9 research outputs found
Electric/magnetic duality for chiral gauge theories with anomaly cancellation
We show that 4D gauge theories with Green-Schwarz anomaly cancellation and
possible generalized Chern-Simons terms admit a formulation that is manifestly
covariant with respect to electric/magnetic duality transformations. This
generalizes previous work on the symplectically covariant formulation of
anomaly-free gauge theories as they typically occur in extended supergravity,
and now also includes general theories with (pseudo-)anomalous gauge
interactions as they may occur in global or local N=1 supersymmetry. This
generalization is achieved by relaxing the linear constraint on the embedding
tensor so as to allow for a symmetric 3-tensor related to electric and/or
magnetic quantum anomalies in these theories. Apart from electric and magnetic
gauge fields, the resulting Lagrangians also feature two-form fields and can
accommodate various unusual duality frames as they often appear, e.g., in
string compactifications with background fluxes.Comment: 37 pages; v2: typos corrected and 1 reference adde
An Inflationary Scenario in Intersecting Brane Models
We propose a new scenario for D-term inflation which appears quite
straightforwardly in the open string sector of intersecting brane models. We
take the inflaton to be a chiral field in a bifundamental representation of the
hidden sector and we argue that a sufficiently flat potential can be brane
engineered. This type of model generically predicts a near gaussian red
spectrum with negligible tensor modes. We note that this model can very
naturally generate a baryon asymmetry at the end of inflation via the recently
proposed hidden sector baryogenesis mechanism. We also discuss the possibility
that Majorana masses for the neutrinos can be simultaneously generated by the
tachyon condensation which ends inflation. Our proposed scenario is viable for
both high and low scale supersymmetry breaking.Comment: 30 pages, 2 figures; v2 references and comments adde
D terms from D-branes, gauge invariance and moduli stabilization in flux compactifications
We elucidate the structure of D terms in N=1 orientifold compactifications
with fluxes. As a case study, we consider a simple orbifold of the type-IIA
theory with D6-branes at angles, O6-planes and general NSNS, RR and
Scherk-Schwarz geometrical fluxes. We examine in detail the emergence of D
terms, in their standard supergravity form, from an appropriate limit of the
D-brane action. We derive the consistency conditions on gauged symmetries and
general fluxes coming from brane-localized Bianchi identities, and their
relation with the Freed-Witten anomaly. We extend our results to other N=1
compactifications and to non-geometrical fluxes. Finally, we discuss the
possible role of U(1) D terms in the stabilization of the untwisted moduli from
the closed string sector.Comment: 1+31 pages, 1 figur
D-brane Spectrum and K-theory Constraints of D=4, N=1 Orientifolds
We study the spectrum of stable BPS and non-BPS D-branes in Z_2 x Z_2
orientifolds for all choices of discrete torsion between the orbifold and
orientifold generators. We compute the torsion K-theory charges in these D=4,
N=1 orientifold models directly from worldsheet conformal field theory, and
compare with the K-theory constraints obtained indirectly using D-brane probes.
The K-theory torsion charges derived here provide non-trivial constraints on
string model building. We also discuss regions of stability for non-BPS
D-branes in these examples.Comment: 40 pages, 5 table
Surveying Standard Model Flux Vacua on
We consider the SU(2)LxSU(2)R Standard Model brane embedding in an
orientifold of T6/Z2xZ2. Within defined limits, we construct all such Standard
Model brane embeddings and determine the relative number of flux vacua for each
construction. Supersymmetry preserving brane recombination in the hidden sector
enables us to identify many solutions with high flux. We discuss in detail the
phenomenology of one model which is likely to dominate the counting of vacua.
While Kahler moduli stabilization remains to be fully understood, we define the
criteria necessary for generic constructions to have fixed moduli.Comment: 30 pages, LaTeX, v2: added reference
Building MSSM Flux Vacua
We construct N=1 and N=0 chiral four-dimensional vacua of flux
compactification in Type IIB string theory. These vacua have the common
features that they are free of tadpole instabilities (both NSNS and RR) even
for models with N=0 supersymmetry. In addition, the dilaton/complex structure
moduli are stabilised and the supergravity background metric is warped. We
present an example in which the low energy spectrum contains the MSSM spectrum
with three generations of chiral matter. In the N=0 models, the background
fluxes which stabilise the moduli also induce soft supersymmetry breaking terms
in the gauge and chiral sectors of the theory, while satisfying the equation of
motion. We also discuss some phenomenological features of these three
generation MSSM flux vacua. Our techniques apply to other closed string
backgrounds as well and, in fact, also allow to find new N=1 D-brane models
which were believed not to exist. Finally, we discuss in detail the consistency
conditions of these flux compactifications. Cancellation of K-theory charges
puts additional constraints on the consistency of the models, which render some
chiral D-brane models in the literature inconsistent.Comment: 33 pages, 1 figure. Minor correction
The effective theory of type IIA AdS4 compactifications on nilmanifolds and cosets
We consider string theory compactifications of the form AdS4 x M6 with
orientifold six-planes, where M6 is a six-dimensional compact space that is
either a nilmanifold or a coset. For all known solutions of this type we obtain
the four-dimensional N=1 low energy effective theory by computing the
superpotential, the Kaehler potential and the mass spectrum for the light
moduli. For the nilmanifold examples we perform a cross-check on the result for
the mass spectrum by calculating it alternatively from a direct Kaluza-Klein
reduction and find perfect agreement. We show that in all but one of the coset
models all moduli are stabilized at the classical level. As an application we
show that all but one of the coset models can potentially be used to bypass a
recent no-go theorem against inflation in type IIA theory.Comment: 47 pages main text, 28 pages appendix, 3 tables, 7 figures, v2: added
references, corrected typo
La participación en política de la mujer: un estudio de caso
Más de un siglo después de haberse iniciado la lucha de las sufragistas por la superación de la desigualdad política femenina, todavía hoy se siguen observando diferencias en las oportunidades de acceso de la mujer a los puestos de poder político, a pesar de que a partir de mediados los años ochenta se introduce el sistema de cuotas en España, de la mano del Partido Socialista Obrero Español (PSOE), para conseguir el aumento de la representación femenina y de la paridad. En este trabajo partimos de la hipótesis de que el sistema de cuotas ha favorecido el acceso de las mujeres a las listas de los partidos pese a que siguen teniendo dificultades para incorporarse a cargos legislativos. De este modo, con el objetivo de saber cuál es la presencia de la mujer en ámbitos de toma de decisión en el presente artículo se analiza empíricamente la relación entre militancia y participación en órganos directivos y la relación entre militancia y acceso a puestos de representación observándose cómo el PSOE consigue un mayor equilibrio entre militancia, participación en órganos directivos y acceso a puestos de representación debido al uso del sistema de cuotas. Del mismo modo, y desde la perspectiva cualitativa consideramos la opinión de mujeres políticas, a través de grupos de discusión, que confirmaron nuestra hipótesis de partida, sobre todo para el caso de los partidos progresistas. Así, algunas mujeres pueden ser candidatas, pero debido a la pésima posición que ocupan en las listas llegar a diputadas es mucho más difíci