We study the behaviour of the thermal conductivity for an ideal ultra-relativistic gas far from equilibrium by using information theory and the fluctuation-dissipation theorem in nonequilibrium steady states. We compare two different proposals for the nonlinear generalization of the fluctuation- dissipation theorem to the far-from-equilibrium regime. Both proposals lead to a saturation of the heat flux for high temperature gradients, but one of them is in better agreement with the expressions most often used in radiation hydrodynamics.
|Journal||Journal of Physics A: Mathematical and General|
|Publication status||Published - 1 Dec 1995|