Massive spin-2 particle from a rank-2 tensor

TL;DR

This paper classifies all second-order theories for a rank-2 tensor describing a massive spin-2 particle, revealing three distinct classes based on their symmetry properties and introducing a new family of theories.

Contribution

It provides a comprehensive classification of second-order massive spin-2 theories from a rank-2 tensor, including a novel family with unique symmetry features.

Findings

Three classes of theories based on symmetry properties

Identification of a new family of spin-2 massive theories

Maximal spin-1 and spin-0 symmetry cases analyzed

Abstract

Here we obtain all possible second-order theories for a rank-2 tensor which describe a massive spin-2 particle. We start with a general second-order Lagrangian with ten real parameters. The absence of lower spin modes and the existence of two local field redefinitions leads us to only one free parameter. The solutions split into three one-parameter classes according to the local symmetries of the massless limit. In the class which contains the usual massive Fierz-Pauli theory, the subset of spin-1 massless symmetries is maximal. In another class where the subset of spin-0 symmetries is maximal, the massless theory is invariant under Weyl transformations and the mass term does not need to fit in the form of the Fierz-Pauli mass term. In the remaining third class neither the spin-1 nor the spin-0 symmetry is maximal and we have a new family of spin-2 massive theories.