350 research outputs found
Spontaneous Magnetization of the O(3) Ferromagnet at Low Temperatures
We investigate the low-temperature behavior of ferromagnets with a
spontaneously broken symmetry O(3) O(2). The analysis is performed within
the perspective of nonrelativistic effective Lagrangians, where the dynamics of
the system is formulated in terms of Goldstone bosons. Unlike in a
Lorentz-invariant framework (chiral perturbation theory), where loop graphs are
suppressed by two powers of momentum, loops involving ferromagnetic spin waves
are suppressed by three momentum powers. The leading coefficients of the
low-temperature expansion for the partition function are calculated up to order
. In agreement with Dyson's pioneering microscopic analysis of the
cubic ferromagnet, we find that, in the spontaneous magnetization, the
magnon-magnon interaction starts manifesting itself only at order . The
striking difference with respect to the low-temperature properties of the O(3)
antiferromagnet is discussed from a unified point of view, relying on the
effective Lagrangian technique.Comment: 23 pages, 4 figure
Cosmological parameters from SDSS and WMAP
We measure cosmological parameters using the three-dimensional power spectrum
P(k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in
combination with WMAP and other data. Our results are consistent with a
``vanilla'' flat adiabatic Lambda-CDM model without tilt (n=1), running tilt,
tensor modes or massive neutrinos. Adding SDSS information more than halves the
WMAP-only error bars on some parameters, tightening 1 sigma constraints on the
Hubble parameter from h~0.74+0.18-0.07 to h~0.70+0.04-0.03, on the matter
density from Omega_m~0.25+/-0.10 to Omega_m~0.30+/-0.04 (1 sigma) and on
neutrino masses from <11 eV to <0.6 eV (95%). SDSS helps even more when
dropping prior assumptions about curvature, neutrinos, tensor modes and the
equation of state. Our results are in substantial agreement with the joint
analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive
consistency check with independent redshift survey data and analysis
techniques. In this paper, we place particular emphasis on clarifying the
physical origin of the constraints, i.e., what we do and do not know when using
different data sets and prior assumptions. For instance, dropping the
assumption that space is perfectly flat, the WMAP-only constraint on the
measured age of the Universe tightens from t0~16.3+2.3-1.8 Gyr to
t0~14.1+1.0-0.9 Gyr by adding SDSS and SN Ia data. Including tensors, running
tilt, neutrino mass and equation of state in the list of free parameters, many
constraints are still quite weak, but future cosmological measurements from
SDSS and other sources should allow these to be substantially tightened.Comment: Minor revisions to match accepted PRD version. SDSS data and ppt
figures available at http://www.hep.upenn.edu/~max/sdsspars.htm
European survey on laboratory preparedness, response and diagnostic capacity for crimean-congo haemorrhagic fever, 2012
Crimean-Congo haemorrhagic fever (CCHF) is an infectious viral disease that has (re-)emerged in the last decade in south-eastern Europe, and there is a risk for further geographical expansion to western Europe. Here we report the results of a survey covering 28 countries, conducted in 2012 among the member laboratories of the European Network for Diagnostics of 'Imported' Viral Diseases (ENIVD) to assess laboratory preparedness and response capacities for CCHF. The answers of 31 laboratories of the European region regarding CCHF case definition, training necessity, biosafety, quality assurance and diagnostic tests are presented. In addition, we identifi
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at = 2.76 TeV
The yield of charged particles associated with high- trigger
particles ( GeV/) is measured with the ALICE detector in
Pb-Pb collisions at = 2.76 TeV relative to proton-proton
collisions at the same energy. The conditional per-trigger yields are extracted
from the narrow jet-like correlation peaks in azimuthal di-hadron correlations.
In the 5% most central collisions, we observe that the yield of associated
charged particles with transverse momenta GeV/ on the
away-side drops to about 60% of that observed in pp collisions, while on the
near-side a moderate enhancement of 20-30% is found.Comment: 15 pages, 2 captioned figures, 1 table, authors from page 10,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/350
Zooplankton composition and distribution off the coast of Galicia, Spain
During June and September 1984, zooplankton samples were collected with other
hydrographic and biological data along the Galician coast (NW of Spain). In June copepods
contributed -60% to the total zooplankton community, with larvaceans, siphonophores and
cladocerans also abundant. In September >90% of the zooplankton sampled were copepods. The
dominant species of copepods in both June and September were Acartia e/ausi, Paracalanus parvus
and Temora longicornis. The meroplankton was dominated by echinoderms, bryozoans, barnacle
larvae and bivalve larvae. In June the average zooplankton biomass was 31.08 mg e m-3; the
September average was 41.69 mg e m-3 The relationship between the slopes of the regression
equations (biomass versus abundance) suggests that the zooplankton assemblage in June was
composed by larger animals than in September. The major concentration of zooplankton was
between O and SO m, with both June and September daytime surface samples having 6-7 times the
amount of organisms than the lower water column (50-100 m). There were no distinct differences in
total zooplankton abundances at the inshore and offshore stations; however, the inshore stations
often had a higher percentage of meroplankton than the offshore stations. In June zooplankton
abundance at the northern transects and the western transects was similar. In September there were
greater concentrations of zooplankton in the western Galician shelf as compared with the northern
shelf. These differences in the horizontal distribution of the zooplankton were related to upwelling
events.Postprin
ARIA 2016: Care pathways implementing emerging technologies for predictive medicine in rhinitis and asthma across the life cycle
The Allergic Rhinitis and its Impact on Asthma (ARIA) initiative commenced during a World Health Organization workshop in 1999. The initial goals were (1) to propose a new allergic rhinitis classification, (2) to promote the concept of multi-morbidity in asthma a
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