Generalizations of the thermal Bogoliubov transformation

Abstract

The thermal Bogoliubov transformation in thermo field dynamics is generalized in two respects. First, a generalization of the $\alpha$--degree of freedom to tilde non--conserving representations is considered. Secondly, the usual $2\times 2$ Bogoliubov matrix is extended to a $4\times 4$ matrix including mixing of modes with non--trivial multiparticle correlations. The analysis is carried out for both bosons and fermions.

20 pages, Latex, Nordita 93/33 P