SKM 2023 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 42: Poster: Active Matter, Soft Matter, Fluids

DY 42.4: Poster

Thursday, March 30, 2023, 13:00–16:00, P1

Advanced Sampling Methods for Non-Equilibrium Particles — •Thomas Kiechl, Michele Caraglio, and Thomas Franosch — Institute for Theoretical Physics, Universität Innsbruck, Innsbruck, Austria.

Active particles or microswimmers are capable of converting energy into directed motion - which is why they are classified as out-of-equilibrium systems. Microswimmers, such as bacteria or spermatozoa often find themselves in a target search situation, where the microswimmers have to make a transition from an initial area to a target area crossing complex environments. Transition Path Theory, a rigorous statistical mechanics description of transition processes, can be generalized to characterize the target search problem. A simple way of modeling a complex environment for the microswimmer is via an external potential, in which the metastable initial position is separated from the target by an energy barrier. This makes the target search a rare event, in which the timescales of the fluctuations in the metastable states and the transition process are separated. Brute force simulations solving the equations of motion are inefficient due to this gap in timescales. The main result is that a more efficient sampling method, Transition Path Sampling (TPS), originally developed for rare transitions of passive systems, can be generalized to Run-and-Tumble systems. TPS is a Monte Carlo simulation of successful trajectories where the new trajectory is accepted according to a metropolis rule based on a path integral formulation.