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In the present work we discuss certain characteristic features encoded insome of the fundamental QCD Green's functions, whose origin can be traced backto the nonperturbative masslessness of the ghost field, in the Landau gauge.Specifically, the ghost loops that contribute to these Green's functionsdisplay infrared divergences, akin to those encountered in the perturbativetreatment, in contradistinction to the gluonic loops, whose perturbativedivergences are tamed by the dynamical generation of an effective gluon mass.In d=4, the aforementioned divergences are logarithmic, thus causing arelatively mild impact, whereas in d=3 they are linear, giving rise to enhancedeffects. In the case of the gluon propagator, these effects do not interferewith its finiteness, but make its first derivative diverge at the origin, andintroduce a maximum in the region of infrared momenta. The three-gluon vertexis also affected, and the induced divergent behavior is clearly exposed incertain special kinematic configurations, usually considered in latticesimulations; the sign of the corresponding divergence is unambiguouslydetermined. The main underlying concepts are developed in the context of asimple toy model, which demonstrates clearly the interconnected nature of thevarious effects. The picture that emerges is subsequently corroborated by adetailed nonperturbative analysis, combining lattice results with the dynamicalintegral equations governing the relevant ingredients, such as thenonperturbative ghost loop and the momentum-dependent gluon mass.

Effects of divergent ghost loops on the Green's functions of QCD