paper

The Dynamics of Supertranslations and Superrotations in 2+1 Dimensions

arXiv:1608.05088

Abstract

Supertranslations, and at least in 2+1 dimensions superrotations, are asymptotic symmetries of the metric in asymptotically flat spacetimes. They are not, however, symmetries of the boundary term of the Einstein-Hilbert action, which therefore induces an action for the Goldstone-like fields that parametrize these symmetries. I show that in 2+1 dimensions, this action is closely related to a chiral Liouville action, as well as the "Schwarzian" action that appears in two-dimensional near-AdS physics.

11 pages; v2: discussion of relation to other work; v3: major revision, errors in discussion of dynamics fixed, crucial "corner terms" added

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