On-shell spinor-helicity formalism

On amplitudes, resonances and the ultraviolet completion of gravity

Using the on-shell spinor-helicity formalism, a possible ultraviolet completion of gravity following a"bottom-up''approach is constructed.The assumptions of locality, unitarity and causality i) require an infinite tower of resonances with increasing spin and quantized mass, ii) introduce aduality relation among crossed scattering channels, and iii) dress all gravitational amplitudes in the standard model with a form factor that closely resembles either the veneziano or the virasoro-shapiro amplitude in string theory.As a consequence of unitarity, the theory predicts leading order deviations from general relativity in the coupling of gravity to fermions that could be explained if space-time has torsion in addition to curvature.