20.12.22 - Thomas Voigtmann "Swimming at High Densities: Brownian Particles between Activity and Arrest"

Swimming at High Densities: Brownian Particles between Activity and Arrest

The possibility to convert thermal energy into mechanical work at the microscopic scale is a key feature of living matter. The resulting "active" motion provides for interesting non-equilibrium features from the perspective
of statistical mechanics. Specifically, active Brownian particles (ABP) constitute a model system that allows to study the joint influence of thermal fluctuations and active motion on the collective dynamics, applicable for
micrometer-sized bacteria or artificial microswimmers such as colloidal Janus particles.

In this talk, we will discuss the dynamics of ABP within a recent nonlinear-response formalism that allows to capture the non-equilibrium features caused by strong active forces. A particular focus shall be on the dynamics at high densities, where a competition emerges between interaction-driven kinetic arrest and activity-driven fluidization of the
system. We will focus on the dynamical signatures that can be observed in the mean-squared displacement (MSD) of ABP: how does the generalized Langevin equation look like for interacting ABP, and what are the tell-tale signatures of the non-equilibrium nature of the dynamics? If time permits, the talk shall conclude with the link between self-propulsion of microswimmers and proper "rocket science".