  An analysis of cosmic string breaking with the formation of black holes
attached to the ends reveals a remarkable feature: the black holes can be
correlated or uncorrelated. We find that, as a consequence, the
number-of-states enhancement factor in the action governing the formation of
uncorrelated black holes is twice the one for a correlated pair. We argue that
when an uncorrelated pair forms at the ends of the string, the physics involved
is more analogous to thermal nucleation than to particle-antiparticle creation.
Also, we analyze the process of intercommuting strings induced by black hole
annihilation and merging. Finally, we discuss the consequences for grand
unified strings. The process whereby uncorrelated black holes are formed yields
a rate which significantly improves over those previously considered, but still
not enough to modify string cosmology.
