Gravitational Scattering in the ADD-model Revisited

Gravitational scattering in the ADD-model is studied and it is argued that no cut-off is needed for the exchange of virtual Kaluza--Klein modes. By introduction of a small coordinate in the extra dimensions a unique form of the Kaluza--Klein-summed propagator is found for an odd number of extra dimensions. The matrix element corresponding to this propagator can also (as opposed to the cut-offed version) be Fourier transformed to position space, giving back the extra-dimensional version of Newton's law. For an even number of extra dimensions the propagator is found by requiring that Newton's law should be recovered

Theoretical Predictions for Collider Searches

I review recent developments in extensions of the Standard Model that address the question of electroweak symmetry breaking and discuss how these theories can be tested at future colliders.Comment: 13 pages, 2 figures, invited talk at the 21st International Symposium on Lepton and Photon Interactions at High Energies (Lepton Photon 2003), 11-16 Aug 2003, Batavia, Illinois, US

Supersymmetry-Breaking Loops from Analytic Continuation into Superspace

We extend to all orders in perturbation theory a method to calculate supersymmetry-breaking effects by analytic continuation of the renormalization group into superspace. A central observation is that the renormalized gauge coupling can be extended to a real vector superfield, thereby including soft breaking effects in the gauge sector. We explain the relation between this vector superfield coupling and the "holomorphic" gauge coupling, which is a chiral superfield running only at 1 loop. We consider these issues for a number of regulators, including dimensional reduction. With this method, the renormalization group equations for soft supersymmetry breaking terms are directly related to supersymmetric beta functions and anomalous dimensions to all orders in perturbation theory. However, the real power of the formalism lies in computing finite soft breaking effects corresponding to high-loop component calculations. We prove that the gaugino mass in gauge-mediated supersymmetry breaking is ``screened'' from strong interactions in the messenger sector. We present the complete next-to-leading calculation of gaugino masses (2 loops) and sfermion masses (3 loops) in minimal gauge mediation, and several other calculations of phenomenological relevance.Comment: 50 pages, 1 ps and 1 eps figure, LaTe

Towards a realistic Standard Model from D-brane configurations

Effective low energy models arising in the context of D-brane configurations with Standard Model (SM) gauge symmetry extended by several gauged abelian factors are discussed. The models are classified according to their hypercharge embeddings consistent with the SM spectrum hypercharge assignment. Particular cases are analyzed according to their perspectives and viability as low energy effective field theory candidates. The resulting string scale is determined by means of a two-loop renormalization group calculation. Their implications in Yukawa couplings, neutrinos and flavor changing processes are also presented.Comment: 22 pages, 12 EPS figures, some clarifications/references adde

Why the Water Bridge does not collapse

In 2007 an interesting phenomenon was discovered: a thread of water, the so-called water bridge (WB), can hang between two glass beakers filled with deionized water if voltage is applied to them. We analyze the available explanations of the WB stability and propose a completely different one: the force that supports the WB is the surface tension of water and the role of electric field is not to allow the WB to reduce its surface energy by means of breaking into separate drops.Comment: 4 pages, 3 figure

The Well-Tempered Neutralino

The dark-matter prediction is usually considered as one of the successes of low-energy supersymmetry. We argue that, after LEP constraints are taken into account, the correct prediction for the dark-matter density, at a quantitative level, is no longer a natural consequence of supersymmetry, but it requires special relations among parameters, highly sensitive to small variations. This is analogous to the problem of electroweak-symmetry breaking, where the correct value of the Z mass is obtained only with a certain degree of fine tuning. In the general parameter space of low-energy supersymmetry, one of the most plausible solution to reproduce the correct value of the dark-matter density is the well-tempered neutralino, which corresponds to the boundary between a pure Bino and a pure Higgsino or Wino. We study the properties of well-tempered neutralinos and we propose a simple limit of split supersymmetry that realizes this situation.Comment: Latex2e, 29 pages, 5 figures, reference added, typo corrected, version to be published in NP

Cold Dark Matter and Neutralinos

Neutralinos are natural candidates for cold dark matter in many realizations of supersymmetry. We briefly review our recent results in the evaluation of neutralino relic abundance and direct detection rates in a class of supergravity models.Comment: 4 pages, 4 figures, uses espcrc2.sty. Proc. of "Sources and detection of dark matter and dark energy in the Universe (DM2002)". The version on the archive has low-resolution figures. The paper with high-resolution figures can be found at http://www.to.infn.it/~fornengo/proceedings/marinadelrey02.ps.gz or through http://www.to.infn.it/astropart

Integrable structures in LGTs near the deconfinement transition

In this contribution we review some recent results about the emergence of 2D integrable systems in 3D Lattice Gauge Theories near the deconfinement transition. We focus on some concrete examples involving the flux tube thickness, the ratio of k-string tensions and Polyakov loops correlators in various models.Comment: 8 pages, Poster contribution to the XXVII International Symposium on Lattice Field Theory, July 26-31, 2009, Peking University, Beijing, Chin

Minimal Gaugomaly Mediation

Mixed anomaly and gauge mediation ("gaugomaly'' mediation) gives a natural solution to the SUSY flavor problem with a conventional LSP dark matter candidate. We present a minimal version of gaugomaly mediation where the messenger masses arise directly from anomaly mediation, automatically generating a messenger scale of order 50 TeV. We also describe a simple relaxation mechanism that gives rise to realistic mu and B mu terms. B is naturally dominated by the anomaly-mediated contribution from top loops, so the mu/B mu sector only depends on a single new parameter. In the minimal version of this scenario the full SUSY spectrum is determined by two continuous parameters (the anomaly- and gauge-mediated SUSY breaking masses) and one discrete parameter (the number of messengers). We show that these simple models can give realistic spectra with viable dark matter.Comment: 18 pages, 4 figures; v2: corrected example generating non-holomorphic Kahler term

Gluino decays with heavier scalar superpartners

We compute gluino decay widths in supersymmetric theories with arbitrary flavor and CP violation angles. Our emphasis is on theories with scalar superpartner masses heavier than the gluino such that tree-level two-body decays are not allowed, which is relevant, for example, in split supersymmetry. We compute gluino decay branching fractions in several specific examples and show that it is plausible that the only accessible signal of supersymmetry at the LHC could be four top quarks plus missing energy. We show another example where the only accessible signal for supersymmetry is two gluon jets plus missing energy.Comment: 17 pages, 8 figures. Added references and minor typos and errors corrected (no change in numerical results