The Effects of Electro-weak Phase Transition Dynamics on Baryogenesis and Primordial Nucleosynthesis

TL;DR

The paper addresses how electroweak phase-transition dynamics, especially bubble-wall velocity and latent-heat reheating, shape baryogenesis and primordial nucleosynthesis. It develops a damping-based framework for wall propagation and analyzes the charge-transport mechanism, showing that baryon production can be substantially enhanced and inhomogeneities can form during the transition, though thermal nucleation-induced inhomogeneities generally dissipate before nucleosynthesis. By categorizing three dynamical regimes (detonations and two deflagration cases) and computing the resulting baryon-density evolution, it demonstrates that phase-transition dynamics can relax constraints on CP-violation parameters while predicting observable but often diffused inhomogeneities. The work also highlights seed-nucleation scenarios (e.g., cosmic strings) as a potential path to larger-scale inhomogeneities that could affect nucleosynthesis, underscoring the interplay between microphysical EW parameters and cosmological observables.

Abstract

The evolution of the electro-weak 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 electro-weak theory such as latent heat and bubble wall surface tension. We show that baryon production, which occurs in the vicinity of the bubble walls of the phase transition, can be a sensitive function of bubble wall velocity, and this velocity dependence is important to include in the calculation of the baryon density of the universe. 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 electro-weak 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 inhomogeneities generated in a thermally nucleated electro-weak phase transition are to small to survive diffusive processes and effect 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 effect