On BMS invariance of gravitational scattering
Abstract
BMS+ transformations act nontrivially on outgoing gravitational scattering data while preserving intrinsic structure at future null infinity ( +). BMS- transformations similarly act on ingoing data at past null infinity ( -). In this paper we apply — within a suitable finite neighborhood of the Minkowski vacuum — results of Christodoulou and Klainerman to link + to - and thereby identify "diagonal" elements BMS0 of BMS+ × BMS-. We argue that BMS0 is a nontrivial infinite-dimensional symmetry of both classical gravitational scattering and the quantum gravity -matrix. It implies the conservation of net accumulated energy flux at every angle on the conformal S 2 at . The associated Ward identity is shown to relate S-matrix elements with and without soft gravitons. Finally, BMS0 is recast as a U(1) Kac-Moody symmetry and an expression for the Kac-Moody current is given in terms of a certain soft graviton operator on the boundary of.
- Publication:
-
Journal of High Energy Physics
- Pub Date:
- July 2014
- DOI:
- 10.1007/JHEP07(2014)152
- arXiv:
- arXiv:1312.2229
- Bibcode:
- 2014JHEP...07..152S
- Keywords:
-
- Scattering Amplitudes;
- Classical Theories of Gravity;
- Space-Time Symmetries;
- High Energy Physics - Theory;
- General Relativity and Quantum Cosmology
- E-Print:
- 24 pages, 1 figure, minor edits in v2