4,513 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
Dual superconducting properties of the QCD vacuum
A consistent description of the confining QCD vacuum as a dual superconductor
requires a determination of fundamental parameters such as the superconductor
correlation length and the field penetration depth , which
determine whether the superconductor is of type I or type II. We illustrate
preliminary results of a lattice determination of for the case of pure
Yang-Mills with two colors, obtained by measuring the temporal correlator of a
disorder parameter detecting dual superconductivity.Comment: 4 pages, 2 figures, talk presented at QCD05 (Montpellier) 4-9 July
200
Topology in QCD with 4 flavours of dynamical fermions
We study the topological properties of full QCD with four flavours of
dynamical staggered fermions. In particular the topological susceptibility is
measured and the problem of the determination of its first derivative is
discussed.Comment: LATTICE99(Topology and Confinement). 3 pages, contains espcrc2.sty
fil
Renormalization and topological susceptibility on the lattice: SU(2) Yang-Mills theory
The renormalization functions involved in the determination of the
topological susceptibility in the SU(2) lattice gauge theory are extracted by
direct measurements, without relying on perturbation theory. The determination
exploits the phenomenon of critical slowing down to allow the separation of
perturbative and non-perturbative effects. The results are in good agreement
with perturbative computations.Comment: 12 pages + 4 figures (PostScript); report no. IFUP-TH 10/9
Magnetic charge superselection in the deconfined phase of Yang-Mills theory
The vacuum expectation value of an operator carrying magnetic charge is
studied numerically for temperatures above the deconfinement temperature in
SU(2) and SU(3) gauge theory. By analyzing its finite size behaviour, this is
found to be exactly zero in the thermodynamical limit for any T > T_c whenever
the magnetic charge of the operator is different from zero. These results show
that magnetic charge is superselected in the hot phase of quenched QCD.Comment: 4 pages, 6 figures, revtex
Order, Disorder and Confinement
Studying the order of the chiral transition for is of fundamental
importance to understand the mechanism of color confinement. We present results
of a numerical investigation on the order of the transition by use of a novel
strategy in finite size scaling analysis. The specific heat and a number of
susceptibilities are compared with the possible critical behaviours. A second
order transition in the O(4) and O(2) universality classes are excluded.
Substantial evidence emerges for a first order transition. Results are in
agreement with those found by studying the scaling properties of a disorder
parameter related to the dual superconductivity mechanism of color confinement.Comment: 7 pages, 11 figures. Talk given at the International Workshop on
Quantum Chromodynamics: QCD@Work 2005, Conversano, Italy, 16-20 June 200
Gauge-invariant quark-antiquark nonlocal condensates in lattice QCD
We study, by numerical simulations on a lattice, the behaviour of the
gauge-invariant quark-antiquark nonlocal condensates in the QCD vacuum with
dynamical fermions. A determination is also done in the quenched approximation
and the results are compared with the full-QCD case. The fermionic correlation
length is extracted and compared with the analogous gluonic quantity.Comment: 14 pages, LaTeX file, + 6 PS figure
Topological susceptibility at zero and finite in SU(3) Yang-Mills theory
We determine the topological susceptibility at T=0 in pure SU(3) gauge
theory and its behaviour at finite across the deconfining transition. We
use an improved topological charge density operator. drops sharply by
one order of magnitude at the deconfining temperature .Comment: Recently appeared erratum added as an "Appendix" to the original
pape
Topological properties of QCD with two dynamical fermions
We investigate the topological susceptibility of the QCD vacuum with two
flavours of dynamical staggered fermions on the lattice both at zero and finite
temperature. At zero temperature we study the dependence of the signal on the
fermion mass and at finite temperature we analyze the behaviour across the
phase transition.Comment: LATTICE99(finite temperature and density). 3 pages, contains
espcrc2.sty fil
Topological susceptibility through the deconfining phase transition
We present a measurement of the topological susceptibility in SU(3)
Yang-Mills theory through the deconfinement phase transition. An improved
operator is used for the topological charge density. A drop by an order of
magnitude is observed from the confined to the deconfined phase.Comment: Talk presented at LATTICE96(topology). 3 pages, 2 postscript figures,
uses espcrc2.sty include
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