Primordial Black Hole Minimum Mass

In this talk I revisit thermodynamic constraints on primordial black hole (PBH) formation in the early universe. Under the assumption that PBH mass is equal to the cosmological horizon mass, one can use the 2nd Law of Black Hole Thermodynamics to put a lower limit on the PBH mass. In models of PBH formation, however, PBHs are created at some fraction of the horizon mass. I show that this thermodynamic constraint still holds for subhorizon PBH formation.