Primordial black holes and short gamma-ray bursts

The possible existence of primordial black holes (PBHs) has long been a key observational question. At present, the only known way to detect low-mass ones (below 10(15) g) is through the Hawking radiation process. This radiat ion in turn depends on the nature of hadron interactions in the 100 MeV reg ion and beyond. In the case of a first-order quantum-chromodynamics phase t ransition, we expect a sharp burst of gamma rays from the PBH. We have poin ted out that there is a class of gamma-ray bursts that have this property a nd could provide evidence for PBHs in the galaxy. Future study of these eve nts is crucial. Recently, we have shown that a diffuse gamma-ray glow shoul d exist in the halo from these PBHs. There now seems to be evidence for thi s effect as well. (C) 1998 Elsevier Science B.V. All rights reserved.