Majorana neutrino masses in gauge-Higgs unification

Abstract: The theory that the extra-space component of the gauge field is identified with the standard model Higgs boson, is called the gauge-Higgs unification (GHU) scenario. We examine how the small neutrino masses are naturally generated in the GHU framework. We find out two model classes where the following matter multiplets are introduced : 1. adjoint rep. lepton $\Psi_{A}$, 2. fundamental rep. lepton $\Psi_{F}$ and scalar $\Sigma_{F}$. We present a concrete model in each class. At the model in class 1, the neutrino masses are generated by the admixture of the seesaw mechanism type-I and -III. At the model in class 2, the masses are generated by the inverse seesaw mechanism.