Gauge Coupling Unification in simplified Grand Gauge-Higgs Unification

Grand gauge-Higgs unification of five dimensional SU(6) gauge theory on an orbifold $S^1\mathrm{/}{Z}_2$ with localized gauge kinetic terms is discussed. The Standard model (SM) fermions on the boundaries and some massive bulk fermions coupling to the SM fermions on the boundary are introduced. Taking the power-law running contributions from the bulk fields into account, perturbative gauge coupling unification is shown to be realized at around ${10}^{14}$ GeV, which is a few order smaller than the unification scale of four dimensional grand unified theories.