Berlin 2012 – scientific programme

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BP: Fachverband Biologische Physik

BP 18: Posters: Statistical Physics in Biological Systems

BP 18.10: Poster

Wednesday, March 28, 2012, 17:30–19:30, Poster A

Nonequilibrium clustering of self-propelled particles — •Fernando Peruani¹ and Markus Bär² — ¹Universite de Nice - Sophia Antipolis, France — ²Physikalisch-Technische Bundesanstalt, Braunschweig und Berlin, Germany

It is known from simulations and experiments that many systems of interacting self-propelled particles (SPP) exhibit two phases: i) a mono-disperse phase where the cluster size distribution (CSD) is dominated by an exponential tail, and ii) an aggregated phase characterized by the presence of non-monotonic cluster size distributions with a peak at large cluster sizes. At the transition between these two phases, the CSD has a power-law shape with a critical exponent. This qualitative change in the functional form of the CSD can be used as a criterion to define the onset of collective motion in SPP systems as this change in the cluster-size distribution is connected with a strong increase of average cluster sizes. This criterion is particularly useful for application in experimental SPP system where other quantities indicating collective motion like a global orientational order parameter are often not observed. We show that a simple kinetic theory is sufficient to reproduce this transition and allows prediction of the exponent of the power-law of the CSD.