Noise induced transitions in semiclassical cosmology

TL;DR

This paper demonstrates that quantum fluctuations and back-reaction effects can induce a transition from a near-zero scale factor to an inflationary universe in semiclassical cosmology, highlighting the importance of matter fields in quantum cosmological models.

Contribution

It introduces a model showing how quantum back-reaction can facilitate universe creation from initial singularity to inflation, emphasizing matter fields' role.

Findings

Quantum fluctuations induce a transition to inflation.

Transition probability is comparable to tunneling from 'nothing'.

Back-reaction effects are significant in quantum cosmology.

Abstract

A semiclassical cosmological model is considered which consists of a closed Friedmann-Robertson-Walker in the presence of a cosmological constant, which mimics the effect of an inflaton field, and a massless, non-conformally coupled quantum scalar field. We show that the back-reaction of the quantum field, which consists basically of a non local term due to gravitational particle creation and a noise term induced by the quantum fluctuations of the field, are able to drive the cosmological scale factor over the barrier of the classical potential so that if the universe starts near zero scale factor (initial singularity) it can make the transition to an exponentially expanding de Sitter phase. We compute the probability of this transition and it turns out to be comparable with the probability that the universe tunnels from "nothing" into an inflationary stage in quantum cosmology. This suggests that in the presence of matter fields the back-reaction on the spacetime should not be neglected in quantum cosmology.