Elastic Unitarity and Regge-Cut Discontinuities

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Abstract
We examine the constraints imposed on Regge-cut discontinuities by elastic unitarity. We find that discontinuities must be singular at their endpoints, and, contrary to published examples, must vanish there. We give particular attention to "wrong-signature" negative integer angular momenta in the spinless problem. There, one Regge cut must exactly mask the elastic unitarity cut; its discontinuity contains a pole in the angular momentum. Our results modify the usual expression for the contribution of a cut to high-energy scattering in crossed channels.