like they have no connection, are secretly connected. To the expert eye, you see there’s an analogy, and you can use these tricks in those settings. And so, a lot has come in that sense, you know. So, I would say very profound consequences. It was also a fulfilment—the Randall-Sundrum work was also kind of a fulfilment of all the earlier, as I said, paralyzed work in trying to make slow, incremental progress understanding these composite systems. So, it kind of backfilled [laugh] my earlier career, almost like it wasn’t the waste that I’d thought—
Now, you came to Hopkins with tenure?
I came to Hopkins with—I almost call it the “threat” of tenure. I came as an associate professor, which, at the time at Johns Hopkins, was not a tenured position. It was still like this sort of Harvard system at the time of non-tenure. But I was told, you know, “You know, look”—and—but I had a kind of a tenured offer elsewhere. And so, they did have to give me something. And so, they said, “Look, well, just prove to us that you’re—you know—you can teach. It’s not even research. It’s just we can’t give you tenure if you’ve never taught a class before.” So, I was like, “OK, well, I’m going to keep the pressure on you guys.”
Raman, I wonder how much of a challenge that was, four postdocs later. I mean, how much were you teaching over the past 10 years, if at all?
Yeah. [laugh] I’d never taught a class. [laugh]
Yeah. So, that’s a legitimate concern on their part?
A completely legitimate concern for which, at the time, I had absolutely no patience.
So, I was like, “You know, I have a tenured offer over here, and why can’t you guys do it?” And so, I was trying to play everybody off everybody. But, anyway, they refused to do it. And you have to remember that this was Maryland, finally—I mean, the state of Maryland, Johns Hopkins—and the homing instinct in me—
—has been powerful through an entire lifetime getting to that point. So, I took it above all other places I could’ve gone to. And it was—of course—it’s a good place. But the teaching was, in a way, kind of second nature, so it wasn’t really a problem. And so, they didn’t—the thing that they feared, which is that “Look, there’s just going to be a catastrophe. He might be a good res…” Like, many times, good researcher; some other quirk of personality makes them an absolutely lousy professor. So, that didn’t happen. And about six months into that, I was getting overtures from Yale that they were interested in a full professor, tenured offer. So, that really did fast-track everything. [laugh] So, by the end of the year, I had tenure and promotion to a full professor. And so, it was a very long delayed faculty ons…of the getting a faculty job. But having got it, it was a very quick set of promotions. Looking back, you know, you say when you’re living through it, you’re like, gosh, nobody recognizes me. I’m just postdoc-ing forever, and I’ll never get anywhere. But, looking back, you think, gosh, that’s the perfect way to have gone, you know. I had so much time to do research.
And so, what classes were you teaching initially? What did they give you to start?
Oh, they were very nice. They gave me, like, you know, advanced topics in particle physics. So, I, like, taught a course on extra dimensions, which was just my research. It still required downloading it and organizing it. You know, so there was really no textbook, so I really had to do it myself. And then I taught another course on string theory, which really required me to learn enough of the material. And I went in with the goal of saying, “Look, string theory is a very rich subject. It’s got a set of miracles.” And I said, “I want to teach the simplest example of every miracle.”
And so, I set myself that goal, and, again, I think that was quite ambitious. I wasn’t thinking how much work was involved. But, anyway, I did it, and it was a great education for me. I don’t know what the students got, but it was a great education for me. So, I only had to teach these advanced courses at that point. But it was enough—I think they just needed a sanity check. And as having told you my story so far, you can see, not unwarranted for them to have that concern.
Raman, I’m curious, Hopkins, did they—the combination of astronomy and physics—and of course there’s a whole interesting story to how that happened—was that useful at all to you in terms of having astronomy embedded within the physics program at Hopkins?
You know, it was not at first in the sense that what maybe many other particle theorists it could’ve been. But I was a little too narrow. And they themselves were not even—now they’ve kind of got these—this cosmology group, and they’re just world-class in it. At the time, there was more astronomy—more astronomy in astrophysics—and they were still fantastic. But I didn’t have the breadth to really overlap with them and take advantage of that. So, they were great people to be around, but I didn’t—it didn’t really rub off on me. It didn’t lead to something very fruitful. And except that while I was there, I was, you know, a great supporter of hiring some of these now world-class cosmologists—well, they were world-class back then—but recognized cosmologists to Johns Hopkins. And once they were there, once—so that was towards the end of my stay. Once those cosmologists were in there, it was starting to have an impact because they were very keen to talk to the particle theorists, and would literally have these jam sessions where they would say, “Look, we can do this, and what would be worth doing? You know, we can observe these kinds of things. What is—has—what actually has significance?” And so, we would have these conversations, trying to brainstorm something worth pursuing. But I suspect the theorists there now, and their cosmo group, are even more closely aligned, partly because the people there now have wider apertures than me—like David Kaplan, who you know. But even now, like members of my group or even myself sometimes drive up to Johns Hopkins just to talk to the cosmology guys, you know. We can do the particle physics ourselves, but we can’t—you know—sometimes we need the part…so, in some sense, my interactions with the cosmo side maybe are more fruitful after I left—
—but just because of me growing up.
Yeah. Did you take on graduate students right away at Hopkins?
I did. You know, it’s kind of a—again, I can’t quite place it. I really thought I would be a little hesitant, or not know what to do. But these are things where you sort of discover that they’re just in your blood. So, you sort of instinctively know what to do. So, yeah, I did take on students immediately and…
I wonder if, from your own experiences, you learned how not to be a mentor, given the kind of graduate student you were?
I think I was maybe wise enough to say I was not the typical graduate student…I was not—even now when I tell people about my experience or anything like that, I always say I don’t think there’s a lesson in me for you because I’m too extreme in some weird way. I don’t even mean it in a good way. I just mean I’m not the regular student with the regular way of thinking and the regular concerns. You know, things like some students are concerned about, you know, job security or landing on your feet or not wasting time but do something in the mainstream, something that’s popular. All of these things would’ve been alien considerations to me. And so, I try not to go and tell them, “No, you got to be like me,” right, because I don’t think it works for everyone…it barely worked for me. So, I don’t know that it would work for everybody. So, I think I’ve mostly just been taking each person at their own worth. I think I didn’t realize this about—you know, nothing in that pre-faculty career era would’ve led me to see this. But I’m pleased to say that post-faculty career, I am able to appreciate other people’s talents even when they’re vastly different, especially when they’re vastly different from my own. And I really view many of the people I come in contact with as works of art—meaning, I can look at a postdoc, and think, you know, I feel like I could write a poem about—you know, mentally, I’m like, wow, look at the set of strengths that person has—totally alien to me, but look at the set of things they do, and how beautifully they do it, and what power is stored there. And the thing that seems to have worked out again and again in those sort of—the last 20 years is that there’s some—you know, you’ve got—there’s some overarching view of the subject that at least seemed to have kicked in post-Lisa that I’ve had—developed with my own taste now that finds in conversation the right kind of interesting problems with a punch to pursue with all these people that I meet. If I spend enough time with them, and if I had enough lunches with people, then I find it regardless of their particular strengths. They come in different forms. And I’m open to sort of like what we work on but looking for a plot. I’m always looking for a good plot. And they seem to want that as well. Like, there’s—somehow, people find enough value in the kind of general conversations we have as we are looking for what to do. You know, this thing of what to do in a subject which is very mature is a little scary because you are—you don’t want to sit still too long. But then how do you see the subtle things, the things that are missed by others that requires you to have a kind of relaxed sitting for a while. I think that’s what I provide. I’m—from that early time, I’m scared in every aspect of life. I’m even scared doing particle physics. But, somehow, I’m able to put that fear [laugh] aside in this one activity called particle physics, I’m able to put it aside long enough not to panic—panic in the sense of rush to do the next project. Like, I don’t need to keep busy. I have—even in my first year at Berkeley when I couldn’t think of anything to do, I just went back down to campus and sat under a tree and said, “I’m not going to do anything unless something pops into my head.” Despite the fact that it’s a publish or perish world, something in me didn’t care, and so I did that until something did pop into my head. Then I went back up the hill and worked on it. But with all these young people full of all these different talents, or even old people full of all these different talents, I seem to have in post-faculty era, (a), appreciate their talents, and (b), provide some hazy overview of what’s worth doing that allows many collaborations to then come together.
But you did not sort of fully embrace the transition to cosmology until after you left Hopkins? That was sort of an incomplete transition at that point?
Yeah, it was mostly—I think that’s fair to say. It was mostly looking for—it’s waiting—I think towards the tail end of my stay at Hopkins, I was starting to write papers in cosmology. And, of course, there was this ancient problem, which is—it is a—it’s the classic cosmology problem, the cosmological constant problem, but it’s a kind of weird outlier. It’s the sort of impossible one which, if you want, when you boil it down, it has an aspect—the tough part of it has little to do with details of direct observation. So, that one is a one that I’ve had a long-standing interest in, but more detailed, pragmatic cosmology in some way. I didn’t find the right set of problems that had a field theory side that I could get my teeth into. So, while I appreciate the subject, I didn’t find what I could do, and so I didn’t, mostly until I left. Now there’s lots of problems like that that I can see to do. So, it was just venturing far enough to get into it. You know, with my strange brain, what I require is I require others to massage a problem—
—in the real world to the point where its field theory roots are seen, so that I don’t have to think in a very detailed way about all the medical physics out there [laugh], the details of this and that. That’s what makes it interesting experimentally. But I can keep a kind of fuzzy picture of that, but then I can get these field theory roots, and I can play with those. I require that from others. I’m too blind to it, too impatient to go into it. But again and again, others do that, you know. And so somewhere in the intellectual ecosystem, there’s room for me because—and what’s happened is that some people have done that in the area of cosmology enough—in theoretical cosmology where I now see the field theory roots, and therefore I can now—it’s safe for me to come out and play in the, you know, cosmology sandpit.
Now, were you looking—by 2010—were you looking for a change of scenery? Did Maryland just sort of recruit you out of the blue?
Again, it goes back to my childhood. You know, from the time at Johns Hopkins, I was like—I liked where I grew up in Bethesda, and—
You were living closer to Hopkins though when you taught there? You were not in—?
That’s where we were living, yeah, we were living in North Baltimore, northern parts of Baltimore. So, there was a homing instinct still going on, and it hadn’t quite—it got close by being in Baltimore, but it wasn’t quite close enough.
And we had some family friends in Bethesda from those days, you know, from many years, decades ago. And so, I kept trying to—you know, we kept trying to see if we could live here. And it was just too far to go to Hopkins. But, eventually, did it anyway. Just moved to Bethesda, and I was commuting to work, and it was getting a bit overwhelming, but I was planning to just do that. And, but the Maryland people, you know, put two and two together, and said, “This guy’s in our vicinity, and we need to hire,” and so they made me an offer. And so, I just took a sabbatical year to try it out. I was not sure about this department at Maryland. But once I had spent a year, and figured out that it was great, I was—I jumped ship.
Now, was the directorship for the Center for Fundamental Physics, was that baked into the offer? Was that part of the consideration?
It was, it was. I mean, roughly speaking, I said to the Maryland people, and in particular their chair, I said, “You know, I just want to have fun. I don’t consider myself—I’m still—my mindset is like a postdoc, and I like being a postdoc. So, I really just want to do the things”—
Well, at that point, you were a postdoc for longer than you were a professor still.
Exactly, [laugh] so it’s something that I knew well.
And I said, “I’d like to return to that. But, of course, there will be things that only I can do, in which case I would like to do them. But can we set up the job so basically everything that somebody else can do, they do it? But then I just get to do only the things I like doing.” And, so we said, “OK, so fine.” I like teaching a certain amount, so that’s the amount of teaching I got. And I said, “You know, administrative duties, like nobody likes administrative duties. But if I have to do some administrative duties, I’d like it to be, you know, in this subject where I feel like at least I have the judgment to exercise, and maybe I have the breadth that I can unite different sorts of intellectual directions in the department.” And so that was sort of baked in. And that’s how it’s worked so far, I think. That I feel like those things that are unique to me are getting used in all the capacities that I’m employed at UMD.
Yeah. Now, the transfer from one department to the other, I mean, they’re both excellent programs, excellent faculty, but one big difference of course is that Maryland is a huge public school, and you had spent so much of your trajectory, you know, at more elite places overall. So, I wonder what kind of adjustment that might’ve been in terms of, you know, your overall teaching experience, the kinds of undergraduates that you might interact with? I’m curious what adjustments there might’ve been in that regard?
Yeah, so, I think I went in with exactly that set of concerns. I was like I’ve never been in a state university, except for Berkeley, which is kind of exceptional. And even there, I was a postdoc. I hardly spent time on campus. I was up at the lab. So, indeed, I had been at a set of elite places, and thought, well, am I going to be in the wrong place? Are they going to be up to snuff, and all of that? And what are the students going to be like? And so, I went in with all the sort of preconceived ideas of how bad it could be, and it was a very, very wrenching decision. And I was really completely—completely—torn. And as I was completely torn, I was starting to get word that the brilliant theoretical cosmologist, Marc Kamionkowski, was starting to be wooed to come to Hopkins, which would make it even—an even more fantastic place for me to stay. So, I was really torn, and I was actually at an impasse. I could not make a decision, and I had not learned the art of just jumping and forgetting about it. But my dad ultimately said, “You know, so you’re completely torn. In those circumstances, why don’t just do the new thing rather than the old thing, which you already know?” And so, on the basis of that, which I think is actually good reasoning—I just gave it as advice to somebody else who was torn [laugh]—I jumped with all the foreboding, etc., etc. Now, as it turned out, there was no reason for that to worry me. The department is absolutely fantastic. The students—which, again, I couldn’t have believed it was true—but the students that I—the graduate students that I get are really fantastic. I always had this feeling though if I had a second-rate student, life would be so much of a drag, and you’d have to carry their—this is not a subject that does well when somebody is not really great at it. But these people are just fantastic. I mean, I don’t know how we’re getting these students, but they’re really great, even though we don’t have the sort of name brand of a Harvard or something like that. And the postdocs I was worried about because we got these fantastic postdocs when I was at Hopkins. But we continue to get [laugh] these fantastic postdocs. So, the final thing was just like undergrads. But, as I’ve told my daughter, who doesn’t go to UMD—but when she was considering where to go, I was saying this is like whatever, 40,000, 50,000 undergrads. Sitting inside that—what I learned but I didn’t know until I had gone there is that sitting inside there is like, yeah, one-tenth of them are like sort of, you know, some sort of Harvard-quality type undergrad, some elite school version of them. The only thing is there’s a whole distribution. And, but some—the top ones totally blow—I mean, I sometimes come back home depressed after work because I can see that some of these undergrads are just better than me [laugh]—
—and better than me certainly at that age. They’re so accomplished, they’re doing so many things, and they’re doing it at very high levels. They’re doing research, blah, blah, blah. It’s frightening. So, they’re—in a sense, UMD’s got everything. It’s diluted because it’s got large numbers. But actually, I really like it there. And I—you know—and both campuses have the kind of grassy, bricky campuses that I really like. Again, the Marylander in me still loves all the bricks. And so, it’s been great, like, for me just to walk across campus, which I used to do all the time just to go to lunch. It’s now a much bigger walk—
—because it’s such a huge campus. But I love it. I love the buildings and the campus. And I like—in a sense, the largeness of it is something I actually enjoy because I’m insulated. I only talk—I only seem to have to talk to people who are interested and motivated.
Yeah. So, Raman, just to bring it up to the present in terms of your own research, what have you been working on in recent years?
Yeah. So, one of the—so lots of very, very different things from very theoretical to things related to collider physics to things related to lots of cosmology. The problem of—one of the interesting questions which is where does the matter of the universe come from? Why do we have more matter than antimatter? With a postdoc at UMD, Yanou Cui (now a faculty member elsewhere), we worked out—I think what one of the, like, simplest such mechanisms, and then showed that it is something that can also—you can attempt to try and reproduce in colliders. And it fits into what from the collider experimental viewpoint is a very challenging, relatively new direction or emphasis of looking for particles that have long lifetimes, so long that they can travel a macroscopic distance before they decay. In an experiment where you’re smashing protons together, and there’s sprays of particles wherever they smash, having something that gets out of the traffic, and then decays, makes it more visible and interesting as a search that, you know, colliders can do. So, this kind of thinking about early cosmology to some actual simple mechanism to seeing how it plays out in experiment. And then one of our postdocs David Curtin, who is now a professor at Toronto, devised by having a workshop at Maryland, got together with some experimentalists, and worked out a new detector that can be added onto the Large Hadron Collider to detect these particles that travel quite far and then decay outside the region of the traditional detectors. So, there’s a kind of a lifecycle of super-exciting ideas about the beginning of the universe, down to practical details like this that’s been sort of one branch of my work. But a lot of the work recently with a couple of my students has been on—well, actually, all three of my students—has been on cosmic inflation, the growth spurt of the universe very early on, which has one remarkable feature that the energy—you know, for particle physicists, E = MC2 is the mantra. And it means that if you give me a lot of energy, I can create particles which are very heavy, and with short lifetimes. They may not exist in large numbers today, but they may have played a pivotal role in the evolution of the universe. OK. So, we’d like to recreate these particles, and see what they’re made of. The early universe, especially inflation, is a source—so particle colliders can provide energies. But vastly higher orders of magnitude of energy were available in the early universe. In particular during inflation, you could’ve had energies which are at the scales that they can probe particle physics related to Grand Unification and things like that, which current colliders on Earth cannot dream of coming close to right now. The problem normally is that what happens back then stays back then, right. Like, where’s the fossil evidence? So, again, in one of these stories of brilliant insights, massaged by others into a thing that a field theorist can sink their teeth into, there’s recently in the last decade been work to show how the particle physics back then beyond the reach of terrestrial colliders could’ve been imprinted on things like the cosmic microwave background or the distribution of galaxies. And that by looking at that as the fossil evidence, we can literally see the ancient particles traveling, right. The “movie” of the distant past is there in what looks like noise to the ordinary eye. So, we’ve been working on maximizing what kind of particle physics that program could have. There is a new set of galaxy surveys figuring out the statistical distribution of galaxies that’ll be kicking in in this decade. And this could really see some of these, you know, awe-inspiring things from way back then where the kind of the ancestors of particles, we might literally see them walking around. And it’s literally—you know—to me, it’s the equivalent of seeing dinosaur footage. Somebody took the video back then, and here it is.
And we start to decode it. So, a lot of my work has sort of been in that direction recently. It’s a combination of cosmology and quantum field theory, and just this amazing set of experiments that humans can actually hope to do. And the other—I’ll just mention one other thing. Another big direction has been—again, going back to these Randall-Sundrum models. But one of the exciting things is that in the early universe, there can be what’s called a phase transition. It’s sort of like water to water vapor kind of transition. Here, it’s one in which as the universe cools, you can go from a behavior in which there is some generalization of a black horizon—a black hole-like horizon, except it’s not a black hole, it’s a black brane horizon—into a later stage of the Randall-Sundrum model, which can liberate gravitational waves copiously, which we can hope in future gravitational wave detectors to be able to see, again, this remnant from near the Big Bang, if theories like Randall-Sundrum are correct. So, working out some of those details has been a big part of my work with Kaustubh Agashe and postdocs and students here.
And it sounds like you’re getting closer and closer to those early interests that you had in those mythologies.
Yeah, yes, yes. Not only it’s the—so much so that a lot of that mythological background and taste and so on comes into even how I tell the story when I give talks, not just to—you know, I’ve given talks to the general public, but I also give talks to other physicists—to place them, so say, “Look, we’re all in—we’re all doing this. But what is its significance? How do we picture it?” And I often will use like the family tree of the gods, right, in, you know, say, Norse mythology or something, or Hindu mythology, and show that we are in very much the same situation. For us, the gods are forces. And amazingly—I didn’t know this when I got into the subject. But amazingly, there is a kind of family tree of forces. There are ancestor forces that died in birth—giving birth, but then they gave birth to daughter forces, and then those are the ones we see. Maybe closer to the Greek Titans giving birth to Gods. And part of the game of looking into the distant past through these fossil records is to see if you can see the ancestor forces in the fossil record, right. So, indeed, it’s all come back. It turns out I didn’t waste my childhood—
—reading all of these stories.
On that note, not in your capacity as a scientist but perhaps just in your capacity as a wonderer, do you have much appetite for metaphysics, for thinking about, you know, the way the universe might work beyond our way of understanding it through observation and deductive logic?
Yes, yes, it is—if not—you know, I would say if not more than my wonder on the scientific front. That is, there are two questions if you are a reader of the epic mythologies or religion or any of these things. How did it all start? What’s it all about on the outside, which is still related to what is quantum mechanics? What is time? But the ultimate “what is” is what am I? And, to me, this is an even more profound mystery. And yet, you know, often I will tell people, you know, “Yeah, there are your interests, and then there are your strengths.” [laugh] So, somehow you have to make peace with—because they don’t—they’re not always the same. And so, I’m not sure that I have great strength in this, what you would call metaphysical questions. But, at this stage in life, it has even more vitality as a question. And yet I feel like I sit in a rather privileged space because I’m also looking at fundamental laws on the outside, and feel like is there no connect…can I not see with both my eyes both things at the same time? But absolutely, I would say I am fascinated by what I’ll call the first-hand experience, not the sense of being me specifically, but the general sense of being. And it connects to every shred of my heritage—
—in Hinduism, or the Buddhism that was current in Burma at my father’s time, and so on.
Maybe this is why you couldn’t get a problem from Lawrence Krauss who has very little patience for these kinds of things.
Indeed. I don’t think he had something that would directly—I think he’s almost spent a good public career on the opposite side. And, in a sense, I like that because I think the danger with these questions very close to your heart is that you lose your marbles. That you say what you want to be true rather than what you can see. So, I stick to one thing that I think I learned from physics, and that is I’m not a believer. I want to see. I think there’s enough mystery to say, well, just see it. You may not even find the words to utter what you’re seeing. But, to me, I’m just saying I think there’s—I have an intimation that there’s something extraordinary in this ordinary world. I think it’s obvious, if you just take away your minor fears, this, that, and the other parochial concerns, and just—if you just open your eyes as if for the first time, you would have to say there’s something just amazing in the fact that you’re even able to see out in these little detectors that there’s something back there. I would not want to then posit lots of like, this is true, this is true, I believe this, I believe that, this is what’s going to happen to me later. And I’m happy if Lawrence shoots all that down. But I stand as someone who’s—there’s something that is still a little outside of what I would call—it’s—in my view, it’s completely scientific, but it’s outside the scientific tradition that is not touched on. And it’s a singular omission, in my view, which is we never talk about the personal experience…us. We talk about this body. We even talk about this brain. But that is not my experience of myself. And you might say, “Oh, that’s just a matter of detail. Eventually, we’ll get there.” And I have no faith—
—that the “matter” approach is going to touch it.
And, of course, it’s inescapable that the us factor is inherent in all of science. It’s the beginning of all inquiry.
It is. It is and, in some sense, you make a lot of mileage by putting it aside scientifically, right, and just build your bridge, damn it, and get on with it. But I consider it put aside only because it’s a hard—it’s like the cosmological constant problem or something, except on steroids. It’s hard, and so you put it aside, and you make a good career doing lesser problems. But, to me, it’s—it is the exciting thing. I’ll pay the bills with the other stuff.
But this is the—as I said, if I had greater talent, which it’s almost like—sometimes I have this in mathematics, it comes up in work, where you’re like I know how great I could be if I could just—
—be better at this math part, right. Here, it’s like wanting to be able just to see but get rid of all the little details that are distracting you on a constant basis. I think this profound question which has been asked in every tradition I know of, “what are you?” is still worth asking. And most people would say, “No, it’s not re…you know, it’s a matter of—it’s scientifically interesting but obviously you are some emergent phenomena from a brain, and that’s it.” So, just like once we didn’t understand the sun in great detail, but we knew roughly it was made out of stuff, and now we understand it in much greater detail all the nuclear reactions, da, da, da, da, it’s only a matter of time before the brain—you are understood in those terms. Something is not sitting right in that view for me. So, something is some…there’s some X factor that’s missing. And so, yes, that would be I think of great interest, and fits with somebody’s who’s interested in physics itself as being not really interested in this or that detail, being a bit impatient about details, late in life learning that the details can be the—they’re not important themselves but they could be the door to something truly fundamental. But as somebody whose interests have been on things fundamental as I’ve seen them, there is another fundamental side that I don’t talk about much to my postdocs and students about, but is a big part of who I am.
Well, Raman, for my last question, I want to bring it full circle, you know, to this theme from your time as a student where you lacked the direction. You lacked being able to focus on the questions that were interesting to you. And hearing you now talk about this extraordinarily rich and broad research agenda that you’re very much in the middle of now, I want to ask generally sort of what has changed? Obviously, maturity, meeting more people, but what has changed that allows you now to delve into all of these different fields, and not have any of the drawbacks, initial problems that left you casting about for quite a significant period of time in your early career?
I’d say mostly two things come to mind. One is as I think I’ve told you, but there’s a number of occasions—not many; maybe less than 20—where somebody has said something where you wake up and you say, “Oh, my gosh, I’ve been keeping my blinders on, obsessed in this direction, and I just didn’t see that there were these other things. And I’m capable of working on these other things, and they’re interesting. And I just needed to hit the right human to point out these new directions.” Like, I couldn’t wake myself up from those—that state until somebody tapped me on the shoulder, and it had to just sort of be that right moment. I am struck by the fact that at least I had the sense to know that I was listening to wisdom when somebody said it, you know. I couldn’t chance on it myself. But many times—again, order 20, so much so that I literally remember all of them—somebody has just said, “Hey, Raman, you know, actually, it’s quite easy. You could just do this thing here instead, or there’s this broader area than just this thing you’re focusing on.” And that has been enough. Or like Markus Luty telling me, “You know, you can act…” No, he didn’t tell me; just by showing. You can actually go from zero to 100 miles an hour. It’s possible. I think there was some critical number of such things that has just added up that then you’ve got all of the things. There’re enough creative sources in terms of blinders that have been removed—not added; just removed. So, I think I needed some set of those. The other thing is that from being very much a kind of “think with only yourself, and don’t talk to anybody else, and avoid everybody else” person, I am in a privileged situation that I can, you know, hire postdocs, and have colleagues, and have helped built groups, and I have many former students and postdocs and so on, that I have the complementary expertise among people who will give me the time of day, which I didn’t have earlier. I mean, you know, through no fault of my own, I didn’t have access to them when I was much younger. And as a loner, there was very little I could do about that. Even if people had taken off some of the blinders, I didn’t have the—I still don’t have a lot of the skills that many of my colleagues have. And I still walk around feeling the insecurity of somebody who’s going to get found out as, “Oh, you’re not as solid as we thought you were.” [laugh]
But, at this point, I don’t even care. I know I’m not solid. And I’m—and I cannot reject what I clearly see in other people when they interact with me, which is they no longer care that I’m not solid.
There’s something, there’s some other factor which meshes well with what they can do. And so, I think there’s a level of relaxation where I feel like I now have—I’m just a bigger entity than this, you know, particular brain. There’re all these other people that are now part of me, and they have all these other skills, and they’ll—like, I can meld with their minds, and we can do our stuff together. It was just—I think it’s just a much lonelier, isolated thing, when I started. It is a tricky thing to have a skill, or a skill set, which is not something that is a standalone skill set that allows you to do things. They might be a very powerful set of skills, but it needs to be enabled by other people. If I look back, I would say I fall into that category, and so it just took time for the opportunities to flower through collaborations with others.
It’s a neural network, and you’ve found your node, essentially.
Exactly, exactly. I am just one node.
And it’s really—it’s a network. This particular node has its own unusual skill set in some way. But it needed the network in order to amount to anything.
Well, Raman, it’s been an absolute pleasure speaking with you today. I want to thank you for your time. And you proved yourself fantastically wrong about this—
—not being an interesting story for—
[laugh] Once again, I’m wrong.
There you go, perfect. [laugh]
Once again, you’re wrong.