On gravitational preheating

TL;DR

This paper investigates gravitationally mediated dark matter production during inflaton oscillations, highlighting the significance of higher-dimensional operators, especially dimension-6, in generating the observed dark matter abundance.

Contribution

It introduces the role of higher-dimensional gravitational operators, particularly dimension-6, in dark matter production during the inflaton epoch, emphasizing their dominance over derivative operators.

Findings

Non-derivative dimension-6 operators dominate production.

Small Wilson coefficients can still yield correct dark matter abundance.

Both perturbative and non-perturbative regimes are analyzed.

Abstract

We consider dark matter production during the inflaton oscillation epoch. It is conceivable that renormalizable interactions between dark matter and inflaton may be negligible. In this case, the leading role is played by higher dimensional operators generated by gravity and thus suppressed by the Planck scale. We focus on dim-6 operators and study the corresponding particle production in perturbative and non-perturbative regimes. We find that the dark matter production rate is dominated by non-derivative operators involving higher powers of the inflaton field. Even if they appear with small Wilson coefficients, such operators can readily account for the correct dark matter abundance.