Analytical Tests for U(1) Charge in Black Holes Using the Backwards One Body Model

Electric charge is generally neglected when considering astrophysical black holes (BHs), though it is an allowed parameter according to the no hair theorem. Einstein-Maxwell theory, our best current model for combining gravity with electromagnetism, works simply by inserting the electromagnetic stress-energy tensor into Einstein’s equations. Though it is the simplest possible way to couple electromagnetism to gravity, this choice is not unique. Thus, the existence of BHs with non-negligible electric charges would present the opportunity to test Einstein-Maxwell theory. The Backwards One Body (BOB) model has been shown to precisely model the strain for the ringdown, merger, and late inspiral for BH mergers forming Kerr BHs. By extending the BOB model to Kerr-Newman BHs we can perform purely analytical and computationally inexpensive tests for charge from detector signals. In order to demonstrate the validity of BOB within the Kerr-Newman regime, numerical relativity simulations were performed with a modified version of the Einstein Toolkit created by Gabriele Bozzola and Vasileios Paschalidis. Furthermore, this treatment is not unique to electric charge and can be generalized to test for magnetic charges, dark-sector charges, gravitational charges in theories of gravity mediated by a vector field, and any other charges arising from a U(1) symmetry, giving potential opportunities for various tests of fundamental physics.