Shadow celestial amplitudes

A bstract We study scattering amplitudes in the shadow conformal primary basis, which satisfies same defining properties as original basis and has many advantages over it. The celestial exhibit locality manifestly on sphere, behave like correlation functions field theory under operator product expansion (OPE) limit. OPE limits for three-point amplitude, general 2 ? n ? from a certain class of Feynman diagrams. In particular, we compute block s -channel four-point amplitude massless scalars at tree-level, show that coefficients factorize products coefficients.