1,729 research outputs found
Single parameter quasi-particle model for QGP
We discuss a new single parameter quasi-particle model and study the
thermodynamics of (2+1)-flavor quark gluon plasma (QGP). Our model with a
single parameter explains remarkably well the lattice simulation results of
Fodor et. al. Phys. Lett. B568, 73 (2003).Comment: 9 pages, 3 figures, articl
The omega meson at high temperatures
The decays of the omega meson in a heat bath of thermally excited pions is
studied within the framework of real-time thermal field theory using an
appropriate effective Lagrangian. We show that the omega meson spectrum
broadens considerably at temperatures T > 100 MeV, primarily because of omega
pi -> pi pi reactions in the thermal environment.Comment: 7 pages, 2 figures; reference and paragraph added; version to appear
in Phys. Lett.
Probing the QCD Equation of State
We propose a novel quasiparticle interpretation of the equation of state of
deconfined QCD at finite temperature. Using appropriate thermal masses, we
introduce a phenomenological parametrisation of the onset of confinement in the
vicinity of the phase transition. Lattice results of bulk thermodynamic
quantities are well reproduced, the extension to small quark chemical potential
is also successful. We then apply the model to dilepton production and charm
suppression in ultrarelativistic heavy-ion collisions.Comment: 6 pages, 8 figures. Invited talk presented by R. A. Schneider at the
XVI International Conference on Particles and Nuclei (PANIC02), Osaka, Japan,
September 30 - October 4, 200
Superconducting Diamagnetic Fluctuations in MgB2
The fluctuating diamagnetic magnetization Mfl at constant field H as a
function of temperature and the isothermal magnetization Mfl vs H are measured
in MgB2, above the superconducting transition temperature. The expressions for
Mfl in randomly oriented powders are derived in the Gaussian approximation of
local Ginzburg-Landau theory and used for the analysis of the data. The scaled
magnetization Mfl/H^{1/2}*T is found to be field dependent. In the limit of
evanescent field the behaviour for Gaussian fluctuations is obeyed while for
H>~ 100 Oe the field tends to suppress the fluctuating pairs, with a field
dependence of Mfl close to the one expected when short wavelength fluctuations
and non-local electrodynamic effects are taken into account. Our data, besides
providing the isothermal magnetization curves for T>Tc(0) in a BCS-type
superconductor such as MgB2, evidence an enhancement of the fluctuating
diamagnetism which is related to the occurrence in this new superconductor of
an anisotropic spectrum of the superconducting fluctuations.Comment: Tex file, 4 pages, 3 ps figures, submitted to Phys. Rev. Let
Phases of QCD, Thermal Quasiparticles and Dilepton Radiation from a Fireball
We calculate dilepton production rates from a fireball adapted to the
kinematical conditions realized in ultrarelativistic heavy ion collisions over
a broad range of beam energies. The freeze-out state of the fireball is fixed
by hadronic observables. We use this information combined with the initial
geometry of the collision region to follow the space-time evolution of the
fireball. Assuming entropy conservation, its bulk thermodynamic properties can
then be uniquely obtained once the equation of state (EoS) is specified. The
high-temperature (QGP) phase is modelled by a non-perturbative quasiparticle
model that incorporates a phenomenological confinement description, adapted to
lattice QCD results. For the hadronic phase, we interpolate the EoS into the
region where a resonance gas approach seems applicable, keeping track of a
possible overpopulation of the pion phase space. In this way, the fireball
evolution is specified without reference to dilepton data, thus eliminating it
as an adjustable parameter in the rate calculations. Dilepton emission in the
QGP phase is then calculated within the quasiparticle model. In the hadronic
phase, both temperature and finite baryon density effects on the photon
spectral function are incorporated. Existing dilepton data from CERES at 158
and 40 AGeV Pb-Au collisions are well described, and a prediction for the
PHENIX setup at RHIC for sqrt(s) = 200 AGeV is given.Comment: 31 pages, 15 figures, final versio
Structural and electrical properties of c-axis oriented Y1-xCaxBa2(Cu1-yZny)3O7-delta thin films grown by pulsed laser deposition
Ca- and Zn-subsituted Y1-xCaxBa2(Cu1-yZny)O7-delta (x = 0, 0.05 and y = 0,
0.02, 0.04, 0.05) thin films were grown on SrTiO3 (100) substrates using the
pulsed laser deposition (PLD) technique. Effects of various growth parameters
on the quality of the film were studied via X-ray diffraction (XRD), atomic
force microscopy (AFM), and in-plane resistivity, rhoab(T), measurements. The
deposition temperature and oxygen partial pressure were gradually increased to
820C and 1.20 mbar respectively. Films grown under these conditions exhibited
good c-axis orientation (primarily limited by the grain size) and low values of
the extrapolated residual resistivity, rho(0), at zero temperature. The planar
hole content, p, was determined from the room temperature thermopower, S[290K],
measurements and the effects of oxygen annealing were also studied. Fully
oxygenated samples were found to be overdoped with p ~ 0.195. The
Superconducting transition temperature Tc(p), and rho(T,p) showed the expected
systematic variations with changing Zn content.Comment: Submitted to Physica C (2003
Living HTA: automating health economic evaluation with R
Background: Requiring access to sensitive data can be a significant obstacle for the development of health models in the Health Economics & Outcomes Research (HEOR) setting. We demonstrate how health economic evaluation can be conducted with minimal transfer of data between parties, while automating reporting as new information becomes available.
Methods: We developed an automated analysis and reporting pipeline for health economic modelling and made the source code openly available on a GitHub repository. The pipeline consists of three parts: An economic model is constructed by the consultant using pseudo data. On the data-owner side, an application programming interface (API) is hosted on a server. This API hosts all sensitive data, so that data does not have to be provided to the consultant. An automated workflow is created, which calls the API, retrieves results, and generates a report.
Results: The application of modern data science tools and practices allows analyses of data without the need for direct access – negating the need to send sensitive data. In addition, the entire workflow can be largely automated: the analysis can be scheduled to run at defined time points (e.g. monthly), or when triggered by an event (e.g. an update to the underlying data or model code); results can be generated automatically and then be exported into a report. Documents no longer need to be revised manually.
Conclusions: This example demonstrates that it is possible, within a HEOR setting, to separate the health economic model from the data, and automate the main steps of the analysis pipeline
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Evaluation of aqueous cleaners as alternatives to vapor degreasing
As part of the preparation process during assembly of thermally activated batteries, the stainless steel piece parts are normally cleaned by vapor degreasing with trichloroethylene. Severe restrictions on the use of chlorinated and fluorinated hydrocarbons in recent years prompted the evaluation of a number of aqueous cleaners as a replacement technology for this application. A total of seven commercial aqueous degreasers was evaluated in this study at several dilution ratios and temperatures. One organic cleaner was also examined under ambient conditions. The effectiveness of the cleaner was determined by the use of x-ray photoelectron spectroscopy (XPS), which is a surface analytical technique that is very sensitive to low levels of surface contaminants. A quartz-crystal microbalance (QCM) that is immersed in the cleaning bath was evaluated as a tool for monitoring the bath cleanliness. The best overall cleaning results were obtained with Micro, Impro-Clean 3800, and Sonicor cleaners
Asymptotics and local constancy of characters of p-adic groups
In this paper we study quantitative aspects of trace characters
of reductive -adic groups when the representation varies. Our approach
is based on the local constancy of characters and we survey some other related
results. We formulate a conjecture on the behavior of relative to
the formal degree of , which we are able to prove in the case where
is a tame supercuspidal. The proof builds on J.-K.~Yu's construction and the
structure of Moy-Prasad subgroups.Comment: Proceedings of Simons symposium on the trace formul
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