Electroweak and Left-Right Phase Transitions in $SO(5) \times U(1) \times SU(3)$ Gauge-Higgs Unification

TL;DR

This paper investigates phase transitions in a gauge-Higgs unification model based on $SO(5) imes U(1) imes SU(3)$, revealing weakly first-order electroweak transition at 163 GeV, a new high-temperature phase, and a left-right transition around 2.5 TeV, with implications for early universe cosmology.

Contribution

It provides a detailed analysis of electroweak and left-right phase transitions in a GUT-inspired gauge-Higgs unification model, including new phase behavior and gauge boson transformations.

Findings

Electroweak phase transition is weakly first order at ~163 GeV.

A new phase appears at high temperatures near the KK scale (~13 TeV).

A first-order left-right phase transition occurs at 2.5-2.6 TeV.

Abstract

The electroweak phase transition in GUT inspired $SO(5)\times U(1) \times SU(3)$ gauge-Higgs unification is shown to be weakly first order and occurs at $T = T_c^{\rm EW} \sim 163\,$GeV, which is very similar to the behavior in the standard model in perturbation theory. A new phase appears at higher temperatures. $SU(2)_L \times U(1)_Y$ ($\theta_H=0$) and $SU(2)_R \times U(1)_{Y'}$ ($\theta_H=\pi$) phases become almost degenerate above $T \sim m_{\rm KK}$ where $m_{\rm KK}$ is the Kaluza-Klein mass scale typically around 13$\,$TeV and $\theta_H$ is the Aharonov-Bohm phase along the fifth dimension. The two phases become degenerate at $T = T_c^{\rm LR} \sim m_{\rm KK}$. As the temperature drops in the evolution of the early Universe the $SU(2)_R \times U(1)_{Y'}$ phase becomes unstable. The tunneling rate from the $SU(2)_R \times U(1)_{Y'}$ phase to the $SU(2)_L \times U(1)_Y$ phase becomes sizable and a first-order phase transition takes place at $T=2.5 \sim 2.6\,$TeV. The amount of gravitational waves produced in this left-right phase transition is small, far below the reach of the sensitivity of Laser Interferometer Space Antenna (LISA). A detailed analysis of the $SU(2)_R \times U(1)_{Y'}$ phase is also given. It is shown that the $W$ boson, $Z$ boson and photon, with $\theta_H$ varying from 0 to $\pi$, are transformed to gauge bosons in the $SU(2)_R \times U(1)_{Y'}$ phase. Gauge couplings and wave functions of quarks, leptons and dark fermions in the $SU(2)_R \times U(1)_{Y'}$ phase are determined.