Gluon mass through massless bound-state excitations

TL;DR

This paper demonstrates that QCD dynamics support the formation of massless bound-state excitations, providing a gauge-invariant explanation for the infrared-finite gluon propagator observed in lattice simulations.

Contribution

It derives and solves the Bethe-Salpeter equation for massless excitations, confirming the Schwinger mechanism's role in gluon mass generation.

Findings

Non-trivial solutions to the Bethe-Salpeter equation are obtained.

Supports the dynamical formation of massless bound states in QCD.

Provides a gauge-invariant explanation for gluon mass.

Abstract

Recent large-volume lattice simulations have established that, in the Landau gauge, the gluon propagator is infrared-finite. The most natural way to explain this observed finiteness is the generation of a nonperturbative, momentum-dependent gluon mass. Such a mass may be generated gauge-invariantly by employing the Schwinger mechanism, whose main assumption is the dynamical formation of massless bound-state excitations. In this work we demonstrate that this key assumption is indeed realized by the QCD dynamics. Specifically, the Bethe-Salpeter equation describing the aforementioned massless excitations is derived and solved under certain approximations, and non-trivial solutions are obtained.