Abstract
The leading soft photon theorem implies that four-dimensional scattering amplitudes are controlled by a two-dimensional (2D) Kac-Moody symmetry that acts on the celestial sphere at null infinity (). This celestial current is realized by components of the electromagnetic vector potential on the boundaries of . Here, we develop a parallel story for Low’s subleading soft photon theorem. It gives rise to a second celestial current, which is realized by vector potential components that are subleading in the large radius expansion about the boundaries of . The subleading soft photon theorem is reexpressed as a celestial Ward identity for this second current, which involves novel shifts by one unit in the conformal dimension of charged operators.
- Received 7 August 2019
DOI:https://doi.org/10.1103/PhysRevD.100.065001
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society