The Λ-BMS ₄ group of dS ₄ and new boundary conditions for AdS ₄

Abstract

Abstract Using the dictionary between Bondi and Fefferman–Graham gauges, we identify the analogues of the Bondi news, Bondi mass and Bondi angular momentum aspects at the boundary of generic asymptotically locally (A)dS 4 spacetimes. We introduce the -BMS 4 group as the residual symmetry group of the metric in Bondi gauge after boundary gauge fixing. This group consists of infinite-dimensional non-abelian supertranslations and superrotations and it reduces in the asymptotically flat limit to the extended BMS 4 group. Furthermore, we present new boundary conditions for asymptotically locally AdS 4 spacetimes which admit times the group of area-preserving diffeomorphisms as the asymptotic symmetry group. The boundary conditions amount to fix two components of the holographic stress-tensor while allowing two components of the boundary metric to fluctuate. They correspond to a deformation of a holographic CFT 3 which is coupled to a fluctuating spatial metric of fixed area.