2,060 research outputs found
Equation of state in 2+1 flavor QCD with improved Wilson quarks by the fixed scale approach
We study the equation of state in 2+1 flavor QCD with nonperturbatively
improved Wilson quarks coupled with the RG-improved Iwasaki glue. We apply the
-integration method to nonperturbatively calculate the equation of state by
the fixed-scale approach. With the fixed-scale approach, we can purely vary the
temperature on a line of constant physics without changing the system size and
renormalization constants. Unlike the conventional fixed- approach, it is
easy to keep scaling violations small at low temperature in the fixed scale
approach. We study 2+1 flavor QCD at light quark mass corresponding to
, while the strange quark mass is chosen around the
physical point. Although the light quark masses are heavier than the physical
values yet, our equation of state is roughly consistent with recent results
with highly improved staggered quarks at large .Comment: 14 pages, 12 figures, v2: Table I and Figure 3 are corrected,
reference updated. Main discussions and conclusions are unchanged, v3:
version to appear in PRD, v4: reference adde
Fixed scale approach to the equation of state on the lattice
We propose a fixed scale approach to calculate the equation of state (EOS) in
lattice QCD. In this approach, the temperature T is varied by Nt at fixed
lattice spacings. This enables us to reduce T=0 simulations which are required
to provide basic data in finite temperature studies but are quite expensive in
the conventional fixed-Nt approach. Since the conventional integral method to
obtain the pressure is inapplicable at fixed scale, we introduce a new method,
"T-integration method", to calculate pressure non-perturbatively. We test the
fixed scale approach armed with the T-integral method in quenched QCD on
isotropic and anisotropic lattices. Our method is found to be powerful to
obtain reliable results for the equation of state, especially at intermediate
and low temperatures. Reduction of the computational cost of T=0 simulations is
indispensable to study EOS in QCD with dynamical quarks. The status of our
study in Nf=2+1 QCD with improved Wilson quarks is also reported.Comment: 4 pages, 4 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee. Fonts in the
figures magnifie
Application of fixed scale approach to static quark free energies in quenched and 2+1 flavor lattice QCD with improved Wilson quark action
Free energies between static quarks and Debye screening masses in the
quark-gluon plasma are studied on the basis of Polyakov-line correlations in
lattice simulations of 2+1 flavors QCD with the renormalization-group improved
gluon action and the -improved Wilson quark action. We perform
simulations at (0.74) for light (strange) flavors
with lattice sizes of with --12. We adopt the
fixed-scale approach, where temperature can be varied without changing the
spatial volume and renormalization factor. We find that, at short distance, the
free energies of static quarks in color-singlet channel converge to the
static-quark potential evaluated from the Wilson-loop at zero-temperature, in
accordance with the expected insensitivity of short distance physics to the
temperature. At long distance, the free energies of static quarks approach to
twice the single-quark free energies, implying that the interaction between
static quarks is fully screened. The screening properties can be well described
by the screened Coulomb form with appropriate Casimir factor at high
temperature. We also discuss a limitation of the fixed-scale approach at high
temperature.Comment: 16 pages, 14 figure
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