229 research outputs found
Test of the Skyrme Effective Field Theory Using Quenched Lattice QCD
The Skyrme effective field theory is tested by evaluating nucleon ground
state matrix elements of the correlation functions for two flavor density
operators and two pseudoscalar density operators in the Skyrme model and
comparing them with results in quenched lattice QCD. The possiblility of using
quenched lattice QCD to study higher-order terms in effective field theory is
also discussed.Comment: 20 pages in TeX, 6 figures added using "figures", MIT-CTP-200
Finite-Size Effect of Hadron Masses with Kogut-Susskind Quarks
We present numerical results and their analyses of finite-size effects of
hadron masses for both quenched and full QCD calculations. We show that they
are much larger for full QCD due to dynamical sea quarks and the associated
breaking of symmetry. We also argue that finite-size effects are
non-negligible even for the largest lattice size simulation currently being
made for a very small quark mass. (talk at lattice93)Comment: 4 pages, compressed, uuencoded PostScript file(name:lat93.ps.Z
Correlation Functions of Hadron Currents in the QCD Vacuum Calculated in Lattice QCD
Point-to-point vacuum correlation functions for spatially separated hadron
currents are calculated in quenched lattice QCD on a lattice
with . The lattice data are analyzed in terms of dispersion
relations, which enable us to extract physical information from small distances
where asymptotic freedom is apparent to large distances where the hadronic
resonances dominate. In the pseudoscalar, vector, and axial vector channels
where experimental data or phenomenological information are available,
semi-quantitative agreement is obtained. In the nucleon and delta channels,
where no experimental data exist, our lattice data complement experiments.
Comparison with approximations based on sum rules and interacting instantons
are made, and technical details of the lattice calculation are described.Comment: 31 pages in REVTeX (with 10 figures to be added using figures
command), MIT CTP #214
Tunneling and the Spectrum of the Potts Model
The three-dimensional, three-state Potts model is studied as a paradigm for
high temperature quantum chromodynamics. In a high statistics numerical
simulation using a Swendson-Wang algorithm, we study cubic lattices of
dimension as large as and measure correlation functions on long lattices
of dimension and . These correlations are
controlled by the spectrum of the transfer matrix. This spectrum is studied in
the vicinity of the phase transition. The analysis classifies the spectral
levels according to an underlying symmetry. Near the phase transition the
spectrum agrees nicely with a simple four-component hamiltonian model. In the
context of this model, we find that low temperature ordered-ordered interfaces
nearly always involve a disordered phase intermediate. We present a new
spectral method for determining the surface tension between phases.Comment: 26 pages plus 13 Postscript figures (Axis versions also provided),
UU-HEP-92/
Orbitally excited and hybrid mesons from the lattice
We discuss in general the construction of gauge-invariant non-local meson
operators on the lattice. We use such operators to study the - and -wave
mesons as well as hybrid mesons in quenched QCD, with quark masses near the
strange quark mass. The resulting spectra are compared with experiment for the
orbital excitations. For the states produced by gluonic excitations (hybrid
mesons) we find evidence of mixing for non-exotic quantum numbers. We give
predictions for masses of the spin-exotic hybrid mesons with $J^{PC}=1^{-+},\
0^{+-}2^{+-}$.Comment: 31 pages, LATEX, 8 postscript figures. Reference adde
The spin content of the proton in quenched QCD
We present preliminary results on the proton spin structure function at zero
momentum, in the quenched approximation. Our calculation makes use of a
nonperturbative means of determining the multiplicative renormalization of the
topological charge density.Comment: REVTEX, 6 pages, 1 PS figure attached. Pisa preprint IFUP-TH-14/9
Manifestation of Sea Quark Effects in the Strong Coupling Constant in Lattice QCD
We demonstrate that sea quark effects of a magnitude expected from
renormalization group considerations are clearly visible in the strong coupling
constant measured in current full QCD simulations. Building on this result an
estimate of is made employing the
charmonium mass splitting calculated on full QCD configurations
generated with two flavors of dynamical Kogut-Susskind quarks to fix the scale.Comment: 10 pages + 2 figures(postscript files), Latex files, compressed,
uuencode tar file, UTHEP-28
More about orbitally excited hadrons from lattice QCD
This is a second paper describing the calculation of spectroscopy for
orbitally excited states from lattice simulations of Quantum Chromodynamics.
New features include higher statistics for P-wave systems and first results for
the spectroscopy of D-wave mesons and baryons, for relatively heavy quark
masses. We parameterize the Coulomb gauge wave functions for P-wave and D-wave
systems and compare them to those of their corresponding S-wave states.Comment: 21 pages plus 14 figs, 3 include
The continuum limit in the quenched approximation
Previous work at with quenched staggered quarks is extended with
new calculations at 5.85 and 6.15 on lattices up to . These
calculations allow a more detailed study of extrapolation in quark mass, finite
volume and lattice spacing than has heretofore been possible. We discuss how
closely the quenched spectrum approaches that of the real world.Comment: 4 pages, uuencoded compressed PostScript, contribution to Lattice '9
Gauge Invariant Smearing and Matrix Correlators using Wilson Fermions at beta=6.2
We present an investigation of gauge invariant smearing for Wilson fermions
on a lattice at . We demonstrate a smearing
algorithm that allows a substantial improvement in the determination of the
baryon spectrum obtained using propagators smeared at both source and sink, at
only a small computational cost. We investigate the matrix of correlators
constructed from local and smeared operators, and are able to expose excited
states of both the mesons and baryons.Comment: at lattice `92. 4 pages latex + 3 postscript figures. Edinburgh
preprint: 92/51
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