Dark Radiation and Dark Matter from Black Holes in the Early Universe
Abstract: If even a relatively small number of black holes were created in theearly universe, they will constitute an increasingly large fraction of thetotal energy density as space expands. It is thus well-motivated to considerscenarios in which the early universe included an era in which primordial blackholes dominated the total energy density. Within this context, I will discussHawking radiation as a mechanism to produce both dark radiation and darkmatter. If the early universe included a black hole dominated era, Hawkingradiation will produce dark radiation at a level ∆Neff ~ 0.03 - 0.2for each light and decoupled species of spin 0, 1/2, or 1. This range is wellsuited to relax the tension between late and early-time Hubble determinations,and is within the reach of upcoming CMB experiments. The dark matter could alsooriginate as Hawking radiation in a black hole dominated early universe,although such dark matter candidates must be very heavy ( mDM ≳ 1011 GeV) ifthey are to avoid exceeding the measured abundance.
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