Inflaton dark matter from incomplete decay

TL;DR

This paper proposes a mechanism where the inflaton field's incomplete decay after inflation can produce a stable dark matter relic, linking inflationary dynamics with dark matter abundance.

Contribution

It introduces a novel scenario where inflaton decay is kinematically forbidden at late times, resulting in a natural dark matter candidate from incomplete decay.

Findings

Inflaton decay can be incomplete yet reheat the universe successfully.

Inflaton particles can thermalize, decouple, and freeze out as dark matter.

The mechanism applies to both single-field and hybrid inflation models.

Abstract

We show that the decay of the inflaton field may be incomplete, while nevertheless successfully reheating the universe and leaving a stable remnant that accounts for the present dark matter abundance. We note, in particular, that since the mass of the inflaton decay products is field-dependent, one can construct models, endowed with an appropriate discrete symmetry, where inflaton decay is kinematically forbidden at late times and only occurs during the initial stages of field oscillations after inflation. We show that this is sufficient to ensure the transition to a radiation-dominated era and that inflaton particles typically thermalize in the process. They eventually decouple and freeze out, yielding a thermal dark matter relic. We discuss possible implementations of this generic mechanism within consistent cosmological and particle physics scenarios, for both single-field and hybrid inflation.