Fluctuations in a nonequilibrium steady state: Basic equations

Abstract

In this paper the correlation functions for fluctuations in a fluid kept in a nonequilibrium steady state are studied. Hydrodynamiclike equations for the unequal- and equal-time correlation functions of the microscopic densities of mass, momentum, and energy are derived both for a dilute gas on the basis of kinetic theory and for a fluid of arbitrary density from the Liouville equation. The connection of these equations with those of fluctuating hydrodynamics is discussed.