Celestial IR divergences and the effective action of supertranslation modes

TL;DR

This paper links infrared divergences in gravitational scattering to an effective action for supertranslation modes, showing how celestial correlators encode soft factors within a path integral framework.

Contribution

It demonstrates that the celestial two-point function for supertranslations arises from an effective action governing infrared divergences in asymptotically flat spacetimes.

Findings

Derivation of the celestial two-point function from an effective action.

Re-derivation of infrared soft factors using celestial correlators.

Connection of the effective action to a path integral formulation of celestial CFT.

Abstract

Infrared divergences in perturbative gravitational scattering amplitudes have been recently argued to be governed by the two-point function of the supertranslation Goldstone mode on the celestial sphere. We show that the form of this celestial two-point function simply derives from an effective action that also controls infrared divergences in the symplectic structure of General Relativity with asymptotically flat boundary conditions. This effective action finds its natural place in a path integral formulation of a celestial conformal field theory, as we illustrate by re-deriving the infrared soft factors in terms of celestial correlators. Our analysis relies on a well-posed action principle close to spatial infinity introduced by Comp\`ere and Dehouck.