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DY: Fachverband Dynamik und Statistische Physik
DY 24: Dynamics and Statistical Physics - Open Session
DY 24.5: Vortrag
Dienstag, 23. März 2021, 12:20–12:40, DYb
Transport coefficients of active particles: reverse perturbations and response theory — •Thomas Ihle1, Arash Nikoubashman2, Sven Stroteich1, and Rüdiger Kürsten1 — 1Greifswald University — 2Johannes-Gutenberg-University Mainz
The reverse perturbation method [1] for shearing simple liquids is extended to the Vicsek model (VM) of self-propelled particles. The sheared systems exhibit a skin effect: Momentum that is fed into the boundaries of a layer decays mostly exponentially toward the center of the layer. It is shown how the shear viscosity and the momentum amplification coefficient can be obtained by fitting this decay with an analytical solution of the hydrodynamic equations for the VM. The viscosity of the VM consists of two parts, a kinetic and a collisional contribution. Here, a novel expression for the collisional part is derived by an Enskog-like kinetic theory [2]. In agent-based simulations, using several methods to measure transport coefficients, we find excellent agreement between these different methods and also good agreement with the theoretical predictions. In addition, we introduce a response theory that allows us to verify the analytical predictions of kinetic theory and to obtain expressions for non-local transport coefficients. [1] F. Müller-Plathe, Phys. Rev. E 59, 4894 (1999), [2] A. Nikoubashman, T. Ihle, Phys. Rev. E 100, 042603 (2019)