48 research outputs found
Thermal features far from equilibrium: Prethermalization
The phenomenon of prethermalization and the subsequent steps of
thermalization are analyzed in the framework of the chiral quark model. We
solve the quantum equations of motion of the field theory derived from the 2PI
effective action and study the time scales of equilibration. We find that
already after a 0.6 fm/c long period of time some equilibrium features appear,
even though the system is still far from equilibrium. This might be an
ingredient for understanding the success of ideal hydrodynamic description.Comment: LaTeX, 5 pages. Contribution to the Proceedings of 6th Conference on
Strong and Electroweak Matter 2004 (SEWM04), Helsinki, Finland, 16-19 Jun
200
Is there a flavor hierarchy in the deconfinement transition of QCD?
We present possible indications for flavor separation during the QCD
crossover transition based on continuum extrapolated lattice QCD calculations
of higher order susceptibilities. We base our findings on flavor specific
quantities in the light and strange quark sector. We propose a possible
experimental verification of our prediction, based on the measurement of higher
order moments of identified particle multiplicities. Since all our calculations
are performed at zero baryochemical potential, these results are of particular
relevance for the heavy ion program at the LHC.Comment: 5 pages, 3 figures, revte
Continuum EoS for QCD with Nf=2+1 flavors
We report on a continuum extrapolated result [arXiv:1309.5258] for the
equation of state (EoS) of QCD with dynamical quark flavors. In this
study, all systematics are controlled, quark masses are set to their physical
values, and the continuum limit is taken using at least three lattice spacings
corresponding to temporal extents up to . A Symanzik improved gauge and
stout-link improved staggered fermion action is used. Our results are available
online [ancillary file to arXiv:1309.5258].Comment: Conference proceedings, 7 pages, 4 figures. Talk presented at 31st
International Symposium on Lattice Field Theory (LATTICE 2013), July 29 -
August 3, 2013, Mainz, German
Determination of SU(2) ChPT LECs from 2+1 flavor staggered lattice simulations
By fitting pion masses and decay constants from 2+1 flavor staggered lattice
simulations to the predictions of NLO and NNLO SU(2) chiral perturbation theory
we determine the low-energy constants l_3 and l_4. The lattice ensembles were
generated by the Wuppertal-Budapest collaboration and cover pion masses in the
range of 135 to 435 MeV and lattice scales between 0.7 and 2.0 GeV. By choosing
a suitable scaling trajectory, we were able to demonstrate that precise and
stable results for the LECs can be obtained from continuum ChPT to NLO. The
pion masses available in this work also allow us to study the applicability of
using ChPT to extrapolate from higher masses to the physical pion mass.Comment: 8 pages, 8 figures, 1 table, talk presented at Xth Quark Confinement
and the Hadron Spectrum, Munich, October 201
SU(2) chiral perturbation theory low-energy constants from 2+1 flavor staggered lattice simulations
We extract the next-to-leading-order low-energy constants \bar\ell_3 and
\bar\ell_4 of SU(2) chiral perturbation theory, based on precise lattice data
for the pion mass and decay constant on ensembles generated by the
Wuppertal-Budapest Collaboration for QCD thermodynamics. These ensembles
feature 2+1 flavors of two-fold stout-smeared dynamical staggered fermions
combined with Symanzik glue, with pion masses varying from 135 to 435 MeV,
lattice scales between 0.7 and 2.0 GeV, while m_s is kept fixed at its physical
value. Moderate taste splittings and the scale being set through the pion decay
constant allow us to restrict ourselves to the taste pseudoscalar state and to
use formulas from continuum chiral perturbation theory. Finally, by dropping
the data points near 135 MeV from the fits, we can explore the range of pion
masses that is needed in SU(2) chiral perturbation theory to reliably
extrapolate to the physical point.Comment: 40 pages, 22 figures, 3 tables; v2: expanded discussion, matches
published versio
QCD transition temperature: full staggered result
We conclude our investigations on the QCD cross-over transition temperatures
with 2+1 staggered flavours and one-link stout improvement. We extend our
previous two studies [Phys. Lett. B643 (2006) 46, JHEP 0906:088 (2009)] by
choosing even finer lattices (N_t=16) and we work again with physical quark
masses. These new results [for details see JHEP 1009:073,2010] support our
earlier findings. We compare them with the published results of the hotQCD
collaboration. All these results are confronted with the predictions of the
Hadron Resonance Gas model and Chiral Perturbation Theory for temperatures
below the transition region. Our results can be reproduced by using the
physical spectrum. The findings of the hotQCD collaboration can be recovered
only by using a distorted spectrum. This analysis provides a simple explanation
for the observed discrepancy in the transition T between our and the hotQCD
collaborations.Comment: presented at the XXVIII. International Symposium on Lattice Field
Theory, June 14-19,2010, Villasimius, Sardinia Ital
Recent results on the Equation of State of QCD
We report on a continuum extrapolated result (arXiv:1309.5258) for the
equation of state (EoS) of QCD with dynamical quark flavors and
discuss preliminary results obtained with an additional dynamical charm quark
(). For all our final results, the systematics are controlled, quark
masses are set to their physical values, and the continuum limit is taken using
at least three lattice spacings corresponding to temporal extents up to
.Comment: Conference proceedings: The 32nd International Symposium on Lattice
Field Theory - Lattice 2014, June 23-28, 2014, Columbia University, New York,
New Yor