The Weak Mixing Angle From TeV Scale Quark-Lepton Unification

Unified theories based on an extended left-right symmetric group, $SU(4) \times SU(2)^4$, are constructed in five dimensions. The compactification scale is assumed to be only a loop factor above the weak scale, so that the weak mixing angle is predicted to be close to its tree level value of 0.239. Boundary conditions in the 5th dimension break $SU(4) \to SU(3) \times U(1)_{B-L}$, removing powerful constraints from $K_L \to \mu e$ while allowing a reliable calculation of the leading logarithm corrections to $\sin^2 \theta$. The compactification scale is expected in the 1--5 TeV region, depending on how $SU(2)^4$ is broken. Two illustrative models are presented, and the experimental signal of the $Z'$ gauge boson is discussed.Comment: 15 page

Realistic Anomaly Mediation with Bulk Gauge Fields

We present a simple general framework for realistic models of supersymmetry breaking driven by anomaly mediation. We consider a 5-dimensional "brane universe" where the visible and hidden sectors are localized on different branes, and the standard model gauge bosons propagate in the bulk. In this framework there can be charged scalar messengers that have contact interactions with the hidden sector, either localized in the hidden sector or in the bulk. These scalars obtain soft masses that feed into visible sector scalar masses at two loop order via bulk gauge interactions. This contribution is automatically flavor-blind, and can be naturally positive. If the messengers are in the bulk this contribution is automatically the same order of magnitude as the anomaly mediated contribution, independent of the brane spacing. If the messengers are localized to a brane the two effects are of the same order for relatively small brane spacings. The gaugino masses and A terms are determined completely by anomaly mediation. In order for anomaly mediation to dominate over radion mediation the radion must be is stabilized in a manner that preserves supersymmetry, with supergravity effects included. We show that this occurs in simple models. We also show that the mu problem can be solved by the vacuum expectation value of a singlet in this framework.Comment: 16 pages, LaTeX2e, no figure

Symmetry Breaking Patterns for the Little Higgs from Strong Dynamics

We show how the symmetry breaking pattern of the simplest little Higgs model, and that of the smallest moose model that incorporates an approximate custodial SU(2), can be realized through the condensation of strongly coupled fermions. In each case a custodial SU(2) symmetry of the new strong dynamics limits the sizes of corrections to precision electroweak observables. In the case of the simplest little Higgs, there are no new light states beyond those present in the original model. However, our realization of the symmetry breaking pattern of the moose model predicts an additional scalar field with mass of order a TeV or higher that has exactly the same quantum numbers as the Standard Model Higgs and which decays primarily to third generation quarks.Comment: 5 pages, 3 figure

Radion Mediated Supersymmetry Breaking

We point out that in supersymmetric theories with extra dimensions, radius stabilization can give rise to a VEV for the $F$ component of the radius modulus. This gives an important contribution to supersymmetry breaking of fields that propagate in the bulk. A particularly attractive class of models is obtained if the standard-model gauge fields propagate in the bulk, while the quark and lepton fields are localized on a brane. This leads to gaugino mediated supersymmetry breaking without the need for singlets in the hidden sector. We analyze a simple explicit model in which this idea is realized

Unconventional fermions: The Price of Quark-Lepton Unification at TeV Scales

The early petite unification (PUT) of quarks and leptons at TeV scales with sin^2 theta_W(M^2_Z) used as a constraint, necessitates the introduction of extra quarks and leptons with unconventional electric charges (up to 4/3 for the quarks and 2 for the leptons). This talk, in honor of Paul Frampton's 60th birthday, will be devoted to the motivation and construction of models of early unification and to their implications, including the issues of rare decays and unconventional fermions.Comment: 10 pages, 2 figures. Talk in honor of Paul Frampton's 60th birthday given at the Coral Gables Conference on Launching of Belle Epoque in High Energy Physics and Cosmology, Ft. lauderdale, Florida, 17-21 December 2003. Added referenc

Fine Structure Constant Variation from a Late Phase Transition

Recent experimental data indicates that the fine structure constant alpha may be varying on cosmological time scales. We consider the possibility that such a variation could be induced by a second order phase transition which occurs at late times (z ~ 1 - 3) and involves a change in the vacuum expectation value (vev) of a scalar with milli-eV mass. Such light scalars are natural in supersymmetric theories with low SUSY breaking scale. If the vev of this scalar contributes to masses of electrically charged fields, the low-energy value of alpha changes during the phase transition. The observational predictions of this scenario include isotope-dependent deviations from Newtonian gravity at sub-millimeter distances, and (if the phase transition is a sharp event on cosmological time scales) the presence of a well-defined step-like feature in the alpha(z) plot. The relation between the fractional changes in alpha and the QCD confinement scale is highly model dependent, and even in grand unified theories the change in alpha does not need to be accompanied by a large shift in nucleon masses.Comment: 9 pages. V2: discussion on the energy density stored in the scalar oscillations after the phase transition expanded. Typos corrected and Refs. added. Version to appear in PL

Doublet-Triplet Splitting in Supersymmetric SU(6) by Missing VEV Mechanism

We present a realistic supersymmetric SU(6) model which implements doublet-triplet splitting by the missing vev mechanism. The model makes use of only the simplest representations, requires no fine tuning of parameters and maintains coupling constant unification as a prediction. Fermion masses also emerge in a very straightforward manner. This is the first time that the missing vev mechanism has been realized in the context of SU(6).Comment: Revtex 4 pages; no figures; UMD-PP-99-01

Calculable Dynamical Supersymmetry Breaking on Deformed Moduli Spaces

We consider models of dynamical supersymmetry breaking in which the extremization of a tree-level superpotential conflicts with a quantum constraint. We show that in such models the low-energy effective theory near the origin of moduli space is an O'Raifeartaigh model, and the sign of the mass-squared for the pseudo-flat direction at the origin is calculable. We analyze vector-like models with gauge groups SU(N) and Sp(2N) with and without global symmetries. In all cases there is a stable minimum at the origin with an unbroken U(1)_R symmetry.Comment: 8 pages, LaTeX2e, no figure