Superconductivity Solves the Monopole Problem for Alice Strings
  Alice strings are cosmic strings that turn matter into antimatter. Although they arise naturally in many GUT's, it has long been believed that because of the monopole problem they can have no cosmological effects. We show this conclusion to be false; by using the Langacker-Pi mechanism, monopoles can in fact be annihilated while Alice strings are left intact. This opens up the possibility that they can after all contribute to cosmology, and we mention some particularly important examples. 
Shahar Ben-Menahem and Adrian Cooper