Absorption Effects due to Spin in the Worldline Approach to Black Hole Dynamics

TL;DR

This paper extends the worldline effective theory to include black hole spin, analyzing absorption effects and superradiance, and predicts spin-related power loss in binary systems, applicable to black holes and neutron stars.

Contribution

It introduces a generalized effective point particle approach incorporating spin and computes associated absorption effects and power loss in binary systems.

Findings

Spin enhances power loss by three powers of velocity.

Superradiance dominates absorption in rotating black holes.

The theory applies to neutron stars and test black holes.

Abstract

We generalize the effective point particle approach to black hole dynamics to include spin. In this approach dissipative effects are captured by degrees of freedom localized on the wordline. The absorptive properties of the black hole are determined by correlation functions which can be matched with the graviton absorption cross section in the long wavelength approximation. For rotating black holes, superradiance is responsible for the leading contribution. The effective theory is then used to predict the power loss due to spin in the dynamics of non-relativistic binary systems. An enhancement of three powers of the relative velocity is found with respect to the non-rotating case. Then we generalize the results to other type of constituents in the binary system, such as rotating neutron stars. Finally we compute the power loss absorbed by a test spinning black hole in a given spacetime background.