Landau-Khalatnikov-Fradkin Transformations, Nielsen Identities, Their Equivalence and Implications for QCD

TL;DR

This paper explores the Landau-Khalatnikov-Fradkin transformations and Nielsen identities in QCD, demonstrating their equivalence and implications for gauge dependence of correlation functions through explicit calculations and theoretical analysis.

Contribution

It derives the LKFTs from first principles in non-Abelian gauge theory and establishes their equivalence with Nielsen identities using BRST symmetry, providing new insights into gauge dependence.

Findings

Explicit one-loop calculation of gluon propagator transformation

Demonstration of equivalence between LKFTs and Nielsen identities

Clarification of gauge dependence in QCD correlation functions

Abstract

The Landau-Khalatnikov-Fradkin transformations (LKFTs) represent an important tool for probing the gauge dependence of the correlation functions within the class of linear covariant gauges. Recently these transformations have been derived from first principles in the context of non-Abelian gauge theory (QCD) introducing a gauge invariant transverse gauge field expressible as an infinite power series in a Stueckelberg field. In this work we explicitly calculate the transformation for the gluon propagator, reproducing its dependence on the gauge parameter at the one loop level and elucidating the role of the extra fields involved in this theoretical framework. Later on, employing a unifying scheme based upon the BRST symmetry and a resulting generalized Slavnov-Taylor identity, we establish the equivalence between the LKFTs and the Nielsen identities which are also known to connect results in different gauges.