Cosmic rays from primordial black holes and constraints on the early universe

The constraints on the number of evaporating primordial black holes imposed by observations of the cosmological gamma-ray background do not exclude th eir making a significant contribution to the Galactic flux of cosmic ray ph otons, electrons, positrons and antiprotons. Even if this contribution is s mall, cosmic ray data place important limits on the number of evaporating b lack holes and thereby on models of the early Universe. Evaporating black h oles are unlikely to be detectable in their final explosive phase unless ne w physics is invoked at the QCD phase transition. (C) 1998 Published by Els evier Science B.V. All rights reserved.