1,364 research outputs found
Asymptotic Behavior for a Nonlocal Diffusion Equation in Domains with Holes
The paper deals with the asymptotic behavior of solutions to a non-local
diffusion equation, , in an exterior domain, , which
excludes one or several holes, and with zero Dirichlet data on
. When the space dimension is three or more this
behavior is given by a multiple of the fundamental solution of the heat
equation away from the holes. On the other hand, if the solution is scaled
according to its decay factor, close to the holes it behaves like a function
that is -harmonic, , in the exterior domain and vanishes in its
complement. The height of such a function at infinity is determined through a
matching procedure with the multiple of the fundamental solution of the heat
equation representing the outer behavior. The inner and the outer behavior can
be presented in a unified way through a suitable global approximation
ON GAUGINO CONDENSATION WITH FIELD-DEPENDENT GAUGE COUPLINGS
We study in detail gaugino condensation in globally and locally
supersymmetric Yang-Mills theories. We focus on models for which gauge-neutral
matter couples to the gauge bosons only through nonminimal gauge kinetic terms,
for the cases of one and several condensing gauge groups. Using only symmetry
arguments, the low-energy expansion, and general properties of supersymmetry,
we compute the low energy Wilson action, as well as the (2PI) effective action
for the composite {\it classical} superfield U\equiv\langle \Tr\WW \rangle,
with the supersymmetric gauge field strength. The 2PI effective
action provides a firmer foundation for the approach of Veneziano and
Yankielowicz, who treated the composite superfield, , as a quantum degree of
freedom. We show how to rederive the Wilson action by minimizing the 2PI action
with respect to . We determine, in both formulations and for global and
local supersymmetry, the effective superpotential, , the non-perturbative
contributions to the low-energy K\"ahler potential , and the leading higher
supercovariant derivative terms in an expansion in inverse powers of the
condensation scale. As an application of our results we include the string
moduli dependence of the super- and K\"ahler potentials for simple orbifold
models.Comment: 54 pages, plain te
Brans-Dicke-type theories and avoidance of the cosmological singularity
We tudy flat Friedmann-Robertson-Walker cosmology in Brans-Dicke-type
theories of gravitation with minimal coupling between the scalar field and the
matter fields in the Einstein frame (general relativity with an extra scalar
field) for arbitrary values of the Brans-Dicke parameter . It is
shown that the cosmological singularity occuring in the Einstein frame
formulation of this theory is removed in the Jordan frame in the range
. This result is interpreted in the ligth of a
viewpoint (first presented in reference gr-qc/9905071) asserting that both
Jordan frame and Einstein frame formulations of general relativity are
physically equivalent. The implications of the obtained result for string
theory are outlined.Comment: 9 pages, LaTeX, no figures. Improved version accepted for publication
in PR
Radiative Electroweak Symmetry-Breaking Revisited
In the absence of a tree-level scalar-field mass, renormalization-group
methods permit the explicit summation of leading-logarithm contributions to all
orders of the perturbative series within the effective potential for
electroweak symmetry. This improvement of the effective
potential function is seen to reduce residual dependence on the renormalization
mass scale. The all-orders summation of leading logarithm terms involving the
dominant three couplings contributing to radiative corrections is suggestive of
a potential characterized by a plausible Higgs boson mass of 216 GeV. However,
the tree potential's local minimum at is restored if QCD is
sufficiently strong.Comment: revtex, 4 pages, 1 eps figure embedded in manuscript. Updated version
contains additional comments and corrects minor error
Near-brane SU(6) origin Higgs in Scherk-Schwarz breaking of five-dimensional SU(6) GUT
The symmetry breaking of five-dimensional SU(6) GUT is realized by
Scherk-Schwarz mechanisms through trivial and pseudo nontrivial orbifold S1/Z2
breakings to produce dimensional deconstruction 5D SU(6) \rightarrow4D SU(6).
The latter also induces near-brane weakly-coupled SU(6) Baby Higgs to further
break the symmetry into SU(3)C \otimes SU(3)H \otimes U(1)C. The model
successfully provides a scenario of the origin of (Little) Higgs from GUT
scale, produces the (intermediate and light) Higgs boson with the most
preferred range and establishes coupling unification and compactification scale
correctly.Comment: 23 pages, 5 figure
Dual geometries and spacetime singularities
The notion of geometrical duality is discussed in the context of both
Brans-Dicke theory and general relativity. It is shown that, in some particular
solutions, the spacetime singularities that arise in usual Riemannian general
relativity may be avoided in its dual representation (Weyl-type general
relativity). This dual representation provides a singularity-free picture of
the World that is physicaly equivalent to the canonical general relativistic
one.Comment: 11 pages, LaTeX, no figures, version accepted for publication in PR
The absolute age of the globular cluster M15 using near-infrared adaptive optics images from PISCES/LBT
We present deep near-infrared (NIR) J, Ks photometry of the old, metal-poor
Galactic globular cluster M\,15 obtained with images collected with the LUCI1
and PISCES cameras available at the Large Binocular Telescope (LBT). We show
how the use of First Light Adaptive Optics system coupled with the (FLAO)
PISCES camera allows us to improve the limiting magnitude by ~2 mag in Ks. By
analyzing archival HST data, we demonstrate that the quality of the LBT/PISCES
color magnitude diagram is fully comparable with analogous space-based data.
The smaller field of view is balanced by the shorter exposure time required to
reach a similar photometric limit. We investigated the absolute age of M\,15 by
means of two methods: i) by determining the age from the position of the main
sequence turn-off; and ii) by the magnitude difference between the MSTO and the
well-defined knee detected along the faint portion of the MS. We derive
consistent values of the absolute age of M15, that is 12.9+-2.6 Gyr and
13.3+-1.1 Gyr, respectively.Comment: 13 pages, 8 figures, ApJ accepte
Liver fibrosis: concordance analysis between APRI and FIB-4 scores, evolution and predictors in a cohort of HIV patients without HCV and HBV infection
evaluation of liver fibrosis concordance analysis between noninvasive scores apri and fib 4 evolution and predictors in a cohort of hiv infected patients without hepatitis c and b infection
Background. There is lack of data on the incidence of liver fibrosis (LF) progression in patients with human immunodeficiency virus (HIV) monoinfection and risk factors for LF. Methods. We performed an observational prospective study in a cohort of HIV-infected patients who had initiated highly active antiretroviral therapy (HAART). FIB-4 and aspartate aminotransferase (AST)-to-platelet ratio index (APRI) were assessed. The concordance between the 2 scores was assessed by weighted kappa coefficient. Kaplan-Meier analysis was used to estimate the incidence of LF. Cox regression analysis was used to assess the predictors of transition. Results. A total of 1112 patients were observed for a mean of 2249 days of follow-up. The concordance between FIB-4 and APRI was moderate (kappa = .573). The incidence of transition to higher FIB-4 classes was 0.064 (95% confidence interval [CI], 0.056â0.072) per person-year of follow-up (PYFU), whereas the incidence of transition to higher APRI classes was 0.099 (95% CI, 0.089-0.110) per PYFU. The incidence of transition to FIB-4 >3.25 was 0.013 per PYFU (95% CI, 0.010-0.017) and 0.018 per PYFU (95% CI, 0.014â0.022) for APRI >1.5. In multivariate analyses, for transition to higher classes, HIV RNA level 3.25 and APRI> 1.5 as study outcomes. Conclusions. Overall, our results suggest a possible benefit associated with earlier HAART initiation, provided that the effectiveness of HAART is sustained and treatment with DDX is avoided
Low-level viraemia, measured as viraemia copy-years, as a prognostic factor for mediumâlong-term all-cause mortality: a MASTER cohort study
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