Towards a precise determination of the topological susceptibility in the SU(3) Yang-Mills theory

An ongoing effort to compute the topological susceptibility for the SU(3) Yang-Mills theory in the continuum limit with a precison of about 2% is reported. The susceptibility is computed by using the definition of the charge suggested by Neuberger fermions for two values of the negative mass parameter s. Finite volume and discretization effects are estimated to meet this level of precision. The large statistics required has been obtained by using PCs of the INFN-GRID. Simulations with larger lattice volumes are necessary in order to better understanding the continuum limit at small lattice spacing values.Comment: 8 pages, 2 figures, The XXVII International Symposium on Lattice Field Theory - LAT2009,July 26-31 2009,Peking University, Beijing, Chin

Large statistics study of the topological charge distribution in the SU(3) gauge theory

We present preliminary results for a high statistics study of the topological charge distribution in the SU(3) Yang-Mills theory obtained by using the definition of the charge suggested by Neuberger fermions. We find statistical evidence for deviations from a gaussian distribution. The large statistics required has been obtained by using PCs of the INFN-GRID.Comment: Talk given at the 24th International Symposium on Lattice Field Theory (Lattice 2006), Tucson, Arizona, 23-28 Jul 200

The String Tension in Gauge Theories

A review article on string tension concept and their relevance as non-perturbative quantity on the study of quark confinement in lattice gauge theories. A detailed description of a variety of methods to measure the string tension on the lattice and an indication of the most promising developments is proposed.Comment: Postscript file, 46 pages and 14 figure

The String Tension in Gauge Theories: a Suggestion for a New Measurement Method

We discuss a new method for testing confinement and measuring the string tension (in the Coulomb gauge). Our numerical simulations demonstrate that the problems related to Gribov copies are not harmful and that the method is effective in the case of pure gauge Q.C.D.. We discuss the relevance of the method for studying gauge theories coupled to fermionic matter.Comment: 9 pages, Latex style, 4 postscript figures appended, ROMA 92-90

Theta dependence of the vacuum energy in the SU(3) gauge theory from the lattice

We report on a precise computation of the topological charge distribution in the SU(3) Yang--Mills theory. It is carried out on the lattice with high statistics Monte Carlo simulations by employing the definition of the topological charge suggested by Neuberger's fermions. We observe significant deviations from a Gaussian distribution. Our results disfavour the theta behaviour of the vacuum energy predicted by instanton models, while they are compatible with the expectation from the large Nc expansion.Comment: Plain latex, 4 pages, 2 figure

Gribov Copies and Smeared Correlation Functions in Lattice QCD

We study the influence of Gribov copies in the Coulomb gauge on the smeared hadronic correlation functions that are involved in the determination of the B meson decay constant. We find that the residual gauge freedom associated to Gribov copies induces observable noise effects, though at the level of numerical accuracy of our simulation these effects are not relevant to the final determination of f_B. Our results indicate that such effects may become important on bigger lattices.Comment: 12pgs., preprint n. 892, June 24, 1992, Dipartimento di Fisica Univ. of Rome "La Sapienza

Gribov Noise on the Lattice Axial Current Renormalisation Constant

We study the influence of Gribov copies, in the Landau gauge, on the lattice renormalisation constant of the axial current, obtained from a Ward identity on quark state correlation functions, with the Clover action, in quenched SU(3) gauge theory. A comparison between the gauge invariant determination of the renorma= lization constant and the gauge dependent one is discussed. We find that the residual gauge freedom associated to Gribov copies induces observable effects, which, at the level of numerical accuracy of our simulation, are included in the statistical uncertainty inherent in a Monte Carlo simulation. Doubling the statistics suggests that the fluctuation due to the lattice Gribov ambiguity scales down at least as fast as a pure statistical error.Comment: 17pp (including figures), LaTe

Large statistics study of QCD topological charge distribution

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