AG — Prof. Heiko Rieger — Statistical Physics

Our research team works on a broad spectrum of projects from statistical physics, which is the branch of theoretical physics that seeks to understand the emergence of specific macroscopic properties of systems with many, microscopic interacting particles. Our research ranges from many body physics (classical and quantum) over stochastic processes to theoretical biophysics, with a particular focus on dynamical processes far from equilibrium.

Biological systems are manifestly far from equilibrium, since they consume continuously energy for instance in the form of ATP. In collaboration with several groups from the life science departments of the Saarland University and within the collaborative research center SFB 1027 we work on the biophysics of killing and study how cytotoxic killer cells of the human body eliminate pathogen-infected or tumorigenic target cells. We are also interested in understanding the physical determinants of tumor growth, in particular the process of vascularization, interstitial fluid flow and drug delivery.

The statistical physics of systems far from equilibrium is still one of the most challenging fields in modern theoretical physics. Most natural systems, not only biological ones, are out of equilibrium. For instance the non-equilibrium dynamics in disordered systems takes place on enormously long time scales (in glasses theoretically even time scales of the order of the age of the universe) that it is called aging, which we studied intensively in the past. Currently we focus on random search processes and search strategies, pattern formation in ensembles of active particles, and imbibition and fluid flow in nano-porous media.

Quantum statistical physics is concerned with collective phenomena in systems with many quantum mechanical degrees of freedom (electrons, bosons, spins, qbits, etc). Paradigmatic examples, also studied in our research group, are quantum phase transitions, where macroscopic properties of a strongly inteacting quantum many body system change dramatically at zero temerature by tuning for instance an external field. Another example is the quantum relaxation of many particle systems after sudden changes of an external field, which is experimentally observable for instance in ultracold atoms in optical lattices. Important issues here are quantum thermalization and the growth of entanglement.