PODCAST

Gravity, Twistors and Amplitudes

by Cambridge University

Over the last ten years, tremendous progress has been made in understanding scattering amplitudes in Yang-Mills and gravity theories. On the technical side, new explicit formulae for general n-particle scattering amplitudes have been discovered that exhibit remarkable new mathematical structures. On the conceptual side, a new proof of GR and Yang-Mills uniqueness has been obtained, in which the basic cubic interaction is fixed (on-shell) from simple scaling considerations, and all other amplitudes are built from the basic cubic ones by the use of recursion relations. Thus, from this perspective, gravity and Yang-Mills theories are the simplest nontrivial quantum field theories. Furthermore, there are remarkable relations between gravity and the `square' of Yang-Mills arising from colour-kinematic duality. Unfortunately, at present we only see manifestations of this simplicity in the perturbative structure of the field equations. An open problem is to understand these structures nonpert