1,542 research outputs found
Observation of a quenched moment of inertia in a rotating strongly interacting Fermi gas
We make a model-independent measurement of the moment of inertia of a
rotating, expanding strongly-interacting Fermi gas. Quenching of the moment of
inertia is observed for energies both below and above the superfluid
transition. This shows that a strongly interacting Fermi gas with angular
momentum can support irrotational flow in both the superfluid and collisional
normal fluid regimes.Comment: 4 pages 5 figure
Singlet-Triplet Excitations in the Unconventional Spin-Peierls System TiOBr
We have performed time-of-flight neutron scattering measurements on powder
samples of the unconventional spin-Peierls compound TiOBr using the
fine-resolution Fermi chopper spectrometer (SEQUOIA) at the SNS. These
measurements reveal two branches of magnetic excitations within the
commensurate and incommensurate spin-Peierls phases, which we associate with n
= 1 and n = 2 triplet excitations out of the singlet ground state. These
measurements represent the first direct measure of the singlet-triplet energy
gap in TiOBr, which is determined to be Eg = 21.2 +/- 1.0 meV.Comment: 5 pages, 4 figures, submitted for publicatio
Catalogue of extreme wave events in Ireland: revised and updated for 14680 BP - 2017
This paper aims to extend and update the survey of extreme wave events in Ireland that was previously carried out by O’Brien et al. (2013). The original catalogue highlighted the frequency of such events dating back as far as the turn of the last ice age through to 2012. Ireland’s marine territory extends far beyond its coastline and is one of the largest seabed
territories in Europe. It is therefore not surprising that extreme waves have continued to occur regularly since 2012, particularly
considering the severity of weather during the winters of 2013-14 and 2015-16. In addition, a large number of storm surges
have been identified since the publication of the original catalogue. This paper updates the O’Brien et al. (2013) catalogue to include events up to the end of 2016. Storm surges are included as a new category and events are categorised into long waves (tsunamis and storm surges) and short waves (storm and rogue waves). New results prior to 2012 are also included and some of the events previously documented are reclassified. Important questions regarding public safety, services and the influence of climate change are also highlighted
Asymptotic Behaviour of Inhomogeneous String Cosmologies
The asymptotic behaviour at late times of inhomogeneous axion-dilaton
cosmologies is investigated. The space-times considered here admit two abelian
space-like Killing vectors. These space-times evolve towards an anisotropic
universe containing gravitational radiation. Furthermore, a peeling-off
behaviour of the Weyl tensor and the antisymmetric tensor field strength is
found. The relation to the pre-big-bang scenario is briefly discussed.Comment: 15 pages, Late
Initial Conditions in String Cosmology
We take a critical look at a recent conjecture concerning the past attractor
in the pre-big-bang scenario. We argue that the Milne universe is unlikely to
be a general past attractor for such models and support this with a number of
examples.Comment: 10 pages standard Latex format, no figures. Submitted to Phys. Rev.
Discovery of Highly Obscured Galaxies in the Zone of Avoidance
We report the discovery of twenty-five previously unknown galaxies in the
Zone of Avoidance. Our systematic search for extended extra-galactic sources in
the GLIMPSE and MIPSGAL mid-infrared surveys of the Galactic plane has revealed
two overdensities of these sources, located around l ~ 47 and 55 degrees and
|b| less than 1 degree in the Sagitta-Aquila region. These overdensities are
consistent with the local large-scale structure found at similar Galactic
longitude and extending from |b| ~ 4 to 40 degrees. We show that the infrared
spectral energy distribution of these sources is indeed consistent with those
of normal galaxies. Photometric estimates of their redshift indicate that the
majority of these galaxies are found in the redshift range z = 0.01 - 0.05,
with one source located at z = 0.07. Comparison with known sources in the local
Universe reveals that these galaxies are located at similar overdensities in
redshift space. These new galaxies are the first evidence of a bridge linking
the large-scale structure between both sides of the Galactic plane at very low
Galactic latitude and clearly demonstrate the feasibility of detecting galaxies
in the Zone of Avoidance using mid-to-far infrared surveys.Comment: Accepted for publication in the Astronomical Journal, 28 pages, 5
tables, 11 figure
Inhomogeneous Einstein-Rosen String Cosmology
Families of anisotropic and inhomogeneous string cosmologies containing
non-trivial dilaton and axion fields are derived by applying the global
symmetries of the string effective action to a generalized Einstein-Rosen
metric. The models exhibit a two-dimensional group of Abelian isometries. In
particular, two classes of exact solutions are found that represent
inhomogeneous generalizations of the Bianchi type VI_h cosmology. The
asymptotic behaviour of the solutions is investigated and further applications
are briefly discussed.Comment: Minor extension of concluding section; 18 pages, to appear in
Phys.Rev.
String cosmology versus standard and inflationary cosmology
This paper presents a review of the basic, model-independent differences
between the pre-big bang scenario, arising naturally in a string cosmology
context, and the standard inflationary scenario. We use an unconventional
approach in which the introduction of technical details is avoided as much as
possible, trying to focus the reader's attention on the main conceptual aspects
of both scenarios. The aim of the paper is not to conclude in favour either of
one or of the other scenario, but to raise questions that are left to the
reader's meditation. Warnings: the paper does not contain equations, and is not
intended as a complete review of all aspects of string cosmology.Comment: 22 pages, Latex (IOP Style), three figures included using epsfig. To
appear in Class. Quantum Grav. (Topical Review Section). Two misprints
correcte
First results on Martian carbon monoxide from Herschel/HIFI observations
We report on the initial analysis of Herschel/HIFI carbon monoxide (CO)
observations of the Martian atmosphere performed between 11 and 16 April 2010.
We selected the (7-6) rotational transitions of the isotopes ^{13}CO at 771 GHz
and C^{18}O at 768 GHz in order to retrieve the mean vertical profile of
temperature and the mean volume mixing ratio of carbon monoxide. The derived
temperature profile agrees within less than 5 K with general circulation model
(GCM) predictions up to an altitude of 45 km, however, show about 12-15 K lower
values at 60 km. The CO mixing ratio was determined as 980 \pm 150 ppm, in
agreement with the 900 ppm derived from Herschel/SPIRE observations in November
2009.Comment: Accepted for publication in Astronomy and Astrophysics (special issue
on HIFI first results); minor changes to match published versio
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