Active matter

Active matter is a relatively new and exciting field that strives to incorporate living matter into the framework of classical statistical mechanics. In our group, we study links between traditional models of statistical mechanics and new models describing active matter. We are especially interested in the link between the XY model for polar rigid
rotors on a 2d lattice and the Vicsek model for active particles with local alignment interactions on a 2d sheet. The XY model is notorious for featuring the famous Berezinskii-Kosterlitz-Thouless (BKT) phase transition. Currently, we investigate how much the Vicsek model, which can in many ways be thought of as an active XY model, still feels the
effect of the BKT transition. We use simulation methods to observe the dynamics of both models and extract correlation functions and with these critical exponents. Parallely, in a theoretical approach using the Zwanzig-Mori projection operator technique and approximations such as mode coupling, we try to identify the underlying properties of the
dynamics that lead to this behavior and how they differ between the XY and the Vicsek model.