Berlin 2018 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 67: Poster: Active Matter, Microswimmers

DY 67.12: Poster

Thursday, March 15, 2018, 15:30–18:00, Poster A

A path-integral approach to active matter — •Thomas Schindler, Sebastian Kapfer, and Patrick Ketzko — Friedrich-Alexander Universität, Erlangen, Deutschland

The statistical physics of active particles are a rapidly evolving field with many unsolved problems. One of them is the discrepancy of definitions of thermodynamic observables. In equilibrium systems e.g. the pressures, defined via the derivative of the free energy and defined via the force per area on the container of a gas, always yield equivalent results. This is not true for nonequilibrium systems [1]. Here we use a path integral approach where we study an ensemble of one dimensional trajectories in discrete time steps of diffusing particles with drift velocity. These particles mimic active Brownian particles, but from the ensemble we can define a partition function and hence a free energy of the system. The free energy can be written down explicitly and is amenable to numeric evaluation by Markov-chain Monte Carlo methods. The diffusion is modelled by Gaussian transition probabilities between time steps. The direction of the drift is prescribed by an Ising-like spin variable with predefined temporal correlations which models directional diffusion of the particles.
[1] A. P. Solon, Y. Fily, A. Baskaran, M. E. Cates, Y. Kafri, M. Kardar, and J. Tailleur, Nat. Phys. 11, 673 (2015)