Toward double copy on arbitrary backgrounds

TL;DR

This paper extends the double copy framework to arbitrary gravitational and gauge backgrounds, constructing a perturbative map for particle production amplitudes and identifying backgrounds that generate FRW spacetimes.

Contribution

It introduces a double copy map for particle production in general backgrounds at next-to-leading order, connecting gauge fields to gravitational metrics and axio-dilatons.

Findings

Constructed a double copy map for scalar QCD amplitudes in arbitrary backgrounds.

Identified gauge fields that produce FRW spacetimes via double copy.

Conjectured the all-orders form of the double copy map for specific backgrounds.

Abstract

Double copy relates scattering amplitudes in a web of gravitational and gauge theories. Although it has seen great success when applied to amplitudes in vacuum, far less is known about double copy in arbitrary gravitational and gauge backgrounds. Focussing on the simplest pair production amplitudes of scalar QCD in a background gauge field, we construct, at next-to-leading order in perturbation theory, a double copy map to particle production in general metrics (and associated axio-dilatons) constructed from the gauge background. We connect our results to convolutional and classical double copy and, turning to examples, identify a class of gauge fields which generate FRW spacetimes via double copy. For this case we are able to conjecture the all-orders form of the double copy map.