642 research outputs found
Spectral Density on the Lattice
Spectral density in the pseudoscalar and vector channels is extracted from
the SU(2) lattice quenched data. It is shown to consist of three sharp poles
within the energy range accessible on the lattice.Comment: 38 pages, uuencoded tar-compressed ps-fil
Charmonium mass splittings at the physical point
We present results from an ongoing study of mass splittings of the lowest
lying states in the charmonium system. We use clover valence charm quarks in
the Fermilab interpretation, an improved staggered (asqtad) action for sea
quarks, and the one-loop, tadpole-improved gauge action for gluons. This study
includes five lattice spacings, 0.15, 0.12, 0.09, 0.06, and 0.045 fm, with two
sets of degenerate up- and down-quark masses for most spacings. We use an
enlarged set of interpolation operators and a variational analysis that permits
study of various low-lying excited states. The masses of the sea quarks and
charm valence quark are adjusted to their physical values. This large set of
gauge configurations allows us to extrapolate results to the continuum physical
point and test the methodology.Comment: 7 pp, 6 figs, Lattice 201
Abelian Dominance in Chiral Symmetry Breaking
Calculations of the chiral condensate on
the lattice using staggered fermions and the Lanczos algorithm are presented.
Three gauge fields are considered: the quenched non-Abelian field, the Abelian
field projected in the maximal Abelian gauge, and the monopole field further
decomposed from the Abelian field. The results show that the Abelian monopoles
largely reproduce the chiral condensate values of the full non-Abelian theory,
both in SU(2) and in SU(3).Comment: 4 pages in Latex with 4 embedded Postscript figures, uses
espcrc2.sty, psfig.sty. All are uuencoded, gzipped in a self-extracting file.
Contribution to Lattice'95, Melbourne, Australi
Remarks on abelian dominance
We used a renormalisation group based smoothing to address two questions
related to abelian dominance. Smoothing drastically reduces short distance
fluctuations but it preserves the long distance physical properties of the
SU(2) configurations. This enabled us to extract the abelian heavy-quark
potential from time-like Wilson loops on Polyakov gauge projected
configurations. We obtained a very small string tension which is inconsistent
with the string tension extracted from Polyakov loop correlators. This shows
that the Polyakov gauge projected abelian configurations do not have a
consistent physical meaning. We also applied the smoothing on SU(2)
configurations to test how sensitive abelian dominance in the maximal abelian
gauge is to the short distance fluctuations. We found that on smoothed SU(2)
configurations the abelian string tension was about 30% smaller than the SU(2)
string tension which was unaffected by smoothing. This suggests that the
approximate abelian dominance found with the Wilson action is probably an
accident and it has no fundamental physical relevance.Comment: 13 pages, LaTeX, 3 eps figure
Chiral logs with staggered fermions
We compute chiral logarithms in the presence of "taste" symmetry breaking of
staggered fermions. The lagrangian of Lee and Sharpe is generalized and then
used to calculate the logs in and masses. We correct an error in Ref.
[1] [C. Bernard, hep-lat/0111051]; the issue turns out to have implications for
the comparison with simulations, even at tree level. MILC data with three light
dynamical flavors can be well fit by our formulas. However, two new chiral
parameters, which describe order hairpin diagrams for taste-nonsinglet
mesons, enter in the fits. To obtain precise results for the physical
coefficients at order , these new parameters will need to be bounded, at
least roughly.Comment: talk presented by C. Bernard at Lattice2002(spectrum); 3 pages, 2
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