Celestial Diamonds: Conformal Multiplets in Celestial CFT

TL;DR

This paper classifies and constructs conformal multiplets called celestial diamonds in 2D celestial CFT, linking 4D scattering amplitudes with conformal primary wavefunctions, and explores their role in symmetries and soft theorems.

Contribution

It provides an explicit wavefunction-based construction of celestial diamonds for massless particles of various spins, revealing their structure and relation to symmetries in celestial CFT.

Findings

Classified all SL(2,C) primary descendants in celestial CFT.

Connected radiative conformal primaries to soft theorems and symmetries.

Showed celestial diamonds encode degeneracies and shadow relations.

Abstract

We examine the structure of global conformal multiplets in 2D celestial CFT. For a 4D bulk theory containing massless particles of spin $s=\{0,\frac{1}{2},1,\frac{3}{2},2\}$ we classify and construct all SL(2,$\mathbb{C}$) primary descendants which are organized into 'celestial diamonds'. This explicit construction is achieved using a wavefunction-based approach that allows us to map 4D scattering amplitudes to celestial CFT correlators of operators with SL(2,$\mathbb{C}$) conformal dimension $\Delta$ and spin $J$. Radiative conformal primary wavefunctions have $J=\pm s$ and give rise to conformally soft theorems for special values of $\Delta \in \frac{1}{2}\mathbb{Z}$. They are located either at the top of celestial diamonds, where they descend to trivial null primaries, or at the left and right corners, where they descend both to and from generalized conformal primary wavefunctions which have $|J|\leq s$. Celestial diamonds naturally incorporate degeneracies of opposite helicity particles via the 2D shadow transform relating radiative primaries and account for the global and asymptotic symmetries in gauge theory and gravity.