Extinction theorem, dispersion forces, and latent heat.

Abstract

We show that multiple dipole scattering of zero-point radiation gives rise to the nonadditive contributions to the van der Waals dispersion interaction, and use the Ewald-Oseen extinction theorem to justify the Lifshitz theory of macroscopic (Casimir) effects of intermolecular van der Waals forces in the limit of continuous media. We derive the interaction energy between an atom and a dielectric medium of identical atoms and obtain, using standard cavity-QED'' methods, results identical to those of the source theory of Schwinger, DeRaad, and Milton (Ann. Phys. (N.Y.) 115, 1 (1978)). Following Schwinger, DeRaad, and Milton, we apply the results to estimate the latent heat of liquid helium. We argue that the macroscopic theory does not unambiguously justify the conclusion that the dispersion interaction makes a significant contribution to the latent heat and surface tension. Simpler and well-established microscopic models, without the divergences incurred in the macroscopic theory, are invoked to support this conclusion.