Phiala Shanahan

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ORAL HISTORIES
Image of Phiala Shanahan

Photo courtesy of Phiala Shanahan

Interviewed by
David Zierler
Interview date
Location
Video conference
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Interview of Phiala Shanahan by David Zierler on September 21, 2020,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
www.aip.org/history-programs/niels-bohr-library/oral-histories/47214

For multiple citations, "AIP" is the preferred abbreviation for the location.

Interview with Phiala Shanahan, assistant professor of physics in the Center for Theoretical Physics at MIT. Shanahan explains the administrative relationship between the department and the Center, and she recounts her childhood in Adelaide, Australia, her experiences at an all-girls school and the benefits this conferred in nurturing her interest in science. She discusses her concentration in computational physics and the mass of the H-dibaryon at the University of Adelaide and her decision to stay on with her undergraduate advisors, Anthony Thomas and Ross Young, for graduate school. Shanahan describes her interest in the proton radius puzzle as a research entry point for her thesis work and why she was interested in how particle physics can be connected more rigorously to quarks, gluons, and ultimately chemistry. She describes the opportunities leading to her postdoctoral research at MIT and some of the cultural adjustments she had to make coming from Australia. Shanahan discusses her collaboration with Will Detmold and she describes her contributions to the NPL-QCD research project and she discusses her first faculty appointment at William & Mary before returning to MIT where she remains in her current appointment and where she is pursuing work on proton structures and in creating ever-faster algorithms. She describes the potential benefits that would be conferred with the availability of true quantum computing for her field, and she describes some of the difficulties she has faced as a woman in getting recognized for her accomplishments in her field of research. At the end of the interview, she emphasizes why her long-term goal is to bridge nuclear physics and chemistry, and why she wants to keep an open mind about pursuing other areas that are both interesting and offer the opportunity to push forward discovery in foundational ways.

Transcript

Zierler:

Okay. This is David Zierler, oral historian for the American Institute of Physics. It is September 21st, 2020. I am so happy to be here with Professor Phiala E. Shanahan. Phiala, thank you so much for joining me today.

Shanahan:

Oh, my pleasure.

Zierler:

Okay, so to start, my first question, I'm sure you get this a lot – there must be an interesting story behind your first name. What is it?

Shanahan:

Oh, yeah, actually there is. My mother is German, and my father was Australian of Irish heritage. And they were looking for a name that sounds the same with both accents. And that turned out to be a reasonably short list, actually.

Zierler:

(Laughter) That's great. So, it purely has phonetic meaning?

Shanahan:

Well, it is an Irish name. As I said, there is Irish heritage as well. But right, ultimately, they were looking for something that I wouldn't get confused about as a small child.

Zierler:

Have you ever met another Phiala before?

Shanahan:

I have not, but there are some on the internet. I have googled the name.

Zierler:

Uh-huh. I've never heard it. It's a beautiful name.

Shanahan:

Thank you.

Zierler:

All right, Phiala, so to start, please tell me your title and institutional affiliation.

Shanahan:

Sure. I'm an assistant professor of physics in the Center for Theoretical Physics at the Massachusetts Institute of Technology.

Zierler:

And what is the institutional or administrative relationship between the Center for Theoretical Physics and the department of physics?

Shanahan:

The Center for Theoretical Physics sits administratively inside the department of physics. So, there's a number of different departments, labs, and centers inside the department of physics, like there's the Kavli Institute for Astrophysics, there's the Center for Theoretical Physics. It’s a somewhat complicated hierarchy, for example the experimentalists in nuclear and particle physics are in the Laboratory for Nuclear Science, LNS, and the Center for Theoretical Physics is also part of that, which is part of the physics department.

Zierler:

And are your teaching responsibilities- how does that work in terms of course loads? Are your teaching responsibilities determined within the center or within the department?

Shanahan:

No, they're determined within the department. There are subgroups, labs and centers where we sit in the physically, which determine our administrative assistants, the research group structure, but we're all part of the same department, so all the teaching, all the service work at a department level is under that umbrella.

Zierler:

And I'm curious about the title, "Class of 1957 Career Development Professorship," that you have through 2022. What is that professorship?

Shanahan:

There are actually a number of these named professorships. Mine is one of those funded by that particular graduating year, that are awarded to junior or senior faculty for research or teaching achievements, sort of broadly defined. So, there's no specific citation that goes along with it, just one day you get tapped on the shoulder and get told there's this chair, this named professorship, and a little bit of funding that goes along with it that you've been selected for.

Zierler:

Okay. All right, well Phiala, let's take it all the way back to the beginning. You alluded to it already, but let's talk a little bit more in detail about first your parents. Where they're from and where they met.

Shanahan:

Yeah. My mother is from Germany. From Niedersachsen. And my father is Australian, and so I might need to check back in with my mother, don't tell her before you write this up, but I'm pretty sure they met when he was at a conference in Germany for his work. (EDIT: My mother confirms, and says they knew each other from work phone calls beforehand.)

Zierler:

And what was your father's field? Or what is his field?

Shanahan:

He was an actuary.

Zierler:

And what about your mom? What was her field? Or what is her field?

Shanahan:

She was a professional assistant.

Zierler:

And they met in Germany, and did your father spend some time-

Shanahan:

I'm pretty sure. I'll have to check with my mother on that. (laughter)

Zierler:

We'll go back, when you edit the transcript, you can talk to everybody, get your facts straight.

Shanahan:

(Laughter) Get my fact straight, yeah. I haven't heard the story for a very long time. I believe they met in Germany.

Zierler:

Did your father stay in Germany, or did he bring her right back to Australia?

Shanahan:

Well actually, she first moved to London where he was, then they both moved to Singapore for my father's work for a while- I think there was some long-distance courtship before that. Eventually they moved back to Australia when my mother was pregnant. They wanted to be closer to family, and I was born in Sydney.

Zierler:

You were born in Sydney?

Shanahan:

Yes.

Zierler:

Did you grow up in Sydney?

Shanahan:

I grew up in Adelaide. We moved to Adelaide within a year or so of my birth, so I don't remember Sydney.

Zierler:

And then you spent your whole childhood in Adelaide?

Shanahan:

Right, until I moved to the U.S. as a postdoc.

Zierler:

Can you talk a little bit about the educational system in Australia? Is there a public and private school divide like we have in the States?

Shanahan:

I don't know so much about how it is in the States, but there's a public and private primary and secondary education divide in Australia, but the university system is very much public. So, there's no such divide in the university system.

Zierler:

And growing up, what kind of school did you go to?

Shanahan:

I was very lucky. I had a scholarship to go to a private school. Wilderness School for Girls. So, it was an all-girls school. A little bit traditional with uniforms and straw hats in summer, and blazers and skirts in winter.

Zierler:

Was there a religious component to the school?

Shanahan:

No, there was not. It was non-denominational.

Zierler:

What were some of the educational philosophies around having an all-girls school?

Shanahan:

The school itself was focused on girls' education and girls in leadership. Girls in STEM fields. The school's philosophy was really about having all girls in classrooms. Force girls into leadership positions. You had entire classrooms, science classrooms, full of girls. The history of the school is that it was founded 140 years ago, now, I think. Am I that old already? We celebrated the 120th when I was at school, I think, so maybe not quite that long ago. The school was founded by a group of sisters, the Brown sisters, and the original schoolhouse is actually still on the school campus. It's now the headmistress's office, or at least it was when I was at school. It began with just that family and a few extra girls and boys. And then it grew to become a girls' school eventually.

Zierler:

And you started there in kindergarten? Right away?

Shanahan:

Yes, actually, they have a kindergarten that I started in, and I ended up staying there through my whole education.

Zierler:

Now, when you say you got a scholarship there, you must have been a pretty bright, small child. You must have already been distinguishing yourself academically?

Shanahan:

Yeah. I remember back in lower primary school, you know, I don't know if they call them differently here in the U.S., but Year One, Year Two, they would put me into a different classroom for English and for Maths, and things like that. And I skipped a year of school in the third year. Actually, halfway through the year. So, they didn't wait until the end of the school year, just halfway through the year I got ripped out of one classroom and put into another, against my family's protests. I remember very clearly that the school wanted me to take some sort of an assessment, and my mother was very much against me being accelerated. So, she kept me up late into night the night before that assessment, so I'd be tired (laughter). And so, they gently encouraged me that I didn't necessarily have to (laughter) you know, do that well on the assessment. But of course, I was very stubborn, and if I was given a test, I wanted to do well.

Zierler:

Phiala, I wonder if there was some natural, underlying interest in math or science that you had that sort of exhibited itself academically, or you just sort of naturally did well on those kinds of tests, and that was sort of the direction that you followed?

Shanahan:

I'm not sure whether my teachers would have picked out maths and science as my strengths. I mean, certainly I wasn't weak in them, but really, I enjoyed everything. I'm bilingual. German is my other first language. So, I had a strength for languages, I pick them up quite readily. I enjoyed everything at school as a child. So yeah. I don't remember specifically in primary school whether- maybe my teachers would say there was a specific aptitude for maths, but I don't quite remember it that way. I just remember I liked everything. Everything anyone gave me, I enjoyed very much.

Zierler:

So, it was one school? Were there different buildings on the campus?

Shanahan:

There's a lower junior school which has reception- I don't know what that's called here- to Year Two, and that's down one end of the campus along with the kindergarten, in basically one connected building. And we ventured out to go to the library, which was in a different part of campus, or to go to sports. And then on a different part of campus, there's the primary school, so Year Three to Year Six. Then the middle and high school are sort of in between the two, all on one campus, at different places on that campus.

Zierler:

At what point did you realize that you wanted to pursue a career in science? Was it early on?

Shanahan:

It was when I was already doing it at university.

Zierler:

Uh-huh, uh-huh. But not before then? You weren't thinking about university, specifically about science programs when you applied?

Shanahan:

No, I really struggled to decide what to do applying to university. In the end I sort of narrowed it down, maybe science, maybe maths, maybe medicine. I got into a medical school and deferred it just in case I changed my mind halfway through my science degree. I considered studying music or history or languages. Actually, in the first year of my science degree I took Latin and Ancient Greek. The things that weren't offered at my school that I would have loved to study, I took them as part of my science degree in the end.

Zierler:

Phiala, can you reflect a little bit about some of the advantages that you might have had going to an all-girls' school in STEM? And I guess my underlying cultural question there is that, is there an emphasis on needing an all-girls environment to encourage them to go into STEM because more broadly in Australia, that might not be something that girls are sort of naturally encouraged to pursue?

Shanahan:

Sure. So, obviously, I only saw one side of this because of the environment I was embedded in. But there was never any question to me that the science classroom was somewhere where I fit in. There was just never a doubt that I fit into leadership positions. And so, I don't know whether that was the result of the all-girls education and if it would have been different if I had been in a different environment. But of course, that's part of the motivation, and there is certainly gender bias in science and maths classrooms in Australia, just judging from the cohort of students I went through undergraduate and university with. There were not very many girls in my classes, and many of them had come from all-girls environments.

Zierler:

Yeah, yeah. Now, when you choose university in Australia, it's very different because they're public and they're all very good, so it doesn't make a big difference where you go, because they're all pretty strong, so it just sort of naturally makes sense to go somewhere closer to home. Is that right?

Shanahan:

Yeah, very much so. Now I looked into various programs. I even looked into going overseas, but I was sixteen. There was a very good university right on my doorstep. There was really nothing offered by other programs at the other universities to make me prefer them.

Zierler:

And what adjustments might you have had to make taking classes with boys, young men, by the time you got to university? Was it an easy transition for you?

Shanahan:

It was fine. This is sort of funny in hindsight, but the very first thing that I noticed was that they smelled. I was sitting in my first-year university class thinking, "What?" I didn't notice that teenage boys smelled before I was sitting next to them. But other than that, which lasted a week of sort of confusion, it was perfectly natural, you know, we were interested in the same things.

Zierler:

These are, you know, guys who had never done their own laundry before or something like that (laughter).

Shanahan:

Probably, yeah.

Zierler:

Phiala, how did you settle on computational physics for an undergraduate major? How did that process come about?

Shanahan:

In complete honesty, that happened partially because of the way the university system is set up in Australia. When you finish high school, you get a number associated with your completion, which is supposed to be related to the percentage of people in Australia whose high school completion yours was better than. So, if you got 99.95, which is the top score, then that's the top bracket, and your high school completion was better than 99.95% of everyone else’s who finished that year. It is supposed to be normalized, so if, you know, you delay a year, that's your "normalized" score which will still work for admissions the following year. Every degree also has a number; essentially what they do is they admit people until they run out of room, and then the lowest score, that becomes the number that goes in the book, that you can look up and see, what was the lowest score that got into the program I want to, last year. So, you can know roughly where the bar is. And so, the bachelor of science had a score of about sixty, and the bachelor of science in high performance computational physics had a score of 99.95. So, you know, I assumed, hey, that must be hard. That sounds challenging. I like that. Ultimately it was basically the same degree program with just a few tweaks. But as a high school student applying, it looked like one of these was easy and one was hard, and I wanted the challenging one.

Zierler:

And that says a lot about how you were really looking to challenge yourself.

Shanahan:

Yeah, and it was good marketing on their part.

Zierler:

Yeah. Did you have any interest in computers or skills in computer science up until that point, that you thought you might pursue?

Shanahan:

I had an interest in computers, no great skills in computer sciences. We didn't have coding or anything at school. So that wasn't something that I was super familiar with. But back then, I already sort of realized how powerful computing can be. And I think even then, I realized that that's a tool that I had to learn how to use, no matter what I wanted to do.

Zierler:

Phiala, I want to ask. By the end of your undergraduate degree, was your identity in terms of the kind of physics you wanted to pursue in graduate school, was that pretty well-set at that point? Or you were still open to a variety of subfields to explore as a graduate student?

Shanahan:

Again, the degree structure is a little bit different at home. So, I did an honors degree, which is a fourth year on the end of a three-year undergraduate degree.

Zierler:

Okay.

Shanahan:

And what that honors degree is, is it has coursework and it has a thesis. And the coursework is much like the graduate coursework here in the United States. So that's when I took field theory, it's when I took general relativity, and there's actually no coursework in graduate school, so that is where you get your graduate coursework. And there's a thesis. And so, I had a brilliant thesis advisor. I wrote my first paper in Physical Review Letters in that honors year. You write a significant document, you know, a fifty-page thesis, something like that. So, it was really by the end of that year that my direction was more or less set. I think that is as it has to be, because if you're going to do a three year PhD and come out competitive with the people doing a five year PhD in the U.S., you sort of need to know where you're going when you start, so at the end of my three year undergraduate, it wasn't really set. At the end of my fourth year it was.

Zierler:

So, I see that your undergraduate supervisors, Anthony Thomas and Ross Young, were also your graduate advisors. Under the system that you just described, is that the normal course, how that usually plays out?

Shanahan:

It's very common. It's not always that way. It's very possible to change. But if things are going well, that's quite common.

Zierler:

And so, let's talk first about the undergraduate thesis. What was that on?

Shanahan:

The thesis was called the Mass of the H-dibaryon, which is a hypothetical particle with the quantum numbers of six quarks. Up, down strange, up, down strange. The point of that thesis was that there had been a number of calculations using lattice field theory, something that I now do, of the mass, or the binding energy, of this state. But they had all been done in calculations where the quark masses, the masses of the fundamental particles, are heavier than they are in nature, just for computational expediency. And so, there were a number of calculations telling you the binding of this state, in this unphysical space, and what you really want to know is, is this bound in nature? And so the work of that thesis was to do a principled extrapolation, using tools called chiral perturbation theory, of the data over here in this unphysical space to the physical point, to say something about whether this state should be bound in nature, so whether experiments should be looking for a bound state or not.

Zierler:

Can you talk a little bit about your advisors? What were they working on, and how closely was this related to your thesis? Particularly because it seems like a remarkably advanced kind of thing for an undergraduate to be working on, even one who is, you know, as much looking for a challenge as you are, and someone who was on their way to graduate school.

Shanahan:

My advisors, I have to say, I owe both of them a lot. Tony Thomas is the reason I went down this path, actually. When I was an undergraduate student, even before my honors thesis, he recognized some potential in me, and before summer break, he said, "Do you have plans this summer?" And I said, "No, not really. I might get a job." And he said, "I'll pay you to do research." And I of course said yes.

Zierler:

Yeah, of course.

Shanahan:

Yeah, of course. And so, for a few years before my honors project, he'd been paying me to do research or read, just gently educating me, on various topics. One was about dark matter, but they were different topics each summer. And then in this honors project, he had sort of prepared me for this challenge. Tony, he was working on a lot of things with a lot of students. It's not like the environment here where you might have one or two students who you spend a lot of time with. So, I saw Tony once a week in a meeting. I told him what I'd been doing, he pointed me in the right direction. Quite often, he looked at a figure and just said, "Nope, that can't be right." And he had that physical intuition that I didn't have at the time yet just to know without even knowing the exact details of what I had done. And very often, he'd do a back of the envelope calculation just to show me something, and push me onto the right path, and he taught me that side of physics.

Ross, my second supervisor, his office was right next to mine, and he was fantastic. His door was always open, which meant very often I would run in, just excited about something, saying, "Hey, Ross, check this out." And then run away again. Or, you know, "Ross, I've been looking for three days, and I don't know where to look next." And he'd point me to the right place- a lot of patience, that man (laughter).

Zierler:

Yeah. Phiala, I'm wondering at what point- Australians are very good about travel and integrating themselves into international collaborations, sort of because they have to. They have to get on those long flights and involve themselves. I wonder at what point you started to get exposed to international physics. At symposia, conferences, and things like that. Was that early on, or did you wait for graduate school for that?

Shanahan:

No, so there was a conference early on- I was quite lucky. One of the major international conferences in my field, the Lattice Field Theory Conference, was held in Australia in Cairns, hosted by the Adelaide group, in 2012, I want to say? So just when I was starting graduate school. And I got to go to that conference and give a talk about my honors work, or actually, about some work I did just after I finished honors. And so that was my first conference I got to speak at, and it was The Conference to go to, so I got to see a lot of what was happening in the community. Didn't understand all of it at the time but had my first exposure to that very early on. Then there was also the COEPP, the Center of Excellence for Particle Physics at the Terascale, which had recently started, which was an Australian Research Council center that joined Adelaide and Melbourne and Monash and Sydney together. So, we had Australian symposia, really for particle physics even though what I was doing was more on the nuclear physics side. Regularly every year or so. And then during my PhD, Tony passed down invitations to conferences that he couldn't attend to me and made sure I got the opportunity to travel internationally and present my work during my PhD as well.

Zierler:

Phiala, what were some of the broader questions in physics that were most compelling to you in terms of the process of a graduate student creating that professional niche for him or herself? What were those broader interests, and how did you go about developing a specialty that were responsive to those bigger interests?

Shanahan:

One thing that really surprised me when I first heard about it, which was at a local talk as an undergraduate student, was the proton radius puzzle. There was this big news in something like 2010, so towards the end of my undergraduate degree, that there'd been a new measurement of the radius of the proton based on muonic hydrogen rather than measurements of the electronic hydrogen. So, hydrogen with a muon instead of an electron in the orbit. And they were different by, at the time, maybe five sigma, then it grew to seven sigma, something like that. And this really sort of hit me as an undergraduate, that we don't even know the size of the proton. It just seemed to me like one of those things you should know, right?

And so that really led to my first interest, which was in proton structure, from realizing that protons and neutrons make up 99% of the visible mass in the universe, but we don't even know the radius of the proton. There are conflicting experiments and there's nothing theory could do to tell us which one is right. That sort of led me to become interested in, well, what is the structure of a proton in terms of quarks and gluons--you see these models of a proton that's three quarks, but you know, really, it's a dynamical boiling mess of quarks and gluons. How do you get the mass, the spin, the three-dimensional structure of the proton, out of field theory? Out of the Standard Model that describes those fundamental particles?

Zierler:

And just to put things in perspective, when you talk about the knowable or observable universe, this excludes dark matter of course, so we're talking about 4%. And what you're saying is-

Shanahan:

Right.

Zierler:

-we have a very primitive understanding even of the 4% that we can see. (laughter).

Shanahan:

Right, exactly. So somehow that captured my imagination more than dark matter. I was interested in dark matter, but the idea that, if there's a bit that we have here to play with.

Zierler:

Right (laughter).

Shanahan:

That we know so little about it. That got me interested. So after that, my PhD thesis was then about proton structure, mostly, from field theory, and then since then, my interest sort of expanded, but always on that foundation. Something I was very interested in during my PhD, but didn't start addressing until later, was that, nuclear physics, in theory, comes out of the same physics. The Standard Model that gives you proton structure. But what we do is show models, you know, many-body effective theory with nucleons. You say nuclei are nucleons stuck together, but that's not right. Nuclei are quarks and gluons stuck together. So even back then, I really wanted to see, how can we connect particle physics, what we know about the quarks and gluons, to nuclei or ultimately to chemistry? How does carbon come out of quarks and gluons? And that along with all of the related things, that's what you need to know if you want to know how dark matter interacts on earth with nuclei and your detectors. That's what you need to know if you need to understand how neutrinos interact with detector- if you're trying to learn something about neutrinos. That's sort of my broader research program now.

Zierler:

Right, right. It's amazing that the questions that you're asking are so fundamental that they were not worked out by the time Niels Bohr came along, for example. It's really amazing. So Phiala, on that note, I'm always interested in how close or not theoretical physicists involve themselves with the experimentation that informs what we know so far. So, on that point about proton structure, were you interested in following the literature or collaborations that were focused specifically on experimentation to better understand proton structure? Up to that point?

Shanahan:

Yeah, very much so. I mean, this is I think partly in the training from Tony Thomas. But I'm really not interested in calculating things that would never be testable. Well, maybe there's a little bit of interest. But mostly, I want to understand the universe, and so I want to know what the Standard Model tells us about the universe that actually matches what we can learn experimentally about the universe and how we can find where our current understanding of nature breaks down. We know the Standard Model doesn't describe everything. Dark matter is just one example. How can we really find the description of our universe?

So yeah, even back then, I was very interested in how can I calculate things from theory that compel the experimentalists to test the Standard Model, and how can I calculate things from theory that will provide a piece of the puzzle to let us remove one of the degrees of freedom to then experimentally measure something else that's hard to calculate to get a full picture by combining theory and experiment. And even now, one of my focuses is on the gluon structure of the proton, because it's something we know far less about than the quark structure, but that's particularly interesting now because there's an actual possibility that that will be measurable within my career.

Zierler:

Yeah, yeah. Phiala, another big question as you're developing these fundamental ideas, did you see or currently see any pathway in your research to possibly integrating gravity into the Standard Model?

Shanahan:

Yeah, so that's something I was very interested in as a student, actually. I spent a while toying with ideas like that. But not at the moment. For a range of reasons. First one being that there's a lot to do to understand the Standard Model to start with, but the second one, and this is perhaps a little bit sad, that that's a really hard thing and I would love to take a crack at it, but I also need to make sure I get tenure, and you know, now is not the time to spend time trying things that might have a slim chance of very big successes.

Zierler:

Yeah, yeah. So right now, the idea is improving the Standard Model as we currently understand it, before revolutionizing the standard model.

Shanahan:

Well, it's more about understanding the Standard Model rather than improving it. Understanding it so that we can find out where we have to improve it, is really- so, the other thing that I think we're suffering from a little bit in trying to write down beyond the Standard Model theories is in lack of data constraining it. We have lots of hints, but I think there's still room to have more information on the physics beyond the Standard Model because right now there are a lot of possible theories that are not yet ruled out that have been written down. And it's a very big space and the only way to narrow that space is to continue to measure and study the Standard Model physics and find where there's a mismatch.

Zierler:

Phiala, at what point did you know that you were going to leave Australia and pursue a career beyond Australia?

Shanahan:

Probably towards the end of my PhD. It's a different culture at home than there is here. I feel like all of my students want to go on to do postdocs. That's not the case at home. Most people do a PhD because they want to do a PhD, not because they want an academic career. And I was one of very few who even wanted to do a postdoc, so it wasn't a given in any sense.

Zierler:

Yeah.

Shanahan:

So, I really had to think, you know, what sort of a career do I want? Do I want one here, at home, do I want to do a postdoc and follow an academic career? And so, I decided to do a postdoc, not even because I was sure I wanted an academic career, but because I thought it would be fantastic to go and live and work in another country for a while. And I loved the work and so it sounded like a great opportunity. But even then, I wasn't thinking I want to become a professor and live in the United States. That was just not on my radar.

Zierler:

Sure, sure. Did you apply to postdocs exclusively in the States or also in Europe?

Shanahan:

Also in Europe. I actually didn't apply to very many. I applied to a small handful, because again, I wasn't looking for safety postdocs. I was looking for if it was a place that really excited me and I wanted to live, sure. If not, well then, you know. Then I'll do something else, right?

Zierler:

Yeah. And so how did the opportunity at MIT for your postdoc, how did that come about?

Shanahan:

Well, I applied, and they offered me the job, more or less. So actually, I was interviewed for the Pappalardo Fellowship at MIT. Which is the prestigious postdoc fellowship, which was quite exciting. They flew me over from Australia for two days to come and do an interview, which was quite something. I was the first one of the day, I had just flown in from Australia, and they want you to- I guess now I should say "we," I do this to other people now-write on a black board for fifteen minutes and explain your research. And so that was very fun, I'd never done anything like this before. I think I actually nailed the interview. And people told me I did as well. But then they asked me a question I couldn't answer, and so I didn't get that fellowship, but they offered me a regular postdoc at MIT.

Zierler:

Do you remember the question?

Shanahan:

It was, something about the Fermi sphere radius of the deuteron, something like that.

Zierler:

Was that a fair question, given your background up to that point?

Shanahan:

No. But it was a fair question given my talk. So actually, I think having now seen the process from the other side, I misjudged a little bit the point. I was telling them what I wanted to do. What I would do if I came as a fellow.

Zierler:

Yeah.

Shanahan:

Which meant I was talking about things I had never worked on in part. Just the things that excited me. And I showed them how that came out of what I'd worked on a little bit. But then they asked me a question about the part that I'd never worked on. And they asked me a question phrased in a language that I didn't know. The question came from a condensed matter physicist, and there were no condensed matter courses at Adelaide, and he introduced himself saying, "So, this is a question from a condensed matter perspective." And I knew nothing about condensed matter physics at that point. I had never even met a condensed matter physicist. And he asked me this question which ended in something about the Fermi sphere radius of the deuteron, something I didn’t know the definition of. So, I just, you know, had to say I didn’t know what he was asking me about.

Zierler:

I guess the response to save yourself there was to say, "I don't know, but that's why I want to come here. I want to be able to answer that question."

Shanahan:

And that's what I said, actually. But what I've seen now is that people most often give a talk about what they've done. With just a very little bit about what they want to do. Which was sort of the opposite of what I did. So, I mis-pitched. But actually, that person mis-remembered recently, and introduced me as, "Phiala Shanahan, who's on the physics faculty, who was a Pappalardo Fellow here." So, they don't remember that, at least.

Zierler:

Had you been to the States before?

Shanahan:

I had, actually, several times. I won a fellowship during my PhD which was a traveling fellowship, which took me to Europe and to the States on this whirlwind month where I was in a different city giving a different talk at least every week, sometimes more than once a week. I gave talks at CERN, and I gave a talk at MIT, and I gave talks all the places that I thought I might want to go for a postdoc, and that let me whittle down the list. So, I'd actually even been to MIT before.

Zierler:

And so, what were your impressions of MIT, you know, when you started as a postdoc, when you got yourself situated and comfortable there? What were some of your impressions culturally, how physics was done there that might have been different than what you were used to?

Shanahan:

Yeah. My first impressions were pretty crazy. So, I got into the office and talked to my office mates, and after the weekend, I would say, "Hey. How was your weekend?" And they would say, "It was great, I did a lot of work” (laughter). And I would say, "Oh. Well, I went hiking in Vermont. And that was great too." But I felt like an alien. It was very interesting. I really felt like there was a bit of a culture of people only talking about work, staying late. Not even any hint towards work-life balance. I found out later this was only some of the postdocs. So, I'd sort of dropped into one particular group. And that's not the culture of the CTP in general, actually. But compared to Australia, where the culture is very much the opposite. As an undergraduate, you'd never admit to someone that you studied, right? The thing was to do well without trying, that was what was cool.

And also in graduate school, you couldn't be seen to work too hard. Not that I avoided that, but it certainly wasn't the case that someone asked you about your weekend and you told them how much work you did, right? So, this was a big cultural shock, and also at home in the morning, people rock up, they go to get coffee, they chat for a while, then you go to work, then after lunch people go get coffee and they chat for a while. I actually don't drink coffee, but I'd always go to the chats because that's where a lot of the physics happened. You know, you'd just be talking, sometimes about physics, sometimes about football, but it was this very relaxed environment. And at MIT it felt like everything was in a rush, even when people go to get lunch, they'd walk fast. So, it was a big change, and at first I wasn't sure if it was a place I wanted to be, actually.

Zierler:

And Phiala, what group did you start with at MIT for your postdoc?

Shanahan:

The Center for Theoretical Physics is particularly wonderful in that when we hire postdocs, we don't try to associate someone with a specific group. So, I was free to work with whoever I wanted in the Center for Theoretical Physics. I ended up working mostly with Will Detmold, now one of my colleagues and close collaborators, who I work with all the time. But that wasn't forced on me, so I was sort of a free agent. Which has mostly positives. Also some negatives, that it took me a little while to find my feet, actually.

Zierler:

And who were some of the key people that you collaborated with, both in terms of peers, fellow postdocs, and perhaps more senior people?

Shanahan:

The first part of my postdoc, I was mostly working on my own and with Will Detmold. I shared offices with Zohreh Davoudi and Mike Endres, who were both brilliant, great to talk to. We didn't necessarily write papers together. Iain Stewart works in effective theories, which is what I spent most of my PhD doing, so that was great. And, I mean, the environment at the Center for Theoretical Physics is really the product of a bunch of great people, there is Krishna Rajagopal, there's Tracy Slatyer, there's Jesse Thaler, and the people I mentioned before, so Will Detmold, Iain Stewart. And this nuclear and particle core group, when we used to go into the office, everyone would sit in the lunchroom at whatever time they were able to have lunch. So, you would go there and all the faculty and the postdocs and sometimes students would sit there and have lunch and talk about physics.

And every day, there was this environment of people who I didn't necessarily collaborate with on projects, but who were forming my physics worldview. Fantastic people who were forming my physics worldview. So that really was what made that happen. And then in terms of collaboration, I also ended up joining the NPLQCD Collaboration. The Nuclear Physics from Lattice QCD Collaboration, where in particular Martin Savage, who was one of the founders of this collaboration a number of years ago, became a pretty important mentor to me too.

Zierler:

Phiala, on the question of, to get back to this idea of seeing a postdoc as an opportunity to involve yourself in new physics versus refining and improving upon what you had already done, what was your basic approach to those two opportunities and challenges?

Shanahan:

I wanted to tackle the same physics questions, but I wanted to learn some new tools. So, what I'd done previously was mostly pen and paper theory calculations, or a small amount of coding. I used input from lattice field theory, which is something I do a lot of now, but I didn't do- well, I did some of, but I didn't do so much of that numerical computation myself. And I wanted to learn more numerical tools in my postdoc. And so, I tried to finish up with all my projects for my PhD, the lingering ones, quite quickly, and dive into this new thing, learning some new tools. So, I pretty much just dove in headfirst. I just stopped what I'd been doing and said, "Now I'm going to do this." Which was pretty challenging, actually.

Zierler:

Yeah. Why? What exactly was challenging about it?

Shanahan:

Well, I guess trying to learn something new is always challenging, right? For that first little bit of time when you're reading papers and you don't even know what they mean. And until you've read enough and absorbed enough that suddenly everything clicks into place, there's that little period of time at the start of something new where you feel like you're just bashing your head against the wall and getting nowhere. So that's always tough, especially after you've just come off the top of feeling like you're on top of everything at the end of the PhD.

But I guess it was also more of a sense of pressure to actually get something done, it was because of the MIT environment. Whereas in Adelaide, it felt very natural to spend three months looking for a minus sign, you know, because that's what you do, it's part of research. At MIT, it felt like spending three months looking for a minus sign was a bit of a dirty thing to admit, even though I'm sure quite normal. So there was some pressure there that was this combination of feeling like I'd done, you know, a great PhD that I was proud of, and now it was taking a really long time to get any papers out from this new thing that I was trying. And I got stuck on some silly things in code, that even though my degree said, “high performance computational physics,” I didn't actually take that much computer science. And so now I was trying to learn the computer science skills that I'd missed at the same time as some new physics at the same time as having moved to a new country where- it seems crazy now, but some of the things people said were just completely mysterious to me. Because of, you wouldn't believe it, but language and cultural barriers. Yeah, so that was really the challenge there for the first year or so.

Zierler:

When did you start thinking about academic jobs? In other words, to go back to this other question about, you know, you're pursuing knowledge. This is what you're interested in, you can sort of push off career and academic considerations. Obviously, at some point you have to come up against those kinds of decisions, so I'm curious at what point you started asking yourself those kinds of questions?

Shanahan:

This is a sort of funny story. When I was in my first year of my postdoc, I got an email inviting me to apply to a faculty position at William & Mary, joint with Jefferson Lab. And I didn't really know what to make of it, so I asked my mentors at MIT, who said, "Yeah, that's a great place. You could think about applying if you want to. It would be good practice for later if you want an academic career." And so, I sort of thought, "Okay, sure. Why not? This looks cool." I prepared an application, I did the interview, and I got the job. Which wasn't exactly what I was expecting. I sort of hadn't really thought through to what if I get the job? I was more thinking, "Well this is interesting. This looks fun. Someone wants me to be a professor. How cool. Virginia looks interesting. Okay." And then I got the job, and I didn't quite know what to do with that. And so, in the end I decided, sure, this, again, this looks exciting. Why not? And so, I deferred it for a year, because by that point I sort of, by the point of having got that offer, I'd begun to really love MIT and the research group. And I felt at home in a way I hadn't really felt at home anywhere else before. And so, I deferred for a year, and ended up spending two of my three postdoc years, because I couldn't defer longer, at MIT. So, I cut my postdoc off a year early unfortunately, and went off to William & Mary and Jefferson Lab to see what being a professor was like.

Zierler:

Yeah. And what was the appointment between the department and Jefferson Lab? Was it a 50/50 kind of appointment?

Shanahan:

This is complicated. It was technically 50/50, but I still had a full teaching load in the department.

Zierler:

So, it was 100/50 basically.

Shanahan:

Yeah, so it was basically that I was a professor in the department, but also expected to show my face at Jefferson Lab, which was a little bit complicated because my husband at the time and I only had one car. And so, the commuting between these two places, which are not that close, was sort of a complicated situation.

Zierler:

Is your husband in physics? Is this a two-body problem you were dealing with?

Shanahan:

Yeah, so this is a complicated story also. My husband- but I'm going to change now to using female pronouns, because she is now a woman. She was doing her PhD in physics, then eventually moved to Boston when I was here as a postdoc. She got some work in computer science areas, but then ended up getting a postdoc at Jefferson Lab. So, she also had to go to Jefferson Lab. So, that's how we ended up making this work, when she got that job, that we solved the two-body problem and the commute problem. But still, it meant that I couldn't go halfway through the day, because she'd already gone earlier taking the car and that sort of thing. Now she works in biology and actually on machine learning for COVID research at Berkeley, and we're divorced.

Zierler:

Oh, okay.

Shanahan:

Sort of a long, complicated story.

Zierler:

Yeah. And how was your experience tea- was this a tenure track job, an assistant professor?

Shanahan:

It was a tenure track job.

Zierler:

So, it was something where you could have stayed if you wanted to.

Shanahan:

Yeah. Yeah.

Zierler:

Was it a good experience at William & Mary?

Shanahan:

Yeah. I mean, yes. It was a great department with wonderful colleagues. Really, really a great group of people and a lovely environment. And great students too, actually. But what I realized reasonably quickly is that the environment's not the same as MIT, which, okay, I probably should have predicted that. But that slightly more relaxed environment. Also, it was a bit further from the airport and I travel quite a lot, so that was a pain. But if I wanted an environment like that, I would rather be at home in Australia close to my family.

Zierler:

Yeah, right.

Shanahan:

And so, it was actually a great place, but I realized that I either wanted to be somewhere with the energy of MIT, which is pretty hard to reproduce elsewhere, where new ideas and excitement were flying and everyone was just intensely working on something great. I either wanted to be in that, or I wanted to be in Australia. So, I applied to MIT for when they had a position opening the next year. And I decided that I was either going to come to MIT or I was going to go home.

Zierler:

I'm curious, Phiala, of how broad your perspective was in terms of your understanding of what a singular place MIT is in terms of the intensity of the research, the energy of the research. For example, like a Chicago or a Caltech or a Stanford. Did you- I'm just curious how broad your purview was in terms of comparing MIT to some of its peers in that regard.

Shanahan:

I would have considered peers. I didn't know them, so I didn't know that they had the same energy, but actually Caltech had an opening I had applied to- if any other top ten-ish schools would have had openings in my field, I would have applied to them too. I knew MIT had what I was looking for. I would have believed other places do too, but I don't know. But there aren't openings every year, etc., and MIT happened to have one and so that ended up being a natural place to go.

Zierler:

And obviously it worked out.

Shanahan:

And it worked out, yeah.

Zierler:

Phiala, now that you were coming back to MIT to join the faculty, the idea that there are different professors who contribute overall to what the department offers in terms of all the kinds of subfields that are presented, as you are continuing to refine your identity, your sort of professional exposure, your collaborations and things like that, I'm curious what kinds of physics, not just that you were interested in academically, but what kinds of physics did you think that you were bringing to that overall sort of representation of what was exciting to be at MIT for?

Shanahan:

Yeah, so that's a complicated question, because actually I think one of the things that I appreciate the most about MIT is that it's not just that there's a group of people who are brilliant at what they do, but that there's a group of people who are adventurous and creative about what they do. So, one of my senior colleagues said to me once about the new hires, that they're not sure what they're going to do.

Zierler:

Yeah.

Shanahan:

In the next five or ten years. And they're not sure what they're going to get tenure for, but they are sure that it's going to be exciting. And that's something that I feel like really is a difference between our department and others that I've seen. So, someone who is the absolute world expert in some area, and just does that, I'm not sure if they'd get hired in the Center for Theoretical Physics, for example. Because we have a real strength in having a group of people who all have broad-ish interests and can talk to each other about these things, and that creates magic. So, some of us might have more of a focus on one thing, but there's a real breadth of interests, and that's, you know, we all have lunch together every day, and talk about common interests, and people dabble in each other’s fields and work together. So, it's not so much that I was bringing a new type of physics. Actually, if you're going to be very strict about that, there’s actually a lot of overlap with Will Detmold, who I worked with in my postdoc, who I now collaborate with a lot as well, we have very similar interests in a lot of the physics we tackle. But new ideas, new connections between things, new energy, is going in various directions.

Zierler:

That's interesting to hear you say that, because I would have thought in some ways the opposite. Coming from a place like William & Mary, which of course is an excellent faculty, but it's a much smaller faculty, that there would be the place where you would feel that need to sort of have a more broad research base because there's simply fewer people. So, it's very interesting to hear you say from an intellectual stimulation environment kind of situation, that you actually want to be broad in your interests and your research, even at a big place like MIT.

Shanahan:

Yeah. Well, I think that's partly what makes it such a great place. At William & Mary, people are brilliant, but as far as I experienced it wasn't so common to see faculty work with each other in the same way. Whereas in MIT, nobody stays in their silos. That's just not a thing. No one has a silo.

Zierler:

Yeah. So, when you joined the faculty, who did you start to get involved with? How did that happen? I mean, you much have known people already. It wasn't like a totally new environment for you.

Shanahan:

It was really convenient, actually. Some of the postdocs who were just starting when I was still a postdoc were still there when I came back, so I had postdocs I worked with who I knew, some of whom I was already collaborating with. I had brought one of my students with me from William & Mary. She was actually an MIT undergraduate who worked with me as an undergraduate, then came to William & Mary to be my graduate student, even though she'd been admitted to some other top places, and then she transferred and came back with me to MIT. So, I already had a student. I recruited some more students quite quickly, actually. I spent my first semester at MIT actually on leave at Perimeter Institute. I had an Emmy Noether fellowship there. And one of the students who was just accepted to MIT's graduate program came to Perimeter to do a one-year masters, and we worked there together, and then he came to MIT to do a PhD right after, so I sort of already had students. I had postdocs. It was sort of like coming home, really.

Zierler:

Yeah. So Phiala, let's get back to the science. We've been talking a lot on the sociological side of academia and things like that. What have been, since you joined the faculty, what have been some of the major interests, the major contributions, the major research that you've been involved with over these past two years?

Shanahan:

There have been a few different directions. There's been proton structure, and especially the gluon structure of the proton. There's been nuclear physics, and over the last few years, I've really taken much more of a leadership role in that and in our collaboration, with some of the more senior people who have stepped away to do other things. So, you know, I have some ownership of that whole research program, which is really exciting. There are some new exploratory aspects of proton structure, the transverse structure, if you imagine a proton going in one direction, how things are moving in the transverse plane.

And then there's a whole different side of algorithmic research, especially in machine learning, but also quantum computing that I'm really excited about. This is- I guess I'm not sure that I would have imagined that I would be doing algorithmic research back when I was a pen and paper theorist, or that I'd have my own computer cluster that I had to assemble. But it's really just a continuation of the same thing. I want to be able to do the physics, and right now we're computation-limited on some things. We know in principle how we would do some calculations of the structure of nuclei, but they're just- the biggest supercomputers in the world aren't enough. So, I'm trying to make faster algorithms, which I'm very excited about.

Zierler:

That's pretty- can you explain, Phiala, some of the science? It's hard to wrap one's head around how the biggest supercomputers today are not powerful enough to ask the questions that you're posing. Can you give some sort of quantitative or qualitative explanation so that we can understand exactly what that means?

Shanahan:

Yeah, I can try to do that. So, the tools we're using to study the structure of the proton or nuclei include lattice field theory. The lattice part is just that you discretize space and time onto a grid, or a lattice, and then you can think of taking samples or snapshots of the background quark and gluon dynamics on those grids or lattices. This bubbling, broiling, dynamical quantum vacuum that creates all of the complications of QCD, you want to integrate over all of that. You want to sum it all up and then take all those contributions together. But we can't do that analytically, so what you resort to numerically is sampling it, so you're taking lots and lots of samples of this quantum dynamics on this lattice. And then on top of those samples, you do calculations. For example, you create a state with the quantum numbers of the thing you want to study, like a proton, then you let that evolve and then you annihilate that state. And the correlations tell you about the mass of the state you're looking at, for example. And you can do other things too. You can create it, you can hit it with a probe, you can evolve it, and that tells you about how that state responds to that probe.

Okay, so then to answer the question of how this gets so expensive; generating these samples is an expensive thing to start with. You need to sample them from a known probability distribution, but each of these samples is something like 1012 degrees of freedom from a complicated known probability distribution. And that's a challenge in itself, and that's actually one of the things we're trying to accelerate with machine learning, with a really exciting collaboration with Google DeepMind. That in itself takes a lot of computing, because the only way to do this other than our new tools which may or may not work at scale, is to make small changes to these samples, and then evolve them. So, you can't just sample. Imagine you have a two-dimensional plane and you want to sample from a circle here. You can just throw things at the two-dimensional plane and sometimes you'll hit the circle, right? But now imagine to go to a much, much higher dimensional plane. 1012 dimensions. I'm sure you can imagine that you will hit the circle a lot less frequently in this higher dimensional plane, right? And so, when you're trying to sample something of such high dimensionality, you can't do it just by random sampling, by Monte Carlo methods. You have to do these chain-based, Markov chain Monte Carlo methods, and they get particularly challenging when you start having a fine grid.

Okay, I can explain this by saying, we're using these samples to tell us about the fluctuating dynamics of the quantum vacuum. But we really want independent samples, right, otherwise you're not learning much different from one sample versus the other. If you're doing small updates at the scale of like one site on your lattice, then if this is your scale of interest, like your proton size, the number of updates you need to do to change physics on that scale gets larger and larger as that scale gets small. And that scale becoming small is one of the limits you have to take to get continuing physics back. And so, this becomes a very challenging thing to do, to sample these configurations. And then on each sample, you have to do a whole bunch of calculation of these states being created and destroyed. Then the challenges we face in particular when it comes to nuclei is that the number of samples you have to take grows exponentially with the atomic number. On top of that, the amount of computation you have to do on each sample grows factorially. So, if you think about exponential and factorial in the atomic number, that blows up really badly. Which means that even if you can study the proton, studying nuclei carries a really, really bad scaling factor on top of the cost of studying just a single proton. So, that's why you end up just not being able to do these calculations anymore on the biggest supercomputers in the world.

Zierler:

What impact would- you know, there's so much exciting stuff in the news about quantum computing, having a real quantum computer in the next X number of years, five years, something like that. Is this particularly relevant to you? Would this be a game changer for your research?

Shanahan:

So. if you could have a quantum computer at the right scale, with the right coherence times, you could do a lot of great physics. And you could even do physics that's very hard to do classically. Because classically, we work in the Euclidean spacetime, whereas spacetime is a Minkowski spacetime, which is much more natural to work with on a quantum computer, so I guess what I'm trying to say is that there are some quantities that you can calculate much more straightforwardly on a quantum computer than you could on a classical computer, but realistically, the scales you need are extreme. It's not just about having a quantum computer that can work and can do something. It's about having a quantum computer that can work and do something at the scale of the biggest current classical supercomputers in the world.

So, something I've been working on with one of my students is, are there ways of using small noisy quantum computers to accelerate classical calculations, rather than trying to say let's scrap the classical computer, let's do everything on the quantum computer. To beat classical computing, which is very advanced, is a really tough ask. And there are people working on that, and it's very exciting research, but I'd be sort of surprised if that happens in my career for my field. What I think might happen, is imagine you have a QPU, like a quantum processing unit, that you can outsource some of your calculations to, like you do these days to a graphical processing unit, a GPU. What if you can do that and take just small quantum calculations as input to your large classical calculation? And so that then, it wouldn't change the types of things we can calculate in the same way that doing the full calculation on a quantum computer might, but it might let you accelerate classical computing using quantum computing, and that I think might happen on a shorter timescale.

Zierler:

Phiala, it's a relatively short amount of time, given the vast span in the history of physics, that you've been involved in proton structure, but I wonder in what ways has the field already changed since you first became interested in this topic?

Shanahan:

It's actually been a very significant change over that time. Most particularly in the theory side, which of course is where I work, that over that time the numerical methods of lattice field theory have moved into a precision era. That wasn't the case when I was a graduate student, except for some quantities maybe. But we're just at the very beginning of an era where theory calculations can get sub-percent uncertainties that you can believe. This was the case for some flavor physics calculations years ago, but for the structure of the proton for like hadron physics, it is really now that this is starting to happen.

Zierler:

And what's changed? What's better now that allows for these more precise calculations to happen?

Shanahan:

Some brilliant new algorithm development, and computers have improved. But mostly it's algorithms. It's smarter ways of doing the theory calculations. There have also been some great new ideas on how to access quantities that people thought you couldn't access. Things that are defined on the light cone, which you can't really access in Euclidean space. People have developed new ways of getting at them by rotating off that light cone and going to very large momentum, which boosts you back onto the light cone. So, there have also been theory developments that give you new ways of trying to access aspects of structure that theory couldn't calculate before. But a lot of it has been algorithm development, making calculations that weren't possible, possible.

Zierler:

Phiala, I want to come back to this intriguing idea that you're encouraged, which sounds like it suits you quite well, to have these broader research interests, because that's what works best within the collaborative environment of the Center. So, I wonder if you can connect these highly specific interests that we've just been talking about with those sort of broader collaborative questions and opportunities, to give an idea of how the specificity connects with some of the bigger issues.

Shanahan:

I can give lots of examples. So the work that I very vaguely alluded to on the transverse structure of a proton- with some postdocs I did a first calculation of a particular aspect of that structure encoded in what's called the Collins Soper kernel, which describes how the distributions, these transverse momentum-dependent parton distributions, evolve. The proposal for how to do that was first designed by Iain Stewart, one of my colleagues in the Center who works more in effective field theory, who is not a lattice QCD practitioner. So, talking to Ian, we took some of those ideas and turned them into some practical calculations on our side.

The work I'm doing in machine learning is focused on machine learning for field theory, but what we're really doing is figuring out ways of building the symmetries of the standard model into machine learning algorithms. And designing machine learning algorithms that work on compact domains, not just on the real line, and things like this. This has applications to work a lot of other people are doing; I was talking to someone in string theory who's interested in building symmetries into machine learning. Jesse Thaler is working on machine learning for jet physics at the large hadron collider. Again, building symmetries in is very relevant there. Tracy Slatyer, one of my other colleagues, works a lot on dark matter. Something I'm very interested in is how dark matter interacts with hadrons and calculating the interactions of dark matter and hadrons. So, we've talked vaguely about, you know, if we could calculate this, do you know how it would constrain things when combined with data from astrophysical surveys? So, it's really, there are connections all over the place.

Zierler:

Yeah. It sounds so exciting, too.

Shanahan:

Oh, it's so much fun.

Zierler:

Yeah. Phiala, I want to talk, one aspect of your career we haven't talked about yet, is your work with graduate students as a mentor, and also your undergraduate teaching. So, let's start first with undergraduate teaching. What are the classes that you enjoy teaching most, and what are the classes where there might be an expectation for you just based on your own expertise?

Shanahan:

Yeah, so at MIT on the undergraduate side, I've only taught the second quantum mechanics course. At William & Mary, I taught introduction to physics. At Adelaide I did some teaching, too. But I loved teaching quantum mechanics. Actually, I like teaching undergraduates in general. Especially motivated undergraduates, which we get a lot of at MIT.

Zierler:

Yeah.

Shanahan:

So, I guess, your question was what do I like teaching, or?

Zierler:

Yeah. Not just what do you like teaching, but based on your own expertise, what are the classes where it's sort of like, this is what's natural for you to teach?

Shanahan:

I guess the very natural ones are the ones I've been teaching at MIT. I've been teaching quantum mechanics to undergraduates, and quantum field theory, which is a graduate class. And in both of those cases, I can very easily give examples from my own research or my own areas of physics. In fact, one of the methods I taught in my undergraduate quantum mechanics class just last week is something that I've been using in my own research in nuclear physics. Not the lattice field theory technique, a different numerical technique. And I got them to do it in a homework problem, something pretty similar to what I'm doing, just at a different scale. So, those are very natural classes to teach, although I do find teaching undergraduates to be a bit of a culture shock in this country.

Zierler:

How so?

Shanahan:

I feel like there's somehow this idea that undergraduates here are children. And I really struggle with this. It feels to me very disrespectful of people who I would like to see as colleague scientists in training.

Zierler:

The way that you were treated as an undergraduate?

Shanahan:

Yeah. So, what happens here feels- it goes so counter to what I believe in and what I believe works, that we give them homework every week and they get grades for it. And we tell them that they can work together, but then we give them grades for it, because I'm told otherwise, they won't do it. We have to give them lots of grades for the homework because otherwise they won't do it. That if they can't do it, they have to go talk to someone from student support services who tells me why they couldn’t. Sometimes it's serious but sometimes it's, they had too much to do, so they didn't do the homework, so you should excuse them. And all of this just seems very bizarre. And it's something that I've struggled with so much. I-

Zierler:

And you're at MIT, by the way, we should just put things in perspective. You're at, you know (laughter)-

Shanahan:

It's bizarre. it's bizarre that I have to spoon feed them because otherwise they won't do it. Or at least, otherwise my colleagues think they won't do it. I think I have brilliant students here, who if I told them all this work is for your education. I'm not going to grade you on it because it's for you to learn. You can't assess someone while they're learning. And then later, we'll assess it with an exam. That that is showing them the respect to manage their own time. The respect to not have to tell me if they have some life event, because how is that my business? I assume they're adults who can manage their time and do the work that needs to be done. Just like I do the work that needs to be done. I struggle with this.

Zierler:

Phiala, for an experimentalist, there's always opportunity, easy opportunity, to involve standout undergraduates in the lab, right? As a theorist, what are opportunities for some very special undergraduates that you might have or have had, where you can sort of give them a window into the kind of physics you're doing at your level?

Shanahan:

The two main directions for that are algorithm development and data analysis, really. Algorithm development, because a lot of that needs to happen in toy theories as you're experimenting because the sorts of calculations, we do at scale are huge, right, and need investments of supercomputing. We're not going to develop algorithms at that same scale, which means that there are small toy systems where we try to develop algorithms using tools that students these days are quite well-educated on at MIT. Certainly, they are in things like machine learning and computer science tools, and so getting them involved in some of those efforts works quite well.

And then the other thing is in analysis. A lot of the projects I work on take years, and so that's not a good timescale for an undergraduate to get involved in, and also they don't necessarily have the skills, but you can teach some of the skills at the end of that pipeline, for example, where you get the fun bits. You get to analyzing data, which requires statistics and a little bit of coding and things like this, and the physics of examining the implications of that. And so, there's really these two different paths that I find quite productive, really, for very technically-inclined undergrads, in algorithm development some of them have been very successful. And on the other side, of course sometimes they spend their whole time reading background material and not actually making significant contributions, but sometimes they do.

Zierler:

Phiala, on the graduate side of things, I wonder if you feel some of those same frustrations that you've experienced with American undergraduates, or as they are graduate students, self-selected enough by at that point that they're at a level of maturity, intellectual development, where those things are really not an issue for you in your capacity as a graduate mentor?

Shanahan:

I want to be clear that I don't actually think there's a problem with the undergraduates here. It's with the attitude towards them.

Zierler:

Oh, I see. Yeah.

Shanahan:

I think the students themselves are perfectly capable. And I have no doubt many of them would be perfectly capable of managing things, if we let them. But the graduate students, the ones I have worked with at least, are brilliant. They're really good. There's a different culture around mentoring here that's much more hands-on, but it's really up to the individual faculty. It’s great. I do find that they are a little less independent when they come in on average than I would expect, but I think that's just a direct consequence of this culture. They catch up very quickly when they get to graduate school. And certainly, every student I've had at MIT is, you know, awesome. I can't complain about my students. They're great.

Zierler:

I wonder if you've taken the opportunity to raise these points in faculty meetings? And if you got any traction in terms of saying that it's not really about the students, it's how we set our expectations of them. I'm curious what kind of feedback you might have gotten if you've raised these kinds of ideas before.

Shanahan:

Oh sure, I’ve said these things, and a lot of the other junior faculty agree with me. But it seems to be very interesting that a lot of the other junior faculty are also international, and that it seems to be mostly all of the international people who can't quite believe how things happen here. Of course I think part of it is just a bit of culture and I need to adapt to that- people make the point that we expect so much of undergraduates at MIT, there's such a heavy load on them, that if you don't force them bit by bit, they just won't have time to do it. And so, what you really need is everyone to stop piling on the grunt work. Doing it in one course won’t work- they would just let that one slide.

Zierler:

Right.

Shanahan:

But I still don't understand that. I also sort of do think at some point this is going to reach a critical point. It's starting to get a little bit absurd. I can't wait until I'm tenured and maybe I'm going to fix this.

Zierler:

(Laughter) Phiala, I want to ask before we get to my last question, where we sort of look to the future, we've talked a lot about some of the cultural differences, coming from the perspective in Australia. And we started our conversation where you didn't have anything else to compare it to because it was only your one experience, but obviously going to an all-girls school served you quite well in a career in STEM, just to state the obvious. I want to ask you about sort of your current experiences as a woman working in the field, where you think things have improved, perhaps from talking to some of your colleagues who are sort of more senior from you, might have experienced in previous decades, and in what areas you think are still major areas ripe for improvement in terms of making physics as inclusive and diverse as it could be, particularly for somebody who will be a leader in the field for some time to come. And some opportunities you might have to be a positive force for those areas that you see that need improvement.

Shanahan:

Yeah so, blatant sexism is something I've rarely encountered. Subtle, of course, very much. I can tell you about that in a moment. But overt is something that's obviously changed. I have rarely been questioned. Once at an airport when I was a graduate student, someone asked the group of us what we were doing and someone said we were at a conference, and they said, "Oh, well what's she doing? Is she making the sandwiches?" But that's about the only instance of very overt sexism that I can remember. And so that's certainly changed over time. Now, I don't think that's true on the racial front, I think there's still more overt racism and a very important shift that needs to happen for diversity and inclusion. So, I think I can say, having talked to more senior women, I've been very lucky. Where we still need to improve is all of the subtle things. It happens to me regularly, that someone reads my paper and they think it's great, and they go up to one of my colleagues and talk to them about their great paper. Because in their mind, they just assumed a paper in this area coming out of MIT was by someone else. Because we have overlapping interests.

Zierler:

And you see that as a gender thing? What about a generational thing? What about if you were, you know, you were a woman, but you were sixty years old, for example? You don't see that as a factor?

Shanahan:

That's probably a factor. It's probably the combination of gender and age. But this happens all the time.

Zierler:

Yeah.

Shanahan:

It happens that something that my colleague's name isn't even on gets ascribed to him instead. That someone says to him, "Oh, I enjoyed your paper." And he has to say, "Actually, I had nothing to do with that."

Zierler:

Yeah.

Shanahan:

It happens all the time that someone sends him emails that he has to forward to me. It happens all the time that I get emails to, "Dear Professor X and Dr. Shanahan, or Mrs. Shanahan." All of them small, but all of them things that make me actually worry for things like tenure. Because of course what happens in tenure evaluations is that letters come in from people where they get asked, "What do you think of Professor Shanahan's work?" And if in their mind, they read all these great papers, but they didn't realize they're mine, because just subconsciously they assigned them to other people, there's nothing you can do about that.

Zierler:

Sounds like a great case for making it standard practice to attach a photo onto the paper itself, so that you have that- you see, no, this is what the person looks like who actually wrote the paper.

Shanahan:

Yeah. That might affect citations though, people wouldn't even read the paper.

Zierler:

Oh. An interesting and depressing point that I hadn't thought about, but-

Shanahan:

This is one of the things that preoccupies me now, also reading reference letters for people. You know, this is so much on my mind when I'm reading reference letters for students. That, is there implicit bias that means that this person is writing differently about this female or this under-represented minority student than they would about any other student? And I think that's something that still needs to be worked on, and it's something that's so hard to counter, because people don't even realize they're doing it. And in some cases, the people who have thought papers of mine belong to someone else, those were people I know think highly of me and respect me and, and-

Zierler:

Right, right.

Shanahan:

You know, they're people who have worked with me.

Zierler:

There's no ill will, it's just-

Shanahan:

Not at all.

Zierler:

Yeah. So, on the productivity, the positive response to things like this, which is it's clearly systemic and so therefore it probably needs a systematized response in some degree. So, have you thought at all about what kinds of things could be done that are responsive to where we are today? Not the blatant stuff that would have been sort of, not easier, but at least- not easier to deal with, but sort of more identifiable, right? You can put your hand sort of like, somebody assumed that I was the person making the sandwich, right? That's something that's like, you know, you can work with that, right?

Shanahan:

Right.

Zierler:

So, with things that are more subtle, microaggressions, whatever you want to call them, have you thought about some ways that these problems also can be systematically dealt with and relegated to the past at some point?

Shanahan:

Yeah. I mean of course this is an ongoing effort in our community, the international community has a committee for inclusion and diversity and equity, and also at MIT in the Center for Theoretical Physics as well. I have various ideas, but there are also people who have done a lot of research on these things, and I think as scientists, we need to not make up our own paths forward, but, you know, respect those people who spend their time actually studying these things. But I feel like my role in this is mostly to let people know what's happening and to push the older, white men to be the ones to visibly address this. Because I feel very strongly that it's the people in power who have to be the ones visibly addressing these things, and that if it comes from a minority person or from a woman, it will automatically take less weight.

Zierler:

Yeah.

Shanahan:

So, my biggest role in this is to say, "No," when people ask me to be on committees, but to behind the scenes push hard on senior men to get them to do it.

Zierler:

Somebody like an Ed Bertschinger certainly understands the issues, but he's obviously a very unique person in his perspective.

Shanahan:

Right. MIT's pretty lucky in terms of our senior, white men. There's quite a few who-

Zierler:

Who get it.

Shanahan:

Who are pretty good, yeah. And I have always had the feeling that MIT is one of those places where when there are problems, a bunch of pretty smart people try pretty hard to fix them. This has happened historically with issues with gender inequity, it's happened with other things over the years, and now recently after the attention's been turned more to these sorts of issues. I'm hopeful that things will go in the right direction, because I think once the attention of the MIT physics faculty gets turned onto something, there's in general a group of, you know, very serious, smart individuals.

Zierler:

And Phiala, the pernicious thing here is that, and you didn't, you can't simply say, "Well, I'm just going to lead by example and do the good work." Because you are doing the good work, and it's still happening even though your name is on the paper. So, it's like, that's not even the sort of, hold up the banner and say, "Here's your solution. Just nose to the grindstone and do the good work."

Shanahan:

Yeah. That's the thing that scares me. I'm actually not that worried about whether or not I will have done enough to get tenure. I'm pretty happy to bet on myself. What I'm worried about is whether people will know I've done that.

Zierler:

The recognition. Right. Do you have allies- not individuals, but infrastructurally, are there outlets for you to go to within MIT that sort of provide advice, protection, sort of a path going forward, so that these things don't sort of get to a point where they're beyond your control? So that you're not treated unfairly?

Shanahan:

No. I don't think infrastructures like that exist anywhere, and I’m not sure that they would work.

Zierler:

Yeah.

Shanahan:

The only thing I can think to do, and this is what I also tell my postdocs and students to do, is talk about these things openly. In the lunchroom, say, "Oh, you know, this happened again. I got an email from this person and they said, 'Dear Professor X, Professor Y, and Mrs. Z.'" And just make sure this is common knowledge that this happens and how often it happens.

Zierler:

Well, Phiala for my last question, to get back to the happier place, which is always science of course, I want to ask you- I don't want to ask you what you're excited about because it's so many things in terms of the future. That's so obvious and it's going to be great to watch from afar what it is that you accomplish. But to go back to the original question about if your only consideration with tenure was, to get back to the gravity and standard model question, right? You don't want to sort of be too far out there because you want to actually produce results.

So, in terms of thinking about tenure within the broader context of everything that we've discussed, about your concerns about recognition, about your concerns of bounding your physics interests within the doable, within whatever clock you understand to be the right timeframe for thinking about tenure. So, with all of that in mind, what are the things that you want to accomplish professionally, personally, that will get you to that place where you have all kinds of ideas post-tenure about more wild physics to pursue. And on the sociological side, being able to more effectively share ideas about pedagogy. And about the ways that faculty interact with students. So, I just want for my last question you to sort of talk broadly about your future objectives within the science specifically and educationally, and then beyond that hump, what are the things that you're looking to accomplish after that point?

Shanahan:

Yeah, okay. That's a lot packed up in there. Yeah, so on the science side, I also want to say that I don't think the worry about tenure has cramped my style too much, actually. It's like a minor factor that sometimes for things that could be extremely risky I decide not to put all of my eggs in that basket. On the science side, what I really want to keep pushing forward is that I want to understand how nuclear physics comes from the Standard Model. That's the big thing. And in some sense, everything I'm doing is in some way or another, whether it's algorithms, whether it's technical developments, whether it's studying glue in the proton, it's all just aspects of the same thing. That I want to bridge between nuclear physics and chemistry and our understanding of the microscopic world, and this beautiful theory that describes the universe as best we understand it. And I would love nothing more than the sort of routine calculational aspect of that to become outsourced to computers or I would love if there was a Standard Model predictor box, and a lot of the things I spend my time worrying about, we didn't have to do anymore because you could just ask the box for the prediction and it would come out. The calculational aspects themselves are really fun, and I enjoy it a lot, but the physics is what's really driving that.

So, if we get to a point where we can set up pipelines that do these calculations and we can just address all of the physics questions, then maybe you can turn your efforts on developing structures and pipelines towards extending it. I guess one of the things that I love about the MIT culture is that it also seems very clear that, I wasn't hired because that's what I'm doing.

Zierler:

Right.

Shanahan:

I was hired because I do interesting things. And that means that-

Zierler:

Right. 'Things,' the emphasis on plural, things.

Shanahan:

Right. And if that means that I find out something exciting and decide to hare off in some other direction, that that would be supported. That's not very likely, but my interests are reasonably broad and it's very- I could imagine spending more time on many-body nuclear physics, for example. It's something that I touched a little bit but not a lot. But I could go, leave lattice field theory. It might be something that I spend a lot of time on right now, but I could leave that behind and do something different. And that would be completely supported within the environment. So, I look forward to that. I can't really predict what it's going to be, but if what I'm doing now triggers something interesting on some slight tangent, but that will tell us more about the universe, and maybe that's something about gravity and the standard model, maybe it's something completely different, that will be great. Then you asked also about the educational side?

Zierler:

Right, right.

Shanahan:

I can't say for sure that I'm not being naive here and missing something that my senior colleagues already know. But my suspicion is that I will still think this, and still want to push on this over the next years, that we've come to a point of piling on too much. and to handholding too much, and that the thing that our students are missing the most is the space to sit and think. That we’re educating brilliant students, but what we're not teaching them to do is to do that exercise that is so important of, when they've done a problem, not asking their friend to check if they've got the answer right, but coming to a point of knowing they have the answer right. Because they know what they did, and they believe it.

Zierler:

Yeah.

Shanahan:

And that that's not something that can be rushed, that's not something that's fixed by giving people more problems and the solutions to those problems to check it against. And I feel like we’re squeezing that out. And then that's what- I think that's one of the most valuable things we could teach people as part of a university education, but at the moment they get that in graduate school, and I think, I mean, the point of a university education is not just to educate people on quantum mechanics- it's to teach people how to think, and we're not doing a great job of that. Some students don't need to be taught, of course, and a lot of MIT students are in that category. They already know this. But for a bulk of students, by trying to teach too much, we're actually teaching too little, and we're not giving people the space to learn. We worry about the students being stressed, and part of that is just the volume of work as opposed to the volume of thought. A lot of them spend so much time on their homework, it would be much faster if they took the first two hours of that to actually study, and then do it, but they don't feel like they have time. Because we don't give them time.

And so, I think when I get the chance, I'm going to try to push a little more towards giving the students a little more space to think. Which actually probably means making assessments harder, not easier, but hopefully changes the grindstone a bit. I find that a little ironic, that we have this culture of "grind" here, quite different to the culture I grew up in, which is the opposite but there are other great things about the U.S. culture compared to Australia too, that in fact excellence is celebrated rather than sort of cut down, as it is at home. Yet the people who are successful here are the people who understood that the grind is not the best way. That the faculty are all the people who took the time to think and understand. And yet that's not what we're cultivating in our students.

Zierler:

And to have fun, right? The other missing piece of the puzzle. You have to have fun.

Shanahan:

Oh yeah, having a balanced life. My colleagues are great about this. They all leave work when they have to pick up their kids and say they're doing it. They model having a balanced work and life. But somehow that's- I feel like the faculty in the CTP are incredibly sane and well-balanced and are modeling everything we would like to educate, but somehow, it's getting lost in translation.

Zierler:

Well, Phiala, on the education, on the culture, and on the science, I wish you a lot of luck in the future as you tackle all of these major issues and responsibilities because we'll all be better for it if you succeed.

Shanahan:

Thank you.

Zierler:

It's been such a pleasure speaking with you today. I'm so happy we were able to do this and thank you so much for spending this time with me.

Shanahan:

My pleasure, it was fun.