A construction of the multiparticle (composite) primary operators required by the flat-space extrapolate dictionary that maps four-dimensional scattering states to a two-dimensional Celestial CFT. Building these operators from both Carrollian and Celestial viewpoints extends the celestial operator spectrum beyond single-particle states and clarifies how the Poincare primary condition emerges in the Carrollian flat-space limit, how principal-series and highest-weight representations coexist with unitarity, and how the celestial OPE block expansion arises from a 2D CFT.
This paper extends the 'flat-space holography' dictionary that maps four-dimensional scattering states to operators of a two-dimensional Celestial CFT living on the celestial sphere. Using the extrap…