96 research outputs found
Screening Masses and Improvement in Pure SU(2) Lattice Gauge Theory at High Temperatures
From the long-distance behaviour of gluon and Polyakov loop correlation
functions we extract masses resp. energies in the electric and magnetic
sectors. We discuss their dependence on the temperature and on the momentum as
well as the relevance of an improvement of the lattice discretization of the
action.Comment: Talk presented at LATTICE97 (Finite Temperature and Density) by J.
Rank, 3 pages, LaTeX File, espcrc2.sty Style File and 2 eps figures include
Microscopic Spectral Density of the Dirac Operator in Quenched QCD
Measurements of the lowest-lying eigenvalues of the staggered fermion Dirac
operator are made on ensembles of equilibrium gauge field configurations in
quenched SU(3) lattice gauge theory. The results are compared with exact
analytical predictions in the microscopic finite-volume scaling regime.Comment: 8 pages, LaTeX, with 2 ps figure
QCD with dynamical Wilson fermions at
We study QCD with two flavors of dynamical Wilson fermions at
and three values of . The corresponding pion masses are 0.375, 0.324
and 0.262 in lattice units, with pion to rho mass ratios of 0.76, 0.71 and
0.62, respectively. We use the configurations to compute the heavy quark
potential, leading to lattice spacings of 0.110, 0.105 and 0.099 fm, and to
compute spectroscopy for several different valence quark 's.Comment: LaTex 4 pages, 4 figures. Talk presented at LATTICE96(spectrum
A Comparison of Clover and Wilson Spectroscopy in the Presence of Dynamical Quarks
We present preliminary results of light hadron spectroscopy using valence,
tadpole-improved, Clover fermions on an ensemble of gauge configurations
generated with 2 flavors of staggered fermions at a beta of 5.6. We compare the
slope and intercept of the curve M_V vs. M_PS^2 for Clover and Wilson fermions.
We show that a higher order chiral perturbation theory ansatz works very well
for chiral extrapolations.Comment: 4 pages latex with 4 Postscript figures, to be published in the
Proceedings of Lattice 9
Looking for Effects of Topology in the Dirac Spectrum of Staggered Fermions
We classify SU(3) gauge field configurations in different topological sectors
by the smearing technique. In each sector we compute the distribution of low
lying eigenvalues of the staggered Dirac operator. In all sectors we find
perfect agreement with the predictions for the sector of topological charge
zero. The smallest Dirac operator eigenvalues of staggered fermions at
presently realistic lattice couplings are thus insensitive to gauge field
topology. On the smeared configurations, eigenvalues go to zero in
agreement with the index theorem.Comment: Poster at Lattice99(topology), 3 page
A Quark-Antiquark Condensate in Three-Dimensional QCD
Three-dimensional lattice QCD is studied by Monte Carlo simulations within
the quenched approximation. At zero temperature a quark-antiquark condensate is
observed in the limit of vanishing quark masses. The condensate vanishes
continuously at the finite-temperature deconfinement phase transition of the
theory. A natural interpretation of this phenomenon in the full theory with
dynamical quarks is in terms of the spontaneous flavor symmetry breaking
. In addition, the spectrum of low-lying
Dirac operator eigenvalues is computed and found to be consistent with a flat
distribution at zero temperature, in agreement with analytical predictions.Comment: Extensive revision of the original version. 11 pages, 6 figures
included as EPS files. The problem with figure encapsulation fixe
Baryonic Operators for Lattice Simulations
The construction of baryonic operators for determining the N* excitation
spectrum is discussed. The operators are designed with one eye towards
maximizing overlaps with the low-lying states of interest, and the other eye
towards minimizing the number of sources needed in computing the required quark
propagators. Issues related to spin identification are outlined. Although we
focus on tri-quark baryon operators, the construction method is applicable to
both mesons and penta-quark operators.Comment: 3 pages, poster presented at Lattice2003(spectrum), Tsukuba, Japan,
July 15-19, 200
Group-theoretical construction of extended baryon operators
The design and implementation of large sets of spatially extended baryon
operators for use in lattice simulations are described. The operators are
constructed to maximize overlaps with the low-lying states of interest, while
minimizing the number of sources needed in computing the required quark
propagators.Comment: 3 pages, 3 tables, talk presented at Lattice2004(spectrum), Fermilab,
June 21-26, 200
A Lower Bound on in the O(4) Model on Anisotropic Lattices
Results of an investigation of the spin model at finite temperature
using anisotropic lattices are presented. In both the large approximation
and numerical simulations using the Wolff cluster algorithm we find that the
ratio of the symmetry restoration temperature to the Higgs mass
is independent of the anisotropy . From the numerical
simulations we obtain a lower bound of at a value for the Higgs mass , which is lowered
further by about at . Requiring certain timelike
correlation functions to coincide with their spacelike counterparts, quantum
and scaling corrections to the anisotropy are determined and are found to be
small, i.e., the anisotropy is found to be close to the ratio of spacelike and
timelike lattice spacings.Comment: 16 pages with 4 ps figures included. LaTeX file. BI-TP 92/27,
FSU-SCRI-92-101, HLRZ-92-40, TIFR/TH/92-4
The heavy quark potential in QCD with 2 flavors of dynamical quarks
We compute the heavy quark potential on configurations generated by the
HEMCGC collaboration with dynamical staggered fermions at and
with dynamical Wilson fermions at . The computations are done on
lattices, corresponding to physical sizes of about 1.6 and 2.3
fm, respectively. Up to the distances probed no sign of string breaking is
detectable. We also compute the recently proposed scale defined by .Comment: 8 pages with 3 figures. uuencoded postscript file. FSU-SCRI-94-0
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