53 research outputs found
Towards the glueball spectrum of full QCD
We present first results on masses of the scalar and tensor glueballs as well
as of the torelon from simulations of QCD with two light flavours of Wilson
fermions. The gauge configurations of extent 16^3*32 at beta = 5.6 and kappa =
0.156, 0.157 and 0.1575 have been generated as part of the SESAM collaboration
programme. The present lattice resolutions correspond to 1/a = 2.0-2.3 GeV and
ratios m(pi)/m(rho) = 0.83, 0.76 and 0.71, respectively. Studies on larger
lattice volumes and closer to the chiral limit are in progress.Comment: 4 pages, LaTeX, espcrc2 and epsf styles required, 4 epsf figures,
poster presented by G. Bali at Lattice '9
Hyper-systolic processing on APE100\/Quadrics: n-loop computations
We investigate the performance gains from hyper-systolic implementations of n^2-loop problems on the massively parallel computer Quadrics, exploiting its 3-dimensional interprocessor connectivity. For illustration we study the communication aspects of an exact molecular dynamics simulation of n particles with Coulomb (or gravitational) interactions. We compare the interprocessor communication costs of the standard-systolic and the hyper-systolic approaches for various granularities. We predict gain factors as large as 3 on the Q4 and 8 on the QH4 and measure actual performances on these machine configurations. We conclude that it appears feasile to investigate the thermodynamics of a full gravitating n-body problem with O(10000) particles using the new method on a QH4 system
Glueballs and string breaking from full QCD
We present results on the static potential, and torelon and glueball masses
from simulations of QCD with two flavours of dynamical Wilson fermions on
and lattices at .Comment: Talk presented by Gunnar Bali at International Symposium on Lattice
Field Theories (Lattice 97), Edinburgh, July 1997, 3 pages LaTeX
(epscrc2.sty) with 4 eps figure
SESAM and TXL Results for Wilson Action--A Status Report
Results from two studies of full QCD with two flavours of dynamical Wilson
fermions are presented. At beta=5.6, the region 0.83 > m_pi/m_rho > 0.56 at
m_pia > 0.23 L^{-1} is explored. The SESAM collaboration has generated
ensembles of about 200 statistically independent configurations on a 16^3 x
32-lattice at three different kappa-values and is entering the final phase of
data analysis. The TXL simulation on a 24^3 x 40-lattice at two kappa-values
has reached half statistics and data analysis has started recently, hence most
results presented here are preliminary. The focus of this report is fourfold:
we demonstrate that algorithmic improvements like fast Krylov solvers and
parallel preconditioning recently introduced can be put into practise in full
QCD simulations, we present encouraging observations as to the critical
dynamics of the Hybrid Monte Carlo algorithm in the approach to the chiral
limit, we mention signal improvements of noisy estimator techniques for
disconnected diagrams to the pi-N sigma term, and we report on SESAM's results
for light hadron spectrum, light quark masses, and heavy quarkonia.Comment: 24 pages, tex + postscript figures, to appear in Proceedings of Int.
Workshop "Lattice QCD on Parallel Computers", University of Tsukuba, Japa
Light Quark Physics with Dynamical Wilson Fermions
We present results for spectroscopy, quark masses and decay constants
obtained from SESAM's and TkL's large statistics simulations of QCD with two
dynamical Wilson fermions.Comment: 3 pages; to appear in the proceedings of Lat.'9
A Parallel SSOR Preconditioner for Lattice QCD
A parallelizable SSOR preconditioning scheme for Krylov subspace iterative
solvers in lattice QCD applications involving Wilson fermions is presented. In
actual Hybrid Monte Carlo and quark propagator calculations it helps to reduce
the number of iterations by a factor of 2 compared to conventional odd-even
preconditioning. This corresponds to a gain in cpu-time of 30\% - 70\% over
odd-even preconditioning.Comment: Talk presented at LATTICE96(algorithms), 3 pages, LaTeX file, 3
epsf-files include
Light Quark Masses with Dynamical Wilson Fermions
We determine the masses of the light and the strange quarks in the
-scheme using our high-statistics lattice simulation of QCD with
dynamical Wilson fermions. For the light quark mass we find
, which is lower than in quenched
simulations. For the strange quark, in a sea of two dynamical light quarks, we
obtain .Comment: 10 pages (latex file, uses epsf-style
First Evidence of -Dependence in the QCD Interquark Potential
We present a lattice calculation of the interquark potential between static
quarks in a ``full'' QCD simulation with 2 flavours of dynamical Wilson-quarks
at three intermediate sea-quark masses. We work at on lattice
size of with 100 configurations per sea-quark mass. We compare
the full QCD potential with its quenched counterpart at equal lattice spacing,
GeV, which is at the onset of the quenched scaling regime.
We find that the full QCD potential lies consistently below that of quenched
QCD. We see no evidence for string-breaking effects on these lattice volumes,
.Comment: 9 pages (1 tex file epsf-style + 6 ps-figures
Critical Dynamics of the Hybrid Monte Carlo Algorithm
We investigate the critical dynamics of the Hybrid Monte Carlo algorithm
approaching the chiral limit of standard Wilson fermions. Our observations are
based on time series of lengths O(5000) for a variety of observables. The
lattice sizes are 16^3 x 32 and 24^3 x 40. We work at beta=5.6, and
kappa=0.156, 0.157, 0.1575, 0.158, with 0.83 > m_pi/m_rho > 0.55. We find
surprisingly small integrated autocorrelation times for local and extended
observables. The dynamical critical exponent of the exponential
autocorrelation time is compatible with 2. We estimate the total computational
effort to scale between V^2 and V^2.25 towards the chiral limit.Comment: 3 pages, Latex with espcrc2.sty and postscript figures, Talk given at
Lattice 9
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