Lattice three-gluon vertex in extended kinematics: planar degeneracy

TL;DR

This paper reports lattice simulation results for the three-gluon vertex in Landau gauge, revealing a planar degeneracy where form factors depend mainly on a single combined kinematic variable, simplifying the vertex's description.

Contribution

The study uncovers a novel planar degeneracy property of the three-gluon vertex form factors, significantly simplifying their kinematic dependence and aiding future numerical analyses.

Findings

Form factors depend mainly on a single combined variable

Planar degeneracy confirmed for specific kinematic configurations

Semi-perturbative analysis aligns with lattice results after gluon mass inclusion

Abstract

We present novel results for the three-gluon vertex, obtained from an extensive quenched lattice simulation in the Landau gauge. The simulation evaluates the transversely projected vertex, spanned on a special tensorial basis, whose form factors are naturally parametrized in terms of individually Bose-symmetric variables. Quite interestingly, when evaluated in these kinematics, the corresponding form factors depend almost exclusively on a single kinematic variable, formed by the sum of the squares of the three incoming four-momenta, $q$, $r$, and $p$. Thus, all configurations lying on a given plane in the coordinate system $(q^2, r^2, p^2)$ share, to a high degree of accuracy, the same form factors, a property that we denominate \emph{planar degeneracy}. We have confirmed the validity of this property through an exhaustive study of the set of configurations satisfying the condition $q^2 = r^2$, within the range $[0, 5\, \rm GeV]$. Moreover, a preliminary exploration reveals that the planar degeneracy persist in the case of more arbitrary configurations. This drastic simplification allows for a remarkably compact description of the main bulk of the data, which is particularly suitable for future numerical applications. A semi-perturbative analysis reproduces the lattice findings rather accurately, once the inclusion of a gluon mass has cured all spurious divergences.