BARYOGENESIS FROM UNSTABLE DOMAIN-WALLS

There exists a class of cosmic strings that turn matter into antimatter (Alice strings). In a GUT where the unbroken gauge group contains charge conjugation (C), such strings form when a phase transition renders C a discrete symmetry. They become boundaries of domain walls at a later, C-breaking transition. These ''Alice walls'' are cosmologically harmless, but can play an important role in baryogenesis. We present a three-generation toy model with scalar baryons, where a quasi-static Alice wall (or a gas of such walls) temporarily gives rise to net baryogenesis of uniform sign everywhere in space. This becomes a permanent baryon excess if the wall shrinks away early enough, We comment on the possible relevance of a similar mechanism to baryogenesis in a realistic SO(10) unification model, where Alice walls would form at the scale of left-right symmetry breaking.