Gamma-ray bursts from the final stage of primordial black hole evaporation

It is now accepted that, within the Standard Model of particles, evaporating primordial black holes cannot produce detectable gamma-ray bursts 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, producing a burst of duration 10(-1)-10(3)s. We show that when the black hole temperature exceeds similar to 10 GeV, the charged particle outflow from a black hole forms a well-defined plasma and the magnetohydrodynamical regime of expansion may be realized, In this case, the kinetic energy of particles may be converted into soft gamma-rays due to the synchrotron radiation and the electromagnetic cascade in the close-to-equipartition turbulent magnetic field, We show that some of the gamma-ray bursts detected by BATSE can be associated with evaporating black holes.