On the occasion of the 70th birthday of Prof. Adriano Di Giacomo we report on
recent numerical computations of the Landau gauge gluon and ghost propagators
as well as of a non-symmetric MOM-scheme ghost-gluon vertex in quenched and
full lattice QCD. Special emphasis is paid to the Gribov copy problem and to
the unquenching effect. The corresponding running coupling \alpha_s(q^2) is
found and shown to decrease for q^2 \le 0.3 GeV^2 in the infrared limit. No
indication for a non-trivial infrared fixed point is seen in agreement with
findings from truncated systems of Dyson-Schwinger equations treated on a
four-dimensional torus.Comment: contribution to "Sense of Beauty in Physics", Festschrift in honor of
Adriano Di Giacomo's 70-th birthda
