The quantum equivalence principle and finite particle creation in expanding universes

Abstract

A formulation of the equivalence principle in quantum field theory is introduced. The quantum equivalence principle yields implementable Bogolyubov transformations. In this way we find a theory for a scalar field in curved space–time where particle creation is finite for every value of the coupling constant. In the particular case of conformal coupling the initial conditions of positive and negative frequency wave functions coincide with the ones of a first order WKB approximation. The coefficients of the Bogolyubov transformations are exactly computed and the created energy density is also finite.