732 research outputs found
Probing the role of Nd3+ ions in the weak multiferroic character of NdMn2O5 by optical spectroscopies
Raman and infrared spectroscopies are used as local probes to study the
dynamics of the Nd-O bonds in the weakly multiferroic NdMn2O5 system. The
temperature dependence of selected Raman excitations reveals the splitting of
the Nd-O bonds in NdMn2O5. The Nd3+ ion crystal field (CF) excitations in
NdMn2O5 single crystals are studied by infrared transmission as a function of
temperature, in the 1800-8000 cm-1 range, and under an applied magnetic field
up to 11 T. The frequencies of all 4Ij crystal-field levels of Nd3+ are
determined. We find that the degeneracy of the ground-state Kramers doublet is
lifted ({\Delta}0 ~7.5 cm-1) due to the Nd3+-Mn3+ interaction in the
ferroelectric phase, below TC ~ 28 K. The Nd3+ magnetic moment mNd(T) and its
contribution to the magnetic susceptibility and the specific heat are evaluated
from {\Delta}0(T) indicating that the Nd3+ ions are involved in the magnetic
and the ferroelectric ordering observed below ~ 28 K. The Zeeman splitting of
the excited crystal field levels of the Nd3+ ions at low temperature is also
analyzed.Comment: This paper is accepted for publication as a Regular Article in
Physical Review
On the discretization of physical momenta in lattice QCD
The adoption of two distinct boundary conditions for two fermions species on
a finite lattice allows to deal with arbitrary relative momentum between the
two particle species, in spite of the momentum quantization rule due to a
limited physical box size. We test the physical significance of this
topological momentum by checking in the continuum limit the validity of the
expected energy-momentum dispersion relations.Comment: 9 pages, 3 figures; references added; no changes in text or results;
version accepted for pubblication in Phys. Lett.
Climate of Earth-Like Planets With and Without Ocean Heat Transport Orbiting a Range of M and K Stars
The mean surface temperature of a planet is now acknowledged as insufficient to surmise its full potential habitability. Advancing our understanding requires exploration with 3D general circulation models (GCMs), which can take into account how gradients and fluxes across a planet's surface influence the distribution of heat, clouds, and the potential for heterogeneous distribution of liquid water. Here we present 3D GCM simulations of the effects of alternative stellar spectra, instellation, model resolution, and ocean heat transport, on the simulated distribution of heat and moisture of an Earth-like planet (ELP)
Finding the Needles in the Haystacks: High-Fidelity Models of the Modern and Archean Solar System for Simulating Exoplanet Observations
We present two state-of-the-art models of the solar system, one corresponding
to the present day and one to the Archean Eon 3.5 billion years ago. Each model
contains spatial and spectral information for the star, the planets, and the
interplanetary dust, extending to 50 AU from the sun and covering the
wavelength range 0.3 to 2.5 micron. In addition, we created a spectral image
cube representative of the astronomical backgrounds that will be seen behind
deep observations of extrasolar planetary systems, including galaxies and Milky
Way stars. These models are intended as inputs to high-fidelity simulations of
direct observations of exoplanetary systems using telescopes equipped with
high-contrast capability. They will help improve the realism of observation and
instrument parameters that are required inputs to statistical observatory yield
calculations, as well as guide development of post-processing algorithms for
telescopes capable of directly imaging Earth-like planets.Comment: Accepted for publication in PAS
Descriptive epidemiology of cleft lip and cleft palate in Western Australia
BACKGROUND: Most national and provincial commissions on healthcare services in Canada over the past decade have recommended that primary care services be strengthened in order to guarantee each citizen access to a family physician. Despite these recommendations, finding a family physician continues to be problematic. The issue of enrollment with a family physician is worrying in Canada, where nearly 21% of the country's population reported not having a family physician in the last Commonwealth Fund survey.To respond to this important need, centralized waiting lists have been implemented in four Canadian provinces to help 'orphan,' or unaffiliated, patients find a family physician. These organizational mechanisms are intended to better coordinate the demand for and supply of family physicians. The objectives of this study are: to assess the effects of centralized waiting lists for orphan patients (GACOs) implemented in the province of Quebec and to explain the variation among their effects by analyzing factors influencing implementation process. METHODS: This study is based on two complementary and sequential research strategies. The first (objective 1) is a quantitative longitudinal design to assess the effects of all the GACOs (n = 93) in Quebec using clinical-administrative data. The second (objective 2) involves using four case studies to explain variations in effects through in-depth analysis of the various factors contributing to the observed effects. The primary source of data will be key actors involved in the GACOs. We expect to conduct around 40 semi-structured interviews. DISCUSSION: This will be the first study in Canada to evaluate the implementation of this innovation. It will provide an exhaustive picture of the effects of GACO implementation in Quebec and to assess their potential for generalization elsewhere in Canada. At the theoretical level, this study will produce new knowledge on the factors having the greatest influence on the implementation of primary care innovations in professional environments
Fermion Back-Reaction and the Sphaleron
Using a simple model, a new sphaleron solution which incorporates finite
fermionic density effects is obtained. The main result is that the height of
the potential barrier (sphaleron energy) decreases as the fermion density
increases. This suggests that the rate of sphaleron-induced transitions
increases when the fermionic density increases. However the rate increase is
not expected to change significantly the predictions from the standard
sphaleron-induced baryogenesis scenarios.Comment: 11 pages, Revtex (2 figures available upon request), to appear in
Phys. Rev. D (Rapid Communication
T2K Results and Future Plans
We present the numu to nue appearance and the numu disappearance results,
using a total of 1.43 x 10^{20} protons on target collected with the T2K
experiment. T2K is long baseline neutrino experiment in Japan with detectors
located at J-PARC, Tokai, and at Kamioka in the Gifu Prefecture, situated 295
km away from J-PARC. The muon neutrino beam is produced and measured at the
near detectors at J-PARC whilst the neutrino rates after oscillation are
measured with the Super-Kamiokande detector, at Kamioka. A total of six events
pass all the selection criteria for numu to nue oscillations at the far
detector Super-Kamiokande, leading to 0.03(0.04) < sin^2 2theta_{13} <
0.28(0.34) for deltaCP = 0 and normal (inverted) hierarchy at 90% C.L. The numu
disappearance analysis excludes no oscillations at 4.3 sigma. At 90% C.L., the
best fit values are sin^2 2theta_{23} > 0.84 and 2.1 x 10^{-3} < Delta m^2_{23}
(eV^2) < 3.1 x 10^{-3}. Finally, we present an overview of the T2K plans from
2011 onwards.Comment: Contribution to NUFACT 11, XIIIth International Workshop on Neutrino
Factories, Super beams and Beta beams, 1-6 August 2011, CERN and University
of Geneva (Submitted to IOP conference series). 8 pages, 7 postscript figure
Holographic Roberge-Weiss Transitions
We investigate N=4 SYM coupled to fundamental flavours at nonzero imaginary
quark chemical potential in the strong coupling and large N limit, using
gauge/gravity duality applied to the D3-D7 system, treating flavours in the
probe approximation. The interplay between Z(N) symmetry and the imaginary
chemical potential yields a series of first-order Roberge-Weiss transitions. An
additional thermal transition separates phases where quarks are bound/unbound
into mesons. This results in a set of Roberge-Weiss endpoints: we establish
that these are triple points, determine the Roberge-Weiss temperature, give the
curvature of the phase boundaries and confirm that the theory is analytic in
mu^2 when mu^2~0.Comment: 37 pages, 13 figures; minor comments added, to appear in JHE
Phase of the Wilson Line at High Temperature in the Standard Model
We compute the effective potential for the phase of the Wilson line at high
temperature in the standard model to one loop order. Besides the trivial vacua,
there are metastable states in the direction of hypercharge. Assuming
that the universe starts out in such a metastable state at the Planck scale, it
easily persists to the time of the electroweak phase transition, which then
proceeds by an unusual mechanism. All remnants of the metastable state
evaporate about the time of the phase transition.Comment: 4 pages in ReVTeX plus 1 figure; Columbia Univ. preprint CU-TP-63
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