Regensburg 2010 – scientific programme

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BP: Fachverband Biologische Physik

BP 1: Statistical Physics of Biological Systems I (joint BP, DY)

BP 1.6: Talk

Monday, March 22, 2010, 11:45–12:00, H45

Clustering in self-propelled particle systems — •Fernando Peruani¹ and Markus Baer² — ¹Service de Physique de l Etat Condense, CEA Saclay, 91191 Gif-sur-Yvette, France — ²Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin, Germany

Self-propelled particle systems exhibit a rich irreversible clustering dynamics. Independently of the initial condition, these systems reach a steady state cluster size distribution which depends on particle density and noise intensity. We show that the aggregation process can be described by a set of Smoluchowski equations whose functional form is independent of the symmetry of the velocity alignment rule or interaction forces. For a given density (noise intensity) there is always a critical noise intensity (density) at which the cluster size distribution becomes critical, with a exponent 4/3. Below the critical point, the cluster size distribution is exponential and the system exhibits a characteristic cluster size. Above the critical point, the cluster size distribution can be well fitted by a power-law with a second peak at large cluster sizes. The exponent of the power-law is a function of the noise intensity, resp. of particle density.