Particle production and Higgs reheating

TL;DR

This paper demonstrates that gravitational effects alone can reheat the Universe after inflation by producing particles through curvature oscillations, specifically in Higgs inflation models with non-minimal coupling.

Contribution

It introduces a curvature-driven particle production mechanism in Higgs inflation, showing how gravity alone can reheat the Universe without explicit couplings.

Findings

Gravitational particle production occurs via curvature oscillations after inflation.

The mechanism efficiently reinitiates the hot thermal bath necessary for the Standard Model.

Reheating can be achieved without direct inflaton couplings in minimal models.

Abstract

Reheating is essential for transforming the cold, vacuum dominated Universe at the end of inflation into the hot thermal bath required by the Standard Model. In many well motivated inflationary models, however, the inflaton has no direct couplings to other fields, raising the question of how the Universe becomes repopulated with particles. We address this question within the framework of geometric reheating, where energy transfer occurs purely through gravitational effects. Focusing on a Higgs inflationary scenario with a non-minimal curvature coupling $\xi \phi^2 R$, we derive the post-inflationary dynamics and compute particle production using the Bogoliubov formalism. We show that the rapid, oscillatory evolution of the curvature scalar after inflaton acts as a time dependent gravitational pump, creating scalar spectator particles even in the absence of explicit interactions. This curvature driven production mechanism provides a natural and efficient route to reheating, demonstrating that gravity alone can initiate the standard thermal history and bridge inflation with radiation domination in minimal, coupling free models of the early Universe.