Aspects of Holography beyond AdS BMS superrotations in higher dimensions

Abstract

A crucial role in the problem of four-dimensional asymptotically flat spacetime holographyis long believed to be played by the Bondi-Metzner-(van der Burg)-Sachs (BMS) asymptotic symmetry group. The discovery of deep relationships between such symmetries andgravitational infrared effects - pertrubative soft theorems and gravitational wave memories - has sparkled new interest in the problem. In this context, superrotations extendthe standard general relativistic definition of BMS group. While there has been somedebate on the extension of BMS to higher dimensions (d > 4), very little has been saidabout superrotations. In this thesis we initiate a systematic study of such structures. We provide evidence that consistency of superrotation Killing fields with a fully non-lineard > 4 gravitational configuration space requires different boundary conditions than thoseconsidered in literature. The first such evidence comes from cosmic (d − 3)-branes, whichare conjectured to be related to superrotations in d > 4 as a natural generalization ofthe relationship between cosmic strings in d = 4 and d = 4 superrotations. The generalboundary conditions may be taken to define asymptotically locally Minkowski spacetimes.
The first part of the thesis recaps fundamentals of AdS/CFT - the most well known example of holographic duality - and the second moves to asymptotically flat spacetimes. Thereview material marks the conceptual and technical differences between AdS holographyand the attempts at flat holography. A recurring theme is that of variational principlesand asymptotic charges. Their mutual consistency is pivotal in dynamically realisingAdS/CFT. We take this requirement as the basis of asymptotically flat holography andthe analysis of the configuration space is fundamental to the construction of well-defined variational principles and the phase space.

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ORCID for Marika Taylor: orcid.org/0000-0001-9956-601X

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