Dynamical structure factor of a fluid in nonequilibrium steady states

The dynamical structure factor of a nonequilibrium fluid is found by a method based on the system of equations for the correlation functions of fluctuating hydrodynamic fields and random fluxes. The nonequilibrium corrections to the Brillouin lines are calculated to the second order in the steady temperature gradient. It is shown that in the presence of velocity and temperature gradients the Rayleigh line is asymmetric because of the resonant interaction of the viscous and thermal fluctuations.