1,536 research outputs found
An effective many-body theory for strongly interacting polar molecules
We derive a general effective many-body theory for bosonic polar molecules in
strong interaction regime, which cannot be correctly described by previous
theories within the first Born approximation. The effective Hamiltonian has
additional interaction terms, which surprisingly reduces the anisotropic
features of dipolar interaction near the shape resonance regime. In the 2D
system with dipole moment perpendicular to the plane, we find that the phonon
dispersion scales as \sqrt{|\bfp|} in the low momentum (\bfp) limit,
showing the same low energy properties as a 2D charged Bose gas with Coulomb
() interactions.Comment: Same as published version (11 pages, 2 figure
Imaging Galactic Dark Matter with High-Energy Cosmic Neutrinos
We show that the high-energy cosmic neutrinos seen by the IceCube Neutrino Observatory can be used to probe interactions between neutrinos and the dark sector that cannot be reached by current cosmological methods. The origin of the observed neutrinos is still unknown, and their arrival directions are compatible with an isotropic distribution. This observation, together with dedicated studies of Galactic plane correlations, suggests a predominantly extragalactic origin. Interactions between this isotropic extragalactic flux and the dense dark matter (DM) bulge of the Milky Way would thus lead to an observable imprint on the distribution, which would be seen by IceCube as (i) slightly suppressed fluxes at energies below a PeV and (ii) a deficit of events in the direction of the Galactic center. We perform an extended unbinned likelihood analysis using the four-year high-energy starting event data set to constrain the strength of DM-neutrino interactions for two model classes. We find that, in spite of low statistics, IceCube can probe regions of the parameter space inaccessible to current cosmological methods.National Science Foundation (U.S.) (Grant PHY-1505858)National Science Foundation (U.S.) (Grant PHY-1505855
Association of acculturation with cardiac structure and function among Hispanics/Latinos: a cross-sectional analysis of the echocardiographic study of Latinos.
OBJECTIVE:Hispanics/Latinos, the largest immigrant population in the USA, undergo the process of acculturation and have a large burden of heart failure risk. Few studies have examined the association of acculturation on cardiac structure and function. DESIGN:Cross-sectional. SETTING:The Echocardiographic Study of Latinos. PARTICIPANTS:1818 Hispanic adult participants with baseline echocardiographic assessment and acculturation measured by the Short Acculturation Scale, nativity, age at immigration, length of US residence, generational status and language. PRIMARY AND SECONDARY OUTCOME MEASURES:Echocardiographic assessment of left atrial volume index (LAVI), left ventricular mass index (LVMI), early diastolic transmitral inflow and mitral annular velocities. RESULTS:The study population was predominantly Spanish-speaking and foreign-born with mean residence in the US of 22.7 years, mean age of 56.4 years; 50% had hypertension, 28% had diabetes and 44% had a body mass index >30 kg/m2. Multivariable analyses demonstrated higher LAVI with increasing years of US residence. Foreign-born and first-generation participants had higher E/e' but lower LAVI and e' velocities compared with the second generation. Higher acculturation and income >20K were associated with higher LVMI, LAVI and E/e' but lower e' velocities. Preferential Spanish-speakers with an income <20K had a higher E/e'. CONCLUSIONS:Acculturation was associated with abnormal cardiac structure and function, with some effect modification by socioeconomic status
Assessing, quantifying and valuing the ecosystem services of coastal lagoons
The natural conservation of coastal lagoons is important not only for their ecological importance, but also because of the valuable ecosystem services they provide for human welfare and wellbeing. Coastal lagoons are shallow semi-enclosed systems that support important habitats such as wetlands, mangroves, salt-marshes and seagrass meadows, as well as a rich biodiversity. Coastal lagoons are also complex social-ecological systems with ecosystem services that provide livelihoods, wellbeing and welfare to humans. This study assessed, quantified and valued the ecosystem services of 32 coastal lagoons. The main findings of the study are: (i) the definitions of ecosystem services are still not generally accepted; (ii) the quantification of ecosystem services is made in many different ways, using different units; (iii) the evaluation in monetary terms of some ecosystem service is problematic, often relying on non-monetary evaluation methods; (iv) when ecosystem services are valued in monetary terms, this may represent very different human benefits; and, (v) different aspects of climate change, including increasing temperature, sea-level rise and changes in rainfall patterns threaten the valuable ecosystem services of coastal lagoons.DEVOTES project, from the European Union's Seventh Framework Programme for research, technological development and demonstration [308392]; networks and communities of Eurolag; Future Earth Coasts; SCOR; Fundacao para a Ciencia e a Tecnologia (FCT) Investigador Programme [IF/00331/2013]; Fundacao para a Ciencia e a Tecnologia [UID/MAR/04292/2013]; CESAM by FCT/MEC national funds (PIDDAC) [UID/AMB/50017/2013 - POCI-01-0145-FEDER-007638]; FEDER; European Commission, under the 7th Framework Programme through the collaborative research project LAGOONS [283157]; FCT [SFRH/BPD/107823/2015, SFRH/BPD/91494/2012
Search for Prompt Neutrino Emission from Gamma-Ray Bursts with IceCube
We present constraints derived from a search of four years of IceCube data
for a prompt neutrino flux from gamma-ray bursts (GRBs). A single
low-significance neutrino, compatible with the atmospheric neutrino background,
was found in coincidence with one of the 506 observed bursts. Although GRBs
have been proposed as candidate sources for ultra-high energy cosmic rays, our
limits on the neutrino flux disfavor much of the parameter space for the latest
models. We also find that no more than of the recently observed
astrophysical neutrino flux consists of prompt emission from GRBs that are
potentially observable by existing satellites.Comment: 15 pages, 3 figure
The contribution of Fermi-2LAC blazars to the diffuse TeV-PeV neutrino flux
The recent discovery of a diffuse cosmic neutrino flux extending up to PeV
energies raises the question of which astrophysical sources generate this
signal. One class of extragalactic sources which may produce such high-energy
neutrinos are blazars. We present a likelihood analysis searching for
cumulative neutrino emission from blazars in the 2nd Fermi-LAT AGN catalogue
(2LAC) using an IceCube neutrino dataset 2009-12 which was optimised for the
detection of individual sources. In contrast to previous searches with IceCube,
the populations investigated contain up to hundreds of sources, the largest one
being the entire blazar sample in the 2LAC catalogue. No significant excess is
observed and upper limits for the cumulative flux from these populations are
obtained. These constrain the maximum contribution of the 2LAC blazars to the
observed astrophysical neutrino flux to be or less between around 10
TeV and 2 PeV, assuming equipartition of flavours at Earth and a single
power-law spectrum with a spectral index of . We can still exclude that
the 2LAC blazars (and sub-populations) emit more than of the observed
neutrinos up to a spectral index as hard as in the same energy range.
Our result takes into account that the neutrino source count distribution is
unknown, and it does not assume strict proportionality of the neutrino flux to
the measured 2LAC -ray signal for each source. Additionally, we
constrain recent models for neutrino emission by blazars.Comment: 18 pages, 22 figure
Lowering IceCube’s energy threshold for point source searches in the southern sky
Observation of a point source of astrophysical neutrinos would be a "smoking gun" signature of a cosmic-ray accelerator. While IceCube has recently discovered a diffuse flux of astrophysical neutrinos, no localized point source has been observed. Previous IceCube searches for point sources in the southern sky were restricted by either an energy threshold above a few hundred TeV or poor neutrino angular resolution. Here we present a search for southern sky point sources with greatly improved sensitivities to neutrinos with energies below 100 TeV. By selecting charged-current nu(mu) interacting inside the detector, we reduce the atmospheric background while retaining efficiency for astrophysical neutrino-induced events reconstructed with sub-degree angular resolution. The new event sample covers three years of detector data and leads to a factor of 10 improvement in sensitivity to point sources emitting below 100 TeV in the southern sky. No statistically significant evidence of point sources was found, and upper limits are set on neutrino emission from individual sources. A posteriori analysis of the highest-energy (similar to 100 TeV) starting event in the sample found that this event alone represents a 2.8 sigma deviation from the hypothesis that the data consists only of atmospheric background
Improved limits on dark matter annihilation in the Sun with the 79-string IceCube detector and implications for supersymmetry
We present an improved event-level likelihood formalism for including
neutrino telescope data in global fits to new physics. We derive limits on
spin-dependent dark matter-proton scattering by employing the new formalism in
a re-analysis of data from the 79-string IceCube search for dark matter
annihilation in the Sun, including explicit energy information for each event.
The new analysis excludes a number of models in the weak-scale minimal
supersymmetric standard model (MSSM) for the first time. This work is
accompanied by the public release of the 79-string IceCube data, as well as an
associated computer code for applying the new likelihood to arbitrary dark
matter models.Comment: 24 pages, 8 figs, 1 table. Contact authors: Pat Scott & Matthias
Danninger. Likelihood tool available at http://nulike.hepforge.org. v2: small
updates to address JCAP referee repor
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