The avoidance of singularity in a friedmann universe by particle production

Abstract

When a self-interacting field presents classically several stable homogeneous ground states of different energy, a semiclassical description of the field predicts transition by barrier penetration to the state of minimum energy. If gravitational effects are considered in a minimally coupled system a singularity of space-time appears when the minimal value of the energy is negative. In this paper we analyze a similar problem, but for a self-interacting field non-minimally coupled to gravitation. First we show that the classical behaviour of the system remains unchanged. Afterwards we prove that when particle production generated by the time-varying gravitational field is taken into account, the singularity can be avoided.