Statistical physics and fluctuations in ballistic non-equilibrium systems

In nonequilibrium systems in the ballistic transport regime, every point of the system contains particles arriving from different regions - each of them at different temperatures - and there are only few collisions, in such a way that equilibrium between the different Populations Will be reached very slowly. Here, we tentatively approach the local distribution function by a superposition of local-equilibrium distribution functions With different temperatures, corresponding to the different starting positions of the particles. In a second-order expansion, we find a distribution function which depends not only oil the Hamiltonian H but also on H-2, and we study the additional contribution to energy fluctuations. (c) 2009 Elsevier B.V. All rights reserved.