Celestial double copy from the worldsheet

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.

BCJ amplitude relations for Anti-de Sitter boundary correlators in embedding space

“…16 Our discussion of the double-copy in AdS space is clearly incomplete; identifying a construction that relates gauge and gravitational theories at finite boundary dimension d is clearly an important problem. Celestial amplitudes are perhaps the closest flat space analog to our AdS boundary correlators and their structure [105][106][107] is analogous to that of the differential representations discussed here. Notably, they are constrained by symmetries [161][162][163][164] exposed by soft-momentum properties of the corresponding momentumspace amplitudes.…”

“…Kinematic numerators as differential operators have already appeared in the study of celestial amplitudes in flat space [105][106][107], so it should not be surprising that it may also happen in AdS space. In this paper, the representation (3.24) is realized manifestly for the NLSM at four and six points.…”

“…Amplitude representations that are similar in spirit are used in the double copy of celestial amplitudes in flat space[105][106][107] 4. In flat space, particular BCJ representations of a variety of theories can be derived from ambitwistor string models[109][110][111][112].…”

Celestial amplitudes from UV to IR

“…This is already an indication that, whatever exotic variety of "conformal field theory" is to be associated with celestial amplitudes, it must produce interesting new sorts of singularities not usually encountered in familiar local CFTs. 1 In recent years, celestial amplitudes have been intensively studied from a variety of viewpoints [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. One theme in these investigations has been the realization that the physics of soft modes in the deep IR -from the leading and subleading soft theorems to the electromagnetic and gravitational "memory effects" -are beautifully understood from enhancements of global to local conformal and U(1) symmetries on the celestial sphere [22][23][24][25][26][27].…”

Asymptotic Weyl double copy

“…Large diffeomorphisms in self-dual gravity and large gauge transformations in self-dual gauge theory have also been related [76], based on the fact that the self-dual theories provide a simple setting for the double copy [77]. The notions of celestial operators and amplitudes that arose recently are also revealing their own versions of the double copy [78][79][80]. Closer to the approach to be taken here, the double copy has been seen to arise in the characteristic value formulation of general relativity, particularly in the example of the Taub-NUT spacetime [73].…”