Null infinity, the BMS group and infrared issues

There has been a recent resurgence of interest in the structure of the gravitational field at null infinity, sparked by new results on soft charges and infrared issues related to the S matrix theory in perturbative quantum gravity. We summarize these developments and put them in the broader context of research in the relativity community that dates back to several decades. In keeping with intent of this series, this overview is addressed to gravitational scientists who are not experts in this specific area.
Comment: 19 pages, no figures. Prepared for the "Introduction to Current Research Series." Clarifications added following correspondence with expert, typos corrected, version to appear in the journal