2,986 research outputs found
Non-perturbative Approach to Equation of State and Collective Modes of the QGP
We discuss a non-perturbative -matrix approach to investigate the
microscopic structure of the quark-gluon plasma (QGP). Utilizing an effective
Hamiltonian which includes both light- and heavy-parton degrees of freedoms.
The basic two-body interaction includes color-Coulomb and confining
contributions in all available color channels, and is constrained by
lattice-QCD data for the heavy-quark free energy. The in-medium -matrices
and parton spectral functions are computed selfconsistently with full account
of off-shell properties encoded in large scattering widths. We apply the
-matrices to calculate the equation of state (EoS) for the QGP, including a
ladder resummation of the Luttinger-Ward functional using a matrix-log
technique to account for the dynamical formation of bound states. It turns out
that the latter become the dominant degrees of freedom in the EoS at low QGP
temperatures indicating a transition from parton to hadron degrees of freedom.
The calculated spectral properties of one- and two-body states confirm this
picture, where large parton scattering rates dissolve the parton quasiparticle
structures while broad resonances start to form as the pseudocritical
temperature is approached from above. Further calculations of transport
coefficients reveal a small viscosity and heavy-quark diffusion coefficient.Comment: 10 pages, 8 figures, proceedings of XLVII International Symposium on
Multiparticle Dynamics (ISMD2017
Spherical harmonic expansions of the Earth's gravitational potential to degree 360 using 30' mean anomalies
Two potential coefficient fields that are complete to degree and order 360 have been computed. One field (OSU86E) excludes geophysically predicted anomalies while the other (OSU86F) includes such anomalies. These fields were computed using a set of 30' mean gravity anomalies derived from satellite altimetry in the ocean areas and from land measurements in North America, Europe, Australia, Japan and a few other areas. Where no 30' data existed, 1 deg x 1 deg mean anomaly estimates were used if available. No rigorous combination of satellite and terrestrial data was carried out. Instead advantage was taken of the adjusted anomalies and potential coefficients from a rigorous combination of the GEML2' potential coefficient set and 1 deg x 1 deg mean gravity anomalies. The two new fields were computed using a quadrature procedure with de-smoothing factors. The spectra of the new fields agree well with the spectra of the fields with 1 deg x 1 deg data out to degree 180. Above degree 180 the new fields have more power. The fields have been tested through comparison of Doppler station geoid undulations with undulations from various geopotential models. The agreement between the two types of undulations is approximately + or - 1.6 m. The use of a 360 field over a 180 field does not significantly improve the comparison. Instead it allows the comparison to be done at some stations where high frequency effects are important. In addition maps made in areas of high frequency information (such as trench areas) clearly reveal the signal in the new fields from degree 181 to 360
Theory and Phenomenology of Heavy Flavor at RHIC
We review the problem of heavy-quark diffusion in the Quark-Gluon Plasma and
its ramifications for heavy-quark spectra in heavy-ion collisions at RHIC. In
particular, we attempt to reconcile underlying mechanisms of several seemingly
different approaches that have been put forward to explain the large
suppression and elliptic flow of non-photonic electron spectra. We also
emphasize the importance of a quantitative description of the bulk medium
evolution to extract reliable values for the heavy-quark diffusion coefficient.Comment: 8 pages latex, including 10 eps figures; plenary talk at SQM08,
Beijing (China), Oct. 06-10, 200
Photon production in relativistic nuclear collisions at SPS and RHIC energies
Chiral Lagrangians are used to compute the production rate of photons from
the hadronic phase of relativistic nuclear collisions. Special attention is
paid to the role of the pseudovector a_1 meson. Calculations that include
reactions with strange mesons, hadronic form factors and vector spectral
densities consistent with dilepton production, as well as the emission from a
quark-gluon plasma and primordial nucleon-nucleon collisions, reproduce the
photon spectra measured at the Super Proton Synchrotron (SPS). Predictions for
the Relativistic Heavy Ion Collider (RHIC) are made.Comment: Work presented at the 26th annual Montreal-Rochester-Syracuse-Toronto
conference (MRST 2004) on high energy physics, Montreal, QC, Canada, 12-14
May 2004. 8 pages, 3 figure
Hadronic Spectral Functions above the QCD Phase Transition
We extract the spectral functions in the scalar, pseudo-scalar, vector, and
axial vector channels above the deconfinement phase transition temperature (Tc)
using the maximum entropy method (MEM). We use anisotropic lattices, 32^3 * 32,
40, 54, 72, 80, and 96 (corresponding to T = 2.3 Tc --> 0.8 Tc), with the
renormalized anisotropy xi = 4.0 to have enough temporal data points to carry
out the MEM analysis. Our result suggests that the spectral functions continue
to possess non-trivial structures even above Tc and in addition that there is a
qualitative change in the state of the deconfined matter between 1.5 Tc and 2
Tc.Comment: 3 pages, 4 figures, Lattice2002(nonzerot
Heavy-Light Susceptibilities in a Strongly Coupled Quark-Gluon Plasma
Quark number susceptibilities as computed in lattice QCD are commonly
believed to provide insights into the microscopic structure of QCD matter, in
particular its degrees of freedom. We generalize a previously constructed
partonic -matrix approach to finite chemical potential to calculate various
susceptibilities, in particular for configurations containing a heavy charm
quark. At vanishing chemical potential and moderate temperatures, this approach
predicts large collisional widths of partons generated by dynamically formed
hadronic resonance states which lead to transport parameters characteristic for
a strongly coupled system. The quark chemical potential dependence is
implemented into the propagators and the in-medium color potential, where two
newly introduced parameters for the thermal and screening masses are fixed
through a fit to the baryon number susceptibility, . With this setup,
we calculate heavy-light susceptibilities without further tuning; the results
qualitatively agree with the lattice-QCD (lQCD) data for both
and . This implies that the lQCD results are compatible with a
significant content of broad -meson and charm-light diquark bound states in
a moderately hot QGP.Comment: 6 pages, 4 figure
Management of an Accessory Bile Duct Leak Following Pancreaticoduodenectomy: A Novel Approach Utilizing a Percutaneous and Endoscopic Rendezvous.
Biliary leaks are uncommon but morbid complications of pancreaticoduodenectomies, which have historically been managed with percutaneous drainage, reoperation, or a combination of both. We report a de novo percutaneous-endoscopic hepaticojejunostomy from an anomalous right hepatic duct injured during pancreaticoduodenectomy to the afferent bowel limb. The percutaneous-endoscopic hepaticojejunostomy was stented to allow for tract formation with successful stent removal after 5.5 months. One year after the creation of the percutaneous-endoscopic hepaticojejunostomy, the patient remains clinically well without evidence of biliary leak or obstruction
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