Near-$AdS_2$ perturbations and the connection with near-extreme Reissner-Nordstrom

TL;DR

This paper analyzes perturbations near the horizon of near-extreme Reissner-Nordstrom black holes, connecting near-$AdS_2$ geometries with the full black hole spacetime, and computes the scattering matrix for gravitational and electromagnetic waves.

Contribution

It provides the first analytical solution for perturbations of near-$AdS_2\times S^2$ and links these to the near-extreme Reissner-Nordstrom geometry, extending previous work on the extreme case.

Findings

Analytical solutions for near-$AdS_2$ perturbations are obtained.

The connection with near-extreme Reissner-Nordstrom geometry is established.

Classical scattering matrix for waves near the black hole horizon is computed.

Abstract

The geometry very near the horizon of a near-extreme Reissner-Nordstrom black hole is described by the direct product of a near-$AdS_2$ spacetime with a two-sphere. While near-$AdS_2$ is locally diffeomorphic to $AdS_2$ the two connect differently with the asymptotically flat part of the geometry of (near-)extreme Reissner-Nordstrom. In previous work, we solved analytically the coupled gravitational and electromagnetic perturbation equations of $AdS_2\times S^2$ and the associated connection problem with extreme Reissner-Nordstrom. In this paper, we give the solution for perturbations of near-$AdS_2\times S^2$ and make the connection with near-extreme Reissner-Nordstrom. Our results here may also be thought of as computing the classical scattering matrix for gravitational and electromagnetic waves which probe the region very near the horizon of a highly charged spherically symmetric black hole.