Graceful exit from inflation and reheating with twin waterfall scalar fields

Abstract

We study hybrid inflation with a pseudo-Nambu-Goldstone boson inflaton and two waterfall scalar fields. The Z2 symmetry for the waterfall fields keeps the inflaton potential flat against quantum corrections coming from the waterfall couplings, and it is broken spontaneously in the vacuum without a domain-wall problem within the Hubble horizon of our Universe. We show that the Z2-invariant Higgs portal couplings to the waterfall fields are responsible for the reheating process, leading to a sufficiently large reheating temperature after inflation. In the presence of an extra Z2′ symmetry, one of the waterfall fields or another singlet scalar field becomes a dark matter candidate. In particular, we find that preheating is sufficient to account for the correct relic density of the waterfall dark matter. © 2023 authors. Published by the American Physical Society.