BMS symmetries and holography: an introductory overview

A short overview of the role of BMS symmetries in various approaches to the flat spacetime holography problem is given. The relevance of BMS symmetries to the infrared structure of gravity is motivated and described at an introductory level with some details, but also the relation between the BMS group and the Carroll group is pointed out. The BMS group—and its proposed extensions—is reviewed in four-dimensional spacetimes in parallel with a discussion of the difficulties related to its definition in higher dimensional spacetimes. The Bondi–Sachs integration scheme is discussed with some details. A short discussion of canonical charges associated to the BMS transformations and the possible relation between superrotations and transition from asymptotically flat to locally asymptotically flat spacetimes is also summarised