Infrared behavior and Gribov ambiguity in SU(2) lattice gauge theory

For SU(2) lattice gauge theory, we study numerically the infrared behavior of the Landau-gauge ghost and gluon propagators with a special accent on the Gribov copy dependence. Applying a very efficient gauge-fixing procedure and generating up to 80 gauge copies, we find that the Gribov copy effect for both propagators is essential in the infrared. In particular, our best copy dressing function of the ghost propagator approaches a plateau in the infrared, while for the random first copy it continues to grow. Our best copy zero-momentum gluon propagator shows a tendency to decrease with growing lattice size, which excludes singular solutions. Our results seem compatible with the so-called decoupling solution with a nonsingular gluon propagator. However, we do not yet consider the Gribov copy problem to be resolved.