John March-Russell (Oxford U.)
We present a gravitational, infra-red-calculable, production mechanism for both the dark matter and the hot Big Bang SM plasma. The source of both is a primordial density of micro black holes, which evaporate via Hawking emission into both the dark and SM sectors. We show the mechanism has four qualitatively different regimes depending upon whether the black hole evaporation is `fast' or `slow' relative to the initial Hubble rate, and whether the mass of the dark matter particle is `light' or `heavy' compared to the initial black hole temperature. In the `slow' regime the dark matter yield is remarkably insensitive to initial conditions. In all cases the dark matter is produced with a highly non-thermal energy spectrum, leading, in the `light' dark matter mass regime, to a strong constraint from free-streaming, but also possible observational signatures in structure formation. The `heavy' dark matter mass regime (~10^8 GeV to Planck mass depending on spin) is free of these constraints and provides new possibilities for dark matter detection. In all cases there is a dark radiation component predicted.