Scalaron-driven Dark Matter during Warm Inflation via UV Freeze--in

Abstract

We investigate the production of Dark Matter (DM) within the warm Higgs--Starobinsky (HS) inflation. By adopting the ultraviolet (UV) freeze--in mechanism -- where the DM number density is initially negligible but is populated over time through non-renormalizable interactions of defined mass dimensions -- we find that the DM production within the HS potential has a characteristic timing. For both DM masses, $m_χ=1$ MeV and $m_χ=100$ GeV, the yield of DM occurs close to the termination of inflation and its transition to the radiation dominated (RD) era. The present--day DM relic abundance is generated for both DM masses with non-renormalizable operators of mass dimension $D=\{8,9\}$ within strong dissipation regimes. The obtained results suggest that the form of the HS potential and the associated scalaron dynamics favor UV freeze--in DM production as the scalaron approaches the minimum of the potential, where energy transfer to the thermal bath becomes particularly efficient. This distinctive transition behavior differentiates the HS model from other inflationary models and advances our understanding of DM production.