Geodesics From Classical Double Copy

TL;DR

This paper extends the classical double copy framework to include probe particles in Kerr-Schild backgrounds, deriving geodesic equations and a new charge map connecting gauge theory and gravity solutions.

Contribution

It introduces a novel double copy map relating conserved charges in gauge theory to gravitational geodesics, applicable to both bound and unbound orbits.

Findings

Derived geodesic equations for charged particles in Kerr-Schild backgrounds.

Established a new double copy map linking gauge charges to gravitational conserved quantities.

Demonstrated the map's effectiveness for Schwarzschild and Kerr spacetimes.

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 $\text{Kerr}$ 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.