Gribov copies, Lattice QCD and the gluon propagator

We address the problem of Gribov copies in lattice QCD. The gluon propagator is computed, in the Landau gauge, using 302 ($\beta = 5.8$) $12^4$ configurations gauge fixed to different copies. The results of the simulation shows that: i) the effect of Gribov copies is small (less than 10%); ii) Gribov copies change essentially the lowest momenta components ($q < 2.6$ GeV); iii) within the statistical accuracy of our simulation, the effect of Gribov copies is resolved if statistical errors are multiplied by a factor of two or three. Moreover, when modelling the gluon propagator, different sets of Gribov copies produce different sets of parameters not, necessarily, compatible within one standard deviation. Finally, our data supports a gluon propagator which, for large momenta, behaves like a massive gluon propagator with a mass of 1.1 GeV

The Infrared Landau Gauge Gluon Propagator from Lattice QCD

The quenched Landau gauge gluon propagator is investigated in lattice QCD with large assimetric lattices, accessing momenta as low as $q \sim 100$ MeV or smaller. Our investigation focus on the IR limit of the gluon dressing function, testing the compatibility with recent solutions of the Dyson-Schwinger equations. In particular, the low energy parameters $\kappa$ and $\alpha (0)$ are measured.Comment: 3 pages, 1 figure. Talk given at Quark Confinement and the Hadron Spectrum VI 2004, Italy, 21-25 Sep. References correc

Towards the continuum limit of the lattice Landau gauge gluon propagator

The infrared behaviour of the lattice Landau gauge gluon propagator is discussed, combining results from simulations with different volumes and lattice spacings. In particular, the Cucchieri-Mendes bounds are computed and their implications for D(0) discussed.Comment: 3 pages, 3 figures. Talk given at "Quark Confinement and the Hadron Spectrum IX", Madrid, Spain, August 30th - September 3rd, 201

Gribov Copies and Gauge Fixing in Lattice Gauge Theories

We address the problem of the gauge fixing versus Gribov copies in lattice gauge theories. For the Landau gauge, results show that a suitable combination of evolutionary algorithms with traditional steepest descent methods identifies the global maximum of the optimisation function. We discuss the performance of the combined algorithm on small cubic lattices for SU(2) and SU(3).Comment: Lattice2001(algorithms