Stochastic thermodynamics for active matter

TL;DR

This paper extends stochastic thermodynamics to active matter, deriving new expressions for pressure and interfacial tension, and discusses the implications of negative tension in phase-separated active systems.

Contribution

It introduces a thermodynamic framework for active matter using stochastic thermodynamics, defining work, heat, and conjugate variables in non-equilibrium steady states.

Findings

Derived expressions for pressure and interfacial tension of active Brownian particles.

Found negative interfacial tension despite stable phase separation.

Highlighted the role of fluctuations in active matter thermodynamics.

Abstract

The theoretical understanding of active matter, which is driven out of equilibrium by directed motion, is still fragmental and model oriented. Stochastic thermodynamics, on the other hand, is a comprehensive theoretical framework for driven systems that allows to define fluctuating work and heat. We apply these definitions to active matter, assuming that dissipation can be modelled by effective non-conservative forces. We show that, through the work, conjugate extensive and intensive observables can be defined even in non-equilibrium steady states lacking a free energy. As an illustration, we derive the expressions for the pressure and interfacial tension of active Brownian particles. The latter becomes negative despite the observed stable phase separation. We discuss this apparent contradiction, highlighting the role of fluctuations, and we offer a tentative explanation.