Ultraviolet Freeze-in with a Time-dependent Inflaton Decay

Understand

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.