Gluon propagator and three-gluon vertex with dynamical quarks

TL;DR

This paper analyzes the gluon propagator and three-gluon vertex in QCD with dynamical quarks, revealing how quarks influence vertex suppression and the effective gauge coupling, thus deepening understanding of nonperturbative QCD dynamics.

Contribution

It provides a novel combined analysis of the gluon propagator and three-gluon vertex with dynamical quarks using lattice data and nonperturbative methods, highlighting subtle effects on vertex suppression and gauge coupling.

Findings

Dynamical quarks mildly reduce vertex suppression effects.

The zero crossing of the three-gluon vertex shifts deeper into the infrared.

The effective gauge coupling is significantly decreased with dynamical quarks.

Abstract

We present a detailed analysis of the kinetic and mass terms associated with the Landau gauge gluon propagator in the presence of dynamical quarks, and a comprehensive dynamical study of certain special kinematic limits of the three-gluon vertex. Our approach capitalizes on results from recent lattice simulations with (2+1) domain wall fermions, a novel nonlinear treatment of the gluon mass equation, and the nonperturbative reconstruction of the longitudinal three-gluon vertex from its fundamental Slavnov-Taylor identities. Particular emphasis is placed on the persistence of the suppression displayed by certain combinations of the vertex form factors at intermediate and low momenta, already known from numerous pure Yang-Mills studies. One of our central findings is that the inclusion of dynamical quarks moderates the intensity of this phenomenon only mildly, leaving the asymptotic low-momentum behavior unaltered, but displaces the characteristic "zero crossing" deeper into the infrared region. In addition, the effect of the three-gluon vertex is explored at the level of the renormalization-group invariant combination corresponding to the effective gauge coupling, whose size is considerably reduced with respect to its counterpart obtained from the ghost-gluon vertex. The main upshot of the above considerations is the further confirmation of the tightly interwoven dynamics between the two- and three-point sectors of QCD.