1,890 research outputs found
Exotic Tetraquark states with two -quarks and and states in a nonperturbatively-tuned Lattice NRQCD setup
We use Wilson-clover gauge-field ensembles from the CLS consortium
in a Lattice NRQCD setup to predict the binding energy of a
tetraquark and a
tetraquark. We determine the binding energies with respect to the relevant
and thresholds respectively to be MeV for the
, and MeV for the . We
also determine the ground-state and mesons
to lie and MeV below the and thresholds
respectively. Our errors are entirely dominated by systematics due to
discretisation effects. To achieve these measurements, we performed a neural
network based nonperturbative tuning of the Lattice NRQCD Hamiltonian's
parameters against the basic bottomonium spectrum. For all lattice spacings
considered we can reproduce the continuum splittings of low-lying bottomonia.
It is worth remarking that our nonperturbative tuning parameters deviate from 1
by significant amounts, particularly the term .Comment: 48 pages, 16 figure
Arrhythmogenic Substrates for Atrial Fibrillation in Obesity
Global obesity rates have nearly tripled since 1975. This obesity rate increase is mirrored by increases in atrial fibrillation (AF) that now impacts nearly 10% of Americans over the age of 65. Numerous epidemiologic studies have linked incidence of AF and obesity and other obesity-related diseases, including hypertension and diabetes. Due to the wealth of epidemiologic data linking AF with obesity-related disease, mechanisms of AF pathogenesis in the context of obesity are an area of ongoing investigation. However, progress has been somewhat slowed by the complex phenotype of obesity; separating the effects of obesity from those of related sequelae is problematic. While the initiation of pathogenic pathways leading to AF varies with disease (including increased glycosylation in diabetes, increased renin angiotensin aldosterone system activation in hypertension, atrial ischemia in coronary artery disease, and sleep apnea) the pathogenesis of AF is united by shared mediators of altered conduction in the atria. We suggest focusing on these downstream mediators of AF in obesity is likely to yield more broadly applicable data. In the context of obesity, AF is driven by the interrelated processes of inflammation, atrial remodeling, and oxidative stress. Obesity is characterized by a constant low-grade inflammation that leads to increased expression of pro-inflammatory cytokines. These cytokines contribute to changes in cardiomyocyte excitability. Atrial structural remodeling, including fibrosis, enlargement, and fatty infiltration is a prominent feature of AF and contributes to the altered conduction. Finally, obesity impacts oxidative stress. Within the cardiomyocyte, oxidative stress is increased through both increased production of reactive oxygen species and by downregulation of scavenging enzymes. This increased oxidative stress modulates of cardiomyocyte excitability, increasing susceptibility to AF. Although the initiating insults vary, inflammation, atrial remodeling, and oxidative stress are conserved mechanisms in the pathophysiology of AF in the obese patients. In this review, we highlight mechanisms that have been shown to be relevant in the pathogenesis of AF across obesity-related disease
Reanalysis of the FEROS observations of HIP 11952
Aims. We reanalyze FEROS observations of the star HIP 11952 to reassess the
existence of the proposed planetary system. Methods. The radial velocity of the
spectra were measured by cross-correlating the observed spectrum with a
synthetic template. We also analyzed a large dataset of FEROS and HARPS
archival data of the calibrator HD 10700 spanning over more than five years. We
compared the barycentric velocities computed by the FEROS and HARPS pipelines.
Results. The barycentric correction of the FEROS-DRS pipeline was found to be
inaccurate and to introduce an artificial one-year period with a semi-amplitude
of 62 m/s. Thus the reanalysis of the FEROS data does not support the existence
of planets around HIP 11952.Comment: 7 pages, 8 figures, 1 tabl
Tilt Modulus and Angle-Dependent Flux Lattice Melting in the Lowest Landau Level Approximation
For a clean high-T superconductor, we analyze the Lawrence-Doniach free
energy in a tilted magnetic field within the lowest Landau level (LLL)
approximation. The free energy maps onto that of a strictly -axis field, but
with a reduced interlayer coupling. We use this result to calculate the tilt
modulus of a vortex lattice and vortex liquid. The vortex contribution
to can be expressed in terms of the squared -axis Josephson plasmon
frequency . The transverse component of the field has very
little effect on the position of the melting curve.Comment: 8 pages, 2 figures, accepted for publication in Physical Review B
(Rapid Communications
HATS-5b: A Transiting hot-Saturn from the HATSouth Survey
We report the discovery of HATS-5b, a transiting hot-Saturn orbiting a G type
star, by the HAT-South survey. HATS-5b has a mass of Mp=0.24 Mj, radius of
Rp=0.91 Rj, and transits its host star with a period of P=4.7634d. The radius
of HATS-5b is consistent with both theoretical and empirical models. The host
star has a V band magnitude of 12.6, mass of 0.94 Msun, and radius of 0.87
Rsun. The relatively high scale height of HATS-5b, and the bright,
photometrically quiet host star, make this planet a favourable target for
future transmission spectroscopy follow-up observations. We reexamine the
correlations in radius, equilibrium temperature, and metallicity of the
close-in gas-giants, and find hot Jupiter-mass planets to exhibit the strongest
dependence between radius and equilibrium temperature. We find no significant
dependence in radius and metallicity for the close-in gas-giant population.Comment: 10 pages, submitted to A
Hadron Spectroscopy with Dynamical Chirally Improved Fermions
We simulate two dynamical, mass degenerate light quarks on 16^3x32 lattices
with a spatial extent of 2.4 fm using the Chirally Improved Dirac operator. The
simulation method, the implementation of the action and signals of
equilibration are discussed in detail. Based on the eigenvalues of the Dirac
operator we discuss some qualitative features of our approach. Results for
ground state masses of pseudoscalar and vector mesons as well as for the
nucleon and delta baryons are presented.Comment: 26 pages, 17 figures, 10 table
The Mass-Radius Relationship for Very Low Mass Stars: Four New Discoveries from the HATSouth Survey
We report the discovery of four transiting F-M binary systems with companions
between 0.1-0.2 Msun in mass by the HATSouth survey. These systems have been
characterised via a global analysis of the HATSouth discovery data, combined
with high-resolution radial velocities and accurate transit photometry
observations. We determined the masses and radii of the component stars using a
combination of two methods: isochrone fitting of spectroscopic primary star
parameters, and equating spectroscopic primary star rotation velocity with
spin-orbit synchronisation. These new very low mass companions are HATS550-016B
(0.110 -0.006/+0.005 Msun, 0.147 -0.004/+0.003 Rsun), HATS551-019B (0.17
-0.01/+0.01 Msun, 0.18 -0.01/+0.01 Rsun), HATS551-021B (0.132 -0.005/+0.014
Msun, 0.154 -0.008/+0.006 Rsun), HATS553-001B (0.20 -0.02/+0.01 Msun, 0.22
-0.01/+0.01 Rsun). We examine our sample in the context of the radius anomaly
for fully-convective low mass stars. Combining our sample with the 13 other
well-studied very low mass stars, we find a tentative 5% systematic deviation
between the measured radii and theoretical isochrone models.Comment: 17 pages, 8 figures, accepted for publication in MNRA
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