Gravitational Portals with Non-Minimal Couplings

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.

Comments: 14 pages, 8 figures