116 research outputs found
Type IIA/M-theory Moduli fixing in a Class of Orientifold Models
We present the study of type II A flux vacua and their M-theory duals for
compactification on a class of Calabi-Yau orientifolds. The Kaehler potential
is derived from toroidal compactifications and the superpotential contains a
contribution from non-Abelian gauge degrees of freedoms. We obtain complete
stabilisation of the moduli. We found one supersymmetric minimum and several
non supersymmetric ones. Consistency of the analysis constrains the parameters
of the models in a finite region containing a finite, although very large,
number of flux vacua. From the M-theory side, we found some differences in the
distributions of the physical quantities with respect to the M-theory ensemble
studied by Acharya et al. In particular, it is easier to find small
supersymmetry breaking scale.Comment: 37 pages, 4 figures, LaTeX. Extended one Section, added reference
Exact Gravitational Dual of a Plasma Ball
We present an exact solution for a black hole localized near an infrared wall
in four-dimensional anti-deSitter space. By computing the holographic stress
tensor we show that the CFT dual of the black hole is a 2+1-dimensional ball
(i.e., a disk) of plasma at finite temperature, surrounded by vacuum. This
confirms some earlier conjectures about plasma balls in AdS/CFT. We also
estimate the value of the surface tension for the ball. The solution displays a
number of peculiarities, most notably a non-trivial curvature of the boundary
geometry, as well as other properties associated to the vanishing deconfinement
temperature of the set up. We discuss how these features are related to
specific physics at the infrared and ultraviolet boundaries for this solution,
and should not be generic properties of plasma balls.Comment: 23 pages, 3 figure
Correction of Italian under-reporting in the first COVID-19 wave via age-specific deconvolution of hospital admissions
When the COVID-19 pandemic first emerged in early 2020, healthcare and
bureaucratic systems worldwide were caught off guard and largely unprepared to
deal with the scale and severity of the outbreak. In Italy, this led to a
severe underreporting of infections during the first wave of the spread. The
lack of accurate data is critical as it hampers the retrospective assessment of
nonpharmacological interventions, the comparison with the following waves, and
the estimation and validation of epidemiological models. In particular, during
the first wave, reported cases of new infections were strikingly low if
compared with their effects in terms of deaths, hospitalizations and intensive
care admissions. In this paper, we observe that the hospital admissions during
the second wave were very well explained by the convolution of the reported
daily infections with an exponential kernel. By formulating the estimation of
the actual infections during the first wave as an inverse problem, its solution
by a regularization approach is proposed and validated. In this way, it was
possible to computed corrected time series of daily infections for each age
class. The new estimates are consistent with the serological survey published
in June 2020 by the National Institute of Statistics (ISTAT) and can be used to
speculate on the total number of infections occurring in Italy during 2020,
which appears to be about double the number officially recorded.Comment: 19 pages, 4 main figures, 2 supplementary figures, 2 table
Bagger-Lambert Theory for General Lie Algebras
We construct the totally antisymmetric structure constants f^{ABCD} of a
3-algebra with a Lorentzian bi-invariant metric starting from an arbitrary
semi-simple Lie algebra. The structure constants f^{ABCD} can be used to write
down a maximally superconformal 3d theory that incorporates the expected
degrees of freedom of multiple M2 branes, including the "center-of-mass" mode
described by free scalar and fermion fields. The gauge field sector reduces to
a three dimensional BF term, which underlies the gauge symmetry of the theory.
We comment on the issue of unitarity of the quantum theory, which is
problematic, despite the fact that the specific form of the interactions
prevent the ghost fields from running in the internal lines of any Feynman
diagram. Giving an expectation value to one of the scalar fields leads to the
maximally supersymmetric 3d Yang-Mills Lagrangian with the addition of two U(1)
multiplets, one of them ghost-like, which is decoupled at large g_YM.Comment: 12 pages, Latex; small corrections and references added; published
version (small typos fixed
The GENIUS Grid Portal and robot certificates: a new tool for e-Science
<p>Abstract</p> <p>Background</p> <p>Grid technology is the computing model which allows users to share a wide <it>pletora </it>of distributed computational resources regardless of their geographical location. Up to now, the high security policy requested in order to access distributed computing resources has been a rather big limiting factor when trying to broaden the usage of Grids into a wide community of users. Grid security is indeed based on the Public Key Infrastructure (PKI) of X.509 certificates and the procedure to get and manage those certificates is unfortunately not straightforward. A first step to make Grids more appealing for new users has recently been achieved with the adoption of robot certificates.</p> <p>Methods</p> <p>Robot certificates have recently been introduced to perform automated tasks on Grids on behalf of users. They are extremely useful for instance to automate grid service monitoring, data processing production, distributed data collection systems. Basically these certificates can be used to identify a person responsible for an unattended service or process acting as client and/or server. Robot certificates can be installed on a smart card and used behind a portal by everyone interested in running the related applications in a Grid environment using a user-friendly graphic interface. In this work, the GENIUS Grid Portal, powered by EnginFrame, has been extended in order to support the new authentication based on the adoption of these robot certificates.</p> <p>Results</p> <p>The work carried out and reported in this manuscript is particularly relevant for all users who are not familiar with personal digital certificates and the technical aspects of the Grid Security Infrastructure (GSI). The valuable benefits introduced by robot certificates in e-Science can so be extended to users belonging to several scientific domains, providing an asset in raising Grid awareness to a wide number of potential users.</p> <p>Conclusion</p> <p>The adoption of Grid portals extended with robot certificates, can really contribute to creating transparent access to computational resources of Grid Infrastructures, enhancing the spread of this new paradigm in researchers' working life to address new global scientific challenges. The evaluated solution can of course be extended to other portals, applications and scientific communities.</p
Singularities and closed time-like curves in type IIB 1/2 BPS geometries
We study in detail the moduli space of solutions discovered in LLM relaxing
the constraint that guarantees the absence of singularities. The solutions fall
into three classes, non-singular, null-singular and time machines with a
time-like naked singularity. We study the general features of these metrics and
prove that there are actually just two generic classes of space-times - those
with null singularities are in the same class as the non-singular metrics.
AdS/CFT seems to provide a dual description only for the first of these two
types of space-time in terms of a unitary CFT indicating the possible existence
of a chronology protection mechanism for this class of geometries.Comment: 34 pages, 7 figures, LaTeX. References adde
Impact of Preoperative Patient Characteristics and Flow Rate on Failure, Early Complications, and Voiding Dysfunction After a Transobturator Tape Procedure: A Multicentre Study
Purpose: To evaluate the impact of preoperative patient characteristics and flow rate on failure, early postoperative complications, and voiding in patients who underwent transvaginal tension-free vaginal tape-obturator (TVT-O) treatment for uncomplicated stress urinary incontinence (SUI).Methods: We retrospectively reviewed patients who underwent TVT-O for SUI at 3 Italian centres. The exclusion criteria were predominant voiding and storage symptoms suggestive of detrusor overactivity, the presence of grade > 1 urogenital prolapse, previous pelvic radiotherapy or other clinical contraindications for surgical procedures, neurogenic bladder dysfunction, and collagen diseases. Multivariate logistic regression models were constructed to identify predictors of early voiding dysfunction after TVT-O.Results: A total of 219 patients underwent TVT-O between January 2010 and December 2015. All patients received follow-up at 3, 6, and 12 months, and underwent a stress test, uroflowmetry, and bladder ultrasound to evaluate the postvoid residual volume. They also responded to the Urogenital Distress Inventory (UDI-6) questionnaire. The rates of persistent incontinence after TVT-O, postoperative complications, and satisfaction were 16.4% (36 of 219), 24.2% (53 of 219), and 86.3% (189 of 219), respectively. Nineteen patients (9.5%) experienced early voiding dysfunction. Based on an analysis of baseline characteristics, we determined that a cutoff value of 9.0 on the UDI-6 predicted postoperative SUI with 62% specificity, 72% sensitivity, and 66% accuracy. In the multivariate logistic regression analysis, a preoperative UDI-6 >= 9.0 was an independent predictor of postoperative SUI. The predictors of complications were menopause (P = 0.04) and the preoperative UDI-6 score (P = 0.01).Conclusions: Menopause and UDI-6 scores could be prognostic factors for persistent SUI after TVT-O. Well-designed prospective studies with a suitable number of patients are needed to corroborate our findings
Microsatellite diversity of the Nordic type of goats in relation to breed conservation: how relevant is pure ancestry?
In the last decades, several endangered breeds of livestock species have been re-established effectively. However, the successful revival of the Dutch and Danish Landrace goats involved crossing with exotic breeds and the ancestry of the current populations is therefore not clear. We have generated genotypes for 27 FAO-recommended microsatellites of these landraces and three phenotypically similar Nordic-type landraces and compared these breeds with central European, Mediterranean and south-west Asian goats. We found decreasing levels of genetic diversity with increasing distance from the south-west Asian domestication site with a south-east-to-north-west cline that is clearly steeper than the Mediterranean east-to-west cline. In terms of genetic diversity, the Dutch Landrace comes next to the isolated Icelandic breed, which has an extremely low diversity. The Norwegian coastal goat and the Finnish and Icelandic landraces are clearly related. It appears that by a combination of mixed origin and a population bottleneck, the Dutch and Danish Land-races are separated from the other breeds. However, the current Dutch and Danish populations with the multicoloured and long-horned appearance effectively substitute for the original breed, illustrating that for conservation of cultural heritage, the phenotype of a breed is more relevant than pure ancestry and the genetic diversity of the original breed. More in general, we propose that for conservation, the retention of genetic diversity of an original breed and of the visual phenotype by which the breed is recognized and defined needs to be considered separately
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