Why did you choose the University of Houston for your Fulbright visit?
It actually came about quite naturally. We started collaborating with Houston about a year ago because we had a similar research goal. The team there developed an equation of state that I wanted to use in my work. It turned out to be suitable for what I needed, but it had to be adjusted a little.
You can imagine it as needing to move between different variables, even though there is no simple analytical relationship between them. So we had to develop numerical code that makes it possible to switch between these different variables. When I received an email saying that the Fulbright application deadline was approaching, I got in touch with my colleagues in Houston and we agreed that I could give it a try. We designed a project, the application was successful, and here we are.
What exactly do you focus on in your research?
In my research, I study what happens to matter under extreme conditions. When heavy atomic nuclei collide in particle accelerators, a state of matter is created for a very brief moment that is similar to what existed shortly after the birth of the universe. Because we cannot observe the collision directly, we use theoretical models and computer simulations to reconstruct from the measured data what actually happened.
I am particularly interested in whether, under certain conditions, this matter can undergo a phase transition, meaning a change of state. If so, we want to find out at what collision energies this happens and what traces of it we can detect in experiments.
Is this something that is also explored at CERN?
There are two major experiments in the world in this area: CERN in Europe and Brookhaven National Laboratory in the United States. CERN is home to the Large Hadron Collider, or LHC, which operates at very high energies. There, scientists study physics corresponding to conditions almost immediately after the Big Bang, when temperatures were extremely high and the baryon density was close to zero.
In the Western Hemisphere, there is Brookhaven and its Relativistic Heavy Ion Collider, or RHIC. It makes it possible to study regions with non-zero baryon density. In that case, we are looking at slightly different physics, and that is where there is potential to search for the collision energy at which a phase transition or critical point might appear.
That is why in my research I focus more on energies relevant to experiments in America than on those at CERN. Of course, all of this is based on theoretical predictions.
When you explain your topic to someone outside your field, how do you describe it?
At home it is a little specific, because my father is a physicist. He studied at the Faculty of Mathematics and Physics and at the Faculty of Electrical Engineering, and he focused more on biophysics. In fact, he is one of the reasons I ended up at the Faculty of Nuclear Sciences and Physical Engineering. When I was deciding where to go after secondary school, he suggested that I should try FNSPE because it would be a challenge. He said it was something like the MIT of the East.
But when I explain it simply, I say that I look at an extreme state of matter at very high temperatures, which existed 13.8 billion years ago, shortly after the universe was created. Today, such matter is produced in particle accelerators. I am mainly interested in the theoretical side: the models that help us understand what happens under these extreme conditions and whether what we see in theory makes sense.
Can such a heavy-ion collision be imagined visually?
Sometimes I try to explain it to the Scouts I have been leading since I was 19. I tell them to imagine two pancakes flying towards each other. At some point they collide, and a very hot and dense form of matter is created and begins to expand. Essentially, it is a kind of fireball.
As it expands, it also cools down and gradually “freezes out”. Once it reaches a certain point, particles begin to form. These then fly into detectors, and through them we try to trace back what happened during the collision.
When did you become interested in theoretical physics?
At secondary school, I really enjoyed mathematics and physics, so I knew I wanted to go in this direction. At FNSPE, it became even clearer. I enjoyed thinking about things on a general level and deriving relationships. These kinds of “crazy” ideas appealed to me more than the idea of building a detector or doing experiments.
During my bachelor’s studies, I had courses related to classical hydrodynamics, solving the Navier–Stokes equations and similar topics. That caught my interest. Then I came across a bachelor’s thesis topic supervised by Professor Tomášik, and we have been working together ever since. It has been about six years now.
What do you need for your work?
It is simple: I only need a laptop. I do not work in a laboratory, I am not at a reactor, nothing like that. I work with models that are available online or that we have in our group and continue to improve. I use data measured by experimental physicists. When I set up a model, I look at specific variables and use them to check whether the whole simulation corresponds to reality, or whether it is nonsense.
So modern physics is also a lot about programming?
Yes, at least the kind of physics I do. You are constantly dealing with details: whether you have made a mistake in the code, whether you are comparing the right quantities, whether what the experimental physicists measured corresponds to what I have in the simulation. There are many small nuances.
Does your research have any application potential?
People often ask me whether I do something related to fusion or reactors. I tell them no. What we do is more theoretical and is mainly about knowledge. I do not expect anyone to see my research in everyday life as a specific technology.
On the other hand, I would like it to have an impact on the scientific community. I am trying to create code that would be open source and publicly available, so that people all over the world could use it. It could be a tool that makes work in our field more efficient. I often feel that scientists are each playing in their own field and do not share their tools enough.
Together with a postdoc from Houston, we have created something that could be universal. In theory, it could also become part of a larger collaboration. We already discussed it at a conference in Budapest, and it resonated there. If it works out, it could become a useful tool in the future.
Have you ever considered doing something other than science?
After my master’s degree, I spent some time thinking about what to do next. I started working at a company focused on real estate market analysis. I had it as a side job two days a week and kept my options open. I could either move more into the private sector or continue in science.
At a certain point, however, I decided that I wanted to give science my maximum effort. I wanted to see where it would take me. And now, when I see people around the world using things I have worked on, and when my name is mentioned at conferences, it feels good. I can see that it has some impact, and I like that.
What are you most looking forward to in America?
Probably the university community. I am interested in how science is done in America. It is a big unknown for me; I have never been there. I cannot fully imagine how the system, the administration and the everyday life of a university work there. I am curious about almost everything. I think that for someone from Central Europe, it will be a big shock, but also a very valuable experience.
I am also looking forward to seeing what is being done there beyond my specific project. In my view, Houston has some of the best people in our field, so I would like to learn things that are not explicitly written into the Fulbright project as well.
Are you planning to attend lectures there?
Yes, I have been thinking about that. I am interested in what lectures look like there, whether they are specialist lectures or more popular science events. I would like to get a proper feel for the American university environment.
At FNSPE, I myself have taught tutorials in general relativity over the past two years. At first I was unsure, because I did not feel I had a strong teaching talent. I admire other people who can speak fluently and pass knowledge on clearly. But over time it improved. I managed to settle more into the teaching role, and I started to enjoy explaining things to others.
Is there someone you would like to meet or hear speak in the United States?
I will definitely go to a lecture by Professor Volodymyr Vovchenko, with whom I will be working. He should also be my supervisor in Houston. From what I have heard, he is among the leading scientists in our field. And if there were a chance to hear a Nobel Prize winner, that would of course be great.
Are you planning to travel during your stay?
I enjoy climbing and I like mountains, so Texas is not exactly the ideal destination for me. On the other hand, I would like to explore the city, visit museums and get to know Houston. It is the third or fourth most populous city in the United States, so there will certainly be plenty to discover.
I would also like to go to a sports game. Ideally the NHL, although for that I would have to go to Dallas. But I am also interested in the NBA or the NFL. I will see what is possible to fit into four months.
Profile
Tomáš Poledníček is a Ph.D. student at the Faculty of Nuclear Sciences and Physical Engineering of the Czech Technical University in Prague. His research focuses on the theory and phenomenology of heavy-ion collisions, with an emphasis on hydrodynamic modelling. Thanks to a Fulbright scholarship, he will leave for a four-month research stay at the University of Houston, where he will build on his collaboration with local experts in theoretical high-energy physics.
Interview by: Karolína Pštross, Science Communication Coordinator at CTU
Photos by: David Březina, FNSPE CTU
