Extended symmetry of the Maxwell theory with a gauge coupling constant as a conserved charge

TL;DR

This paper extends Maxwell theory by promoting the gauge coupling to a conserved charge through auxiliary fields, restoring local symmetries without introducing new conserved charges, and analyzing the implications via Hamiltonian and BFT formalisms.

Contribution

It demonstrates how to restore local symmetries in Maxwell theory with auxiliary fields using the BFT formalism, clarifying the relationship between extended and original theories.

Findings

Restoring local symmetries does not add new conserved charges.

The extended theory is a gauge-fixed version of the original Maxwell theory.

Hamiltonian analysis reveals some constraints are second-class.

Abstract

It has been proposed that any coupling constant in a covariant action can be treated as a conserved charge by promoting the coupling constant to auxiliary fields, typically realized by a scalar field paired with a higher-form gauge field. However, the procedure may break local symmetries, which can be explicitly shown in a simpler setting such as Maxwell theory. The Hamiltonian analysis of Maxwell theory with the auxiliary fields reveals that some of the constraints are second-class. Applying the BFT formalism, we restore the broken local symmetries and obtain a fully symmetric action defined on an extended configuration space. Despite the restoration of the local symmetries, no additional conserved charges are associated with the recovered symmetries. Consequently, the original theory turns out to be the gauge-fixed version of the extended theory.