A novel characterisation of gravitational radiation in asymptotically flat space-times

TL;DR

This paper introduces a new geometric criterion for detecting gravitational radiation at null infinity in asymptotically flat space-times, providing a gauge-invariant and unambiguous method that relates to classical approaches.

Contribution

It presents a novel, geometric, and gauge-friendly criterion for gravitational radiation at null infinity, enhancing the classical News tensor method.

Findings

New geometric criterion for gravitational radiation

Relationship established with classical News tensor

A new balance law at null infinity

Abstract

A novel criterion to determine the presence of gravitational radiation arriving to, or departing from, null infinity of any weakly asymptotically-simple space-time with vanishing cosmological constant is given. The quantities involved are geometric, of tidal nature, with good gauge behaviour and univocally defined at null infinity. The relationship with the classical characterisation using the News tensor is analysed in detail. A new balance law at infinity is presented, which may be useful to define `radiation states'.