Finite-temperature electromagnetic-field quantization in a medium: The thermofield approach

Abstract

Starting from a Lagrangian, an electromagnetic field is quantized in the presence of a medium in thermal equilibrium and also in a medium with time-varying temperature. The vector potential for both equilibrium and nonequilibrium cases is obtained and vacuum fluctuations of the fields are calculated. As an illustrative example, the finite-temperature decay rate and level shift of an atom in a polarizable medium are calculated in this approach. © 2011 American Physical Society.