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We study in a systematic and modular invariant way gaugino condensation in the hidden sector as a potential source of hierarchical supersymmetry breaking and a non–trivial potential for the dilaton S whose real part corresponds to the tree level gauge coupling constant (Re S ∼ g gut). For the case of pure Yang–Mills condensation, we show that no realistic… (More)

We examine the electroweak breaking mechanism in the minimal supersymmetric standard model (MSSM) using the complete one-loop effective potential V1. First, we study what is the region of the whole MSSM parameter space (i.e. M1/2, mo, μ, ...) that leads to a succesful SU(2) × U(1) breaking with an acceptable top quark mass. In doing this it is observed that… (More)

Tiago Barreiro,* Beatriz de Carlos, Ed Copeland, and Nelson J. Nunes4,x Centro Multidisciplinar de Astrofı́sica (CENTRA), Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QJ, United Kingdom The School of Physics and Astronomy,… (More)

In this paper we analyze the structure of supersymmetric vacua in compactifications of the heterotic string on certain manifolds with SU(3) structure. We first study the effective theories obtained from compactifications on half-flat manifolds and show that solutions which stabilise the moduli at acceptable values are hard to find. We then derive the… (More)

We study moduli stabilization in the context of M-theory on compact manifolds with G2 holonomy, using superpotentials from flux and membrane instantons, and recent results for the Kähler potential of such models. The existence of minima with negative cosmological constant, stabilizing all moduli, is established. While most of these minima preserve… (More)

We perform a complete classification of the flux-induced 12d algebras compatible with the set of N = 1 type II orientifold models that are T-duality invariant, and allowed by the symmetries of the T/(Z2×Z2) isotropic orbifold. The classification is performed in a type IIB frame, where only H̄3 and Q fluxes are present. We then study no-go theorems,… (More)

We investigate the stability against inhomogeneous perturbations and the appearance of ghost modes in Gauss–Bonnet gravitational theories with a non minimally coupled scalar field, which can be regarded as either the dilaton or a compactification modulus in the context of string theory. Through cosmological linear perturbations we extract four no-ghost and… (More)

We present the results of a detailed investigation into the consequences of adding specific string motivated non-perturbative corrections to the usual tree level Kähler potential in dilaton dominated scenarios. The success of the model is judged through our ability to obtain a realistic vacuum expectation value for the dilaton ^ReS&;2, corresponding to the… (More)

We consider domain walls that appear in supersymmetric QCD with Nf , Nc massive flavors. In particular, for 2Nf , Nc we explicitly construct the domain walls that interpolate between vacua labeled by i and i 1 Nf . We show that these solutions are Bogomol’nyi-Prasad-Sommerfield saturated for any value of the mass of the matter fields. This fact allows us to… (More)

We study the localization of gravity on a string-like topological defect within a 6-dimensional space-time. Assuming zero cosmological constant we find complete numerical solutions to a set of first-order, Bogomol’nyi-Prasad-Sommeferld (BPS)-like, equations for the metric and the scalar field, where the dynamics of the latter are dictated by a… (More)