Speaker
Description
It was recently remarked that the hypersurface of null infinity of asymptotically flat spacetimes is a non-expanding horizon. We utilize this observation and propose a duality between the asymptotic structure of asymptotically flat spacetimes and the near-horizon structure of extremal black holes. The link between these two classes of geometries comes in the form of spatial inversions that conformally map one onto the other. An explicit manifestation of this duality is the four-dimensional extremal Reissner-Nordström geometry, which has the special property of being self-dual under the mapping, better known in the literature as the Couch-Torrence inversion. The existence of the Couch-Torrence inversion then provides matching conditions between near-horizon and near-null-infinity modes of perturbations of the extremal Reissner-Nordström black hole. We demonstrate that a direct consequence of this is the identification between an infinite tower of near-horizon (Aretakis) and near-null-infinity (Newman-Penrose) conserved charges.
