New dual gravitational charges

TL;DR

The paper reveals an infinite set of dual gravitational charges at null infinity, arising from a dual Barnich-Brandt construction and tied to the imaginary part of the leading Newman-Penrose quantity $ψ_2^0$. Through an EM analogy, it shows how electric and magnetic charges appear as real and imaginary parts of a generalized NP charge, and extends this insight to gravity by defining dual BB charges whose integrable parts yield new, bona fide charges beyond the standard BMS set. The resulting framework expresses the full generalized charge as $\mathcal{Q} = \mathcal{Q}^{(int)} - i\tilde{\mathcal{Q}}^{(int)}$, with the dual charges conserved in the absence of Bondi news and reducing to familiar Bondi momentum for $\ell=0,1$. However, the method is restricted to supertranslations at null infinity and does not extend straightforwardly to the full SL(2, C) part of the BMS group, leaving open questions about connections to soft theorems and information paradox considerations.

Abstract

We show that there are a further infinite number of, previously unknown, supertranslation charges. These can be viewed as duals of the known BMS charges corresponding to supertranslations. In Newman-Penrose language, these new supertranslation charges roughly correspond to the imaginary part of the leading term in $ψ_2$. We find these charges by dualising the Barnich-Brandt asymptotic charges and argue that this prescription gives rise to new bona fide charges at null infinity.