Radiative corrections to the Casimir Pressure under the influence of temperature and external fields

Generalizing the quantum field theory (QFT) with boundary conditions in covariant gauge to the case of finite temperature, we develop the quantum electrodynamics (QED) with boundary conditions in the Matsubara approach as well as in the thermofield formulation. We rederive the known results of the free-field theory for the pressure and the free energy of the Casimir problem. For infinitely thin plates we calculate the radiative corrections in second-order perturbation theory at finite temperature. Thereby it turns out that the calculation in of the vacuum energy at the vanishing temperature via the Z functional is much simplier than the calculation via the energy momentum tensor. This observation allows determination of the influence of static electromagnetic fields on the Casimir problem. copyright 1987 Academic Press, Inc