title: Casimir-lifshitz force out of thermal equilibrium and asymptotic nonadditivity.
abstract: We investigate the force acting between two parallel plates held at different temperatures. The force reproduces, as limiting cases, the well-known Casimir-Lifshitz surface-surface force at thermal equilibrium and the surface-atom force out of thermal equilibrium recently derived by M. Antezza et al., Phys. Rev. Lett. 95, 113202 (2005)10.1103/PhysRevLett.95.113202. The asymptotic behavior of the force at large distances is explicitly discussed. In particular when one of the two bodies is a rarefied gas the force is not additive, being proportional to the square root of the density. Nontrivial crossover regions at large distances are also identified.
authors.affiliation: Dipartimento di Fisica, Università di Trento and CNR-INFM R&D Center on Bose-Einstein Condensation, Via Sommarive 14, I-38050 Povo, Trento, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Antezza
authors.forename: Lev P
authors.initials: LP
authors.lastname: Pitaevskii
authors.forename: Sandro
authors.initials: S
authors.lastname: Stringari
authors.forename: Vitaly B
authors.initials: VB
authors.lastname: Svetovoy