Gravitational Portals with Non-Minimal Couplings

TL;DR

This paper investigates how non-minimal couplings of scalar fields to gravity influence dark matter production and reheating temperature, revealing significant effects for couplings greater than one.

Contribution

It provides a detailed analysis of non-minimal scalar-curvature couplings' impact on dark matter abundance and reheating, offering model-independent temperature limits.

Findings

Non-minimal couplings can significantly increase reheating temperature.

Couplings greater than one dominate over minimal gravitational interactions.

A model-independent maximum temperature of about 10^{12} GeV is established.

Abstract

We consider the effects of non-minimal couplings to curvature of the form $\xi_S S^2 R$, for three types of scalars: the Higgs boson, the inflaton, and a scalar dark matter candidate. We compute the abundance of dark matter produced by these non-minimal couplings to gravity and compare to similar results with minimal couplings. We also compute the contribution to the radiation bath during reheating. The main effect is a potential augmentation of the maximum temperature during reheating. A model independent limit of $\mathcal{O}(10^{12})$ GeV is obtained. For couplings $\xi_S \gtrsim \mathcal{O}(1)$, these dominate over minimal gravitational interactions.