Abstract

Celestial Holography proposes a duality between gravitational scattering in spacetimes with vanishing cosmological constant and a conformal field theory living on the celestial sphere. It maps four-dimensional scattering matrix elements to objects that transform as two-dimensional conformal correlators, termed Celestial Amplitudes. This map possesses a number of surprising features. It emphasizes infinite-dimensional symmetry enhancements, which are typically hidden in infrared factorization theorems for amplitudes; reorganizes collinear limits as conformal field theory operator product expansions, and mixes ultraviolet and infrared behavior in a manner that may allow us to make general claims about scattering not obvious from perturbation theory.

We will start by reviewing how infrared physics points to symmetry enhancements, show why this footing leads us to Celestial Holography, and then review recent progress in constructing the holographic dictionary.