Abstract
Gravitational interactions of higher spin fields are generically plagued by
inconsistencies. We present a simple framework that couples higher spins to a broad class
of gravitational backgrounds (including Ricci flat and Einstein) consistently at the
classical level. The model is the simplest example of a Yang--Mills detour complex, which
recently has been applied in the mathematical setting of conformal geometry. An analysis of
asymptotic scattering states about the trivial field theory vacuum in the simplest version
of the theory yields a rich spectrum marred by negative norm excitations. The result is a
theory of a physical massless graviton, scalar field, and massive vector along with a
degenerate pair of zero norm photon excitations. Coherent states of the unstable sector of
the model do have positive norms, but their evolution is no longer unitary and their
amplitudes grow with time. The model is of considerable interest for braneworld scenarios
and ghost condensation models, and invariant theory.
