Sub-subleading soft gravitons and large diffeomorphisms

TL;DR

This paper provides evidence that the sub-subleading soft graviton theorem corresponds to new asymptotic symmetries in gravity, revealing a richer structure of large diffeomorphisms and associated charges at null infinity.

Contribution

It establishes a link between the sub-subleading soft theorem and novel asymptotic charges, expanding the understanding of symmetries in gravitational theories.

Findings

Sub-subleading soft theorem is equivalent to conservation of new asymptotic charges.

Discovery of magnetic charges related to the dual of the Weyl tensor.

Reinterpretation of soft theorems as Ward identities for extended symmetries.

Abstract

We present strong evidence that the sub-subleading soft theorem in semi-classical (tree level) gravity discovered by Cachazo and Strominger is equivalent to the conservation of asymptotic charges associated to a new class of vector fields not contained within the previous extensions of BMS algebra. Our analysis crucially relies on analyzing the hitherto established equivalences between soft theorems and Ward identities from a new perspective. In this process we naturally (re)discover a class of `magnetic' charges at null infinity that are associated to the dual of the Weyl tensor.