Amplitude basis for conformal correlators

Abstract

We present a classification of conformally-invariant three-point tensor structures in d dimensions that parallels the classification of three-particle scattering amplitudes in d + 1 dimensions. Using a set of canonically-normalized weight-shifting operators, we construct a basis of three-point structures involving conserved currents or stress tensors and non-conserved spinning operators, directly from their amplitude counterparts. As an application, we also examine the conformal block expansion of the four-point functions of external currents and stress tensors in this amplitude basis. Our results can be useful for conformal bootstrap applications involving spinning correlators as well as Witten diagram computations in anti-de Sitter space.