Celestial Holography

TL;DR

Celestial holography proposes a holographic duality between 4D gravitational scattering in asymptotically flat spacetimes and a 2D celestial CFT on the celestial sphere, with a symmetry-driven dictionary anchored by asymptotic Ward identities and soft theorems. By Mellin-transforming the S-matrix to celestial amplitudes, the framework defines a spectrum $\Delta = 1 + i\\lambda$, connects translations and soft data to poles in $\Delta$, and constrains OPE data via Virasoro symmetry, enabling bootstrap-like progress. The paper surveys applications to memory effects, black hole evaporation, and a CCFT bootstrap program, and discusses connections to string theory and worldsheet constructions as benchmarks for consistency. Overall, the program aims to unify 4D quantum gravity in flat space with a 2D conformal description through symmetry principles, potentially yielding experimental tests and new computational tools.

Abstract

Celestial holography proposes a duality between the gravitational $\mathcal{S}$-matrix and correlators in a conformal field theory living on the celestial sphere. In this white paper, solicited for the 2022 Snowmass process, we review the motivation from asymptotic symmetries, fundamentals of the proposed holographic dictionary, potential applications to experiment and theory, and some important open questions.