Primordial Black Holes

Abstract

Primordial black holes are the most plausible realization of quantum black holes. Although there is no definite evidence for their existence, they could provide a unique probe of the early Universe, high-energy physics, extra dimensions and even quantum gravity. In particular, the many limits on the fraction of the Universe going into evaporating ones in the mass range (Forumala Presented). provide important constraints on models of the early Universe. The strongest limits in this range are associated with their effects on big bang nucleosynthesis and the extragalactic photon background. There would also be a strong constraint at lower masses if evaporating black holes leave stable relics and this would have important implications for models of quantum gravity.