Wee partons in QCD and gravity: double copy and universality

Abstract

We discuss a quantitative "double copy" between radiation from shockwave collisions in Einstein gravity and in QCD. The correspondence extends to $2\to N$ amplitudes in Regge asymptotics. The classicalization and unitarization of these amplitudes at maximal occupancy, corresponding to black hole and Color Glass Condensate (CGC) states respectively, are described by the emergent Goldstone dynamics of wee partons. We outline some consequences of the universal dynamics on both sides of the correspondence.

Comments: 4 pages, Talk in "Proceedings of XXXth International Conference on Ultra-relativistic Nucleus-Nucleus Collisions (Quark Matter 2023)"