Regensburg 2016 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 29: Poster - Active Matter, Microswimmers and -fluidics, Statistical Physics Biosystems

DY 29.2: Poster

Dienstag, 8. März 2016, 18:15–21:00, Poster C

Large deviation statistics for self-propelled particles — •Kevin Kleinbeck, Patrick Pietzonka, and Udo Seifert — II. Institut für Theoretische Physik, Universität Stuttgart

For a self-propelled particle, e.g., a Janus particle, we calculate the probability of fluctuations in the displacement during long time intervals. The particle is modeled with a translational and a rotational degree of freedom, with the latter affecting the direction of the constant self-propelling force. Moreover, we assume that the particle has a permanent magnetic moment that interacts with an external magnetic field. This symmetry breaking leads to a non-vanishing average velocity. We apply large deviation theory to calculate extreme fluctuations beyond the Gaussian regime.

For externally driven particles, the displacement along individual trajectories is proportional to the entropy production. As a central result of stochastic thermodynamics, the probability distribution of such an observable satisfies a fluctuation theorem relating the left and the right wing of the distribution. We show how the lack of the proportionality to entropy production for the displacement of self-driven particles affects the characteristic shape of the probability distribution. Moreover, we prove that the distribution satisfies a symmetry that is similar to the fluctuation theorem, but contains an additional term that depends only on the ratio between the field strength and the propulsion force.