Local symmetries of non-expanding horizons

TL;DR

This paper investigates the local symmetries of non-expanding horizons in gravity, revealing that only a U(1) subgroup remains in spherically symmetric cases, which aids in developing effective horizon theories.

Contribution

It demonstrates that the residual local symmetry of spherically symmetric non-expanding horizons is a U(1) subgroup of the Lorentz group, informing effective horizon models.

Findings

Residual symmetry is U(1) in spherical symmetry

Effective horizon theories can utilize this U(1) symmetry

Analysis is based on 1st order gravity formulation

Abstract

Local symmetries of a non-expanding horizon has been investigated in the 1st order formulation of gravity. When applied to a spherically symmetric isolated horizon only a U(1) subgroup of the Lorentz group survives as residual local symmetry that one can make use of in constructing an effective theory on the horizon.