BRST-Symmetry Breaking and Bose-Ghost Propagator in Lattice Minimal Landau Gauge

TL;DR

This study numerically evaluates the Bose-ghost propagator in lattice SU(2) gauge theory, revealing infrared enhancement and providing evidence of BRST-symmetry breaking caused by gauge fixing restrictions.

Contribution

First numerical analysis of the Bose-ghost propagator in lattice minimal Landau gauge, demonstrating BRST-symmetry breaking effects in the confining regime.

Findings

Bose-ghost propagator shows infrared enhancement

Data compatible with a massive gluon and free ghost propagator

First numerical evidence of BRST-symmetry breaking in this context

Abstract

The Bose-ghost propagator has been proposed as a carrier of the confining force in Yang-Mills theories in minimal Landau gauge. We present the first numerical evaluation of this propagator, using lattice simulations for the SU(2) gauge group in the scaling region. Our data are well described by a simple fitting function, which is compatible with an infrared-enhanced Bose-ghost propagator. This function can also be related to a massive gluon propagator in combination with an infrared-free (Faddeev-Popov) ghost propagator. Since the Bose-ghost propagator can be written as the vacuum expectation value of a BRST-exact quantity and should therefore vanish in a BRST-invariant theory, our results provide the first numerical manifestation of BRST-symmetry breaking due to restriction of gauge-configuration space to the Gribov region.