Celestial double copy from the worldsheet

TL;DR

The paper develops all-multiplicity tree-level celestial amplitudes for biadjoint scalars, Yang–Mills, and gravity using ambitwistor-string–derived CHY-like formulas in a conformal primary (celestial) basis. It introduces operator-valued celestial scattering equations and propagators, enabling a universal scalar contact vertex to drive amplitudes and revealing a robust celestial double copy. A generalized twisted cohomology framework is formulated to define celestial color–kinematics duality and to extract celestial numerators from ambitwistor-string data, extending Mizera’s construction to the celestial setting. The results provide compact, all-multiplicity expressions in any dimension, highlight the role of Gelfand–A-hypergeometric structures, and suggest avenues to extend double copy ideas to curved backgrounds and loop-level celestial amplitudes, with potential holographic implications on the celestial sphere.

Abstract

Using the ambitwistor string, we compute tree-level celestial amplitudes for biadjoint scalars, Yang-Mills and gravity to all multiplicities. They are presented in compact CHY-like formulas with operator-valued scattering equations and numerators acting on a generalized hypergeometric function. With these we extend the celestial double copy to tree-level amplitudes with arbitrary number of external states. We also show how color-kinematics duality is implemented in celestial amplitudes and its interpretation in terms of a generalized twisted cohomology theory.

Figures (2)

• Figure 1: Graphs related by BCJ moves
• Figure 2: Neighborhood of the three degenerations related by BCJ moves.