BLACK-HOLES FROM NUCLEATING STRINGS

We evaluate the probability that a loop of string that has spontaneous ly nucleated during inflation will form a black hole upon collapse, af ter the end of inflation. We then use the observational bounds on the density of primordial black holes to put constraints on the parameters of the model. Combining these constraints with current upper limits o n the expansion rate during inflation, we conclude that the density of black holes formed from nucleating strings is too low to be observed. Also, constraints on domain wall nucleation and monopole pair product ion during inflation are briefly discussed.