GAMMA-RAY BURSTS FROM THE FINAL STAGE OF PRIMORDIAL BLACK-HOLE EVAPORATION

It is now accepted that, within the Standard Model of particles, evapo rating primordial black holes cannot produce detectable gamma-ray burs ts because the expected photon flux from black hole explosions is too weak, and consists mainly of GeV photons, Contrary to this verdict, we put forward a scenario in which a large fraction of black black hole power is converted into photon luminosity in the MeV spectral range, p roducing a burst of duration 10(-1)-10(3)s. We show that when the blac k hole temperature exceeds similar to 10 GeV, the charged particle out flow from a black hole forms a well-defined plasma and the magnetohydr odynamical regime of expansion may be realized, In this case, the kine tic energy of particles may be converted into soft gamma-rays due to t he synchrotron radiation and the electromagnetic cascade in the close- to-equipartition turbulent magnetic field, We show that some of the ga mma-ray bursts detected by BATSE can be associated with evaporating bl ack holes.