EFFECTS OF ELECTROWEAK PHASE-TRANSITION DYNAMICS ON BARYOGENESIS AND PRIMORDIAL NUCLEOSYNTHESIS

The evolution of the electroweak phase transition, including reheating due to the release of latent heat in shock waves, is calculated for various values of as yet unknown parameters of electroweak theory such as latent heat and bubble wall surface tension. We find that, for a wide range of parameter space, the bubble walls of the phase transition slow down by as much as a few orders of magnitude. Consequently, we also show that since baryon production can be a sensitive function of bubble wall velocity, it is important to include the effects of reheating in the calculation of the baryon density of the Universe. We show that there is a sensitive velocity dependence for all mechanisms of baryon production, depending on the magnitude of velocity of the bubble wall, and we examine in particular an inverse velocity dependence on baryon production, which is predicted by the charge transport mechanism of baryon production. For this mechanism we find both an enhancement of baryon production and the generation of inhomogeneities during the electroweak phase transition. We calculate the magnitude of the baryon enhancement, which can be as large as a few orders of magnitude, depending on the parameters of the theory, and we calculate the size and amplitude of the inhomogeneities generated. We determine that the inhomogenities generated in a thermally nucleated electroweak phase transition are too small to survive diffusive processes and affect the nucleosynthesis epoch. We also examine the possibility that a phase transition nucleated by other means, such as by the presence of cosmic strings, may produce inhomogeneities that could affect nucleosynthesis. © 1995 The American Physical Society.