  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.
