Defrosting in an Emergent Galileon Cosmology

TL;DR

This paper investigates the transition from an emergent Galileon condensate phase to a radiation-dominated universe, demonstrating that matter coupling leads to efficient defrosting analogous to preheating in inflationary models.

Contribution

It shows that minimal matter coupling to the Galileon field suffices for efficient defrosting, considering universe expansion effects, extending understanding of early universe transitions.

Findings

Minimal matter coupling enables efficient defrosting.

Expansion effects influence the coupling requirements.

Efficient transition from Galileon phase to radiation era.

Abstract

We study the transition from an Emergent Galileon condensate phase of the early universe to a later expanding radiation phase. This "defrosting" or "preheating" transition is a consequence of the excitation of matter fluctuations by the coherent Galileon condensate, in analogy to how preheating in inflationary cosmology occurs via the excitation of matter fluctuations through coupling of matter with the coherent inflaton condensate. We show that the "minimal" coupling of matter (modeled as a massless scalar field) to the Galileon field introduced by Creminelli, Nicolis and Trincherini in order to generate a scale-invariant spectrum of matter fluctuations is sufficient to lead to efficient defrosting, provided that the effects of the non-vanishing expansion rate of the universe are taken into account. If we neglect the effects of expansion, an additional coupling of matter to the Galileon condensate is required. We study the efficiency of the defrosting mechanism in both cases.