Generalized Green-Kubo formulas for fluids with impulsive, dissipative, stochastic, and conservative interactions

Abstract

We present a generalization of the Green-Kubo expressions for thermal transport coefficients mu in complex fluids of the generic form mu=mu(infinity)+integral(infinity)(0) dtV(-1)< J(epsilon)exp(tL)J >(0), i.e. a sum of an instantaneous transport coefficient mu(infinity), and a time integral over a time correlation function in a state of thermal equilibrium between a current J and its conjugate current J(epsilon). The streaming operator exp(tL) generates the trajectory of a dynamical variable J(t)=exp(tL)J when used inside the thermal average <(...)>(0). These formulas are valid for conservative, impulsive (hard spheres), stochastic, and dissipative forces (Langevin fluids), provided the system approaches a thermal equilibrium state. In general mu(infinity)not equal 0 and J(epsilon)not equal J, except for the case of conservative forces, where the equality signs apply. The most important application in the present paper is the hard sphere fluid.