Response theory of symmetry restricted interactions

Abstract

It is known that, in general, outside the linear regime, Kubo relations evaluated in nonequilibrium steady states do not have any simple Green-Kubo relation to steady state fluctuations. We have recently shown that for a restricted but practically important class of symmetry restricted, boundary driven processes, steady state Green-Kubo relations do hold. This class is composed of those pairs of processes which are prevented by symmetry considerations (Curie's principle) from coupling in linear theory. Outside the linear regime these couplings may be allowed. In this paper we show that for the analogous mechanical transport processes, where the nonequilibrium state is driven by mechanical fields which appear explicitly in the equations of motion, steady state Green-Kubo relations do not apply.