Can the primordial monopole problem be solved by annihilation

It has been known for some time that grand unified theories, when combined with standard hot big bang cosmology, appear to predict a density of primordial superheavy magnetic monopoles which is far in excess of the known bounds on the present monopole abundance. A possible solution to this ''monopole problem'' is offered by the inflationary universe scenario. However, it remains to be established that the universe passed through an inflationary period; certainly most GUTs do not imply inflation. Even in an inflationary cosmology, a problem can arise from monopoles produced after the inflationary era; this is particularly true in examples (e.g., SO(10)models) with relatively low mass monopoles. It is therefore still worth examining non-inflationary approaches to the problem. The author argues in this article that the most natural of these are those which invoke some particularly efficacious annihilation scheme, and then derives a rather general constraint on such schemes