Astrophysical constraints on primordial black hole formation from collapsing cosmic strings

Primordial black holes (PBH) may have formed from the collapse of cosmic st ring loops. The spectral shape of the PBH mass spectrum can be determined b y the scaling argument for string networks. Limits on the spectral amplitud e derived from extragalactic gamma-ray and galactic gamma-ray and cosmic ra y flux observations as well as constraints from the possible formation of s table black holes remnants are reanalyzed. The new constraints are remarkab ly close to those derived from the normalization of the cosmic string model to the cosmic microwave background anisotropies. (C) 1998 Published by Els evier Science B.V. All rights reserved.