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DY: Fachverband Dynamik und Statistische Physik

DY 33: Brownian Motion, Stochastic Processes, Transport I

DY 33.9: Talk

Thursday, March 17, 2011, 16:15–16:30, HÜL 186

Brownian motion with active fluctuations — •Pawel Romanczuk and Lutz Schimansky-Geier — Department of Physics, Humboldt Universität zu Berlin, Germany

We analyze dynamics of particles with fluctuating velocity and orientation in two spatial dimensions. We distinguish passive (e.g. thermal fluctuations) and active fluctuations which emerge in active systems far from equilibrium as for example living organisms or chemically driven colloids. We derive analytical expressions for the speed and velocity distributions for generic models of (active) Brownian particles in two spatial dimensions. The presence of active fluctuations already for simple Stokes friction results in speed and velocity distributions which differ from the classical Maxwell distribution. Active Gaussian fluctuations lead to speed distributions increasing as ∼ |v|^α with α<1 at small speeds |v|≪1 which results in a divergence of the corresponding stationary Cartesian velocity distributions at the origin. Finally we show that such a behavior occurs also for non-Gaussian active fluctuations (shot noise).