Amplitudes and partial wave unitarity bounds

Abstract

We develop a formalism, based on spinor-helicity techniques, to generalize the formulation of partial wave unitarity bounds. We discuss unitarity bounds for $N\to M$ (with $N,M\ge 2$) scattering processes -- relevant for high-energy future colliders -- and spin-2 or higher-spin theories -- relevant for effective field theories of gravity -- that are not approachable by standard methods. Moreover, we emphasize the power and complementarity of positivity and partial wave unitarity bounds to constrain the parameter space of effective field theories.

Comments: 6 pages + appendix, published version