Gluon propagator in the Landau gauge fixed lattice QCD simulation

We measured the gluon propagator in the Landau gauge fixed QCD Langevin simulation[2] and studied the infra-red behaviour of the gluon propagator. The (4(3) x 8) lattice simulation was done for quenched beta = 3, 4 and 5 and unquenched beta = 4, kappa = 0.1, 0.15 and 0.2, using each 100 independent samples. The Landau gauge fixing was done by an extension of the Fourier acceleration method with the condition \div A\ < 10(-4), and the field A is related to the link variable by U = expA instead of the usual U-linear definition. We confirmed gauge fixing with smearing preconditioning[3] works perfectly for the purpose of finding the global minimum of the squared norm of the gauge field when <beta> is large (e.g. beta = 5). Our simulation results suggests the possibility of a realization of the infrared behaviour of the Gribov-Zwanziger theory.