1,805 research outputs found
Heavy Quark Interactions in Finite Temperature QCD
We study the free energy of a heavy quark-antiquark pair in a thermal medium.
We constuct a simple ansatz for the free energy for two quark flavors motivated
by the Debye-H\"uckel theory of screening.Comment: 4 pages, 4 figures, contribution to the proceedings of the
International Conference on Hard and Electromagnetic Probes of High Energy
Nuclear Collisions, Ericeira, Portugal, Nov. 4-10, 200
Heavy Quark Interactions and Quarkonium Binding
We consider heavy quark interactions in quenched and unquenched lattice QCD.
In a region just above the deconfinement point, non-Abelian gluon polarization
leads to a strong increase in the binding. Comparing quark-antiquark and
quark-quark interaction, the dependence of the binding on the separation
distance is found to be the same for the colorless singlet and
the colored anti-triplet state. In a potential model description of
in-medium behavior, this enhancement of the binding leads to a
survival up to temperatures of 1.5 or higher; it could also result in
flow.Comment: 8 pages, 8 Figures; invited talk at "Strangeness in Quark Matter
2008", Beijing/China, to appear in the Proceeding
A non-perturbative estimate of the heavy quark momentum diffusion coefficient
We estimate the momentum diffusion coefficient of a heavy quark within a pure
SU(3) plasma at a temperature of about 1.5Tc. Large-scale Monte Carlo
simulations on a series of lattices extending up to 192^3*48 permit us to carry
out a continuum extrapolation of the so-called colour-electric imaginary-time
correlator. The extrapolated correlator is analyzed with the help of
theoretically motivated models for the corresponding spectral function.
Evidence for a non-zero transport coefficient is found and, incorporating
systematic uncertainties reflecting model assumptions, we obtain kappa = (1.8 -
3.4)T^3. This implies that the "drag coefficient", characterizing the time
scale at which heavy quarks adjust to hydrodynamic flow, is (1.8 - 3.4)
(Tc/T)^2 (M/1.5GeV) fm/c, where M is the heavy quark kinetic mass. The results
apply to bottom and, with somewhat larger systematic uncertainties, to charm
quarks.Comment: 18 pages. v2: clarifications adde
Critical point and scale setting in SU(3) plasma: An update
We explore a method developed in statistical physics which has been argued to
have exponentially small finite-volume effects, in order to determine the
critical temperature Tc of pure SU(3) gauge theory close to the continuum
limit. The method allows us to estimate the critical coupling betac of the
Wilson action for temporal extents up to Nt ~ 20 with < 0.1% uncertainties.
Making use of the scale setting parameters r0 and sqrt{t0} in the same range of
beta-values, these results lead to the independent continuum extrapolations Tc
r0 = 0.7457(45) and Tc sqrt{t0} = 0.2489(14), with the latter originating from
a more convincing fit. Inserting a conversion of r0 from literature
(unfortunately with much larger errors) yields Tc / LambdaMSbar = 1.24(10).Comment: 12 pages. v2: clarifications and references added, published versio
Towards the continuum limit in transport coefficient computations
The analytic continuation needed for the extraction of transport coefficients
necessitates in principle a continuous function of the Euclidean time variable.
We report on progress towards achieving the continuum limit for 2-point
correlator measurements in thermal SU(3) gauge theory, with specific attention
paid to scale setting. In particular, we improve upon the determination of the
critical lattice coupling and the critical temperature of pure SU(3) gauge
theory, estimating r0*Tc ~ 0.7470(7) after a continuum extrapolation. As an
application the determination of the heavy quark momentum diffusion coefficient
from a correlator of colour-electric fields attached to a Polyakov loop is
discussed.Comment: 7 pages. To appear in the Proceedings of the 31st International
Symposium on Lattice Field Theory, July 29 - August 3, 2013, Mainz, German
Preparation and characterization of interpenetrating networks based on polyacrylates and poly(lactic acid)
Three different, multifunctional acrylic monomers were photopolymerized in a matrix of poly(lactic acid), PLA, using 2-hydroxy-2-methyl-1-phenyl-propan-1-one as a photoinitiator. The kinetics of the photopolymerization of monomers in PLA, studied with Fourier Transform Infrared Spectroscopy, has been compared to analogous processes of pure monomers under the same conditions (room temperature, air atmosphere). Additionally, poly(ethylene glycol) was added to acrylate/PLA blends as plasticizer.The highly crosslinked networks obtained were characterized by FTIR and optical microscopy. The amount of insoluble gel has been estimated gravimetrically. It was found that the studied systems are characterized by very high polymerization rate, moreover, efficient grafting of polyacrylates on PLA takes place. The observed morphology indicates the heterogeneity of formed networks. The glass transition temperature of PLA in studied blends has been determined by differential scanning calorimetry
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