Baryon Asymmetry from Electroweak-Symmetric Domain Walls

Abstract: We investigate electroweak baryogenesis from domain walls with electroweak-symmetric cores moving through the electroweak-broken plasma. In the thick-wall regime, CP-violating semiclassical forces generate chiral asymmetries that source baryon number through transport and weak sphaleron processes. We show that the baryon yield is governed by the hierarchy between the wall width, the CP-violating source width, and the diffusion length, and we identify the corresponding scaling behavior in the relevant parametric limits. A distinctive feature of this mechanism is the interference between the two faces of the domain wall, which leads to qualitatively different behavior for CP-violating sources that are even or odd under wall-orientation reversal. We construct a simplified description that captures these effects and reproduces the predictions of the full transport system in a broad range of parameter space. Applying our framework to a singlet-extended Standard Model, we delineate the region in which electroweak-symmetric domain walls can generate the observed baryon asymmetry.