Fractional Branes and N=1 Gauge Theories

We discuss fractional D3-branes on the orbifold C^3/Z_2*Z_2. We study the open and the closed string spectrum on this orbifold. The corresponding N=1 theory on the brane has, generically, a U(N_1)*U(N_2)*U(N_3)*U(N_4) gauge group with matter in the bifundamental. In particular, when only one type of brane is present, one obtains pure N=1 Yang-Mills. We study the coupling of the branes to the bulk fields and present the corresponding supergravity solution, valid at large distances. By using a probe analysis, we are able to obtain the Wilsonian beta-function for those gauge theories that possess some chiral multiplet. Although, due to the lack of moduli, the probe technique is not directly applicable to the case of pure N=1 Yang-Mills, we point out that the same formula gives the correct result also for this case.Comment: 21 pages, AMS-LaTeX, v2: references added and typos correcte

Direct CP violation in K->3pi decays induced by SUSY chromomagnetic penguins

An analysis of the CP violating asymmetry in $K^\pm \to (3\pi)^\pm$ decays in the Standard Model and, by means of the mass insertion approximation, in a wide class of possible supersymmetric extensions, is presented. We find that the natural order of magnitude for this asymmetry is \cO(10^{-5}) in both cases. Within supersymmetric models effects as large as \cO(10^{-4}) are possible, but only in a restricted range of the relevant parameters.Comment: Latex, 11 pages, 1 figur

Quark-Squark Alignment Revisited

We re-examine the possibility that the solution to the supersymmetric flavor problem is related to small mixing angles in gaugino couplings induced by approximate horizontal Abelian symmetries. We prove that, for a large class of models, there is a single viable structure for the down quark mass matrix with four holomorphic zeros. Consequently, we are able to obtain both lower and upper bounds on the supersymmetric mixing angles and predict the contributions to various flavor changing neutral current processes. We find that the most likely signals for alignment are $\Delta m_D$ close to the present bound, significant CP violation in $D^0-\bar{D^0}$ mixing, and shifts of order a few percent in various CP asymmetries in $B^0$ and $B_s$ decays. In contrast, the modifications to radiative B decays, to $\epsilon^\prime/\epsilon$ and to $K\to\pi\nu\bar\nu$ decays are small. We further investigate a new class of alignment models, where supersymmetric contributions to flavor changing processes are suppressed by both alignment and RGE-induced degeneracy.Comment: 20 pages, 3 figure

D-branes, Orientifolds and K-theory

The complete D-brane spectrum in ZZ[squared] orientifolds is computed. Stable non-BPS D-branes with both integral and torsion charges are found. The relation to K-theory is discussed and a new K-theory relevant to orientifolds is suggested

Aerial inventory of surficial geological effects induced by the recent Emilia earthquake (Italy): preliminary report.

As a consequence of the two main shocks that recently struck the central alluvial Po Plain (May 20, 2012, ML 5.9, and May 29, 2012, ML 5.8), a great number of surficial geologic disturbances appeared over a wide area (ca. 500 km2), which extended up to 20 km from the epicenters. The affected area includes Mirabello, San Carlo, Sant'Agostino (Province of Ferrara), San Felice, Cavezzo, Concordia (Modena), Moglia and Quistello (Mantova). Most of the surficial effects that were observed during this study were clearly induced (directly or indirectly) by sand liquefaction phenomena, such as sand volcanoes, burst of water and sand from domestic wells, tension cracks, lateral spreading and associated deformation, graben-like fracturing, and sink-holes. Other effects can probably be ascribed simply to the shaking of the ground (e.g., small collapses of irrigation canal walls). Lastly, there were also some features of dubious origin, such as two 'yellow crop spots' that are cited here with reservations. All of these data were surveyed by means of a small airplane that was especially adapted for this purpose. The aim of this study was to furnish a wide-ranging image of the surface deformation over the whole area impacted by these recent earthquakes, as an instrument towards more exhaustive research, both at the scientific and technical levels (e.g., seismic microzonation)

N=1 Matter from Fractional Branes

We study a bound state of fractional D3-branes localized inside the world-volume of fractional D7-branes on the orbifold C^3/Z_2 x Z_2. We determine the open string spectrum that leads to N=1 U(N1)xU(N2)xU(N3)xU(N4) gauge theory with matter having the number of D7-branes as a flavor index. We derive the linearized boundary action of the D7-brane on this orbifold using the boundary state formalism and we discuss the tadpole cancellation. After computing the asymptotic expression of the supergravity solution the anomalies of the gauge theory are reproduced.Comment: LaTeX 20 pages, 1 figure, small changes and references adde