Role of interactions in non-equilibrium transformations

TL;DR

This paper introduces a decomposition method for non-equilibrium transformations in complex systems, separating independent effects from interactions using mutual information, and demonstrates its practical relevance through experiments with colloidal particles.

Contribution

It presents a novel decomposition framework for non-equilibrium transformations that isolates the effects of interactions among system variables, applicable to systems with controllable interaction strengths.

Findings

Increasing pairwise interaction prolongs non-equilibrium states.

The approach distinguishes contributions of pairwise and triplet interactions.

Method helps identify interactions that facilitate transformations.

Abstract

For arbitrary non-equilibrium transformations in complex systems, we show that the distance between the current state and a target state can be decomposed into two terms: one corresponding to an independent estimate of the distance, and another corresponding to interactions, quantified using the relative mutual information between the variables. This decomposition is a special case of a more general decomposition involving successive orders of correlation or interactions among the degrees of freedom of the system. To illustrate its practical significance, we study the thermal relaxation of two interacting, optically trapped colloidal particles, where increasing pairwise interaction strength is shown to prolong the longevity of the time-dependent non-equilibrium state. Additionally, we study a system with both pairwise and triplet interactions, where our approach identifies their distinct contributions to the transformation. In more general setups where it is possible to control the strength of different orders of interactions, our findings provide a way to disentangle their effects and identify interactions that facilitate the transformation.