Located in the Barra Funda district of São Paulo, the second floor of the Institute of Theoretical Physics building at São Paulo State University (IFT-UNESP) has been home to the International Center for Theoretical Physics (ICTP) of the South American Institute for Fundamental Research (SAIFR) since 2012. Nathan Jacob Berkovits, 59, a professor at IFT and a naturalized Brazilian citizen from the United States, is the first and current director of ICTP-SAIFR, an initiative funded by UNESP, FAPESP, and the original ICTP founded in 1964 in Trieste, Italy.
In October, Berkovits shared the 2021 John Wheatley Award with Fernando Quevedo of Guatemala, who is the former director of ICTP in Trieste, and a professor at the University of Cambridge, England. The honor is awarded every two years by the American Physical Society (APS) to researchers who have made contributions to the advancement of physics in developing countries. The APS noted that Berkovits was selected “for exceptional leadership in fundamental physics research in South America.”
In this interview, the researcher talks about how ICTP-SAIFR operates, how he came to Brazil, and about conducting research in his specific field of expertise, string theory. According to this physical-mathematical model, instead of being point objects, the elementary particles of matter are described as unidimensional microscopic filaments, like strings, that vibrate in ten dimensions of space-time.
How important is this award?
I hope it will make life easier for the center, such that we’ll maintain the support we have and gain new partnerships. It’s important in creating visibility for the activities we’re doing now, and want to do in the future. I know the people who typically judge these awards and I know how they work. I don’t want to say that I deserve the prize more than anyone else. That’s not true. There are researchers who do great work, but they’re less well known simply because they have fewer connections in the field. I grew up in the United States and I know a lot of people. Quevedo is also well known.
You graduated from Harvard University in 1983, completed your doctorate at the University of California at Berkeley in 1988, and then did three postdoctoral internships before moving to Brazil in 1994. Why did you decide to come here?
My first wife, also a physicist, was a Brazilian, and I had already visited the country before moving here. I was at King’s College London, in the U.K., and I could have stayed there. But I liked Brazil, and I liked the idea of trying something new somewhere else. I arrived in the country with a good grant from the CNPq [National Council for Scientific and Technological Development], which at the time paid even more than some professors earned in universities. I entered an academic competition at the University of São Paulo [USP]. I thought I would pass, but I didn’t, and the position went to another researcher. IFT was about to open a position and I ended up passing their competition. Working here is really great. We only have a graduate program and there’s very little bureaucracy. We teach one semester per year. We have the opportunity to do research and travel to events in our field.
We have only graduate programs here and very little bureaucracy. We teach one semester per year and we have the opportunity to do research
When you first got here, did the working conditions at IFT already stand out?
The only thing I missed was seminars with top researchers. The meetups at that time didn’t reach the same level that they began to have after the creation of ICTP-SAIFR. The current crisis is the first I’ve had to face in the country. Just before I arrived in Brazil, the high inflation had been brought under control. The currency had already switched [from the cruzeiro] to the real, and things worked. I never seriously thought about leaving the country.
How did the idea of creating the center come about?
There’s a center like this in the field of theoretical physics on every continent, where there are events and studies that attract the best researchers in the region. Before us, Argentina offered something similar in Buenos Aires, but it was only in operation for two or three years. Quevedo, who was then the director of the ICTP in Trieste, had the idea of creating partner centers and we were the first. At the time, I was doing a thematic project at FAPESP, but I didn’t know the Foundation director or the dean of UNESP. I was working on my research and I was happy. But when the possibility of having a center came up, I talked to Herman Voorwald, the dean at that time, who liked the idea, and the money was available. And FAPESP also liked it. From an administrative point of view, the center in Trieste helped a lot at the beginning, but not financially. Initially, they gave €50,000 per year. Then, they stopped providing a fixed annual amount and started supporting us through financing joint activities.
How is the center financed today?
For our scientific activities, FAPESP invests approximately R$2 million per year. This allows us to provide scholarships, including at the post-doctoral level and for the Junior Researcher category, and for one science journalist. We have four permanent employees, paid by UNESP, in addition to me and Rogério Rosenfeld. We’re both at IFT and, respectively, director and vice-president of ICTP-SAIFR. Today we also offer outreach activities, which have become important; they’re financed by the Serrapilheira Institute. For the last seven years we’ve also received grants from the Simons Foundation in the United States. Given all that, we attract very good researchers, who stay here for five years. The problem is that they leave the country when their scholarships end if the universities haven’t opened any vacancies here. We also have one professor in coordination with the Perimeter Institute of Canada, theoretical physicist Pedro Vieira, who’s 38. He’s won several international awards, including the 2020 Breakthrough-New Horizons, which is funded by the owners of Google and Facebook. He has a permanent position there, but he spends six months a year here through FAPESP’s São Paulo Excellence Chair [SPEC] program. We now also have a professor from Spain, Ricardo Martínez-Garcia, who did his post-doctorate at Princeton University and is going to coordinate a new program, funded by the Serrapilheira Institute, on quantitative biology. This subject is all the rage, especially now, with the Covid pandemic. And finally, Italian physicist Riccardo Sturani is back; he is participating in the LIGO/Virgo experiment aimed at observing gravitational waves. Sturani came from Italy to ICTP-SAIFR in 2013 as a Junior Researcher at FAPESP. Then he went to the Federal University of Rio Grande do Norte as a visiting professor, and this year returned to the center.
How many graduate students attend IFT each year?
IFT has about 60 students, with a little over half pursuing doctorates and the rest master’s degrees. Since the center’s creation, the IFT graduate program has received the maximum score of 7 from CAPES, and many of the students who want to do theoretical physics are attracted to IFT by our activities. They know that they’re going to have access to between 15 and 20 activities a year, not all in their specific area, obviously. The students who participate in our activities, such as courses, workshops, seminars, and themed schools, number around 800 per year. One of our typical events receives 20 students from South America and 40 from Brazil, and half of those are from São Paulo. Most of our lecturers are from the United States and Europe, with some from South America. I always wanted to avoid doing events that bring in a lot of speakers. They’re very expensive and don’t generate as much return for students. In our themed schools, we bring in no more than six speakers from abroad.
Are you inspired by any specific model for guiding the center?
For me, the only model that works in Brazil is that of IMPA [the Institute of Pure and Applied Mathematics, in Rio de Janeiro]. I was there for the first time 15 years ago. I was amazed. The universities in Brazil have one or two really good departments. But there’s no university like Harvard here. If someone is at Harvard, he’s the best. This is also the case at IMPA. The salaries are excellent, they only work with graduate programs, teach only a few classes, and do a lot of research. ICTP-SAIFR wouldn’t be able to have a center the size of IMPA, only something smaller. But to do it, we’d need more private donations like those from the Simons Foundation.
After the pandemic hit, did all the center’s activities go online?
Yes. The number of people participating in the activities is enormous. But we don’t know if they’re really attending the lectures and courses or if they just have their computers on. Some organizers prefer to postpone events until the pandemic is over. But I think the cost-effectiveness of online events pays off. For a researcher participating in the workshop, not that much is lost. For students, much more is lost. They don’t have the same interaction with researchers and may be afraid to ask questions.
Why did you decide to work in string theory?
I always liked the fields of physics and mathematics but working with string theory was an accident. In the United States, unlike Brazil, doctoral students enter a graduate program first, then seek an advisor. At Berkeley, there were two famous professors in physics. I chose one of them, Stanley Mandelstam [1928-2016], but I didn’t know what he was working on. I wanted to do a doctorate with him just because he was famous. So, I knocked on his door, and he asked me what I wanted to study. I ended up answering him with what I didn’t want to do. So, he told me that I should work with strings, which was what he was studying back then. At the time, there were few people in the area. In the 1970s, string theory had been popular with physicists, but interest had waned and by the 1980s few people were working on it. I started working on the subject and I liked it. Later, when the field began to attract more interest again, I was already in a good position.
How do you introduce the central ideas of string theory to the layperson?
I begin by talking about the standard model of particle physics [the theory that explains what matter is made of and how it behaves at the subatomic level]. Then, I address the problems that impede gravitational theory, due to quantum problems, from fitting into this model. Then I point out that the standard model is based on the idea that particles are points. The electron, the photon, the Higgs boson [the elementary particle that gives mass to other particles] are described as objects that are at a point in space. Then I introduce the idea that, in another theory, in string theory, these elementary particles could be the various vibrations of a one-dimensional string, with smoother interactions, which would solve the problems of quantum gravity. Finally, I talk about the properties of the strings, such as supersymmetry [for each particle in the standard model there is one more particle, called a superpartner] and the extra dimensions.
One very common criticism of string theory is the lack of experimental evidence for its validity.
Most physicists believe that the standard model is a good approximation [of reality], but that we need to go beyond it. There are people trying to do this, but there hasn’t been an experiment that shows which way to go. So we have to use theoretical arguments to look for the right path forward. The main problem for me is that the standard model accounts for every force except gravity. It is true that experimental evidence for strings could take a long time to appear because quantum gravitation involves such enormous energies. There probably won’t be an experiment directly proving string theory during my lifetime. And other ways may appear to modify the standard model. At a certain point, some people thought there was a problem with the model and that the Higgs boson wouldn’t be found. Many began to search for other particles. But when the Higgs boson was found in 2012, it became clear that there was no need to look for other particles. I hope that some kind of experimental evidence appears soon that can’t be explained by the standard model, but I don’t have much hope of discovering something like that in experiments with particle accelerators. They’re becoming very expensive and people are going to invest in other projects. I would bet on the area of cosmology. So far, we don’t know what dark matter is made of, and it could comprise about 85% of the total matter in the universe.
Could the eventual discovery of the nature of dark matter have implications for string theory?
If it’s just composed of another unknown particle, it will be easy to simply incorporate it into the standard model. That wouldn’t lead to any kind of revolution. I hope that dark matter is something that no one has thought of, or evidence of supersymmetry, something more than simply a new particle.
Are there any other ways to unify the standard model with gravitation?
In my view, string theory combines the standard model with gravitation in a more conservative way. It preserves some pillars of the model that one doesn’t want to abandon, such as special relativity and quantum mechanics. There are other, more radical ways of doing this unification in which these concepts are abandoned. One of this year’s Nobel Prize winners in physics, Roger Penrose of England, for example, doesn’t like string theory. For him, quantum mechanics only makes sense in four dimensions. He does not adopt the idea that there could be more dimensions, which are necessary in formulating string theory. In my view, strings would have different properties, but there aren’t any scientific reasons why extra dimensions wouldn’t exist. Even Einstein thought that there could be extra dimensions.