260 research outputs found
Relaxation of 2+1 dimensional classical O(2) symmetric scalar fields
Real time thermalization and relaxation phenomena are studied in the low energy density phase of the 2+1 dimensional classical O(2) symmetric scalar theory by solving numerically its dynamics. The near-equilibrium decay rate of on-shell waves and the power law governing the large time asymptotics of the off-shell relaxation agree with the analytic results based on linear response theory. The realisation of the Mermin-Wagner theorem is also studied in the final equilibrium ensemble
Freeze-out parameters: lattice meets experiment
We present our results for ratios of higher order fluctuations of electric
charge as functions of the temperature. These results are obtained in a system
of 2+1 quark flavors at physical quark masses and continuum extrapolated. We
compare them to preliminary data on higher order moments of the net electric
charge distribution from the STAR collaboration. This allows us to determine
the freeze-out temperature and chemical potential from first principles. We
also show continuum-extrapolated results for ratios of higher order
fluctuations of baryon number. These will allow to test the consistency of the
approach, by comparing them to the corresponding experimental data (once they
become available) and thus extracting the freeze-out parameters in an
independent way.Comment: 5 pages, 7 figures, revte
Freeze-out parameters from electric charge and baryon number fluctuations: is there consistency?
Recent results for moments of multiplicity distributions of net-protons and
net-electric charge from the STAR collaboration are compared to lattice QCD
results for higher order fluctuations of baryon number and electric charge by
the Wuppertal-Budapest collaboration, with the purpose of extracting the
freeze-out temperature and chemical potential. All lattice simulations are
performed for a system of 2+1 dynamical quark flavors, at the physical mass for
light and strange quarks; all results are continuum extrapolated. We show that
it is possible to extract an upper value for the freeze-out temperature, as
well as precise baryo-chemical potential values corresponding to the four
highest collision energies of the experimental beam energy scan. Consistency
between the freeze-out parameters obtained from baryon number and electric
charge fluctuations is found. The freeze-out chemical potentials are now in
agreement with the statistical hadronization model.Comment: 5 pages, 4 figures, references added, discussion added to the
introduction, results unchange
Lattice SU(3) thermodynamics and the onset of perturbative behaviour
We present the equation of state (pressure, trace anomaly, energy density and
entropy density) of the SU(3) gauge theory from lattice field theory in an
unprecedented precision and temperature range. We control both finite size and
cut-off effects. The studied temperature window () stretches
from the glueball dominated system into the perturbative regime, which allows
us to discuss the range of validity of these approaches. From the critical
couplings on fine lattices we get T_c/\Lambdamsbar=1.26(7) and use this ratio
to express the perturbative free energy in units. We also determine the
preferred renormalization scale of the Hard Thermal Loop scheme and we fit the
unknown order perturbative coefficient at extreme high temperatures
. We furthermore quantify the nonperturbative contribution to the
trace anomaly using two simple functional forms.Comment: 7 pages, Contribution to the The XXVIII International Symposium on
Lattice Field Theory; June 14 - 19, 2010, Villasimius, Sardinia, Ital
Three-loop HTLpt thermodynamics at finite temperature and chemical potential
In this proceedings we present a state-of-the-art method of calculating
thermodynamic potential at finite temperature and finite chemical potential,
using Hard Thermal Loop perturbation theory (HTLpt) up to
next-to-next-leading-order (NNLO). The resulting thermodynamic potential
enables us to evaluate different thermodynamic quantities including pressure
and various quark number susceptibilities (QNS). Comparison between our
analytic results for those thermodynamic quantities with the available lattice
data shows a good agreement.Comment: 5 pages, 6 figures, conference proceedings of XXI DAE-BRNS HEP
Symposium, IIT Guwahati, December 2014; to appear in 'Springer Proceedings in
Physics Series
QCD thermodynamics with dynamical overlap fermions
We study QCD thermodynamics using two flavors of dynamical overlap fermions
with quark masses corresponding to a pion mass of 350 MeV. We determine several
observables on N_t=6 and 8 lattices. All our runs are performed with fixed
global topology. Our results are compared with staggered ones and a nice
agreement is found.Comment: 14 pages, 6 figures, 1 tabl
The QCD phase diagram from analytic continuation
We present the crossover line between the quark gluon plasma and the hadron
gas phases for small real chemical potentials. First we determine the effect of
imaginary values of the chemical potential on the transition temperature using
lattice QCD simulations. Then we use various formulas to perform an analytic
continuation to real values of the baryo-chemical potential. Our data set
maintains strangeness neutrality to match the conditions of heavy ion physics.
The systematic errors are under control up to MeV. For the
curvature of the transition line we find that there is an approximate agreement
between values from three different observables: the chiral susceptibility,
chiral condensate and strange quark susceptibility. The continuum extrapolation
is based on 10, 12 and 16 lattices. By combining the analysis for these
three observables we find, for the curvature, the value .Comment: 14 pages, 4 figures, revised versio
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