872 research outputs found
Strong contribution to octet baryon mass splittings
We calculate the contribution to the mass splittings in baryonic
isospin multiplets using SU(3) chiral perturbation theory and lattice QCD.
Fitting isospin-averaged perturbation theory functions to PACS-CS and
QCDSF-UKQCD Collaboration lattice simulations of octet baryon masses, and using
the physical light quark mass ratio as input, allows ,
and to be evaluated from the
full SU(3) theory. The resulting values for each mass splitting are consistent
with the experimental values after allowing for electromagnetic corrections. In
the case of the nucleon, we find , with the
dominant uncertainty arising from the error in
The Effects of Atmospheric Dispersion on High-Resolution Solar Spectroscopy
We investigate the effects of atmospheric dispersion on observations of the
Sun at the ever-higher spatial resolutions afforded by increased apertures and
improved techniques. The problems induced by atmospheric refraction are
particularly significant for solar physics because the Sun is often best
observed at low elevations, and the effect of the image displacement is not
merely a loss of efficiency, but the mixing of information originating from
different points on the solar surface. We calculate the magnitude of the
atmospheric dispersion for the Sun during the year and examine the problems
produced by this dispersion in both spectrographic and filter observations. We
describe an observing technique for scanning spectrograph observations that
minimizes the effects of the atmospheric dispersion while maintaining a regular
scanning geometry. Such an approach could be useful for the new class of
high-resolution solar spectrographs, such as SPINOR, POLIS, TRIPPEL, and ViSP
Scaling and self-averaging in the three-dimensional random-field Ising model
We investigate, by means of extensive Monte Carlo simulations, the magnetic
critical behavior of the three-dimensional bimodal random-field Ising model at
the strong disorder regime. We present results in favor of the two-exponent
scaling scenario, , where and are the
critical exponents describing the power-law decay of the connected and
disconnected correlation functions and we illustrate, using various finite-size
measures and properly defined noise to signal ratios, the strong violation of
self-averaging of the model in the ordered phase.Comment: 8 pages, 6 figures, to be published in Eur. Phys. J.
A Green's function approach to transmission of massless Dirac fermions in graphene through an array of random scatterers
We consider the transmission of massless Dirac fermions through an array of
short range scatterers which are modeled as randomly positioned -
function like potentials along the x-axis. We particularly discuss the
interplay between disorder-induced localization that is the hallmark of a
non-relativistic system and two important properties of such massless Dirac
fermions, namely, complete transmission at normal incidence and periodic
dependence of transmission coefficient on the strength of the barrier that
leads to a periodic resonant transmission. This leads to two different types of
conductance behavior as a function of the system size at the resonant and the
off-resonance strengths of the delta function potential. We explain this
behavior of the conductance in terms of the transmission through a pair of such
barriers using a Green's function based approach. The method helps to
understand such disordered transport in terms of well known optical phenomena
such as Fabry Perot resonances.Comment: 22 double spaced single column pages. 15 .eps figure
[Letter] A distinct genotype of XP complementation group A: surprisingly mild phenotype highly prevalent in Northern India/ Pakistan/ Afghanistan
No description supplie
Dynamical properties of liquid Al near melting. An orbital-free molecular dynamics study
The static and dynamic structure of liquid Al is studied using the orbital
free ab-initio molecular dynamics method. Two thermodynamic states along the
coexistence line are considered, namely T = 943 K and 1323 K for which X-ray
and neutron scattering data are available. A new kinetic energy functional,
which fulfills a number of physically relevant conditions is employed, along
with a local first principles pseudopotential. In addition to a comparison with
experiment, we also compare our ab-initio results with those obtained from
conventional molecular dynamics simulations using effective interionic pair
potentials derived from second order pseudopotential perturbation theory.Comment: 15 pages, 12 figures, 2 tables, submitted to PR
Measurement of the Proton and Deuteron Spin Structure Functions g2 and Asymmetry A2
We have measured the spin structure functions g2p and g2d and the virtual
photon asymmetries A2p and A2d over the kinematic range 0.02 < x < 0.8 and 1.0
< Q^2 < 30(GeV/c)^2 by scattering 38.8 GeV longitudinally polarized electrons
from transversely polarized NH3 and 6LiD targets.The absolute value of A2 is
significantly smaller than the sqrt{R} positivity limit over the measured
range, while g2 is consistent with the twist-2 Wandzura-Wilczek calculation. We
obtain results for the twist-3 reduced matrix elements d2p, d2d and d2n. The
Burkhardt-Cottingham sum rule integral - int(g2(x)dx) is reported for the range
0.02 < x < 0.8.Comment: 12 pages, 4 figures, 1 tabl
Fractionalization patterns in strongly correlated electron systems: Spin-charge separation and beyond
We discuss possible patterns of electron fractionalization in strongly
interacting electron systems. A popular possibility is one in which the charge
of the electron has been liberated from its Fermi statistics. Such a
fractionalized phase contains in it the seed of superconductivity. Another
possibility occurs when the spin of the electron, rather than its charge, is
liberated from its Fermi statistics. Such a phase contains in it the seed of
magnetism, rather than superconductivity. We consider models in which both of
these phases occur and study possible phase transitions between them. We
describe other fractionalized phases, distinct from these, in which fractions
of the electron themselves fractionalize, and discuss the topological
characterization of such phases. These ideas are illustrated with specific
models of p-wave superconductors, Kondo lattices, and coexistence between
d-wave superconductivity and antiferromagnetism.Comment: 28 pages, 11 fig
Explaining the social gradient in smoking and cessation: the peril and promise of social mobility
Smoking in high-income countries is now concentrated in poor communities whose relatively high smoking prevalence is explained by greater uptake but above all by lower quit rates. Whilst a number of barriers to smoking cessation have been identified, this is the first paper to situate cessation itself as a classed and cultural practice. Drawing on ethnographic research carried out in a working class community in the North of England between 2012 and 2015, I theorise smoking cessation as a symbolic practice in relation to the affective experience of class and social mobility. I show that ambivalence about upward mobility as separation and loss translated into ambivalence about smoking cessation. The reason for this was that the social gradient in smoking operated dynamically at the level of the individual life course i.e. smoking cessation followed upward mobility. A serious health problem was an appropriate reason to quit but older women continued to smoke despite serious health problems. This was linked to historical gender roles leading to women placing a low priority on their own health as well as the intergenerational reproduction of smoking through close affective links with smoking parents
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