Statistical mechanics of stationary states. III. Fluctuations in dense fluids with applications to light scattering

The detailed structure of correlation functions in nonequilibrium stationary states is analyzed. The theory is applied to time-correlation functions and static-correlation functions in simple dense fluids. We find that the breaking of time-reversal symmetry induces important changes that cannot be predicted from local-equilibrium theories. The spectrum of light scattered from argon at 235 K and 1 g/${\mathrm{cm}}^3$ subject to a temperature gradient of 0.5 K/cm is computed. We find a pronounced asymmetry in the Brillouin peaks. The static-correlation functions that are usually zero due to time-reversal symmetry are calculated and found to be nonzero and show the existence of a long-range order (1/r decay in physical space). The connection to phenomenology is discussed and a regressionlike hypothesis is shown to be consistent with the microscopic theory once the changes due to symmetry breaking are made.