Very short gamma-ray bursts and primordial black hole evaporation

The search for high energy gamma-ray bursts from primordial black holes has continued for the past 20 years. No positive evidence for the existence of evaporating black holes has been reported. We discuss a very interesting group of gamma-ray bursts of very short time duration and an increasing hard spectrum from the published BATSE catalog. We point out that the trend, i.e., anti-correlation of hardness ratio versus gamma-ray burst duration, would be expected if some of the short gamma-ray bursts came from black holes evaporation. We also study the spatial distribution of these event and a possible fireball model of the PBH evaporation. Future tests for the black hole hypothesis is suggested.