Geodesics from classical double copy

Abstract

We extend the Kerr-Schild double copy to the case of a probe particle moving in the Kerr-Schild background. In particular, we solve Wong’s equations for a test color charge in a Coulomb non-Abelian potential (\(\sqrt{\text{Schw}}\)) and on the equatorial plane for the potential generated by a rotating disk of charge known as the single copy of the Kerr background (\(\sqrt{\text{Kerr}}\)). The orbits, as the corresponding geodesics on the gravity side, feature elliptic, circular, hyperbolic and plunge behaviour for the charged particle. We then find a new double copy map between the conserved charges on the gauge theory side and the gravity side, which enables us to fully recover geodesic equations for Schwarzschild and Kerr. Interestingly, the map works naturally for both bound and unbound orbits.