From harmonic to Newman-Unti coordinates at the second post-Minkowskian order

TL;DR

This paper derives the full coordinate transformations from harmonic to Newman-Unti coordinates at the second post-Minkowskian order, enabling detailed analysis of asymptotic quantities like shear, mass, and angular momentum.

Contribution

It provides the first complete transformation formulas at this order, facilitating advanced studies of gravitational radiation and asymptotic structure.

Findings

Derived transformations up to second post-Minkowskian order

Computed asymptotic shear, Bondi mass, and angular momentum aspects

Enhanced understanding of gravitational wave asymptotics

Abstract

In this paper, we present the complete transformations of a generic metric from (generalized) harmonic to Newman-Unti coordinates up to the second post-Minkowskian order $(G^2)$. This allows us to determine the asymptotic shear, the Bondi mass aspect, and the angular-momentum aspect at both orders.