Gaugino Mediated Supersymmetry Breaking

We consider supersymmetric theories where the standard-model quark and lepton fields are localized on a "3-brane" in extra dimensions, while the gauge and Higgs fields propagate in the bulk. If supersymmetry is broken on another 3-brane, supersymmetry breaking is communicated to gauge and Higgs fields by direct higher-dimension interactions, and to quark and lepton fields via standard-model loops. We show that this gives rise to a realistic and predictive model for supersymmetry breaking. The size of the extra dimensions is required to be of order 10-100 times larger than fundamental scale (e.g. the string scale). The spectrum is similar to (but distinguishable from) the predictions of "no-scale" models. Flavor-changing neutral currents are naturally suppressed. The \mu term can be generated by the Giudice-Masiero mechanism. The supersymmetric CP problem is naturally solved if CP violation occurs only on the observable sector 3-brane. These are the simplest models in the literature that solve all supersymmetric naturalness problems.Comment: Refs. added. 12 pages, 1 figur

Warped Fermions and Precision Tests

We analyze the behavior of Standard Model matter propagating in a slice of AdS_5 in the presence of infrared-brane kinetic terms. Brane kinetic terms are naturally generated through radiative corrections and can also be present at tree level. The effect of the brane kinetic terms is to expell the heavy KK modes from the infrared-brane, and hence to reduce their coupling to the localized Higgs field. In a previous work we showed that sizable gauge kinetic terms can allow KK mode masses as low as a few TeV, compatible with present precision measurements. We study here the effect of fermion brane kinetic terms and show that they ameliorate the behavior of the theory for third generation fermions localized away from the infrared brane, reduce the contribution of the third generation quarks to the oblique correction parameters and mantain a good fit to the precision electroweak data for values of the KK masses of the order of the weak scale.Comment: 25 pages, 4 figures, latex2

On the one-loop Kahler potential in five-dimensional brane-world supergravity

We present an on-shell formulation of 5d gauged supergravity coupled to chiral matter multiplets localized at the orbifold fixed points. The brane action is constructed via the Noether method. In such set-up we compute one-loop corrections to the Kahler potential of the effective 4d supergravity and compare the result with previous computations based on the off-shell formalism. The results agree at lowest order in brane sources, however at higher order there are differences. We explain this discrepancy by an ambiguity in resolving singularities associated with the presence of infinitely thin branes.Comment: 20 page

Springtime sensible heat, nutrients and phytoplankton in the northwater Polynya, Canadian Arctic

Sampling was conducted in the Northwater Polynya (between 70°20' and 77°20'N), on 17 and 19 May 1991. At each of the 14 sampling stations, CTD profiles were recorded from surface to bottom and nutrients and phytoplankton were determined at four depths down to 30 m. The presence, between 220 and 400 m, of water temperatures > 0°C is an indication that, in winter, the West Greenland Current enters the Northwater along the Greenland coast. The worm water is progressively mixed as it moves northward and eastward. It was thus hypothesized that sensible heat is as an important factor in keeping the Northwater open. Measured chemical and biological variables were quite homogeneous on the vertical down to 30 m and they showed longitudinal gradients. From east to west, the average concentrations of nutrients increased (phosphate from 0.5 to 1.4, nitrate from 3.7 to 10.8, and silicate from 6.8 to 34.2 mmol/m3), whereas the areal concentrations of phytoplankton decreased (from 47 to 9 x 10 to the ninth power cells/m2 and from 506 to 50 mg Chla/m2). Nutrient ratios indicated possible silicon deficiency in the easternmost part of the polynya. Diatoms dominated cell numbers (greater or equal to 87% at all stations). Concentrations of the three nutrients were inversely correlated with both Chla and cell numbers. The Y-intercepts of regressions of Chla on nutrients provided an estimate of potential maximum biomass in the upper 30 m, which was ca. 600 mg Chla/m2, or lower if there was silicon limitation. The overall picture was that of a diatom bloom, moving westward and progressively exhausting the nutrients. Initiation of the bloom appeared to have been linked to the absence of sea ice. A source of heat for this would have been the above sensible-heat process. (Résumé d'auteur

Radiative corrections to the lightest KK states in the T^2/(Z_2\times Z_2') orbifold

We study radiative corrections localized in the fixed points of the orbifold for the field theory in six dimensions with two dimensions compactified on the $T_2/(Z_2\times Z_2')$ orbifold in a specific realistic model for low energy physics that solves the proton decay and neutrino mass problem. We calculate corrections to the masses of the lightest stable KK modes, which could be the candidates for the dark matter.Comment: 14 pages, 2 figure

Ghosts and Tachyons in the Fifth Dimension

We present several solutions for the five dimensional gravity models in the presence of bulk ghosts and tachyons to argue that these "troublesome" fields can be a useful model-building tool. The ghost-like signature of the kinetic term for a bulk scalar creates a minimum in the scale factor, removing the necessity for a negative tension brane in models with the compactified fifth dimension. It is shown that the model with the positive tension branes and a ghost field in the bulk leads to the radion stabilization. The bulk scalar with the variable sign kinetic term can be used to model both positive and negative tension branes of a finite width in the compact dimension. Finally, we present several ghost and tachyon field configurations in the bulk that lead to the localization of gravity in four dimensions, including one solution with the Gaussian profile for the metric, g_{\mu\nu}(y)=\eta_{\mu\nu}\exp{-\alpha y^2}, which leads to a stronger localization of gravity than the Randall-Sundrum model.Comment: New references adde

Quantum Horizons of the Standard Model Landscape

The long-distance effective field theory of our Universe--the Standard Model coupled to gravity--has a unique 4D vacuum, but we show that it also has a landscape of lower-dimensional vacua, with the potential for moduli arising from vacuum and Casimir energies. For minimal Majorana neutrino masses, we find a near-continuous infinity of AdS3xS1 vacua, with circumference ~20 microns and AdS3 length 4x10^25 m. By AdS/CFT, there is a CFT2 of central charge c~10^90 which contains the Standard Model (and beyond) coupled to quantum gravity in this vacuum. Physics in these vacua is the same as in ours for energies between 10^-1 eV and 10^48 GeV, so this CFT2 also describes all the physics of our vacuum in this energy range. We show that it is possible to realize quantum-stabilized AdS vacua as near-horizon regions of new kinds of quantum extremal black objects in the higher-dimensional space--near critical black strings in 4D, near-critical black holes in 3D. The violation of the null-energy condition by the Casimir energy is crucial for these horizons to exist, as has already been realized for analogous non-extremal 3D black holes by Emparan, Fabbri and Kaloper. The new extremal 3D black holes are particularly interesting--they are (meta)stable with an entropy independent of hbar and G_N, so a microscopic counting of the entropy may be possible in the G_N->0 limit. Our results suggest that it should be possible to realize the larger landscape of AdS vacua in string theory as near-horizon geometries of new extremal black brane solutions.Comment: 44 pages, 9 figure