927 research outputs found
Dilaton as the Higgs boson
We propose a model where the role of the electroweak Higgs field is played by
the dilaton. The model contains terms which explicitly violate gauge
invariance, however it is shown that this violation is fictitious, so that the
model is a consistent low energy effective theory. In the simplest version of
the idea the resulting low energy effective theory is the same as the top mode
standard model.Comment: 6 pages, v2 with expanded discussio
Bulk Gauge Fields in Warped Space and Localized Supersymmetry Breaking
We consider five dimensional supersymmetric warped scenarios in which the
Standard Model quark and lepton fields are localized on the ultraviolet brane,
while the Standard Model gauge fields propagate in the bulk. Supersymmetry is
assumed to be broken on the infrared brane. The relative sizes of supersymmetry
breaking effects are found to depend on the hierarchy between the infrared
scale and the weak scale. If the infrared scale is much larger than the weak
scale the leading supersymmetry breaking effect on the visible brane is given
by gaugino mediation. The gaugino masses at the weak scale are proportional to
the square of the corresponding gauge coupling, while the dominant contribution
to the scalar masses arises from logarithmically enhanced radiative effects
involving the gaugino mass that are cutoff at the infrared scale. While the LSP
is the gravitino, the NLSP which is the stau is stable on collider time scales.
If however the infrared scale is close to the weak scale then the effects of
hard supersymmetry breaking operators on the scalar masses can become
comparable to those from gaugino mediation. These operators alter the relative
strengths of the couplings of gauge bosons and gauginos to matter, and give
loop contributions to the scalar masses that are also cutoff at the infrared
scale. The gaugino masses, while exhibiting a more complicated dependence on
the corresponding gauge coupling, remain hierarchical and become proportional
to the corresponding gauge coupling in the limit of strong supersymmetry
breaking. The scalar masses are finite and a loop factor smaller than the
gaugino masses. The LSP remains the gravitino.Comment: 36 pages, 2 figure
Electromagnetic Dissociation of Nuclei in Heavy-Ion Collisions
Large discrepancies have been observed between measured Electromagnetic
Dissociation(ED) cross sections and the predictions of the semiclassical
Weiz\"acker-Williams-Fermi(WWF) method. In this paper, the validity of the
semiclassical approximation is examined. The total cross section for
electromagnetic excitation of a nuclear target by a spinless projectile is
calculated in first Born approximation, neglecting recoil. The final result is
expressed in terms of correlation functions and convoluted densities in
configuration space. The result agrees with the WWF approximation to leading
order(unretarded electric dipole approximation), but the method allows an
analytic evaluation of the cutoff, which is determined by the details of the
electric dipole transition charge density. Using the Goldhaber-Teller model of
that density, and uniform charge densities for both projectile and target, the
cutoff is determined for the total cross section in the nonrelativistic limit,
and found to be smaller than values currently used for ED calculations. In
addition, cross sections are calculated using a phenomenological momentum space
cutoff designed to model final state interactions. For moderate projectile
energies, the calculated ED cross section is found to be smaller than the
semiclassical result, in qualitative agreement with experiment.Comment: 28 page
Field localization in warped gauge theories
We present four-dimensional gauge theories that describe physics on
five-dimensional curved (warped) backgrounds, which includes bulk fields with
various spins (vectors, spinors, and scalars). Field theory on the AdS
geometry is examined as a simple example of our formulation. Various properties
of bulk fields on this background, e.g., the mass spectrum and field
localization behavior, can be achieved within a fully four-dimensional
framework. Moreover, that gives a localization mechanism for massless vector
fields. We also consider supersymmetric cases, and show in particular that the
conditions on bulk masses imposed by supersymmetry on warped backgrounds are
derived from a four-dimensional supersymmetric theory on the flat background.
As a phenomenological application, models are shown to generate hierarchical
Yukawa couplings. Finally, we discuss possible underlying mechanisms which
dynamically realize the required couplings to generate curved geometries.Comment: 24 pages, 12 figures; more explanation of nonuniversal gauge
couplings added, typos corrected, references update
Gravitational field of domain wall in Lyra geometry
In this paper, we study the domain wall with time dependent displacement
vectors based on Lyra geometry in normal gauge i.e. displacement vector . The field theoretic energy momentum tensor is
considered with zero pressure perpendicular to the wall. We find an exact
solutions of Einstein equation for a scalar field with a potential
describing the gravitational field of a plane symmetric domain wall.
We have seen that the hyper surfaces parallel to the wall ()
are three dimensional de-sitter spaces. It is also shown that the gravitational
field experienced by test particle is attractive.Comment: 11 pages, 6 figures; Submitted in Astrophysics and Space Science
after minor revisio
Quintessence from Shape Moduli
We show that shape moduli in sub-millimeter extra dimensional scenarios,
addressing the gauge hierarchy problem, can dominate the energy density of the
universe today. In our scenario, the volume of the extra dimensions is
stabilized at a sufficiently high scale to avoid conflicts with nucleosynthesis
and solar-system precision gravity experiments, while the shape moduli remain
light but couple extremely weakly to brane-localized matter and easily avoid
these bounds. Nonlocal effects in the bulk of the extra dimension generate a
potential for the shape moduli. The potential has the right form and order of
magnitude to account for the present day cosmic acceleration, in a way
analogous to models of quintessence as a pseudo Nambu-Goldstone boson.Comment: 8 pages, 1 figur
Weight gain after HIV therapy initiation : pathophysiology and implications
DATA AVAILABILITY : Data sharing is not applicable to this article as no data sets were generated or analyzed during the current study.Rapid advances in the potency, safety, and availability of modern HIV antiretroviral therapy (ART) have yielded a near-normal life expectancy for most people living with HIV (PLWH). Ironically, considering the history of HIV/AIDS (initially called “slim disease” because of associated weight loss), the latest dilemma faced by many people starting HIV therapy is weight gain and obesity, particularly Black people, women, and those who commenced treatment with advanced immunodeficiency. We review the pathophysiology and implications of weight gain among PLWH on ART and discuss why this phenomenon was recognized only recently, despite the availability of effective therapy for nearly 30 years. We comprehensively explore the theories of the causes, from initial speculation that weight gain was simply a return to health for people recovering from wasting to comparative effects of newer regimens vs prior toxic agents, to direct effects of agents on mitochondrial function. We then discuss the implications of weight gain on modern ART, particularly concomitant effects on lipids, glucose metabolism, and inflammatory markers. Finally, we discuss intervention options for PLWH and obesity, from the limitations of switching ART regimens or specific agents within regimens, weight-gain mitigation strategies, and potential hope in access to emerging antiobesity agents, which are yet to be evaluated in this population.The National Institutes of Health (NIH) and the HLB-SIMPLe Alliance, sponsored by the National Heart, Lung and Blood Institute and funded with the US Department of Health and Human Services, NIH, National Heart, Lung and Blood Institute (NIH/NHLBI).https://academic.oup.com/jcemhj2024School of Health Systems and Public Health (SHSPH)SDG-03:Good heatlh and well-bein
Functional gene group analysis indicates no role for heterotrimeric G proteins in cognitive ability
Previous functional gene group analyses implicated common single nucleotide polymorphisms (SNPs) in heterotrimeric G protein coding genes as being associated with differences in human intelligence. Here, we sought to replicate this finding using five independent cohorts of older adults including current IQ and childhood IQ, and using both gene- and SNP-based analytic strategies. No significant associations were found between variation in heterotrimeric G protein genes and intelligence in any cohort at either of the two time points. These results indicate that, whereas G protein systems are important in cognition, common genetic variation in these genes is unlikely to be a substantial influence on human intelligence differences
Shared genetic aetiology between cognitive functions and physical and mental health in UK Biobank (N=112 151) and 24 GWAS consortia.
Causes of the well-documented association between low levels of cognitive functioning and many adverse neuropsychiatric outcomes, poorer physical health and earlier death remain unknown. We used linkage disequilibrium regression and polygenic profile scoring to test for shared genetic aetiology between cognitive functions and neuropsychiatric disorders and physical health. Using information provided by many published genome-wide association study consortia, we created polygenic profile scores for 24 vascular-metabolic, neuropsychiatric, physiological-anthropometric and cognitive traits in the participants of UK Biobank, a very large population-based sample (N=112?151). Pleiotropy between cognitive and health traits was quantified by deriving genetic correlations using summary genome-wide association study statistics and to the method of linkage disequilibrium score regression. Substantial and significant genetic correlations were observed between cognitive test scores in the UK Biobank sample and many of the mental and physical health-related traits and disorders assessed here. In addition, highly significant associations were observed between the cognitive test scores in the UK Biobank sample and many polygenic profile scores, including coronary artery disease, stroke, Alzheimer's disease, schizophrenia, autism, major depressive disorder, body mass index, intracranial volume, infant head circumference and childhood cognitive ability. Where disease diagnosis was available for UK Biobank participants, we were able to show that these results were not confounded by those who had the relevant disease. These findings indicate that a substantial level of pleiotropy exists between cognitive abilities and many human mental and physical health disorders and traits and that it can be used to predict phenotypic variance across samples.Molecular Psychiatry advance online publication, 26 January 2016; doi:10.1038/mp.2015.225
From Household Size to the Life Course
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66696/2/10.1177_000276427702100207.pd
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