Dressing vs. Fixing: On How to Extract and Interpret Gauge-Invariant Content

TL;DR

This paper clarifies the differences between the dressing field method and gauge fixing in gauge theories, addressing foundational concerns about gauge invariance and the interpretation of physical quantities.

Contribution

It provides a precise technical and conceptual distinction between the dressing field method and gauge fixing, clarifying misconceptions in physics and philosophy.

Findings

The DFM is mathematically subtle and distinct from gauge fixing.

Common confusions between DFM and gauge transformations are clarified.

The paper enhances understanding of gauge-invariant content in gauge theories.

Abstract

There is solid consensus among physicists and philosophers that, in gauge field theory, for a quantity to be physically meaningful or real, it must be gauge-invariant. Yet, every "elementary" field in the Standard Model of particle physics is actually gauge-variant. This has led a number of researchers to insist that new manifestly gauge-invariant approaches must be established. Indeed, in the foundational literature, dissatisfaction with standard methods for reducing gauge symmetries has been expressed: Spontaneous symmetry breaking is deemed conceptually dubious, while gauge fixing suffers the same limitations and is subject to the same criticisms as coordinate choices in General Relativity. An alternative gauge-invariant proposal was recently introduced in the literature, the so-called "dressing field method" (DFM). It is a mathematically subtle tool, and unfortunately prone to be confused with simple gauge transformations, hence with standard gauge~fixings. As a matter of fact, in the physics literature the two are often conflated, and in the philosophy community some doubts have been raised about whether there is any substantial difference between them. Clarifying this issue is of special significance for anyone interested in both the foundational issues of gauge theories and their invariant formulation. It is thus our objective to establish as precisely as possible the technical and conceptual distinctions between the DFM and gauge fixing.