title: Nonequilibrium temperatures in steady-state systems with conserved energy.
abstract: We study a class of nonequilibrium lattice models describing local redistributions of a globally conserved quantity, which is interpreted as an energy. A particular subclass can be solved exactly, allowing us to define a statistical temperature T(th) along the same lines as in the equilibrium micro-canonical ensemble. We compute the response function and find that when the fluctuation-dissipation relation is linear, the slope T(FD)(-1) of this relation differs from the inverse temperature T(th)(-1). We argue that T(th) is physically more relevant than T(FD), since in the steady-state regime, it takes equal values in two subsystems of a large isolated system. Finally, a numerical renormalization group procedure suggests that all models within the class behave similarly at a coarse-grained level, leading to a parameter that describes the deviation from equilibrium. Quantitative predictions concerning this parameter are obtained within a mean-field framework.
authors.affiliation: Department of Theoretical Physics, University of Geneva, CH-1211 Geneva 4, Switzerland.
authors.forename: Eric
authors.initials: E
authors.lastname: Bertin
authors.forename: Olivier
authors.initials: O
authors.lastname: Dauchot
authors.forename: Michel
authors.initials: M
authors.lastname: Droz