1/L2 corrected soft photon theorem from a CFT3 Ward identity

Abstract

Classical soft theorems applied to probe scattering processes on AdS4 spacetimes predict the existence of perturbative 1/L2 corrections to the soft photon and soft graviton factors of asymptotically flat spacetimes. In this paper, we establish that the 1/L2 corrected soft photon theorem can be derived from a large N CFT3 Ward identity. We derive a perturbed soft photon mode operator on a flat spacetime patch in global AdS4 in terms of an integrated expression of the boundary CFT current. Using the same in the CFT3 Ward identity, we recover the 1/L2 corrected soft photon factor derived from classical soft theorems.