In a system of massive fermions in interaction with massless tensor and scalar mesons, the existence of a massless vector bound state in the fermion-antifermion channel gives a mass to the spin-2 particle and leads to a gauge-invariant and unitary S matrix which is completely free of massless poles.
No takes yet. Share an insight, caveat, or question.
M. J. Duff (1975) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: