The lattice Landau gauge gluon propagator: lattice spacing and volume dependence

The interplay between the finite volume and finite lattice spacing is investigated using lattice QCD simulations to compute the Landau gauge gluon propagator. Comparing several ensembles with different lattice spacings and physical volumes, we conclude that the dominant effects, in the infrared region, are associated with the use of a finite lattice spacing. The simulations show that decreasing the lattice spacing, while keeping the same physical volume, leads to an enhancement of the infrared gluon propagator. In this sense, the data from $\beta=5.7$ simulations, which uses an $a \approx 0.18$ fm, provides a lower bound for the infinite volume propagator.