A Journey through theoretical physics in Brazil
- Chico Lustosa
- Aug 15, 2023
- 10 min read
Hi! My name is Francisco Bento Lustosa, people call me Chico. This is my academic website and this is my first ever post. Welcome! I will take this opportunity to introduce myself in a way that tells a little about how becoming a physicist in Brazil works. More specifically, I will talk about the subjects I pursued and why, showing how the road through academia can be a tortuous, difficult, bumpy and also fun ride.
Undergraduate years
I started my Bachelor's undergraduate Physics course at Rio de Janeiro Federal University (UFRJ). It is a very big and important university in South America, and its physics department is full of accomplished scientists in multiple subfields. As a first-year student, I only had access to those more accomplished scientists in a course where each class was a lecture by a different physicist on his or her general research topic. From this course, I have a few good memories, especially from a talk about the Standard Model of Cosmology. After the presentation, I asked the question that unsettles anyone who thinks about the Big Bang model: what was around and/or before that initial singularity? I remember that the professor very patiently tried to explain that, considering the universe as all there is, the question of what is around it does not make much sense. The singularity was the beginning of time and space, and there is nothing around or before space-time itself. That did not sit well with me. Still doesn't.
After my first year, I moved to a northeastern city in Brazil called Fortaleza. There I continued my Bachelor's course at the Federal University of Ceará (UFC), where there was a promising medium-to-small department of physics that had great success in condensed matter physics research but was still in its infancy in other subfields. It took me a while to find a place in the only theoretical group in our department. The group was focused on Quantum Field Theory and Topological effects. I was interested in gravity and Cosmology. My professor suggested I study kinks, solitons, domain walls, and then the Randall-Sundrum models. These types of models suggested our three space dimensions were embedded in a fourth dimension, and that was used to explain the apparent weakness of gravity in our universe.
The basic Bachelor's course in Brazil does not cover any topic of Quantum Field Theory or General Relativity so I had to learn that studying alone or with members of our group. It was a very exciting time for me, discovering and visualizing the details of the geometry of space-time and learning how we calculate the dynamics of quantum systems in different kinds of geometry. I did not know if I was more interested in the quantum part that would lead me to String Theory or the Cosmology part that would lead me to the study of singularities and Black Holes.
Back to Rio: Master's and beginning of PhD
In some weird and nonlinear ways, I was accepted into the Master's program at the Federal Fluminense University (UFF), in Niterói, a city across the Guanabara Bay from Rio. It was not my first choice, but I found an advisor who worked on related subjects to my undergraduate project, namely topological defects and gravitation. I was not ready to propose anything at that point, so the first problem she suggested for me was the one I took on as a project. I worked on extending a previous analysis on the space-time of a global monopole inside a black hole in a specific modified gravity theory. Again, it had all the ingredients that interested me: Quantum Field Theory to understand Hawking radiation, general relativity, and cosmology to understand the modifications that the f(R) theory proposed. However, I was left too much to do alone or guided by a PhD student and could not find a way to be satisfied with the limitations of the model I was using. I finished my dissertation and correctly found that the approximations used in the f(R) theory limited the space where we could actually calculate the temperature of the Hawking radiation to a region where it was not clear if there would be enough energy to have particle creation. I was extremely frustrated, but I blamed it on the problem that was given to me. The whole period of my Master's was actually fun for other academic reasons.
Rio de Janeiro is home to an extremely lively Gravity and Cosmology community. It was more alive before the pandemic, but things are heating up again. In my undergraduate years in Fortaleza, I did not attend any international conferences because they were always held in Rio or Sao Paulo. Now, I was close to everything. Mainly the Brazilian Center for Research in Physics (CBPF), where most events and interesting courses in Rio take place. There I took classes in Yang-Mills theories and String Theory. I attended many interesting meetings and conferences, and I had the opportunity to meet important international figures in physics. One funny and memorable moment happened when I met a grandson of Niels Bohr and we chatted about his meetings with Jimmy Handrix, and he tried to talk me out of my interest in String Theory. He would be glad to know I came to agree with him in the end.
Although my Master's project had somewhat failed, I was determined not to let the same thing happen with my PhD. I thought I knew a lot more physics and had a better idea of what I wanted. And what was that? I got that the hardest problem in physics was to unify, or at least describe in a compatible manner, gravitation and the other fundamental forces. To get a peak at what is going on at the fundamental level, we had to go to extremely high energies, inaccessible on earthly accelerators. I learned that although Black Holes provide an interesting scenario to think about the problems of gravitation and quantum mechanics, we are far from having direct tests of quantum gravitational effects in their vicinities. And I learned that cosmology was in a golden age of precision and that we had a window to the earliest moments of the universe in the CMB that was only going to get clearer. So I wanted to go there—to the quantum origins of cosmological perturbations. And I did. But it took me a while.
Working on these field theory-inspired models (Randall-Sundrum and Global Monopole Space-Times) I was kind of unknown to the more cosmology and astrophysicist-related side of our community here in Rio. So when I started my PhD at the Rio de Janeiro State University (UERJ), I did not know well who to look for as an advisor. I knew that there was an expert in Black Holes and Bouncing Cosmology that I would like to work with, but at the interview stage, he said he couldn't because he had too many students already. I asked my contact and mentor at CBPF for a referral to a cosmologist and ended up with an advisor that worked with models of preheating and reheating after inflation. I thought that this was close enough to the CMB that I wanted, so I started my PhD with this advisor.
It took me less than 6 months to learn that reheating (the process of reheating the universe after the accelerated expansion driven by inflation) was very far from probing the energy scales that I wanted, and in fact, almost all of the physics could be done with known quantum field theory in curved space-times. Or at least that was what I thought. At that point, I was not familiar with the problems of the inflationary model, but they became increasingly clear to me as I tried to ask my advisor how to connect the different stages of early universe expansion (where quantum and classical behaviors were assumed to be separate in some sense) and got unsatisfactory answers.
Discovering Quantum Bounces and landing a Postdoc
I was 8 months into my PhD, taking courses and studying the numerical simulations necessary to test (p)reheating models, when I went to the Workshop on the Foundations of Quantum Theory and Cosmology at the ICTP-SAIFR in So Paulo. I went without expecting more than a few interesting talks and a fun week, as the topics covered were not closely related to anything I was working on. I will leave recounting that week to a post of its own, but after that week, my perspectives were radically transformed. Two things that bothered me so much about what I was doing were extensively discussed, and many paths to solutions were presented. One was the fundamental issues of Quantum Mechanics that I suspected (and still do) were behind the problems facing the Standard Model and its extensions, and the other was the confusing frontier between classical and quantum behaviors in the study of cosmological perturbations. It turns out that both things are closely related, and there is a lively and ongoing debate about what is the correct way to interpret and calculate the evolution of those perturbations from their quantum origins before inflation starts to their classical effects at the stage of structure formation.
One way to deal with these problems and solve most of the fundamental paradoxes of Quantum Mechanics is by using the de Broglie-Bohm Theory and applying it to the dynamics of the geometry of the background as well as the perturbations. Through this approach, it can be shown that the singularity at the beginning of our universe could be replaced by a quantum bounce preceded by a period of contraction. That sounded like music to my ears! And better yet, there was a way to differentiate between the observations of one interpretation and the others if there were violations of the Born rule in the early universe. I was excited about Physics again! But how do I tell my advisor that? He certainly would not want to work with these fringe ideas, if not for anything else, just because he had no experience with them. I was too excited not to do anything, so I scheduled a meeting and told him straight: I want to change subjects; I like this de Broglie-Bohm cosmology and would like to work with that. He had no problem with that but suggested I talk with another colleague who had worked with Bouncing Models before and could be interested in working with me.
The colleague turned out to be the advisor I wanted to be with in the first place, and a spot had just opened with him. It worked out perfectly; he wanted to work on some quantum foundations issues for a while, and there was a direct line to what I wanted to do. It was a long line, but it was direct. So we started to work. I had to learn all about this "new" quantum mechanics from scratch and also all the techniques involved in simulating the dynamical relaxation of quantum systems that had been done by two or three people before. The theory part was an intense process; I discovered a whole universe of discussions that put into question a lot of what I took as resolved in physics. I had a lot of fun but also got really pissed that this had not been shown to me (and to every physics student) before. More on that another time.
The numerical side took literally years to master and delayed my papers, my PhD, and my whole career. I had never written a single program and suddenly had to learn two different languages, write and improve code, analyze large amounts of data, and run programs in clusters using parallel computing. This was very hard, but I can say now that I do those simulations with relative ease and confidence (it took almost ten years, though).
When I finally defended my thesis, I was exhausted in several different ways. But most importantly, I was panicking because I had not published anything from my work. My numerical simulations were still limited, and I was not ready to publish conclusions without more data. So, landing a postdoctoral position seemed almost impossible. It was again in a nonlinear way that I discovered a possible fellowship at CBPF with the professor who had initiated the program of de Broglie-Bohm quantum cosmology in Brazil and got it a week later, securing the position I hold to this day. In that position, I was able to finish my simulations using the CBPF cluster, continue further analysis on the effects of couplings in the dynamical relaxation of harmonic oscillators, and am now finally working on the quantum-to-classical transition of cosmological perturbations. To sum it up, I am doing what I love, the way I want to, at the place I always dreamt of working. It took me a long while, lots of hard work, the salary is low, the future is uncertain but there are things to be very happy about.
Taking stock and redefining priorities
I started my academic career believing that at the end of my PhD I would be well positioned to get a long-term position, have lots of publications, and start working on some personal projects and developing new theories. I am none of that today. It was harder than I ever could have imagined to finish my PhD, and it took a lot of mental stamina to continue pressing on when the odds of having the career you want are close to zero. But whatever career I wanted at the beginning was based on assumptions about Physics that have long been dropped by me. I could have stayed working on safe topics, collaborated on numerical simulations of preheating models, published a lot in a well-established field, and stopped asking about the damn origins of the inflaton field and the cosmological perturbations. Shut up and calculate; I would have probably heard. Gladly, that is not the way of theoretical physics in Rio, at least in the Cosmology and Gravitation communities. My first PhD advisor was happily amused by my change of subject and pointed me in the right direction to get the orientation I needed. I would not have liked to keep working on a physical model that seems fundamentally flawed to me, even if only in its phenomenology.
I have positioned myself in a very specific and niche sub-subfield. However, with the acumulated knowledge of the several topics I had to study to get to be an specialized physicists of this sub-subfield I can work on many topics of fundamental importance in the frontiers of physics. That cannot pay my bills but certainly makes me feel that my hard work has and is leading to something good. At this stage of life, however, just knowing a lot of stuff is not enough. So I am thinking of ways to apply the large amount of acumulated knowledge to solvable problems that can lead to some form of stability in the near future. This might be through another postdoc or some other job, that is what the next months will tell. The only certain thing in academic life (and in Physics) is there will always be uncertainty.
Have I got any advice? Not really. If I had worked a little harder, focused on more mainstream problems, or stayed in one place for more time, maybe I would be better off now. But I would also not have discovered a lot of the interesting and possibly important theories I did. So the advice I can give young physicists is to try as hard as you can to work on what you love, not be too frustrated when it is not exactly the problem you wanted to work with, and keep an open mind to change directions as you discover new things. It will be hard either way, so you might as well have fun along the way.
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