Dynamical Electroweak Symmetry Breaking in SO(5)xU(1) Gauge-Higgs Unification with Top and Bottom Quarks

An SO(5)xU(1) gauge-Higgs unification model in the Randall-Sundrum warped space with top and bottom quarks is constructed. Additional fermions on the Planck brane make exotic particles heavy by effectively changing boundary conditions of bulk fermions from those determined by orbifold conditions. Gauge couplings of a top quark multiplet trigger electroweak symmetry breaking by the Hosotani mechanism, simultaneously giving a top quark the observed mass. The bottom quark mass is generated by combination of brane interactions and the Hosotani mechanism, where only one ratio of brane masses is relevant when the scale of brane masses is much larger than the Kaluza-Klein scale (\sim 1.5 TeV). The Higgs mass is predicted to be 49.9 (53.5) GeV for the warp factor 10^{15} (10^{17}). The Wilson line phase turns out \pi/2 and the Higgs couplings to W and Z vanish so that the LEP2 bound for the Higgs mass is evaded. In the flat spacetime limit the electroweak symmetry is unbroken.Comment: 35 pages, 2 figures. A few corrections are mad

Renormalizability of Massive Gravity in Three Dimensions

We discuss renormalizability of a recently established, massive gravity theory with particular higher derivative terms in three space-time dimensions. It is shown that this massive gravity is certainly renormalizable as well as unitary, so it gives us a physically interesting toy model of perturbative quantum gravity in three dimensions.Comment: 13 pages, no figure

Locally Localized Gravity Models in Higher Dimensions

We explore the possibility of generalizing the locally localized gravity model in five space-time dimensions to arbitrary higher dimensions. In a space-time with negative cosmological constant, there are essentially two kinds of higher-dimensional cousins which not only take an analytic form but also are free from the naked curvature singularity in a whole bulk space-time. One cousin is a trivial extension of five-dimensional model, while the other one is in essence in higher dimensions. One interesting observation is that in the latter model, only anti-de Sitter ($AdS_p$) brane is physically meaningful whereas de Sitter ($dS_p$) and Minkowski ($M_p$) branes are dismissed. Moreover, for $AdS_p$ brane in the latter model, we study the property of localization of various bulk fields on a single brane. In particular, it is shown that the presence of the brane cosmological constant enables bulk gauge field and massless fermions to confine to the brane only by a gravitational interaction. We find a novel relation between mass of brane gauge field and the brane cosmological constant.Comment: 20 pages, LaTex 2e, revised version (to appear in Phys. Rev. D