1,401 research outputs found
Robustness of Sound Speed and Jet Quenching for Gauge/Gravity Models of Hot QCD
We probe the effectiveness and robustness of a simple gauge/gravity dual
model of the QCD fireball that breaks conformal symmetry by constructing a
family of similar geometries that solve the scalar/gravity equations of motion.
This family has two parameters, one of which is associated to the temperature.
We calculate two quantities, the speed of sound and the jet-quenching
parameter. We find the speed of sound to be universal and robust over all the
geometries when appropriate units are used, while the jet-quenching parameter
varies significantly away from the conformal limit. We note that the overall
structure of the jet-quenching depends strongly on whether the running scalar
is the dilaton or not. We also discuss the variation of the scalar potential
over our family of solutions, and truncate our results to where the associated
error is small.Comment: 21 pages, 9 figures, LaTeX. v2:references added, minor correction to
speed of sound; conclusions unchange
Is the Sun Embedded in a Typical Interstellar Cloud?
The physical properties and kinematics of the partially ionized interstellar
material near the Sun are typical of warm diffuse clouds in the solar vicinity.
The interstellar magnetic field at the heliosphere and the kinematics of nearby
clouds are naturally explained in terms of the S1 superbubble shell. The
interstellar radiation field at the Sun appears to be harder than the field
ionizing ambient diffuse gas, which may be a consequence of the low opacity of
the tiny cloud surrounding the heliosphere. The spatial context of the Local
Bubble is consistent with our location in the Orion spur.Comment: "From the Outer Heliosphere to the Local Bubble", held at
International Space Sciences Institute, October 200
Enlarged Galilean symmetry of anyons and the Hall effect
Enlarged planar Galilean symmetry, built of both space-time and field
variables and also incorporating the ``exotic'' central extension is
introduced. It is used to describe non-relativistic anyons coupled to an
electromagnetic field. Our theory exhibits an anomalous velocity relation of
the type used to explain the Anomalous Hall Effect. The Hall motions,
characterized by a Casimir of the enlarged algebra, become mandatory for some
critical value(s) of the magnetic field. The extension of our scheme yields the
semiclassical effective model of the Bloch electron.Comment: LaTeX, 7 pages. No figures. One more reference adde
Drag and jet quenching of heavy quarks in a strongly coupled N=2* plasma
The drag of a heavy quark and the jet quenching parameter are studied in the
strongly coupled N=2* plasma using the AdS/CFT correspondence. Both increase in
units of the spatial string tension as the theory departs from conformal
invariance. The description of heavy quark dynamics using a Langevin equation
is also considered. It is found that the difference between the velocity
dependent factors of the transverse and longitudinal momentum broadening of the
quark admit an interpretation in terms of relativistic effects, so the
distribution is spherical in the quark rest frame. When conformal invariance is
broken there is a broadening of the longitudinal momentum distribution. This
effect may be useful in understanding the jet distribution observed in
experiments.Comment: 30 pages, 5 figures, references added, minor corrections. To be
published in JHE
Gerbes, M5-Brane Anomalies and E_8 Gauge Theory
Abelian gerbes and twisted bundles describe the topology of the NS-NS 3-form
gauge field strength H. We review how they have been usefully applied to study
and resolve global anomalies in open string theory. Abelian 2-gerbes and
twisted nonabelian gerbes describe the topology of the 4-form field strength G
of M-theory. We show that twisted nonabelian gerbes are relevant in the study
and resolution of global anomalies of multiple coinciding M5-branes. Global
anomalies for one M5-brane have been studied by Witten and by Diaconescu, Freed
and Moore. The structure and the differential geometry of twisted nonabelian
gerbes (i.e. modules for 2-gerbes) is defined and studied. The nonabelian
2-form gauge potential living on multiple coinciding M5-branes arises as
curving (curvature) of twisted nonabelian gerbes. The nonabelian group is in
general , the central extension of the E_8 loop group. The
twist is in general necessary to cancel global anomalies due to the
nontriviality of the 11-dimensional 4-form G field strength and due to the
possible torsion present in the cycles the M5-branes wrap. Our description of
M5-branes global anomalies leads to the D4-branes one upon compactification of
M-theory to Type IIA theory.Comment: 19 page
Observation and Assignment of Silent and Higher Order Vibrations in the Infrared Transmission of C60 Crystals
We report the measurement of infrared transmission of large C60 single
crystals. The spectra exhibit a very rich structure with over 180 vibrational
absorptions visible in the 100 - 4000 cm-1 range. Many silent modes are
observed to have become weakly IR-active. We also observe a large number of
higher order combination modes. The temperature (77K - 300K) and pressure (0 -
25KBar) dependencies of these modes were measured and are presented. Careful
analysis of the IR spectra in conjunction with Raman scattering data showing
second order modes and neutron scattering data, allow the selection of the 46
vibrational modes C60. We are able to fit *all* of the first and second order
data seen in the present IR spectra and the previously published Raman data
(~300 lines total), using these 46 modes and their group theory allowed second
order combinations.Comment: REVTEX v3.0 in LaTeX. 12 pages. 8 Figures by request. c60lon
Attitudes and practices in the laboratory monitoring of conventional synthetic disease modifying anti-rheumatic drugs by rheumatologists and rheumatology trainees
Published online: 17 October 2022Objectives: There is scant research about laboratory monitoring in people taking conventional synthetic diseasemodifying anti-rheumatic drugs (csDMARDs) for rheumatic disease. Our objective was to conduct a scoping study to assess the range of current attitudes and the variation in practice of laboratory monitoring of csDMARDs by rheumatologists and trainees. Methods: Australian and overseas rheumatologists or trainees were invited through newsletter, Twitter and personal e-mail, to complete an anonymous online survey between 1 February and 22 March 2021. Questions focused on laboratory tests requested by csDMARD prescribed, frequency/pattern of monitoring, influence of additional factors and combination therapy, actions in response to abnormal tests, and attitudes to monitoring frequencies. Results were presented descriptively and analysed using linear and logistic regression. Results: There were 221 valid responses. Most respondents were from Australia (n = 53, 35%) followed by the US (n = 39, 26%), with a slight preponderance of women (n = 84, 56%), â„ 11 years in rheumatology practice (n = 83, 56%) and in mostly public practice (n = 79, 53%). Respondents had a wide variation in the frequency and scheduling of tests. In general, respondents reported increasing monitoring frequency if patients had numerous comorbidities or if both methotrexate and leflunomide were being taken concurrently. There was a wide variety of responses to abnormal monitoring results and 27 (40%) considered that in general, monitoring tests are performed too frequently. Conclusions: The results demonstrated a wide variation in the frequency of testing, factors that should influence this, and what responses to abnormal test results are appropriate, indicates a likely lack of evidence and the need to define the risks, benefits and costs of different csDMARD monitoring regimens.James J. Tsakas, David F. L. Liew, Cameron L. Adams, Catherine L. Hill, Susanna Proudman, Samuel Whittle, Rachelle Buchbinder, and Philip C. Robinso
Why Study Interstellar Matter Very Close to the Sun?
Interstellar matter (ISM) sets the boundary conditions of the heliosphere and
dominates the interplanetary medium. The heliosphere configuration has varied
over recent history, as the Sun emerged from the Local Bubble and entered a
turbulent outflow of cloudlets originating from the Scorpius-Centaurus
Association direction. Several indicators suggest that the local interstellar
magnetic field is weak and parallel to the galactic plane. Observations of the
interaction products of the ISM with the heliosphere, such as pickup ions and
anomalous cosmic rays, when combined with data on the ISM towards nearby stars,
provide unique constraints on the composition and physical properties of nearby
gas. These data suggest abundances in nearby ISM are subsolar, and that gas and
dust are not well mixed at the solar location.Comment: 10 pages, 4 figures; Proceedings Houston 2002 COSPAR Outer
Heliosphere meetin
European Union enlargement, post-accession migration and imaginative geographies of the âNew Europeâ: media discourses in Romania and the United Kingdom.
This paper is concerned with re-imaginings of âEuropeâ following the accession to the European Union (EU) of former âEastern Europeanâ countries. In particular it explores media representations of post-EU accession migration from Romania to the United Kingdom in the UK and Romanian newspaper press. Todorovaâs (1997) notion of Balkanism is deployed as a theoretical construct to facilitate the analysis of these representations as first, the continuation of long-standing and deeply embedded imaginings of the âEastâ of Europe and, second, as a means of contesting these discourses. The paper explores the way in which the UK press construct Balkanist discourses about Romania and Romanian migrants, and then analyses how the Romanian press has contested such discourses. The paper argues that the idea of the âEastâ remains important in constructing notions of âEuropeâ within popular media geographies
Calculating the jet-quenching parameter in STU background
In this paper we use the AdS/CFT correspondence to compute the jet-quenching
parameter in a N=2 thermal plasma. We consider the general three-charge black
hole and discuss some special cases. We add a constant electric field to the
background and find the effect of the electric field on the jet-quenching
parameter. Also we include higher derivative terms and obtain the first-order
correction for the jet-quenching parameter.Comment: 17 pages, 3 figures, revised versio
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