K. Scharnhorst, D. Robaschik, E. Wieczorek: Quantum field theoretic treatment of the Casimir effect at T > 0 (Real time formulation - free field approximation). Annalen der Physik (Leipzig), 7. Series, 44(1987)351-360 (DOI: 10.1002/andp.19874990507). [SPIRES record]
Abstract: The framework of real time quantum field theory at finite temperature is generalized to include boundary conditions for the electromagnetic field strength tensor. In the perturbation theory the usual Feynman rules remain, only the photon propagator is modified. As a first application the Casimir effect is studied in the free field approximation and the known results are rederived with the new method.