= Bondi news function
{c}
{title2=$N_{AB}$}
The Bondi news function is the outgoing-null-time derivative of <Bondi shear> at <future null infinity>. Write the angular metric as $g_{AB}=r^2q_{AB}+rC_{AB}+O(1)$, with $q^{AB}C_{AB}=0$. One convention defines $N_{AB}=\tfrac12\partial_uC_{AB}$; its two components encode changing gravitational-wave polarizations.
The outgoing <gravitational-wave energy flux> is quadratic in the news, decreasing total <Bondi mass> in an isolated vacuum system. Time-independent shear supplies no such flux. The shear also sets the leading detector strain at large distance.<Bondi-Sachs Formalism by Thomas Mädler and Jeffrey Winicour>[Equations (34), (40)–(43), (58): strain, normalization and mass loss]{ref}
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