B. Taglienti

Problems on lattice gauge fixing

We review many topics and results about numeric gauge fixing in lattice QCD.

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 Neubergers fermions. We observe significant deviations from a Gaussian distribution. Our results disfavor the

Gribov Noise on the Lattice Axial Current Renormalisation Constant

\ensuremath{\theta}

SU (3) lattice gauge fixing with overrelaxation and Gribov copies

behavior of the vacuum energy predicted by dilute instanton models, while they are compatible with the expectation from the large

On the definition of gauge field operators in lattice gauge fixed theories

{N}_{c}

Gribov copies and smeared correlation functions in lattice QCD

expansion.

Phase transition analysis in Z2 and U(1) lattice gauge theories

Abstract We study the influence of Gribov copies, in the Landau gauge, on the lattice renormalisation constant Z A 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 Z A and the gauge dependent one is discussed. On a 16 3 ×32 lattice at β =6.0 and with K = 0.1425, the values, on a sample of 36 configurations, are Z A =1.08(5) (gauge dependent calculation) and Z A =1.06(2) (gauge independent calculation). 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.

Results on the gluon propagator in lattice covariant gauges

Abstract We report on the phenomenology of SU (3) lattice Landau gauge fixing as obtained by using an overrelaxation algorithm. An interesting result obtained using this very efficient algorithm is that distinct Gribov copies are generated by simply modifying the value ω of the overrelaxation parameter for a fixed starting configuration. By generating random gauge equivalent configurations, we study the variation of the number of copies with the lattice volume and gauge coupling.

Lattice gauge fixing for parameter dependent covariant gauges

Abstract We address the problem of defining the four-potential, A a μ ( x ), on the lattice, in terms of the natural link variables, U μ ( x ). Different regularized definitions are shown, through non perturbative numerical computation, to converge towards the same continuum renormalized limit.

Glueballs and the superfluid phase of Two-Color QCD

Abstract 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 ƒ B . Our results indicate that such effects may become important on bigger lattices.