Improved Gauge-Unfixing Formalism through a Prototypical Second-Class System

TL;DR

This paper enhances the gauge-unfixing formalism by applying it to a general second-class system, enabling gauge-invariant descriptions without auxiliary variables, demonstrated through the nonlinear sigma model.

Contribution

It introduces an improved gauge-unfixing method applicable to a broad class of models, preserving degrees of freedom and avoiding auxiliary variables.

Findings

Derived a gauge-invariant formulation from a second-class system.

Applied the method to the nonlinear sigma model.

Maintained the original degrees of freedom in the conversion.

Abstract

We contextualize the improved gauge-unfixing (GU) formalism within a rather general prototypical second-class system, obtaining a corresponding first-class equivalent description enjoying gauge invariance which can be applied to several situations. The prototypical system is chosen to represent a considerable class of relevant models in field theory. By considering the improved version of the GU formalism, we show that any gauge-invariant function can be obtained in terms of a specific deformation in phase space, benefiting thus from the fact that no auxiliary variables are needed in the process. In this way, the resulting converted first-class system is constructed out of the same original canonical variables, preserving the number of degrees of freedom. We illustrate the technique with an application to the nonlinear sigma model.