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Effects of divergent ghost loops on the Green’s functions of QCD
David Ibanez Gil de Ramales
In the last years our understanding of the infrared sector of QCD has advanced considerably, thanks to the intense activity devoted to the study and development of nonperturbative methods in quantum field theories. At one hand, the well-known Schwinger-Dyson equations, allow to describe nonperturbatively the Green’s functions of QCD while, on the other hand, lattice simulations have provided valuable information about its infrared behaviour. Within the framework of the Schwinger-Dyson equations, a recent study in the Landau gauge has revealed that some of the fundamental QCD Green’s functions, containing virtual ghost loops, display infrared divergences due to the nonperturbative masslessness of the ghost field. It turns out that these infrared divergences and their effects have been also observed in lattice simulations. In this talk I will discuss what appears to be a profound connection between the masslessness of the ghost, the precise form of the gluon propagator in the deep infrared, and the divergences observed in certain kinematic limits of the three-gluon vertex.