Physical charges in QED and QCD

TL;DR

This paper explores how physical charges are represented as gauge-invariant composites of matter and gauge bosons in QED and QCD, highlighting the role of dressing and the impact of Gribov copies on color charge construction.

Contribution

It introduces the natural emergence of the dressing approach in gauge theories and demonstrates how Gribov copies hinder non-perturbative color charge definitions in QCD.

Findings

Dressing approach arises naturally in gauge theories.

Explicit perturbative examples of dressings for asymptotic charges.

Gribov copies obstruct non-perturbative color charge construction.

Abstract

We show that the `dressing' approach, which describes physical charges as gauge invariant composites of matter and clouds of gauge bosons, arises naturally in gauge theories. We give perturbative examples of dressings for both asymptotic charges and for states in which the fields are confined to a compact volume as is required, for example, by causality in pair creation. In QCD, we use dressed states to demonstrate explicitly how Gribov copies obstruct the non-perturbative construction of colour charges.