Reheating predictions in Gravity Theories with Derivative Coupling

TL;DR

This paper explores how non-minimal derivative coupling in gravity theories affects inflationary predictions, especially reheating and CMB observables, offering potential tests for such models.

Contribution

It demonstrates that NMDC influences reheating temperature and spectral tilt, providing a way to distinguish these models observationally.

Findings

NMDC models predict higher reheating temperatures.

Different ranges for spectral tilt $n_s$ and tensor-to-scalar ratio $r$.

Potential for observational tests with current and future CMB data.

Abstract

We investigate the inflationary predictions of a simple Horndeski theory where the inflaton scalar field has a non-minimal derivative coupling (NMDC) to the Einstein tensor. The NMDC is very motivated for the construction of successful models for inflation, nevertheless its inflationary predictions are not observationally distinct. We show that it is possible to probe the effects of the NMDC on the CMB observables by taking into account both the dynamics of the inflationary slow-roll phase and the subsequent reheating. We perform a comparative study between representative inflationary models with canonical fields minimally coupled to gravity and models with NMDC. We find that the inflation models with dominant NMDC generically predict a higher reheating temperature and a different range for the tilt of the scalar perturbation spectrum $n_s$ and scalar-to-tensor ratio $r$, potentially testable by current and future CMB experiments.