1,064 research outputs found
A scalable PC-based parallel computer for lattice QCD
A PC-based parallel computer for medium/large scale lattice QCD simulations
is suggested. The Eotvos Univ., Inst. Theor. Phys. cluster consists of 137
Intel P4-1.7GHz nodes. Gigabit Ethernet cards are used for nearest neighbor
communication in a two-dimensional mesh. The sustained performance for
dynamical staggered(wilson) quarks on large lattices is around 70(110) GFlops.
The exceptional price/performance ratio is below $1/Mflop.Comment: 3 pages, 2 figures, Lattice2002(machines
Topological susceptibility in full QCD at zero and finite temperature
We present a study of the topological susceptibility on the lattice
for full QCD with 2 and 4 flavours of staggered fermions at zero and finite
temperature T. We find that presents a sharp drop across the
deconfinement transition. We also study the dependence of on the quark
mass at T=0: we have no conclusive evidence for the expected chiral behaviour.Comment: latex source, 8 pages, 4 figure
Better than $1/Mflops sustained: a scalable PC-based parallel computer for lattice QCD
We study the feasibility of a PC-based parallel computer for medium to large
scale lattice QCD simulations. The E\"otv\"os Univ., Inst. Theor. Phys. cluster
consists of 137 Intel P4-1.7GHz nodes with 512 MB RDRAM. The 32-bit, single
precision sustained performance for dynamical QCD without communication is 1510
Mflops/node with Wilson and 970 Mflops/node with staggered fermions. This gives
a total performance of 208 Gflops for Wilson and 133 Gflops for staggered QCD,
respectively (for 64-bit applications the performance is approximately halved).
The novel feature of our system is its communication architecture. In order to
have a scalable, cost-effective machine we use Gigabit Ethernet cards for
nearest-neighbor communications in a two-dimensional mesh. This type of
communication is cost effective (only 30% of the hardware costs is spent on the
communication). According to our benchmark measurements this type of
communication results in around 40% communication time fraction for lattices
upto 48^3\cdot96 in full QCD simulations. The price/sustained-performance ratio
for full QCD is better than 1.5/Mflops for
staggered) quarks for practically any lattice size, which can fit in our
parallel computer. The communication software is freely available upon request
for non-profit organizations.Comment: 14 pages, 3 figures, final version to appear in Comp.Phys.Com
The Second Moment of the Pion Light Cone Wave Function
We present a preliminary result for second moment of the light cone wave
function of the pion. This parameter is the subject of a discrepancy between
theoretical predictions (coming from lattice and sum rules) and a recent
experimental result (that remarkably agrees with purely perturbative
predictions). In this work we exploit lattice hypercubic symmetries to remove
power divergences and, moreover, implement a full 1-loop matching for all the
contributing operators.Comment: 3 pages, proceedings of the Lattice 2002 conferenc
Field strength correlators in QCD with dynamical fermions
We determine, by numerical simulations on a lattice, the gauge-invariant
two-point correlation functions of the gauge field strengths in the QCD vacuum
with four flavours of dynamical staggered fermions.Comment: Talk given at the ``XVth International Symposium on Lattice Field
Theory'', Edinburgh (UK), July 22nd-26th 1997 (LATTICE 97); 3 pages, LaTeX
file, uses ``espcrc2.sty''+ 2 PS figure
The spin content of the proton in full QCD
We present preliminary results on the proton spin structure function in full
QCD. The measurement has been done using 4 flavours of staggered fermions and
an improved definition of the lattice topological charge density.Comment: 3 pages, 3 figures, contribution to Lattice-97. Latex file including
espcrc2.sty. The colour of a line in the first figure has been changed to
avoid problems on some printer
Light hadrons with improved staggered quarks: approaching the continuum limit
We have extended our program of QCD simulations with an improved
Kogut-Susskind quark action to a smaller lattice spacing, approximately 0.09
fm. Also, the simulations with a approximately 0.12 fm have been extended to
smaller quark masses. In this paper we describe the new simulations and
computations of the static quark potential and light hadron spectrum. These
results give information about the remaining dependences on the lattice
spacing. We examine the dependence of computed quantities on the spatial size
of the lattice, on the numerical precision in the computations, and on the step
size used in the numerical integrations. We examine the effects of
autocorrelations in "simulation time" on the potential and spectrum. We see
effects of decays, or coupling to two-meson states, in the 0++, 1+, and 0-
meson propagators, and we make a preliminary mass computation for a radially
excited 0- meson.Comment: 43 pages, 16 figure
Field strength correlators in full QCD
We study, by numerical simulations on a lattice, the behaviour of the
gauge-invariant two-point correlation functions of the gauge field strengths in
the QCD vacuum with dynamical fermions.Comment: 11 pages, LaTeX file, + 2 PS figure
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