ELECTROWEAK BARYOGENESIS IN THE ADIABATIC LIMIT

Electroweak baryogenesis can occur in the ''adiabatic limit'', in whic h expanding bubbles of true vacuum are assumed to have rather thick wa lls and be slowly moving. Here the problem of calculating the baryon a symmetry in this limit is reconsidered. A simple prescription for obta ining the relevant kinetic equations is given. An additional suppressi on beyond that usually assumed is found. This arises because the gener ation of an asymmetry requires violation of approximately conserved cu rrents by Higgs expectation values, which are small near the front of the walls. As applications, the asymmetries in multi-Higgs models and the minimal supersymmetric standard model are estimated to be proporti onal to alpha(w)8 and alpha(w)6 respectively. Also, in this limit the baryon asymmetry in the minimal standard model is extraordinarily smal l.