Differential transport coefficients and the fluctuation-dissipation theorem for nonequilibrium steady states

Abstract

In order to establish a fluctuation-dissipation theorem for a system in a nonequilibrium steady state, a general formalism is given of the quantum statistical mechanics for nonequilibrium systems imposed on constant external fields. In terms of a single function, we can prove our fluctuation-dissipation theorem in the simplest form. The theorem proved is applied to the study of differential transport coefficients. A generalization of Onsager's reciprocity relation is derived for differential transport coefficients. It is shown that a measurement of differential transport coefficients yields auto-correlation functions of macroscopic operators.