UC Irvine

While the Standard Model of particle physics has been extremely successful in describing particle interactions, there are still phenomena that remain unexplained. The asymmetry between matter and antimatter in our universe is one of the most obvious unanswered questions, and the lack of a fundamental understanding of the origin of the parameters in the flavor sector is another important unanswered question. It might be possible for a mechanism to address both of the above issues. If the electroweak phase transition was first order, it could be possible to create the observed matter-antimatter asymmetry during this time. Additionally, it has been proposed that large Yukawa couplings could generate the necessary CP-violation to produce the observed baryon asymmetry that the Standard Model currently lacks. This may be implemented via the Froggatt-Nielsen mechanism, which would have the additional benefit of addressing the problem in the flavor sector as well. It has been proposed that implementing the Froggatt-Nielsen mechanism to produce large Yukawa couplings that vary during the electroweak phase transition could produce a strong enough phase transition needed for successful electroweak baryogenesis. First order phase transitions proceed via the nucleation of bubbles, which percolate and expand, eventually filling the entire universe with the new phase. Calculating the bubble nucleation rate is not always simple, and it has been pointed out that in some models with an additional scalar, bubbles actually fail to nucleate. This means that where a first-order phase transition is naively expected, there is actually no phase transition at all. The study of bubble nucleation in the case of large Yukawa couplings that vary during the electroweak phase transition will be undertaken here, and we will see that the potential barrier height plays an important role in the nucleation of bubbles.