Fluctuation-Response Relation in Non-Equilibrium Systems and Active Matter

T. R. Kirkpatrick; D. Belitz

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arXiv · 2407.01821

Fluctuation-Response Relation in Non-Equilibrium Systems and Active Matter

T. R. Kirkpatrick·D. Belitz

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Abstract

We use dynamic equations to derive a relation between correlation functions and response or relaxation functions in many-body systems. The relation is very general and holds both in equilibrium, when the usual fluctuation-dissipation theorem is valid, and to linear order in an expansion about arbitrary non-equilibrium states, when it is not. We illustrate our results by discussing fluids, both in equilibrium and non-equilibrium states, as well as several active-matter systems.

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T. R. Kirkpatrick, D. Belitz. 2024-07-01. Fluctuation-Response Relation in Non-Equilibrium Systems and Active Matter. https://arxiv.org/abs/2407.01821

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