Regensburg 2025 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 22: Poster: Statistical Physics
DY 22.11: Poster
Mittwoch, 19. März 2025, 10:00–12:00, P3
Barrier crossing and rare fluctuations of active Brownian particles — •Rafael Diaz Hernandez Rojas1, Karthik Cheruvary1,2, and Peter Sollich1 — 1University of Göttingen — 2IISER Pune
Understanding noise-induced transitions is crucial for modelling complex systems where random fluctuations can affect both the local stability and the global behaviour of a system. Noise-activated escape processes are a key instance, and were solved by Kramers long ago for barrier crossing driven by thermal noise. A natural question is how different noise sources might change the picture, in particular those postulated in active matter models. Here we study the escape problem for the paradigmatic case of an Active Brownian Particle, where the direction of the self-propulsion velocity rotates randomly on a timescale known as persistence time. Using a path integral formalism in the weak thermal noise limit. We map the problem of finding the most likely escape trajectory to the minimisation of an appropriate action. We show that optimal trajectories always consist of an initial relaxation in a tilted potential, beyond which the escape becomes genuinely activated. We apply our approach to convex potentials (to study barrier climbing by rare fluctuations) as well as potentials with multiple minima (to analyse barrier crossing). We highlight the effects of directionality induced by the self-propulsion and its non-trivial interplay with the shape of the potential. A key result is that, for potentials with a symmetry axis along the line between two minima, activity can generate optimal escape paths that break this symmetry.
Keywords: Active Browninan Particles; Escape problems; Path integrals; Noise driven transitions