title: Thermal Casimir versus Casimir-Polder forces: equilibrium and nonequilibrium forces.
abstract: We critically discuss whether and under what conditions Lifshitz theory may be used to describe thermal Casimir-Polder forces on atoms or molecules. An exact treatment of the atom-field coupling reveals that for a ground-state atom (molecule), terms associated with virtual-photon absorption lead to a deviation from the traditional Lifshitz result; they are identified as a signature of nonequilibrium dynamics. Even the equilibrium force on a thermalized atom (molecule) may be overestimated when using the ground-state polarizability instead of its thermal counterpart.
authors.affiliation: Quantum Optics and Laser Science, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom.
authors.forename: Stefan Yoshi
authors.initials: SY
authors.lastname: Buhmann
authors.forename: Stefan
authors.initials: S
authors.lastname: Scheel