Electroweak Baryogenesis without the Phase Transition

Abstract

Radiation domination at the electroweak epoch is a simplifying assumption, but one for which there is no observational basis. Treating the expansion rate as a variable, I re-examine electroweak baryogenesis in various scenarios. At a first order phase transition the main effect is on the sphaleron bound, which becomes a lower bound on the expansion rate in any given theory. At a second-order or cross-over phase transition, the created baryon asymmetry is directly proportional to the expansion rate. I sketch an alternative post-inflationary cosmology, in which the kinetic energy of a scalar field dominates the Universe until shortly before nucleosynthesis, and argue that the observed baryon asymmetry could be produced in this case even at an analytic cross-over.