5,548 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
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
Chiral transition and deconfinement in N_f = 2 QCD
The transition is studied by means of a disorder parameter detecting
condensation of magnetic monopoles in the vacuum. The deconfining transition is
found to coincide with the chiral transition and the susceptibility \rho,
related to the disorder parameter, is consistent with a first order phase
transition.Comment: 3 pages, 2 figures. Poster presented at Lattice2004(topology),
Fermilab, June 21-26, 200
Dual Superconductivity and Chiral Symmetry in Full QCD
A disorder parameter detecting dual superconductivity of the vacuum is
measured across the chiral phase transition in full QCD with two flavours of
dynamical staggered fermions. The observed behaviour is similar to the quenched
case.Comment: Lattice2001(confinement) proceedings, 3 pages, 2 eps figure
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
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
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