Propagators and running coupling from SU(2) lattice gauge theory

We perform numerical studies of the running coupling constant alpha(R) (p(2)) and of the gluon and ghost propagators for pure SU(2) lattice gauge theory in the minimal Landau gauge. Different definitions of the gauge fields and different gauge-fixing procedures are used, respectively, for gaining better control over the approach to the continuum limit and for a better understanding of Gribov-copy effects. We find that the ghost-ghost-gluon vertex renormalization constant is finite in the continuum limit, confirming earlier results by all-order perturbation theory. In the low momentum regime, the gluon form factor is suppressed while the ghost form factor is divergent. Correspondingly, the ghost propagator diverges faster than 1/p(2) and the gluon propagator appears to be finite. Precision data for the running coupling alpha(R) (p(2)) are obtained. These data are consistent with an IR fixed point given by lim(p-->0)alpha(R) (p(2)) = 5(1). (C) 2004 Elsevier B.V. All rights reserved.