Generalized SU(2) Proca theory reconstructed and beyond

TL;DR

This paper reconstructs the generalized SU(2) Proca theory by implementing secondary constraints, clarifying its structure, and introduces an extended version beyond the original formulation.

Contribution

It provides a detailed reconstruction of GSU2P with secondary constraints and introduces a beyond GSU2P extension, enhancing the theoretical framework.

Findings

Successfully implemented secondary constraint-enforcing relation.

Reconstructed the GSU2P theory from first principles.

Discovered and formulated the beyond GSU2P extension.

Abstract

As a modified gravity theory that introduces new gravitational degrees of freedom, the generalized SU(2) Proca theory (GSU2P for short) is the non-Abelian version of the well-known generalized Proca theory where the action is invariant under global transformations of the SU(2) group. This theory was formulated for the first time in Phys. Rev. D 94 (2016) 084041, having implemented the required primary constraint-enforcing relation to make the Lagrangian degenerate and remove one degree of freedom from the vector field in accordance with the irreducible representations of the Poincar\'e group. It was later shown in Phys. Rev. D 101 (2020) 045008, ibid 045009, that a secondary constraint-enforcing relation, which trivializes for the generalized Proca theory but not for the SU(2) version, was needed to close the constraint algebra. It is the purpose of this paper to implement this secondary constraint-enforcing relation in GSU2P and to make the construction of the theory more transparent. Since several terms in the Lagrangian were dismissed in Phys. Rev. D 94 (2016) 084041 via their equivalence to other terms through total derivatives, not all of the latter satisfying the secondary constraint-enforcing relation, the work was not so simple as directly applying this relation to the resultant Lagrangian pieces of the old theory. Thus, we were motivated to reconstruct the theory from scratch. In the process, we found the beyond GSU2P.