ABSTRACT
This chapter describes fluctuation phenomena are automatically neglected. It is well known, however, that various fluctuations, in particular electromagnetic fluctuations, play a very significant role in physics and astrophysics. The energy of the electromagnetic field in an absorbing medium is generally just a small part of the total energy of the thermal motion in a medium. Energy dissipation in macroscopic systems with significant quantum effects has attracted increasing interest and has been studied using various methods. The role played by this energy is perhaps not quite clear and must be additionally analysed, at least for "unusual" media. The permittivities are, of course, assumed to be arbitrary at the end of the calculations, so that they correspond to real media. The energy levels for the total system are, of course, discrete.
