68 research outputs found
Testing the cosmic distance duality with X-ray gas mass fraction and supernovae data
In this paper we discuss a new cosmological model-independent test for the
cosmic distance duality relation (CDDR), , where and are the angular
and luminosity distances, respectively. Using the general expression for X-ray
gas mass fraction () of galaxy clusters, , we show that observations jointly with type Ia
supernovae (SNe Ia) data furnish a validity test for the CDDR. To perform our
analysis we use 38 measurements recently studied by two groups
considering different assumptions to describe the clusters (La Roque {\it{et
al.}} 2006 and Ettori {\it{et al.}} 2009) and two subsamples of SNe Ia distance
luminosity extracted from the Union2 compilation. In our test we consider the
parameter as a function of the redshift parameterized by two different
functional forms. It is found that the La Roque {\it{et al.}} (2006) sample is
in perfect agreement with the duality relation () whereas the Ettori
{\it{et al.}} (2009) sample presents a significant conflict.Comment: 5 pages, 2 figures, 1 table, Letter to MNRAS (in press
New Constraints (and Motivations) for Abelian Gauge Bosons in the MeV-TeV Mass Range
We survey the phenomenological constraints on abelian gauge bosons having
masses in the MeV to multi-GeV mass range (using precision electroweak
measurements, neutrino-electron and neutrino-nucleon scattering, electron and
muon anomalous magnetic moments, upsilon decay, beam dump experiments, atomic
parity violation, low-energy neutron scattering and primordial
nucleosynthesis). We compute their implications for the three parameters that
in general describe the low-energy properties of such bosons: their mass and
their two possible types of dimensionless couplings (direct couplings to
ordinary fermions and kinetic mixing with Standard Model hypercharge). We argue
that gauge bosons with very small couplings to ordinary fermions in this mass
range are natural in string compactifications and are likely to be generic in
theories for which the gravity scale is systematically smaller than the Planck
mass - such as in extra-dimensional models - because of the necessity to
suppress proton decay. Furthermore, because its couplings are weak, in the
low-energy theory relevant to experiments at and below TeV scales the charge
gauged by the new boson can appear to be broken, both by classical effects and
by anomalies. In particular, if the new gauge charge appears to be anomalous,
anomaly cancellation does not also require the introduction of new light
fermions in the low-energy theory. Furthermore, the charge can appear to be
conserved in the low-energy theory, despite the corresponding gauge boson
having a mass. Our results reduce to those of other authors in the special
cases where there is no kinetic mixing or there is no direct coupling to
ordinary fermions, such as for recently proposed dark-matter scenarios.Comment: 49 pages + appendix, 21 figures. This is the final version which
appears in JHE
Association of toll-interacting protein gene polymorphisms with atopic dermatitis
BACKGROUND: Atopic dermatitis (AD) is a common inflammatory skin disorder, affecting up to 15% of children in industrialized countries. Toll-interacting protein (TOLLIP) is an inhibitory adaptor protein within the toll-like receptor (TLR) pathway, a part of the innate immune system that recognizes structurally conserved molecular patterns of microbial pathogens, leading to an inflammatory immune response. METHODS: In order to detect a possible role of TOLLIP variation in the pathogenesis of AD, we screened the entire coding sequence of the TOLLIP gene by SSCP in 50 AD patients. We identified an amino acid exchange in exon 6 (Ala222Ser) and a synonymous variation in exon 4 (Pro139Pro). Subsequently, these two variations and four additional non-coding polymorphisms (-526 C/G, two polymorphisms in intron 1 and one in the 3'UTR) were genotyped in 317 AD patients and 224 healthy controls. RESULTS: The -526G allele showed borderline association with AD in our cohort (p = 0.012; significance level after correction for multiple testing 0.0102). Haplotype analysis did not yield additional information. Evaluation of mRNA expression by quantitative real-time polymerase chain reaction in six probands with the CC and six with the GG genotype at the -526 C/G locus did not reveal significant differences between genotypes. CONCLUSION: Variation in the TOLLIP gene may play a role in the pathogenesis of AD. Yet, replication studies in other cohorts and populations are warranted to confirm these association results
Micron-scale mapping of megagauss magnetic fields using optical polarimetry to probe hot electron transport in petawatt-class laser-solid interactions
The transport of hot, relativistic electrons produced by the interaction of an intense petawatt laser pulse with a solid has garnered interest due to its potential application in the development of innovative x-ray sources and ion-acceleration schemes. We report on spatially and temporally resolved measurements of megagauss magnetic fields at the rear of a 50-μm thick plastic target, irradiated by a multi-picosecond petawatt laser pulse at an incident intensity of ~1020 W/cm2. The pump-probe polarimetric measurements with micron-scale spatial resolution reveal the dynamics of the magnetic fields generated by the hot electron distribution at the target rear. An annular magnetic field profile was observed ~5 ps after the interaction, indicating a relatively smooth hot electron distribution at the rear-side of the plastic target. This is contrary to previous time-integrated measurements, which infer that such targets will produce highly structured hot electron transport. We measured large-scale filamentation of the hot electron distribution at the target rear only at later time-scales of ~10 ps, resulting in a commensurate large-scale filamentation of the magnetic field profile. Three-dimensional hybrid simulations corroborate our experimental observations and demonstrate a beam-like hot electron transport at initial time-scales that may be attributed to the local resistivity profile at the target rear
Interpreting a 750 GeV diphoton resonance
We discuss the implications of the significant excesses in the diphoton final
state observed by the LHC experiments ATLAS and CMS around a diphoton invariant
mass of 750 GeV. The interpretation of the excess as a spin-zero s-channel resonance implies
model-independent lower bounds on both its branching ratio and its coupling to photons,
which stringently constrain dynamical models. We consider both the case where the
excess is described by a narrow and a broad resonance. We also obtain model-independent
constraints on the allowed couplings and branching fractions to final states other than
diphotons, by including the interplay with 8 TeV searches. These results can guide attempts
to construct viable dynamical models of the resonance. Turning to specific models,
our findings suggest that the anomaly cannot be accounted for by the presence of only an
additional singlet or doublet spin-zero field and the Standard Model degrees of freedom; this
includes all two-Higgs-doublet models. Likewise, heavy scalars in the MSSM cannot explain
the excess if stability of the electroweak vacuum is required, at least in a leading-order analysis.
If we assume that the resonance is broad we find that it is challenging to find a weakly
coupled explanation. However, we provide an existence proof in the form of a model with
vectorlike quarks with large electric charge that is perturbative up to the 100 TeV scale.
For the narrow-resonance case a similar model can be perturbative up to high scales also
with smaller charges. We also find that, in their simplest form, dilaton models cannot
explain the size of the excess. Some implications for flavor physics are briefly discussed
Impaired flow-induced arterial remodeling in DOCA-salt hypertensive rats
Arteries from young healthy animals respond to chronic changes in blood flow and blood pressure by structural remodeling. We tested whether the ability to respond to decreased (-90%) or increased (+100%) blood flow is impaired during the development of deoxycorticosterone acetate (DOCA)-salt hypertension in rats, a model for an upregulated endothelin-1 system. Mesenteric small arteries (MrA) were exposed to low blood flow (LF) or high blood flow (HF) for 4 or 7 weeks. The bioavailability of vasoactive peptides was modified by chronic treatment of the rats with the dual neutral endopeptidase (NEP)/endothelin-converting enzyme (ECE) inhibitor SOL1. After 3 or 6 weeks of hypertension, the MrA showed hypertrophic arterial remodeling (3 weeks: media cross-sectional area (mCSA): 10 +/- 1 x 10(3) to 17 +/- 2 x 10(3) mu m(2); 6 weeks: 13 +/- 2 x 10(3) to 24 +/- 3 x 10(3) mu m(2)). After 3, but not 6, weeks of hypertension, the arterial diameter was increased (empty set: 385 +/- 13 to 463 +/- 14 mu m). SOL1 reduced hypertrophy after 3 weeks of hypertension (mCSA: 6 x 10(3) +/- 1 x 10(3) mu m(2)). The diameter of the HF arteries of normotensive rats increased (empty set: 463 +/- 22 mu m) but no expansion occurred in the HF arteries of hypertensive rats (empty set: 471 +/- 16 mu m). MrA from SOL1-treated hypertensive rats did show a significant diameter increase (empty set: 419 +/- 13 to 475 +/- 16 mu m). Arteries exposed to LF showed inward remodeling in normotensive and hypertensive rats (mean empty set between 235 and 290 mu m), and infiltration of monocyte/ macrophages. SOL1 treatment did not affect the arterial diameter of LF arteries but reduced the infiltration of monocyte/ macrophages. We show for the first time that flow-induced remodeling is impaired during the development of DOCA-salt hypertension and that this can be prevented by chronic NEP/ECE inhibition. Hypertension Research (2012) 35, 1093-1101; doi:10.1038/hr.2012.94; published online 12 July 201
A megaxion at 750 GeV as a first hint of low scale string theory
Journal of High Energy Physics 2016.7 (2016): 021 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)Low scale string models naturally have axion-like pseudoscalars which couple directly to gluons and photons (but not W’s) at tree level. We show how they typically get tree level masses in the presence of closed string fluxes, consistent with the axion discrete gauge symmetry, in a way akin of the axion monodromy of string inflation and relaxion models. We discuss the possibility that the hints for a resonance at 750 GeV recently reported at ATLAS and CMS could correspond to such a heavy axion state (megaxion). Adjusting the production rate and branching ratios suggest the string scale to be of order Ms ≈ 7–104 TeV, depending on the compactification geometry. If this interpretation was correct, one extra Z’ gauge boson could be produced before reaching the string threshold at LHC and future collidersThis work is partially supported by the grants FPA2012-32828 and FPA2015-65929-P from the MINECO, the ERC Advanced Grant SPLE under contract ERC-2012-ADG-20120216-320421, the Consolider-Ingenio 2010 programme under grant MULTIDARK CSD2009-00064 and the grant SEV-2012-0249 of the “Centro de Excelencia Severo Ochoa” Programm
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