Numerical study of lattice Landau gauge QCD and the Gribov copy problem

The Gribov noise problem was studied by performing a fundamental modular gauge (FMG) fixing by making use of the parallel tempering method with β=2.2 on 164 SU(2) configurations. In conclusion we found that while the gluon propagator almost noise free, the Kugo-Ojima parameter and the ghost propagator in the FMG become ∼ 5% less in the infrared region therefore they are noisy. It is expected that these qualitative aspects seen in SU(2) will be reflected in the infrared properties of SU(3) QCD as well.