388 research outputs found
Eigenvalue distribution of the Dirac operator at finite temperature with (2+1)-flavor dynamical quarks using the HISQ action
We report on the behavior of the eigenvalue distribution of the Dirac
operator in (2+1)-flavor QCD at finite temperature, using the HISQ action. We
calculate the eigenvalue density at several values of the temperature close to
the pseudocritical temperature. For this study we use gauge field
configurations generated on lattices of size with two light
quark masses corresponding to pion masses of about 160 and 115 MeV. We find
that the eigenvalue density below receives large contributions from
near-zero modes which become smaller as the temperature increases or the light
quark mass decreases. Moreover we find no clear evidence for a gap in the
eigenvalue density up to 1.1. We also analyze the eigenvalue density near
where it appears to show a power-law behavior consistent with what is
expected in the critical region near the second order chiral symmetry restoring
phase transition in the massless limit.Comment: 7 pages, 7 figures, talk presented at the XXIX International
Symposium on Lattice Field Theory, July 10-16 2011, Squaw Valley, Lake Tahoe,
California, US
QCD matter within a quasi-particle model and the critical end point
We compare our quasi-particle model with recent lattice QCD results for the
equation of state at finite temperature and baryo-chemical potential. The
inclusion of the QCD critical end point into models is discussed. We propose a
family of equations of state to be employed in hydrodynamical calculations of
particle spectra at RHIC energies and compare with the differential azimuthal
anisotropy of strange and charm hadrons.Comment: talk at Quark Matter 2005, August 4 - 9, 2005, Budapest, Hungar
The Gluon Propagator at High Temperature: Screening, Improvement and Non-Zero Momenta
We study the gluon propagator and the singlet potential in Landau gauge in the deconfined phase of SU(2) lattice gauge theory, using both the standard Wilson action and a tree-level Symanzik improved action. From the long-distance behavior of correlation functions of temporal and spatial components of the gauge fields we extract electric (m_e) and magnetic (m_m) screening masses. For the magnetic mass we find m_m(T) = 0.456(6) g^2(T) T. The electric mass can be described by a next-to leading order ansatz, obtained from one loop resummed perturbation theory. However, the best description is given by m_e(T) = lowest order perturbative prediction even for temperatures as high as T \sim 10^4 T_c
Equation of State and Collective Dynamics
This talk summarizes the present status of a program to quantitatively relate
data from the Relativistic Heavy Ion Collider (RHIC) on collective expansion
flow to the Equation of State (EOS) of hot and dense strongly interacting
matter, including the quark-gluon plasma and the quark-hadron phase transition.
The limits reached with the present state of the art and the next steps
required to make further progress will both be discussed.Comment: 8 pages, 6 two-part figures. Invited talk given at the 5th
International Conference on the Physics and Astrophysics of Quark-Gluon
Plasma (ICPAQGP 2005), Kolkata (India), Feb 8-12, 2005. Proceedings to be
published in Journal of Physics: Conference Series (Jan-E Alam et al., eds.
A Family of Equations of State Based on Lattice QCD: Impact on Flow in Ultrarelativistic Heavy-Ion Collisions
We construct a family of equations of state within a quasiparticle model by
relating pressure, energy density, baryon density and susceptibilities adjusted
to first-principles lattice QCD calculations. The relation between pressure and
energy density from lattice QCD is surprisingly insensitive to details of the
simulations. Effects from different lattice actions, quark masses and lattice
spacings used in the simulations show up mostly in the quark-hadron phase
transition region which we bridge over by a set of interpolations to a hadron
resonance gas equation of state. Within our optimized quasiparticle model we
then examine the equation of state along isentropic expansion trajectories at
small net baryon densities, as relevant for experiments and hydrodynamic
simulations at RHIC and LHC energies. We illustrate its impact on azimuthal
flow anisotropies and transverse momentum spectra of various hadron species
Critical exponents of a three dimensional O(4) spin model
By Monte Carlo simulation we study the critical exponents governing the
transition of the three-dimensional classical O(4) Heisenberg model, which is
considered to be in the same universality class as the finite-temperature QCD
with massless two flavors. We use the single cluster algorithm and the
histogram reweighting technique to obtain observables at the critical
temperature. After estimating an accurate value of the inverse critical
temperature \Kc=0.9360(1), we make non-perturbative estimates for various
critical exponents by finite-size scaling analysis. They are in excellent
agreement with those obtained with the expansion method with
errors reduced to about halves of them.Comment: 25 pages with 8 PS figures, LaTeX, UTHEP-28
From SPS to RHIC: Maurice and the CERN heavy-ion programme
Maurice Jacob played a key role in bringing together different groups from
the experimental and theoretical nuclear and particle physics communities to
initiate an ultrarelativistic heavy-ion collision program at the CERN SPS, in
order to search for the quark-gluon plasma. I review the history of this
program from its beginnings to the time when the Relativistic Heavy Ion
Collider (RHIC) at Brookhaven National Laboratory (BNL) started operation. I
close by providing a glimpse of the important discoveries made at RHIC and
giving an outlook towards heavy-ion collisions at the Large Hadron Collider
(LHC). During Maurice's life and not least through his perpetually strong
influence, relativistic heavy-ion physics has matured and led to discoveries
that radiate into many other fields of physics. Heavy-ion physicists owe a
great deal to Maurice Jacob.Comment: 12 pages, including 2 Figs. Invited talk given at the "Maurice Jacob
Memorial Meeting", CERN, 11 September 2007. To appear in a special issue of
Comments on Nuclear and Particle Physics which is published as a Section of
Physica Script
Quarkonium Suppression
I discuss quarkonium suppression in equilibriated strongly interacting
matter. After a brief review of basic features of quarkonium production I
discuss the application of recent lattice data on the heavy quark potential to
the problem of quarkonium dissociation as well as the problem of direct lattice
determination of quarkonium properties in finite temperature lattice QCD.Comment: Invited plenary talk presented on 4th International Conference on
Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP-2001), November
26-30, 2001, Jaipur; 12 pp, LaTeX, uses pramana.st
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