Gamma-ray bursts from the final stage of primordial black hole evaporation
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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 hole power is converted into photon luminosity in the MeV spectral range, producing a burst of duration 10-1-103 s. We show that when the black hole temperature exceeds 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.