The lattice ghost propagator in Landau gauge up to three loops using numerical stochastic perturbation theory

Abstract

We complete our high-accuracy studies of the lattice ghost propagator in Landau gauge in Numerical Stochastic Perturbation Theory up to three loops. We present a systematic strategy which allows to extract with sufficient precision the non-logarit hmic parts of logarithmically divergent quantities as a function of the propagator momentum squared in the infinite-volume and a → 0 limits. We find accurate coincidence with the one-loop resul t for the ghost self-energy known from standard Lattice Perturbation Theory and improve our previous estimate for the two-loop constant contribution to the ghost self-energy in Landau gauge. Our results for the perturbative ghost propagator are compared with Monte Carlo measurements of the ghost propagator performed by the Berlin Humboldt university group which has used the exponential relation between potentials and gauge links.