Direct evaluation of rare events in active matter from variational path sampling

TL;DR

This paper introduces a variational path sampling method to evaluate rare events in active matter systems, enabling the study of conformational changes in nonequilibrium conditions.

Contribution

The authors develop a novel simulation approach that accurately estimates rare event rates in active matter by optimizing control forces, addressing challenges posed by nonequilibrium dynamics.

Findings

Active bath increases conformational switching rates.

Method provides exact estimates of rare event probabilities.

Results align with stochastic thermodynamics bounds.

Abstract

Active matter represents a broad class of systems that evolve far from equilibrium due to the local injection of energy. Like their passive analogues, transformations between distinct metastable states in active matter proceed through rare fluctuations, however their detailed balance violating dynamics renders these events difficult to study. Here, we present a simulation method for evaluating the rate and mechanism of rare events in generic nonequilibrium systems and apply it to study the conformational changes of a passive solute in an active fluid. The method employs a variational optimization of a control force that renders the rare event a typical one, supplying an exact estimate of its rate as a ratio of path partition functions. Using this method we find that increasing activity in the active bath can enhance the rate of conformational switching of the passive solute in a manner consistent with recent bounds from stochastic thermodynamics.