3,749 research outputs found
Gauge-invariant nonlocal quark condensates in QCD
We study, by numerical simulations on a lattice, the behaviour of the
gauge-invariant nonlocal quark condensates in the QCD vacuum both in the
quenched approximation and with four flavours of dynamical staggered fermions.
The correlation length of the condensate is determined to be roughly twice as
big as in the case of the gluon field strength correlators.Comment: LATTICE98(confine
Field strength correlators in QCD at zero and non-zero temperature
We study, by numerical simulations on a lattice, the behaviour of the
gauge--invariant field strength correlators in QCD both at zero temperature,
down to a distance of 0.1 fm, and at finite temperature, across the
deconfinement phase transition.Comment: Talk given at the ``High Energy Conference on Quantum
Chromodynamics'', Montpellier (France), 4-12 July 1996 (QCD 96); 5 pages,
LaTeX file, uses ``espcrc2.sty''+ 5 PS figure
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
On the dependence of the gauge-invariant field-strength correlators in QCD on the shape of the Schwinger string
We study, by numerical simulations on a lattice, the dependence of the
gauge-invariant two-point field-strength correlators in QCD on the path used to
perform the color parallel transport between the two points.Comment: 9 pages, LaTeX file, + 5 PS figures. Revised version (accepted for
publication in Physics Letters B) with new comments on the result
Improving the topological charge density operator on the lattice
We analyze the properties of a class of improved lattice topological charge
density operators, constructed by a smearing-like procedure. By optimizing the
choice of the parameters introduced in their definition, we find operators
having (i) a much better statistical behavior as estimators of the topological
charge density on the lattice, i.e. much less noisy; (ii) a multiplicative
renormalization much closer to one; (iii) a large suppression of the
perturbative tail in the corresponding lattice topological susceptibility.Comment: 4 pages, to be published in the Proceedings of Lattice 95, uuencoded
postscript fil
Gauge--invariant field correlators in QCD at finite temperature
We study by numerical simulations on a lattice the behaviour of the
gauge--invariant two--point correlation functions of the gauge field strengths
across the deconfinement phase transition.Comment: 12 pages, LaTeX file, + 5 PS figures, uuencoded-tar-compresse
Gauge invariant Field Strength Correlators in QCD
Gauge invariant correlators in QCD are studied on the lattice.A Systematic
determination of the correlation lengths for gluon field strength correlators
and quark correlators is made.The measurement of the gluon and quark
condensates is discussed.Comment: 5 pages,4 figures.Presented by A.Di Giacomo to ICHEP98. To appear in
the proceedings Misprints correcte
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
Topological susceptibility in Yang-Mills theory in the vacuum correlator method
We calculate the topological susceptibility of the Yang-Mills vacuum using
the field correlator method. Our estimate for the SU(3) gauge group, \chi^{1/4}
= 196(7) MeV, is in a very good agreement with the results of recent numerical
simulations of the Yang-Mills theory on the lattice.Comment: 5 pages (JETP Letters style
Two flavor QCD and Confinement
We argue that the order of the chiral transition for N_f=2 is a sensitive
probe of the QCD vacuum, in particular of the mechanism of color confinement. A
strategy is developed to investigate the order of the transition by use of
finite size scaling analysis. An in-depth numerical investigation is performed
with staggered fermions on lattices with N_t=4 and N_s=12,16,20,24,32 and quark
masses am_q ranging from 0.01335 to 0.307036. The specific heat and a number of
susceptibilities are measured and compared with the expectations of an O(4)
second order and of a first order phase transition. A second order transition
in the O(4) and O(2) universality classes are excluded. Substantial evidence
emerges for a first order transition. A detailed comparison with previous works
is performed.Comment: 46 pages, 20 eps figures, 9 tables, REVTeX
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