Gauge-Higgs EW and Grand Unification

Four-dimensional Higgs field is identified with the extra-dimensional component of gauge potentials in the gauge-Higgs unifiation scenario. SO(5) × U(1) gauge-Higgs EW unification in the Randall–Sundrum warped space is successful at low energies. The Higgs field appears as an Aharonov–Bohm phase θ_H in the fifth dimension. Its mass is generated at the quantum level and is finite. The model yields almost the same phenomenology as the standard model for θ_H < 0.1, and predicts Z^′ bosons around 6–10 TeV with very broad widths. The scenario is generalized to SO(11) gauge-Higgs grand unification. Fermions are introduced in the spinor and vector representations of SO(11). Proton decay is naturally forbidden.