Research Groups at the Physikalisches Institut

The group is involved in the study of the properties of heavy beauty quarks. Beauty quarks provide a unique telescope into the early universe: through their diverse decays, they enable the measurement of many fundamental parameters of the Standard Model of particle physics and the search for new physical phenomena. The research group is one of the world's leading facilities for the experimental and phenomenological study of the semileptonic and leptonic decays of beauty hadrons. We carry out this branch of research with the Japanese Belle and Belle II experiments. In addition, we search for weakly interacting particles (FIPs) with the FASER experiment at CERN.

Investigation of the interactions between the heaviest known elementary particles: the top quark and the Higgs, Z and W bosons to test the Standard Model of particle physics and to explore physics beyond the Standard Model. Measurements are made with proton-proton collisions in the Large Hadron Collider at CERN in Geneva. Data are collected using the ATLAS experiment. Machine learning is an integral part of most analyses, and new machine learning methods are being investigated.

I am interested in string theory. String theory is a candidate for all known interactions. In a certain limit it should reproduce known theories of particle physics. I have worked with this aspect in the past, focusing on overlapping brane models and heterotic orbifolds. Although unification with gravity is straightforward, it is complicated to really learn anything about quantum gravity from string theory. Perturbation-free string theory has not been formulated for general curved spacetimes, for which one would expect quantum gravity to be important. Dualities between strongly and weakly coupled strings help. In 1997, inspired by such dualities, Maldacena proposed the AdS/CFT correspondence. This allows quantum gravity on AdS spaces to be replaced by a conformal field theory at their edge. Currently, I am interested in exploring quantum gravity using the AdS/CFT duality.

The Experimental Quantum Physics group is engaged in the study of quantum phenomena and the development of quantum technologies. For this purpose, ultracold atoms at temperatures of a few billionths of a degree above absolute zero are used to simulate strongly correlated states of matter from solid state physics. Furthermore, the group investigates entangled states of light and matter in optical microresonators.

The research of the group is in the field of theoretical quantum physics. We are interested in complex phenomena that arise from the interaction of many particles. Experimental realizations of such complex quantum systems include ultracold atomic gases, hybrid atom-light systems, and quantum materials. Our research tries to overcome the challenges of the theoretical description of such quantum many-particle systems, their fascinating quantum phases and their collective phenomena by numerical and analytical methods.

The interactions of many quantum particles can lead to a fascinating array of phenomena ranging from magnetism to superconductivity to non-equilibrium states such as time crystals. Our research focuses on developing computational approaches to quantum many-particle systems, in particular quantum Monte Carlo, tensor networks, and exact diagonalization techniques, to gain a deeper understanding of their rich physics. In addition, we are exploring the use of quantum computers to make advances in this field.