Dynamical radion superfield in 5D action

We derive 5D N=1 superspace action including the radion superfield. The radion is treated as a dynamical field and identified as a solution of the equation of motion even in the presence of the radius stabilization mechanism. Our derivation is systematic and based on the superconformal formulation of 5D supergravity. We can read off the couplings of the dynamical radion superfield to the matter superfields from our result. The correct radion mass can be obtained by calculating the radion potential from our superspace action.Comment: 29 pages, no figures, LaTeX, some comments adde

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

Superfield description of 5D supergravity on general warped geometry

We provide a systematic and practical method of deriving 5D supergravity action described by 4D superfields on a general warped geometry, including a non-BPS background. Our method is based on the superconformal formulation of 5D supergravity, but is easy to handle thanks to the superfield formalism. We identify the radion superfield in the language of 5D superconformal gravity, and clarify its appearance in the action. We also discuss SUSY breaking effects induced by a deformed geometry due to the backreaction of the radius stabilizer.Comment: 25 pages, no figures, LaTeX, final version to appear in JHE

Effective theory for wall-antiwall system

We propose a useful method for deriving the effective theory for a system where BPS and anti-BPS domain walls coexist. Our method respects an approximately preserved SUSY near each wall. Due to the finite width of the walls, SUSY breaking terms arise at tree-level, which are exponentially suppressed. A practical approximation using the BPS wall solutions is also discussed. We show that a tachyonic mode appears in the matter sector if the corresponding mode function has a broader profile than the wall width.Comment: LaTeX file, 30 page, 5 eps figures, references adde

Supersymmetry breaking in a warped slice with Majorana-type masses

We study the five-dimensional (5D) supergravity compactified on an orbifold S^1/Z_2, where the U(1)_R symmetry is gauged by the graviphoton with Z_2-even coupling. In contrast to the case of gauging with Z_2-odd coupling, this class of models has Majorana-type masses and allows the Scherk-Schwarz (SS) twist even in the warped spacetime. Starting from the off-shell formulation, we show that the supersymmetry is always broken in an orbifold slice of AdS_5, irrespective of the value of the SS twist parameter. We analyze the spectra of gaugino and gravitino in such background, and find the SS twist can provide sizable effects on them in the small warping region.Comment: 1+20 pages, 6 figure

Low-Scale Axion from Large Extra Dimensions

The mass of the axion and its decay rate are known to depend only on the scale of Peccei-Quinn symmetry breaking, which is constrained by astrophysics and cosmology to be between $10^9$ and $10^{12}$ GeV. We propose a new mechanism such that this effective scale is preserved and yet the fundamental breaking scale of $U(1)_{PQ}$ is very small (a kind of inverse seesaw) in the context of large extra dimensions with an anomalous U(1) gauge symmetry in our brane. Unlike any other (invisible) axion model, there are now possible collider signatures in this scenario.Comment: 11 pages, no figur

SUSY flavor structure of generic 5D supergravity models

We perform a comprehensive and systematic analysis of the SUSY flavor structure of generic 5D supergravity models on $S^1/Z_2$ with multiple $Z_2$-odd vector multiplets that generate multiple moduli. The SUSY flavor problem can be avoided due to contact terms in the 4D effective K\"ahler potential peculiar to the multi-moduli case. A detailed phenomenological analysis is provided based on an illustrative model.Comment: 37 pages, 7 figures, Sec.4 is modifie

Supersymmetric Boundaries and Junctions in Four Dimensions

We make a comprehensive study of (rigid) N=1 supersymmetric sigma-models with general K\"ahler potentials K and superpotentials w on four-dimensional space-times with boundaries. We determine the minimal (non-supersymmetric) boundary terms one must add to the standard bulk action to make it off-shell invariant under half the supersymmetries without imposing any boundary conditions. Susy boundary conditions do arise from the variational principle when studying the dynamics. Upon including an additional boundary action that depends on an arbitrary real boundary potential B one can generate very general susy boundary conditions. We show that for any set of susy boundary conditions that define a Lagrangian submanifold of the K\"ahler manifold, an appropriate boundary potential B can be found. Thus the non-linear sigma-model on a manifold with boundary is characterised by the tripel (K,B,w). We also discuss the susy coupling to new boundary superfields and generalize our results to supersymmetric junctions between completely different susy sigma-models, living on adjacent domains and interacting through a "permeable" wall. We obtain the supersymmetric matching conditions that allow us to couple models with different K\"ahler potentials and superpotentials on each side of the wall.Comment: 38 pages, 1 figur