13 research outputs found
Meson Correlators in Finite Temperature Lattice QCD
We analyze temporal and spatial meson correlators in quenched lattice QCD at T>0. Below T_c we observe little change in the meson properties as compared with T=0. Above T_c we observe new features: chiral symmetry restoration and signals of plasma formation, but also indication of persisting mesonic (metastable) states and different temporal and spatial masses in the mesonic channels. This suggests a complex picture of QGP in the region 1 - 1.5 T_c
Quenched charmonium near the continuum limit
We study relativistic charmonium on very fine quenched lattices (beta=6.4 and 6.6). We concentrate on the calculation of the hyperfine splitting between eta_c and J/psi, aiming for a controlled continuum extrapolation of this quantity. Results for the eta_c and J/psi wave functions are also presented
Screening mass responses to chemical potential at finite temperature
Responses to chemical potential of the pseudoscalar meson screening mass and the chiral condensate in lattice QCD are investigated. On a lattice with two flavors of staggered quarks the first and second responses below and above are evaluated. Different behavior in the low and the high temperature phases are observed, which may be explained as a consequence of the chiral symmetry breaking and restoration
Reducing Residual-Mass Effects for Domain-Wall Fermions
It has been suggested to project out a number of low-lying eigenvalues of the
four-dimensional Wilson--Dirac operator that generates the transfer matrix of
domain-wall fermions in order to improve simulations with domain-wall fermions.
We investigate how this projection method reduces the residual chiral
symmetry-breaking effects for a finite extent of the extra dimension. We use
the standard Wilson as well as the renormalization--group--improved gauge
action. In both cases we find a substantially reduced residual mass when the
projection method is employed. In addition, the large fluctuations in this
quantity disappear.Comment: 18 pages, 10 figures, references updated, comments adde
Quenched charmonium spectrum
We study charmonium using the standard relativistic formalism in the quenched
approximation, on a set of lattices with isotropic lattice spacings ranging
from 0.1 to 0.04 fm. We concentrate on the calculation of the hyperfine
splitting between eta_c and J/psi, aiming for a controlled continuum
extrapolation of this quantity. The splitting extracted from the
non-perturbatively improved clover Dirac operator shows very little dependence
on the lattice spacing for fm. The dependence is much stronger for
Wilson and tree-level improved clover operators, but they still yield
consistent extrapolations if sufficiently fine lattices, fm (), are used. Our result for the hyperfine splitting is
77(2)(6) MeV (where Sommer's parameter, r_0, is used to fix the scale). This
value remains about 30% below experiment. Dynamical fermions and OZI-forbidden
diagrams both contribute to the remainder. Results for the eta_c and J/psi wave
functions are also presented.Comment: 22 pages, 7 figure
Lattice calculations of meson correlators and spectral functions at finite temperature
I review recent progress in relating meson spectral function to imaginary
time correlation function at finite temperature calculated on isotropic as well
as on anisotropic lattices. Special attention is payed for the lattice
artifacts present in calculation of meson spectral functions. Results in the
case of light quarks as well as heavy quarks are reviewed which indicate in
particular that even in the chiral limit meson spectral functions have
non-trivial structure and the ground state quarkonia survive up to temperature
1.5T_cComment: Invited plenary talk presented at SQM03 (Atlantic Beach, March 12-17,
2003), 10 pages LaTeX, uses iopams.sty, iopart.cl
Quantum Chromodynamics Simulations on a Nondedicated Parallel Computer
A parallelization study of Quantum Chromodynamics (QCD) simulation on a nondedicated computer, AP1000, is reported. AP1000 is a highly parallel computer with distributed memory. Data communication is fast not only among the nearest neighbor processing units, but also among long distance ones. We study SU(3) quenched QCD simulation with lattice sizes of 32 4 and 32 3 \Theta 48, on the 512-processor 1 system of AP1000, and report parallelization techniques and physical results for the renormalization group study and the hadron spectroscopy. AP1000 has proved its efficiency in these QCD simulations and shows good performance. A bottleneck at the current simulation is the data storing through the frontend processor. 1. Introduction Recently there have been several QCD simulation projects on massively parallel computers: some of them have already produced successful results and many ambitious ones are planed [1]. This is a natural consequence of the rapid progress in computer technol..