Ultraviolet freeze-in with a time-dependent inflaton decay

It is typically assumed that during reheating the inflaton decays with a constant decay width. However, this is not guaranteed and can have a strong impact on the dark matter (DM) genesis. In the context of the ultraviolet (UV) freeze-in mechanism, if the operators connecting the dark and visible sectors are of sufficiently high mass dimension, the bulk of the DM abundance is produced during and not after reheating. We study here the impact of a time-dependent decay width of the inflaton on the DM abundance, emphasizing the differences with respect to the cases where the decay is either instantaneous or constant. We also provide concrete examples for DM production via UV freeze-in, e.g., from 2-to-2 scatterings of standard model particles, or from inflaton scatterings or decays, elucidating how the time-dependence influences the DM yield.

Automated summary

This paper investigates the impact of the time-dependent decay width of the inflaton on the abundance of dark matter (DM) during the reheating period. The study demonstrates that the time-dependence of the decay width has different effects on the DM abundance compared to instantaneous or constant decay. Concrete examples of DM production through 2-to-2 scatterings of standard model particles or via inflaton scatterings or decays are provided to elucidate how the time-dependence influences the yield of DM.