Spectral Cauchy Characteristic Extraction of strain, news and gravitational radiation flux

TL;DR

This paper introduces a novel spectral Cauchy-characteristic extraction method that accurately computes gravitational radiation, energy, momentum, and angular momentum fluxes at null infinity, improving the analysis of gravitational wave data.

Contribution

It develops a new approach to transform the full metric into an inertial frame, enabling uniform calculation of all radiation fluxes associated with asymptotic symmetries.

Findings

Successfully implemented and calibrated with Spectral Einstein Code (SpEC)

Provides a comprehensive treatment of all fluxes at null infinity

Enhances the physical interpretation of gravitational wave data

Abstract

We present a new approach for the Cauchy-characteristic extraction of gravitational radiation strain, news function, and the flux of the energy-momentum, supermomentum and angular momentum associated with the Bondi-Metzner-Sachs asymptotic symmetries. In Cauchy-characteristic extraction, a characteristic evolution code takes numerical data on an inner worldtube supplied by a Cauchy evolution code, and propagates it outwards to obtain the space-time metric in a neighborhood of null infinity. The metric is first determined in a scrambled form in terms of coordinates determined by the Cauchy formalism. In prior treatments, the waveform is first extracted from this metric and then transformed into an asymptotic inertial coordinate system. This procedure provides the physically proper description of the waveform and the radiated energy but it does not generalize to determine the flux of angular momentum or supermomentum. Here we formulate and implement a new approach which transforms the full metric into an asymptotic inertial frame and provides a uniform treatment of all the radiation fluxes associated with the asymptotic symmetries. Computations are performed and calibrated using the Spectral Einstein Code (SpEC).