A Confining Strong First-Order Electroweak Phase Transition
Germano Nardini, Mariano Quiros, Andrea Wulzer
TL;DR
The paper investigates a confining, strong first-order electroweak phase transition within a Randall-Sundrum framework where the radion is stabilized by the Goldberger-Wise mechanism and the Higgs is localized on the IR brane. This setup yields a supercooled transition: the nucleation temperature is much lower than the Standard Model scale, leading to a potential out-of-equilibrium window for electroweak baryogenesis. The authors analyze the GW parameter space under backreaction and consistency constraints, finding that sphalerons are typically inactive inside bubbles, while requiring activity outside yields an upper bound on the number of e-folds (Ne < ~26) and imposes reheating-temperature constraints that favor heavier Higgs masses. Overall, the study connects holographic phase structure, radion stabilization, and electroweak baryogenesis, with implications for inflationary e-folds and TeV-scale physics in warped extra dimensions.
Abstract
In the Randall-Sundrum model where the radion is stabilized by a Goldberger-Wise (GW) potential there is a supercooled transition from a deconfined to a confined phase at temperatures orders of magnitude below the typical Standard Model critical temperature. When the Higgs is localized at the IR brane the electroweak phase transition is delayed and becomes a strong first-order one where the Universe expands by a few e-folds. This generates the possibility of having the out-of-equilibrium condition required by electroweak baryogenesis in the electroweak phase transition. We have studied numerically the region of the GW parameter space where the theory is consistent and the latter possibility is realized. We have found that in most of the parameter space the nucleation temperature is so low that sphalerons are totally inactive inside the bubbles. The condition for sphalerons to be inactive after reheating imposes an upper bound on the reheating temperature that is weaker for heavy Higgs bosons so that the out-of-equilibrium condition seems to favor heavy over light Higgses. The condition for sphalerons to be active outside the bubbles puts an upper bound on the number of e-folds at the phase transition, roughly consistent with the critical value required by low-scale inflation to solve the cosmological horizon problem.