Key points are not available for this paper at this time.
Four-dimensional Minkowskian scattering amplitudes can also be presented in a basis of a different group (S0{0ex}L (2, C) ), which acts as the conformal group on the celestial two-sphere at null infinity. This type of representation is useful for understanding the flat-space holography. The authors propose a procedure for taking the (conformally) soft limit of tree-level scattering amplitudes in this basis.
Pate et al. (Thu,) studied this question.