  Solitons in extensions of the Standard Model can serve as localized sources
of CP violation. Depending on their stability properties, they may serve either
to create or to deplete the baryon asymmetry. The conditions for existence of a
particular soliton candidate, the membrane solution of the two-Higgs model, are
presented. In the generic case, investigated by Bachas and Tomaras, membranes
exist and are metastable for a wide range of parameters. For the more viable
supersymmetric case, it is shown that the present-day existence of CP-violating
membranes is experimentally excluded, but preliminary studies suggest that they
may have existed in the early universe soon after the electroweak phase
transition, with important consequences for the baryon asymmetry of the
universe.
