1,191 research outputs found
Lattice constraints on the thermal photon rate
We estimate the photon production rate from an SU(3) plasma at temperatures
of about 1.1Tc and 1.3Tc. Lattice results for the vector current correlator at
spatial momenta k ~ (2-6)T are extrapolated to the continuum limit and analyzed
with the help of a polynomial interpolation for the corresponding spectral
function, which vanishes at zero frequency and matches to high-precision
perturbative results at large invariant masses. For small invariant masses the
interpolation is compared with the NLO weak-coupling result, hydrodynamics, and
a holographic model. At vanishing invariant mass we extract the photon rate
which for k \gsim 3T is found to be close to the NLO weak-coupling prediction.
For k \lsim 2T uncertainties remain large but the photon rate is likely to fall
below the NLO prediction, in accordance with the onset of a strongly
interacting behaviour characteristic of the hydrodynamic regime.Comment: 20 pages. v2: clarifications adde
Numerical study of the equation of state for two flavor QCD at finite density
We discuss the equation of state for 2 flavor QCD at non-zero temperature and
density. Derivatives of with respect to quark chemical potential
up to fourth order are calculated, enabling estimates of the pressure,
quark number density and associated susceptibilities as functions of
via a Taylor series expansion. It is found that the fluctuations in the quark
number density increase in the vicinity of the phase transition temperature and
the susceptibilities start to develop a pronounced peak as is
increased. This suggests the presence of a critical endpoint in the plane.Comment: 5 pages, 4 figures, Talk at Confinement 200
The non-zero baryon number formulation of QCD
We discuss the non-zero baryon number formulation of QCD in the quenched
limit at finite temperature. This describes the thermodynamics of gluons in the
background of static quark sources. Although a sign problem remains in this
theory, our simulation results show that it can be handled quite well
numerically. The transition region gets shifted to smaller temperatures and the
transition region broadens with increasing baryon number. Although the action
is in our formulation explicitly Z(3) symmetric the Polyakov loop expectation
value becomes non-zero already in the low temperature phase and the heavy quark
potential gets screened at non-vanishing number density already this phase.Comment: LATTICE99(Finite Temperature and Density), Latex2e using espcrc2.sty,
3 pages, 7 figure
QCD at non-zero chemical potential and temperature from the lattice
A study of QCD at non-zero chemical potential, mu, and temperature, T, is
performed using the lattice technique. The transition temperature (between the
confined and deconfined phases) is determined as a function of mu and is found
to be in agreement with other work. In addition the variation of the pressure
and energy density with mu is obtained for small positive mu. These results are
of particular relevance for heavy-ion collision experiments.Comment: Invited paper presented at the Joint Workshop on Physics at the
Japanese Hadron Facility, March 2002, Adelaide. 10 pages, uses
ws-procs9x6.cls style file (provided
The QCD equation of state for two flavours at non-zero chemical potential
We present results of a simulation of 2 flavour QCD on a
lattice using p4-improved staggered fermions with bare quark mass .
Derivatives of the thermodynamic grand canonical partition function
with respect to chemical potentials for
different quark flavours are calculated up to sixth order, enabling estimates
of the pressure and the quark number density as well as the chiral condensate
and various susceptibilities as functions of via Taylor series
expansion. Results are compared to high temperature perturbation theory as well
as a hadron resonance gas model. We also analyze baryon as well as isospin
fluctuations and discuss the relation to the chiral critical point in the QCD
phase diagram. We moreover discuss the dependence of the heavy quark free
energy on the chemical potential.Comment: 4 pages, 7 figures, talk presented at Quark Matter 2005, Budapes
Heavy Quarkonia and Quark Drip Lines in Quark-Gluon Plasma
Using the potential model and thermodynamical quantities obtained in lattice
gauge calculations, we determine the spontaneous dissociation temperatures of
color-singlet quarkonia and the `quark drip lines' which separate the region of
bound states from the unbound region. The dissociation temperatures
of and in quenched QCD are found to be 1.62 and
respectively, in good agreement with spectral function analyses. The
dissociation temperature of in full QCD with 2 flavors is found to be
1.42. For possible bound quarkonium states with light quarks, the
characteristics of the quark drip lines severely limit the stable region close
to the phase transition temperature. Bound color-singlet quarkonia with light
quarks may exist very near the phase transition temperature if their effective
quark mass is of the order of 300-400 MeV and higher.Comment: 8 pages, 2 figures, in LaTex, invited talk presented at the
International Conference on Strangeness in Quark Matter, UCLA, March 26-31,
200
Magnetic Component of Quark-Gluon Plasma
We describe recent developments of the "magnetic scenario" of sQGP. We show
that at there is a dense plasma of monopoles, capable of
supporting metastable flux tubes. Their existence allows to quantitatively
explained the non-trivial -dependence of the static potential
energy calculated on the lattice. By molecular dynamics simulation we derived
transport properties (shear viscosity and diffusion constant) and showed that
the best liquid is given by most symmetric plasma, with 50%-50% of electric and
magnetic charges. The results are close to those of the ``perfect liquid''
observed at RHIC.Comment: Contribution to the 20th International Conference on Nucleus Nucleus
Collisions (Quark Matter 2008
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