THERMAL AND DYNAMICAL PARTICLE CREATION IN A CURVED GEOMETRY

A generalization of thermo field dynamics to a curved geometry is prop osed. In particular a neutral scalar field minimally coupled to gravit y is considered as matter content in a Robertson-Walker metric. A nonl inear amplification in the particle creation is obtained, due to the a ltogether action of thermal and geometric effects. As a consequence th e frequencies in the system look red-shifted with respect to the case where the thermal creation is not taken into account. (C) 1998 Academi c Press.