A Thermodynamic Non-Linear Response Relation

TL;DR

This paper extends the fluctuation-dissipation-theorem to far-from-equilibrium thermodynamic systems by deriving a relation that connects responses of arbitrary order to entropy production correlations, validated on a 4-state model.

Contribution

It introduces a new thermodynamic response relation linking higher-order responses to lower-order entropy production correlations, broadening the theorem's applicability.

Findings

Validated the relation on a 4-state model

Extended fluctuation-dissipation-theorem to nonlinear, far-from-equilibrium regimes

Demonstrated thermodynamic consistency of the new relation

Abstract

The fluctuation-dissipation-theorem connects equilibrium to mildly (linearly) perturbed situations in a thermodynamic manner: It involves the observable of interest and the entropy production caused by the perturbation. We derive a relation which connects responses of arbitrary order in perturbation strength to correlations of entropy production of lower order, thereby extending the fluctuation-dissipation-theorem to cases far from equilibrium in a thermodynamic way. The relation is validated and studied for a 4-state-model.