The Inflaton Portal to Dark Matter

TL;DR

This paper explores a model where the inflaton is part of the dark sector, interacting with the standard model via a portal, leading to a natural, non-thermal dark matter relic density through freeze-in production.

Contribution

It introduces a unified complex field for inflaton and dark matter, charged under different global symmetries, and demonstrates a natural freeze-in production mechanism post-reheating.

Findings

Dark matter relic density achieved via inflaton decay suppression

Model naturally avoids initial condition tuning

Dark matter and pseudo-scalar are light pseudo Nambu-Goldstone bosons

Abstract

We consider the possibility that the inflaton is part of the dark sector and interacts with the standard model through a portal interaction with a heavy complex scalar field in equilibrium with the standard model at high energies. The inflaton and dark matter are encapsulated in a single complex field and both scalar sectors are charged under different (approximate) global U(1)'s such that the dark matter, as well as the visible pseudo-scalar are taken to be relatively light, as pseudo Nambu-Goldstone bosons of the theory. The dark matter relic density is populated by Freeze-In productions through the inflaton portal. In particular, after the reheating, production of dark matter by inflaton decay is naturally suppressed thanks to Planck stringent constraints on the dark quartic coupling, therefore preserving the non thermal scenario from any initial condition tuning.