1) - THE INFLUENCE OF GRIBOV COPIES ON GLUON AND GHOST PROPAGATORS INLANDAU GAUGE AND 2) A NEW IMPLEMENTATION OF THE FOURIER ACCELERATION METHOD

We study the influence of Gribov copies on gluon and ghost propagators in lattice Landau gauge. For the gluon propagator, Gribov noise seems to be of the order of magnitude of the numerical accuracy. On the con trary, for the ghost propagator, Gribov noise is clearly observable, a t least in the strong-coupling regime. We also observe, in the limit o f large lattice volume, a gluon propagator decreasing as the momentum goes to aero. Finally, we introduce an implementation of the method of Fourier Acceleration which avoids the use of the fast Fourier transfo rm, being well suited for parallel and vector machines. We apply it to the case of Landau gauge fixing, and study its performance on APE com puters.