Derivative Expansion for the Electromagnetic Casimir Free Energy at High Temperatures

C. D. FOSCO, F. C. LOMBARDO, AND F. D. MAZZITELLI

PHYSICAL REVIEW D - PARTICLE AND FILDS

American Institute of Physics

Lugar: New York; Año: 2015 vol. 92 p. 1250071 - 1250079

0556-2821

We study the contribution of the thermal zero modes to the Casimir freeenergy, in the case of a fluctuating electromagnetic (EM) field in the presenceof real materials described by frequency-dependent, local and isotropicpermittivity (ϵ) and permeability (μ) functions.Those zero modes, present at any finite temperature, become dominant at hightemperatures, since the theory is dimensionally reduced. Our work, within thecontext of the Derivative Expansion (DE) approach, focusses on the emergence ofnon analyticities in that dimensionally reduced theory. We conclude that the DEis well defined whenever the function Ω(ω), defined by[Ω(ω)]2≡ω2ϵ(ω), vanishes in thezero-frequency limit, for at least one of the two material media involved.