Asymptotic gravitational charges

TL;DR

This work proposes that a complete set of asymptotic gravitational charges arises by allowing all action terms that yield the same Einstein equations, including topological contributions. Using a first‑order formulation and covariant phase space methods, the authors derive electric charges corresponding to the standard BMS symmetries and, crucially, magnetic/dual charges from the Nieh‑Yan term, providing a Hamiltonian interpretation of these dual charges. They show that while the Palatini action yields integrable Bondi mass charges with a nonintegrable radiative flux component, the Nieh‑Yan term introduces dual, topological charges associated with NUT-like data; Pontryagin and Gauss–Bonnet terms do not contribute leading charges but may yield subleading ones. The results link topology with asymptotic charges, clarifying how soft and hard sectors of gravitational radiation are encoded in a Hamiltonian framework and suggesting broader implications for gravitational scattering and information questions.

Abstract

We present a method for finding, in principle, all asymptotic gravitational charges. The basic idea is that one must consider all possible contributions to the action that do not affect the equations of motion for the theory of interest; such terms include topological terms. As a result we observe that the first order formalism is best suited to an analysis of asymptotic charges. In particular, this method can be used to provide a Hamiltonian derivation of recently found dual charges.