Evidence for a New Soft Graviton Theorem

TL;DR

This paper presents evidence for a new universal soft graviton theorem's finite subleading term, extending the understanding of quantum gravity scattering amplitudes and suggesting a potential new symmetry in the S-matrix.

Contribution

It conjectures and verifies a universal formula for the subleading soft graviton term, linked to a new superrotation Virasoro symmetry in quantum gravity.

Findings

Verification for all tree-level amplitudes using BCFW recursion

Proposal of a new superrotation Virasoro symmetry

Extension of soft theorems beyond leading order

Abstract

The single-soft-graviton limit of any quantum gravity scattering amplitude is given at leading order by the universal Weinberg pole formula. Gauge invariance of the formula follows from global energy-momentum conservation. In this paper evidence is given for a conjectured universal formula for the finite subleading term in the expansion about the soft limit, whose gauge invariance follows from global angular momentum conservation. The conjecture is non-trivially verified for all tree-level graviton scattering amplitudes using a BCFW recursion relation. One hopes to understand this infinity of new soft relations as a Ward identity for a new superrotation Virasoro symmetry of the quantum gravity S-matrix.