Dissipation and fluctuations in nonequilibrium thermodynamics

Abstract

A relationship between dissipation and fluctuations is described which leads to a unified theory of irreversible processes far from equilibrium. The development is based on the principle that dissipation and fluctuations are caused by elementary molecular processes. This permits the formulation of a canonical form for the rate of dissipation of the extensive variables. The canonical form depends on the thermodymanic quantities which are conjugate to the extensive variables, and it is shown that the canonical form leads to the customary transport equations for a variety of linear and nonlinear relaxation processes. Because fluctuations are also caused by molecular events, this formulation of dissipation can be used to examine deviations from the average. The theory associates a nonstationary, Markov stochastic process with fluctuations away from the conditionally averaged extensive variables. This description of nonequilibrium thermodynamics does not require the entropy to be introduced, and for rate processes close to equilibrium, but away from a critical point, reduces to the usual linear theory.