Asymptotic states in flat 4D space are usually constructed so as to transform simply under translations, however if instead it is their Lorentz group SL(2,C) which is made manifest (which acts as the global conformal group on the celestial sphere at null infinity), their scattering amplitudes can be related to correlators in a 2D CFT.

A hyperbolic slicing of Minokwski naturally leads to AdS subspaces on which Witten-like diagrams can be employed. This a step towards using holography to determine flat space scattering amplitudes.