Dual gravitational charges and soft theorems

TL;DR

The paper addresses how dual gravitational charges, related to NUT parameters, fit into the asymptotic structure of spacetime. It introduces a complexified supertranslation charge to couple the usual and dual sectors, and demonstrates its action on radiative data reproduces time translations on one mode and a supertranslation on another, removing the need for boundary conditions at spacelike infinity. By rederiving BMS/dual charges to include total-derivative terms, it clarifies the role of nonregular sphere data and shows Taub-NUT yields a nonzero dual charge, thereby motivating a generalized notion of asymptotic flatness. Finally, it derives a Weinberg-like soft NUT/graviton theorem from a Ward identity for the complexified charge, extending soft theorems to incorporate dual gravitational data and enriching the asymptotic symmetry framework.

Abstract

We consider the consequences of the dual gravitational charges for the phase space of radiating modes, and find that they imply a new soft NUT theorem. In particular, we argue that the existence of these new charges removes the need for imposing boundary conditions at spacelike infinity that would otherwise preclude the existence of NUT charges.