What holds matter together at its most fundamental level? This is the question explored by Dr. Raffaele Del Grande from the Department of Physics at our faculty, who has been awarded a prestigious ERC Starting Grant. With his project HUNTING-3BFs (Hunting Three-Body Forces), he became the only researcher from the Czech Republic to succeed this year in the field of physics. In this exclusive interview, he talks about the challenges behind this success, his passion for nuclear physics, and what drives his scientific curiosity.
Could you explain what your project is about and why this is such a crucial question in nuclear physics?
My project, HUNTING-3BFs, focuses on understanding what we call three-body forces. Normally, when we describe atomic nuclei, we think of them as collections of protons and neutrons interacting in pairs. This “two-body picture” works surprisingly well — but it is not the whole story. When three particles come very close together, new short-range effects appear as additional contributions to the force that exist only if all three are present at once.
These three-body forces are extremely important: they help explain why nuclei have the structure they do and are essential for understanding how matter behaves under the most extreme densities in our universe — such as in the cores of neutron stars.
In particular, three-body forces involving Λ hyperons (particles containing a strange quark) are essentially unknown because we have almost no direct experimental information about them. This is a critical gap, since Λ hyperons are expected to appear in neutron stars for energetic reasons. If we cannot describe their three-body interactions correctly, we cannot reliably model how dense matter behaves or solve long-standing puzzles about neutron-star stability. My project aims to provide the first concrete insights into these forces.
When we talk about “three-body forces,” it may sound quite abstract to a non-expert. Could you give us a simple example of what exactly you are investigating?
Imagine three people linking arms in a triangle. The stability of that triangle does not come simply from two pairs holding hands — it emerges only when all three are connected. In the same way, inside a nucleus, interactions are not just the sum of pairs. Sometimes the close presence of a third particle changes the entire situation.
That is what we mean by a three-body force: a short-range “extra glue” that appears only when three particles interact together. Without including this in our theories, we miss essential parts of how nuclear matter really works.
Three-body forces involving Λ hyperons play a key role in your research. Why are they so important, and why have they attracted so little attention until now?
Λ hyperons contain a strange quark, which makes them heavier and different from the protons and neutrons of ordinary matter. They do not usually appear around us, but in the extremely dense environment of neutron stars they are expected to form in large numbers. Their presence would significantly change the structure and stability of the star.
The problem is that if hyperons interact only through two-body forces, neutron stars could not reach the high masses we actually observe. This discrepancy is known as the hyperon puzzle. Three-body forces involving hyperons may provide the missing piece by reconciling astronomical observations with theoretical models. Until now, however, we have lacked the data needed to study these forces with precision.
For the first time, direct data on three-body scattering will be used. How will the data from the ALICE experiment at CERN help you push the boundaries of our understanding?
Traditionally, two-body interactions have been studied by colliding particles in scattering experiments. For three particles, however, that’s impossible — you simply cannot make three protons collide simultaneously in an accelerator.
My project proposes a new approach. In high-energy collisions at the Large Hadron Collider, many particles are produced at once. Among them, we can identify rare cases where three particles — for example, three protons or two protons and a Λ hyperon — are emitted very close to each other.
Here we use a technique called femtoscopy. In simple terms, femtoscopy is like a microscope for distances a million times smaller than an atom. It allows us to study how particles are correlated when they are only about a femtometer apart — the scale where nuclear forces act. By doing so, we can uncover the fingerprints of interactions, including three-body forces, directly in the data.
It is an ambitious idea because it requires analyzing an enormous number of collisions to collect enough of these rare triplets. But it represents a true breakthrough: it allows us to test theoretical models against experimental data and to build a more realistic picture of nuclear matter, including matter containing strange hadrons.
How could the results of your project change our understanding of nuclear matter — not only in the laboratory but also in astrophysics?
The project could reshape the way we think about the equation of state of dense matter — the relationship between pressure and energy density inside objects like neutron stars. By understanding three-body forces involving hyperons, we will finally have the information needed to build more realistic models of stellar structure.
This will directly impact astrophysics by helping us determine how massive neutron stars can be, what their interiors look like, and how they evolve. At the same time, refining our nuclear models with strange hadrons benefits laboratory physics and even applications beyond astrophysics, since nuclear theory underpins a wide range of technologies.
The ERC only awards grants to the most ambitious projects. What does this achievement mean to you personally and to our faculty?
For me personally, it is both a great honor and a tremendous responsibility. The ERC grant allows me to dedicate several years to a problem I have been passionate about for a long time.
For the faculty, it represents international recognition. It shows that our research here at the Czech Technical University in Prague stands at the very forefront of nuclear and particle physics. It also brings resources and visibility that will help us attract talented students and collaborators from around the world.
The ERC only awards grants to the most ambitious projects. What does this achievement mean to you personally and to our faculty?
For me personally, it is both a great honor and a tremendous responsibility. The ERC grant allows me to dedicate several years to a problem I have been passionate about for a long time.
For the faculty, it represents international recognition. It shows that our research here at the Czech Technical University in Prague stands at the very forefront of nuclear and particle physics. It also brings resources and visibility that will help us attract talented students and collaborators from around the world.
Could you give our readers an idea of what the path toward such a prestigious ERC grant looks like?
It’s a very demanding process. First, you need a ground-breaking idea — something that could truly change the field. Then you must develop a detailed plan that shows how to turn that vision into concrete steps.
The competition is intense: thousands of applications are submitted each year, and only a small percentage are funded. So persistence and resilience are essential, because success often comes only after several attempts — as it did in my case.
What was the most challenging part of the process for you?
The hardest part was finding the right balance between ambition and feasibility. The ERC seeks projects that are high-risk but high-gain. That means showing that the potential impact is enormous, while also proving that you have a realistic strategy to achieve it.
You work at the Department of Physics at FNSPE. What is your role within the Nuclear and Particle Physics study programme?
Since January, I have been an Assistant Professor at FNSPE. In the next summer semester, I will be teaching Nuclear Physics for bachelor’s students and Astrophysics for master’s students. I am really looking forward to inspiring students in both courses, and I see this as a great opportunity to connect the two fields — nuclear physics and astrophysics — also in relation to the topics of my ERC project.
In addition, I have enthusiastically taken part in outreach activities aimed at attracting high-school students to our university. I find it very rewarding to share the excitement of science with younger generations.
You have studied and worked at universities in Italy, Poland, and Germany. Since January you have been at CTU in Prague. How do you like it here so far?
Prague is a wonderful city to live in, and CTU offers an incredibly dynamic scientific environment. The faculty is international and forward-looking, which makes it an inspiring place to work. I have felt very welcome here, and I see great potential for building strong collaborations in the years ahead.
I especially appreciate that my colleagues are involved not only in LHC experiments but also in experiments at RHIC in the USA and FAIR in Germany. If I were a student looking for a place to study particle physics, CTU would be the right choice.
Where would you like your research to be in five years?
In five years, I hope we will have developed the first reliable description of hyperonic three-body forces. My dream is that our models will be used not only in nuclear physics but also in astrophysics — helping scientists interpret data from neutron stars and from future high-energy experiments.
What advice would you give to young people and students who are considering a career in science?
My advice is to follow your curiosity. Don’t be discouraged if the questions seem too big or the path uncertain. Science is about persistence and creativity. You will face challenges, but you will also have the unique privilege of contributing to our understanding of the universe — and that is profoundly rewarding.
We invite you to the FNSPE CTU colloquium with Dr. Raffaele Del Grande on the topic: Hunting three-body forces.
Photo: David Březina, FJFI ČVUT