Double-soft limit and celestial shadow OPE from charge bracket
Daniele Pranzetti, Domenico Giuseppe Salluce
TL;DR
This work connects celestial OPEs with asymptotic phase-space charges, using a charge bracket correspondence to resolve the double-soft ambiguity in the mixed-helicity sector and to compute shadow celestial OPEs. By enforcing the OPE/bracket relationship across gravity and Yang-Mills, the authors establish a canonical first-entry-soft-first prescription and develop an algorithm that handles shadow transforms consistently, including dual and shadow operators. They organize conformal primaries via celestial diamonds, test the procedure on the energy-momentum tensor, and extend to shadow OPEs in both gravity and YM, finding that shadow/dual OPEs share the same structure up to nonlocal kernels. The results advance flat-space holography by providing a practical, symmetry-consistent framework to derive shadow OPEs and to analyze the interplay between soft theorems, higher-spin charges, and celestial CFT algebras.
Abstract
The dual formulations of an infinite tower of tree-level soft theorems in asymptotically flat spacetimes for scattering amplitudes in the standard energy-momentum basis and for correlators of a 2D celestial conformal field theory imply a correspondence between the celestial operator product expansion (OPE) and the higher spin charge bracket. We apply such correspondence to provide first a prescription to solve the double-soft limit ambiguity in the mixed-helicity sector of celestial OPEs. Furthermore, demanding the charge OPE/bracket correspondence to remain valid when operators are shadow transformed, we construct an algorithm to compute shadow celestial OPEs. We first test the algorithm by recovering results in the previous literature involving the celestial energy-momentum tensor; we then apply it to both gravity and Yang-Mills theory and generalize the OPE derivation to arbitrary spins.
