Exterior-Polynomial Classification of Gravitino Mass Bilinears and Their Superspace Projection in Four Dimensions
We distinguish two algebraic classification problems for a four-dimensional Majorana vector-spinor. In the full derivative-free Lorentz-covariant sector, direct contraction of the vector indices produces independent scalar and gamma-trace bilinears; consequently, Lorentz covariance and parity alone do not uniquely select the Rarita--Schwinger mass operator. We then define the first-order exterior-polynomial algebra generated by the coframe and the gravitino under wedge and Clifford multiplication, excluding inverse coframes, interior products, and Hodge duals acting directly on the gravitino. In this restricted Cartan sector, the Lorentz-equivariant quadratic tensor structures have rank two after scalar coefficient functions are factored out. In the Majorana conventions used here a manifestly real basis of action four-forms is $\barψ\wedgeγ^{(2)}\wedgeψ$ and $i\barψ\wedgeγ_5γ^{(2)}\wedgeψ$; parity selects the conventional Rarita--Schwinger mass line. We separate systematically the complex Lorentz-equivariant classification, the Majorana real structure, and Hermitian action densities. We also prove the form-to-component identities, compare the restricted algebra with the unrestricted vector-spinor sector, and give a local integral-form calculation showing how a body picture-changing operator extracts an already specified super-four-form mass structure. The new contribution is the completeness proof for the restricted two-generator sector together with its systematic comparison with the unrestricted algebra and the clarification of its relation to superspace projection.