Kerr-Schild Double Copy and Complex Worldlines

Understand

We use the classical double copy to identify a necessary condition for Maxwell theory sources to constitute single copies of Kerr-Schild solutions to Einstein's equations.

• In the case of four-dimensional Kerr-Schild spacetimes on Minkowski backgrounds, we extend this condition to a parameterization of the corresponding single copies.
• These are given by Li\'enard-Wiechert fields of charges on complex worldlines.
• This unifies the known instances of the Kerr-Schild double copy black holes on flat four-dimensional backgrounds into a single framework.