A New Lorentz Violating Nonlocal Field Theory From String-Theory

A four-dimensional field theory with a qualitatively new type of nonlocality is constructed from a setting where Kaluza-Klein particles probe toroidally compactified string theory with twisted boundary conditions. In this theory fundamental particles are not pointlike and occupy a volume proportional to their R-charge. The theory breaks Lorentz invariance but appears to preserve spatial rotations. At low energies, it is approximately N=4 Super Yang-Mills theory, deformed by an operator of dimension seven. The dispersion relation of massless modes in vacuum is unchanged, but under certain conditions in this theory, particles can travel at superluminal velocities.Comment: references adde

N=4 Supersymmetric Yang-Mills Multiplet in Non-Adjoint Representations

We formulate a theory for N=4 supersymmetric Yang-Mills multiplet in a non-adjoint representation R of SO(N) as an important application of our recently-proposed model for N=1 supersymmetry. This system is obtained by dimensional reduction from an N=1 supersymmetric Yang-Mills multiplet in non-adjoint representation in ten dimensions. The consistency with supersymmetry requires that the non-adjoint representation R with the indices i, j, ... satisfy the three conditions \eta^{i j} = \delta^{i j}, (T^I)^{i j} = - (T^I)^{j i} and (T^I)^{[ i j |} (T^I)^{| k ] l} = 0 for the metric \eta^{i j} and the generators T^I, which are the same as the N=1 case.Comment: 6 pages, no figures, accepted for publication in Phys. Rev.

Supersymmetry without the Desert

Naturalness of electroweak symmetry breaking in weak scale supersymmetric theories may suggest the absence of the conventional supersymmetric desert. We present a simple, realistic framework for supersymmetry in which (most of) the virtues of the supersymmetric desert are naturally reproduced without having a large energy interval above the weak scale. The successful supersymmetric prediction for the low-energy gauge couplings is reproduced due to a gauged R symmetry present in the effective theory at the weak scale. The observable sector superpotential naturally takes the form of the next-to-minimal supersymmetric standard model, but without being subject to the Landau pole constraints up to the conventional unification scale. Supersymmetry breaking masses are generated by the F-term and D-term VEVs of singlet and U(1)_R gauge fields, as well as by anomaly mediation, at a scale not far above the weak scale. We study the resulting patten of supersymmetry breaking masses in detail, and find that it can be quite distinct. We construct classes of explicit models within this framework, based on higher dimensional unified theories with TeV-sized extra dimensions. A similar model based on a non-R symmetry is also presented. These models have a rich phenomenology at the TeV scale, and allow for detailed analyses of, e.g., electroweak symmetry breaking.Comment: 42 page

Twisted Flavors and Tri/bi-Maximal Neutrino Mixing

A new framework for handling flavor symmetry breaking in the neutrino sector is discussed where the source of symmetry breaking is traced to the global property of right-handed neutrinos in extra-dimensional space. Light neutrino phenomenology has rich and robust predictions such as the tri/bi-maximal form of generation mixing, controlled mass spectrum, and no need of flavor mixing couplings in the theory.Comment: 11 page

Orbifold Reduction Of The Quark-Lepton Symmetric Model

We investigate the quark-lepton symmetric gauge group in five dimensions, with the gauge symmetry broken by a combination of orbifold compactification of the extra dimension and the Higgs mechanism. The gauge sector of the model is investigated and contrasted with the four dimensional case. We obtain lower bounds on the mass of the exotic gauge bosons, the inverse compactification scale and the exotic leptons. Light neutrinos are obtained without requiring any scale larger than a TeV. However an ultra-violet cut-off of order $10^{11}$ GeV is required to suppress proton decay inducing non-renormalizable operators.Comment: References added to match PRD versio

Supersymmetry Breaking by Constant Boundary Superpotentials in Warped Space

Supersymmetry breaking by constant (field independent) superpotentials localized at boundaries is studied in a supersymmetric warped space model. We calculate the Kaluza-Klein mass spectrum of the hypermultiplet. We take into account of the radion and the compensator supermultiplets, as well as the bulk mass $c$ for the hypermultiplet. The mass splitting is similar to that of the Scherk-Schwarz supersymmetry breaking (in flat space) for large $|c|$, and has an interesting dependence on the bulk mass parameter $c$. We show that the radius is stabilized by the presence of the constant boundary superpotentials.Comment: 24 pages, 9 figures; Section 5 is replaced by the new analysis of the radius stabilization, small modifications mad

Freed-Witten anomaly in general flux compactification

Turning on a NS-NS three-form flux in a compact space drives some D-branes to be either Freed-Witten anomalous or unstable to decay into fluxes by the appearance of instantonic branes. By applying T-duality on a toroidal compactification, the NS-flux is transformed into metric fluxes. We propose a T-dual version of the Atiyah-Hirzebruch Spectral Sequence upon which we describe the Freed-Witten anomaly and the brane-flux transition driven by NS and metric fluxes in a twisted torus. The required conditions to cancel the anomaly and the appearance of new instantonic branes are also described. In addition, we give an example in which all D6-branes wrapping Freed-Witten anomaly-free three-cycles in the twisted torus T^6/Z(2)XZ(2) are nevertheless unstable to be transformed into fluxes. Evenmore we find a topological transformation between RR, NS-NS and metric fluxes driven by a chain of instantonic branes.Comment: v3: Shortened version. Examples added. Main results unchange

Monodromy in the CMB: Gravity Waves and String Inflation

We present a simple mechanism for obtaining large-field inflation, and hence a gravitational wave signature, from string theory compactified on twisted tori. For Nil manifolds, we obtain a leading inflationary potential proportional to phi^(2/3) in terms of the canonically normalized field phi, yielding predictions for the tilt of the power spectrum and the tensor-to-scalar ratio, $n_s\approx 0.98$ and $r\approx 0.04$ with 60 e-foldings of inflation; we note also the possibility of a variant with a candidate inflaton potential proportional to phi^(2/5). The basic mechanism involved in extending the field range -- monodromy in D-branes as they move in circles on the manifold -- arises in a more general class of compactifications, though our methods for controlling the corrections to the slow-roll parameters require additional symmetries.Comment: 43 pages, latex. 4 figure

Gauge coupling Unification and SO(10) in 5D

We analyze the gauge unification in minimal supersymmetric SO(10) grand unified theories in 5 dimensions. The single extra spatial dimension is compactified on the orbifold S^1/(Z_2 x Z_2') reducing the gauge group to that of Pati-Salam SU(4)_c x SU(2)_L x SU(2)_R. The Standard Model gauge group is achieved by the further brane-localized Higgs mechanism on one of the fixed points. There are two main different approaches developed in literature. Higgs mechanism can take place on the Pati Salam brane, or on the SO(10) preserving brane. We show, both analytically and numerically, that in the first case a natural and succesfull gauge coupling unification can be achieved, while the second case is highly disfavoured. For completeness, we consider either the case in which the brane breaking scale is near the cutoff scale or the case in which it is lower than the compactification scale.Comment: 18 Pages and 8 PostScript Figure

Supersymmetry in gauge theories with extra dimensions

We show that a quantum-mechanical N=2 supersymmetry is hidden in 4d mass spectrum of any gauge invariant theories with extra dimensions. The N=2 supercharges are explicitly constructed in terms of differential forms. The analysis can be extended to extra dimensions with boundaries, and for a single extra dimension we clarify a possible set of boundary conditions consistent with 5d gauge invariance, although some of the boundary conditions break 4d gauge symmetries.Comment: 18 page