VACUUM RADIATION IN COVARIANT PERTURBATION-THEORY

As a step in approaching the problem of backreaction of the vacuum rad iation, the energy of massless particles created from the vacuum by ex ternal fields is calculated as a functional of these fields. The calcu lation is done for a quantum field coupled to all external fields ente ring the general second-order operator. The mechanism by which the qua ntum noise gets averaged and the positive radiation energy obtains is completely different from the one in two dimensions. For external elec tromagnetic and gravitational fields there appears a quantity, the rad iation moment, that governs both the radiation of classical waves and the quantum particle production. (C) 1997 Elsevier Science B.V.