title: Dependence of the fluctuation-dissipation temperature on the choice of observable.
abstract: On general grounds, a nonequilibrium temperature can be consistently defined from generalized fluctuation-dissipation relations only if it is independent of the observable considered. We argue that the dependence on the choice of observable generically occurs when the phase-space probability distribution is nonuniform on constant energy shells. We relate quantitatively this observable dependence to a fundamental characteristics of nonequilibrium systems, namely, the Shannon entropy difference with respect to the equilibrium state with the same energy. This relation is illustrated on a mean-field model in contact with two heat baths at different temperatures.
authors.affiliation: Department of Theoretical Physics, University of Geneva, CH-1211 Geneva 4, Switzerland.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Martens
authors.forename: Eric
authors.initials: E
authors.lastname: Bertin
authors.forename: Michel
authors.initials: M
authors.lastname: Droz