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

The electroweak phase transition in GUT inspired $SO(5) \times U(1) \times SU(3)$ gauge-Higgs unification is shown to be of 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. There appears a new phase at higher temperature. $SU(2)_L \times U(1)_Y$ ($ \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 13TeV 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. 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.