Reheating in Gauss-Bonnet-coupled inflation

TL;DR

This paper explores the potential of Gauss-Bonnet-coupled inflation models to produce favorable cosmological power spectra while addressing the challenges of reheating, proposing a minimal model extension that allows perturbative reheating and analyzing its implications.

Contribution

The paper identifies limitations of inverse power law coupling in reheating and introduces a minimal generalization enabling perturbative reheating in Gauss-Bonnet inflation models.

Findings

Reheating cannot occur in inverse power law coupling models due to lack of oscillatory solutions.

Instant preheating and gravitational particle production are ineffective in these models.

A minimal model extension allows perturbative reheating with modified dynamics and power spectrum predictions.

Abstract

We investigate the feasibility of models of inflation with a large Gauss-Bonnet coupling at late times, which have been shown to modify and prevent the end of inflation. Despite the potential of Gauss-Bonnet models in predicting favourable power spectra, capable of greatly lowering the tensor-to-scalar-ratio compared to now-disfavoured models of standard chaotic inflation, it is important to also understand in what context it is possible for post-inflationary (p)reheating to proceed and hence recover an acceptable late-time cosmology. We argue that in the previously-studied inverse power law coupling case, reheating cannot happen due to a lack of oscillatory solutions for the inflaton, and that neither instant preheating nor gravitational particle production would avoid this problem due to the persistence of the inflaton's energy density, even if it were to partially decay. Hence we proceed to define a minimal generalisation of the model which can permit perturbative reheating and study the consequences of this, including heavily modified dynamics during reheating and predictions of the power spectra.