Horizon Shells and BMS-like soldering transformationsBlau, Matthias (Avtor)
O'Loughlin, Martin (Avtor)
Black HolesClassical Theories of GravitySpace-Time SymmetriesWe revisit the theory of null shells in general relativity, with a particular
emphasis on null shells placed at horizons of black holes. We study in detail the considerable
freedom that is available in the case that one solders two metrics together across null
hypersurfaces (such as Killing horizons) for which the induced metric is invariant under
translations along the null generators. In this case the group of soldering transformations
turns out to be infinite dimensional, and these solderings create non-trivial horizon shells
containing both massless matter and impulsive gravitational wave components. We also
rephrase this result in the language of Carrollian symmetry groups. To illustrate this
phenomenon we discuss in detail the example of shells on the horizon of the Schwarzschild
black hole (with equal interior and exterior mass), uncovering a rich classical structure
at the horizon and deriving an explicit expression for the general horizon shell energy-
momentum tensor. In the special case of BMS-like soldering supertranslations we find a
conserved shell-energy that is strikingly similar to the standard expression for asymptotic
BMS supertranslation charges, suggesting a direct relation between the physical properties
of these horizon shells and the recently proposed BMS supertranslation hair of a black hole.20162016-03-10 12:15:51Delo ni kategorizirano2164COBISS_ID: 4159995URN: URN:SI:UNG:REP:AHLKCEA2sl