2,433 research outputs found
Temporal meson correlators at finite temperature on quenched anisotropic lattice
We study charmonium correlators at finite temperature in quenched anisotropic
lattice QCD. The smearing technique is applied to enhance the low energy part
of the correlator. We use two analysis procedures: the maximum entropy method
for extraction of the spectral function without assuming specific form, as an
estimate of the shape of spectral function, and the fit assuming
typical forms as quantitative evaluation of the parameters associated to the
forms. We find that at the ground state peak has almost the
same mass as at T=0 and almost vanishing width. At , our result
suggests that the correlator still has nontrivial peak structure at almost the
same position as below with finite width.Comment: Lattice 2002 Nonzero temperature 3page
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
GaAs-GaAlAs distributed-feedback diode lasers with separate optical and carrier confinement
Remarkable reduction of the threshold current density is achieved in GaAs-GaAlAs distributed-feedback diode lasers by adopting a separate-confinement heterostructure. The diodes are lased successfully at temperatures up to 340 °K under pulsed operation. The lowest threshold current density is 3 kA/cm^2 at 300 °K
Histograms in heavy-quark QCD at finite temperature and density
We study the phase structure of lattice QCD with heavy quarks at finite
temperature and density by a histogram method. We determine the location of the
critical point at which the first-order deconfining transition in the
heavy-quark limit turns into a crossover at intermediate quark masses through a
change of the shape of the histogram under variation of coupling parameters. We
estimate the effect of the complex phase factor which causes the sign problem
at finite density, and show that, in heavy-quark QCD, the effect is small
around the critical point. We determine the critical surface in 2+1 flavor QCD
in the heavy-quark region at all values of the chemical potential mu including
mu=infty.Comment: 26 pages, 21 figures, 1 tabl
- …