Supertranslation-Invariant Formula for the Angular Momentum Flux in Gravitational Scattering
Reza Javadinezhad, Massimo Porrati
Abstract
The angular momentum radiated in gravitational scattering can be changed by performing a supertranslation of the asymptotic metric, i.e., by adding radiation with infinite wavelength to the metric. This puzzling property can be avoided by adopting a supertranslation-invariant definition of the angular momentum flux in general relativity. Definitions currently available in the literature cannot reproduce the flux necessary to obtain the correct radiation reaction effects in gravitational scattering. They also disagree with computations of the flux performed using scattering amplitudes and soft-graviton theorems. In this Letter, we provide a new supertranslation-invariant definition of the angular momentum flux in gravitational scattering that uses only asymptotic metric data and reproduces the flux necessary to obtain the correct radiation reaction effects.