Quantum Corrections to the Cosmological Evolution of Conformally Coupled Fields

TL;DR

This paper calculates quantum corrections to the evolution of conformally coupled scalar fields in the early universe, revealing potential phases of contraction and bounce that impact relic abundances and cosmological models.

Contribution

It introduces finite temperature radiative corrections to the source term of conformally coupled fields, affecting their cosmological evolution and potential early universe dynamics.

Findings

Quantum corrections induce a non-zero source term during radiation era.

Possible early contraction and bounce phases in the universe's evolution.

Implications for relic abundances and the gravitino problem.

Abstract

Because the source term for the equations of motion of a conformally coupled scalar field, such as the dilaton, is given by the trace of the matter energy momentum tensor, it is commonly assumed to vanish during the radiation dominated epoch in the early universe. As a consequence, such fields are generally frozen in the early universe. Here we compute the finite temperature radiative correction to the source term and discuss its consequences on the evolution of such fields in the early universe. We discuss in particular, the case of scalar tensor theories of gravity which have general relativity as an attractor solution. We show that, in some cases, the universe can experience an early phase of contraction, followed by a non-singular bounce, and standard expansion. This can have interesting consequences for the abundance of thermal relics; for instance, it can provide a solution to the gravitino problem. We conclude by discussing the possible consequences of the quantum corrections to the evolution of the dilaton.