216 research outputs found
The Minkowski and conformal superspaces
We define complex Minkowski superspace in 4 dimensions as the big cell inside
a complex flag supermanifold. The complex conformal supergroup acts naturally
on this super flag, allowing us to interpret it as the conformal
compactification of complex Minkowski superspace. We then consider real
Minkowski superspace as a suitable real form of the complex version. Our
methods are group theoretic, based on the real conformal supergroup and its
Lie superalgebra.Comment: AMS LaTeX, 44 page
Torsion formulation of gravity
We make it precise what it means to have a connection with torsion as
solution of the Einstein equations. While locally the theory remains the same,
the new formulation allows for topologies that would have been excluded in the
standard formulation of gravity. In this formulation it is possible to couple
arbitrary torsion to gauge fields without breaking the gauge invariance.Comment: AMS-LaTeX, 25 pages. Appendices have been eliminated and the
necessary concepts have been inroduced in the text. We have added some
reference
Gauged extended supergravity without cosmological constant: no-scale structure and supersymmetry breaking
We consider the interplay of duality symmetries and gauged isometries of
supergravity models giving N-extended, spontaneously broken supergravity with a
no-scale structure. Some examples, motivated by superstring and M-theory
compactifications are described.Comment: AMS-LaTeX, 16 pages. Invited paper to appear in the review section of
the IJMP
A Seventeen-Year Epidemiological Surveillance Study of Borrelia burgdorferi Infections in Two Provinces of Northern Spain
This paper reports a 17-year seroepidemiological surveillance study of Borrelia burgdorferi infection, performed with the aim of improving our knowledge of the epidemiology of this pathogen. Serum samples (1,179) from patients (623, stratified with respect to age, sex, season, area of residence and occupation) bitten by ticks in two regions of northern Spain were IFA-tested for B. burgdorferi antibodies. Positive results were confirmed by western blotting. Antibodies specific for B. burgdorferi were found in 13.3% of the patients; 7.8% were IgM positive, 9.6% were IgG positive, and 4.33% were both IgM and IgG positive. Five species of ticks were identified in the seropositive patients: Dermacentor marginatus (41.17% of such patients) Dermacentor reticulatus (11.76%), Rhiphicephalus sanguineus (17.64%), Rhiphicephalus turanicus (5.88%) and Ixodes ricinus (23.52%). B. burgdorferi DNA was sought by PCR in ticks when available. One tick, a D. reticulatus male, was found carrying the pathogen. The seroprevalence found was similar to the previously demonstrated in similar studies in Spain and other European countries
Analysing Food-Porn Images for Usersâ Engagement in the Food Business
PonĂšncia presentada a 24th International Conference of the Catalan Association for Artificial Intelligence, celebrada a Barcelona en 2022.This paper presents an approach for analysing food-porn images and
their related comments published by the cooking school Getcookingcanada Instagram account. Our approach processes the published images to extract colour parameters, counts the number of likes, and also analyses the comments related to
each publication. A dataset containing all these was built, and methods were applied to study correlations among the data: a regression analysis, an ANOVA and a
sentiment analysis of the comments on the dataset to explain the relation between
the quantity of likes and the sentiment obtained from the food images. Our results
show a correlation between the number of likes and the sentiment analysis of the
comments. Images that evoke a positive sentiment have a higher number of likes
and comments. Usersâ experience on creating posts is also analysed and confirms a
positive correlation between the number of likes and the publisherâs experience
The Scherk-Schwarz mechanism as a flux compactification with internal torsion
The aim of this paper is to make progress in the understanding of the
Scherk-Schwarz dimensional reduction in terms of a compactification in the
presence of background fluxes and torsion. From the eleven dimensional
supergravity point of view, we find that a general E6(6) S-S phase may be
obtained by turning on an appropriate background torsion, together with
suitable fluxes, some of which can be directly identified with certain
components of the four-form field-strength. Furthermore, we introduce a novel
(four dimensional) approach to the study of dualities between flux/torsion
compactifications of Type II/M-theory. This approach defines the action that
duality should have on the background quantities, in order for the E7(7)
invariance of the field equations and Bianchi identities to be restored also in
the presence of fluxes/torsion. This analysis further implies the
interpretation of the torsion flux as the T-dual of the NS three-form flux.Comment: Version published on J. High Energy Phy
Effective supergravity descriptions of superstring cosmology
This text is a review of aspects of supergravity theories that are relevant
in superstring cosmology. In particular, it considers the possibilities and
restrictions for `uplifting terms', i.e. methods to produce de Sitter vacua. We
concentrate on N=1 and N=2 supergravities, and the tools of superconformal
methods, which clarify the structure of these theories. Cosmic strings and
embeddings of target manifolds of supergravity theories in others are discussed
in short at the end.Comment: 12 pages, contribution to the proceedings of the 2nd international
conference on Quantum Theories and Renormalization Group in Gravity and
Cosmology, Barcelona, July 11-15, 2006, Journal of Physics
Integration of massive states as contractions of non linear -models
We consider the contraction of some non linear sigma models which appear in
effective supergravity theories. In particular we consider the contractions of
maximally symmetric spaces corresponding to N=1 and N=2 theories, as they
appear in certain low energy effective supergravity actions with mass
deformations.
The contraction procedure is shown to describe the integrating out of massive
modes in the presence of interactions, as it happens in many supergravity
models after spontaneous supersymmetry breaking.Comment: AMS-LaTeX, 33 page
Gauging of Flat Groups in Four Dimensional Supergravity
We show that N=8 spontaneously broken supergravity in four dimensions
obtained by Scherk-Schwarz generalized dimensional reduction can be obtained
from a pure four dimensional perspective by gauging a suitable electric
subgroup of E_{7,7}. Owing to the fact that there are non isomorphic choices of
maximal electric subgroups of the U-duality group their gaugings give rise to
inequivalent theories. This in particular shows that the Scherk-Schwarz
gaugings do not fall in previous classifications of possible gauged N=8
supergravities. Gauging of flat groups appear in many examples of string
compactifications in presence of brane fluxes.Comment: Version to appear on JHE
N=2 Super-Higgs, N=1 Poincare' Vacua and Quaternionic Geometry
In the context of N=2 supergravity we explain the occurrence of partial
super-Higgs with vanishing vacuum energy and moduli stabilization in a model
suggested by superstring compactifications on type IIB orientifolds with 3-form
fluxes.
The gauging of axion symmetries of the quaternionic manifold, together with
the use of degenerate symplectic sections for special geometry, are the
essential ingredients of the construction.Comment: 18 page
- âŠ