General properties of response functions of nonequilibrium steady states

TL;DR

This paper establishes universal properties of response functions in nonequilibrium steady states, applicable to both quantum and classical systems, including sum rules and asymptotic behaviors, supported by molecular dynamics simulations.

Contribution

It derives general, assumption-free properties of response functions in nonequilibrium steady states, highlighting differences from equilibrium and demonstrating applicability through simulations.

Findings

Derived sum rules for response functions.

Established asymptotic behaviors of response functions.

Validated results with molecular dynamics simulations.

Abstract

We derive general properties, which hold for both quantum and classical systems, of response functions of nonequilibrium steady states. We clarify differences from those of equilibrium states. In particular, sum rules and asymptotic behaviors are derived, and their implications are discussed. Since almost no assumptions are made, our results are applicable to diverse physical systems. We also demonstrate our results by a molecular dynamics simulation of a many-body interacting system.