Improved Landau gauge fixing and the suppression of finite-volume effects of the lattice gluon propagator

Abstract

For the gluon propagator of pure $SU(2)$ lattice gauge theory in the Landau gauge we investigate the effect of Gribov copies and finite-volume effects. Concerning gauge fixing, we enlarge the accessible gauge orbits by adding nonperiodic $\mathbb{Z}(2)$ gauge transformations and systematically employ the simulated annealing algorithm. Strategies to keep all $\mathbb{Z}(2)$ sectors under control within reasonable CPU time are discussed. We demonstrate that the finite-volume effects in the infrared regime become ameliorated. Reaching a physical volume of about $(6.5\text{ }\text{ }\mathrm{fm}{)}^{4}$, we find that the propagator, calculated with the indicated improvements, becomes flat in the region of smallest momenta. There are first signs in four dimensions of a decrease towards vanishing momentum.