On the Scattering of Waves inside Charged Spherically Symmetric Black Holes

TL;DR

This paper demonstrates a fundamental breakdown in wave scattering within charged black holes, revealing that certain operators lose their invertibility due to low-frequency and high-angular-momentum behaviors, with implications for black hole interior dynamics.

Contribution

It shows that scattering operators in charged black holes are not invertible inside the horizon, due to generic low-frequency and high-angular-momentum obstructions.

Findings

Scattering operators lack bounded inverses inside the black hole horizon.

Breakdown of scattering is caused by low-frequency and high-angular-momentum behaviors.

The phenomenon is demonstrated through analysis of a 1+1 wave equation with decaying potential.

Abstract

In this paper we show that there is a breakdown of scattering between the event horizon (or the Cauchy horizon) and an intermediate Cauchy hypersurface in the dynamic interior of a Reissner-Nordstr\"om-like black hole. More precisely, we show that the trace operators and their analytic counterparts, the inverse wave operators, do not have bounded inverses, even though these operators themselves are bounded. This result holds for the natural energy given by the energy-momentum tensor of the wave equation using the timelike vector field of the Regge-Wheeler variable, which asymptotically becomes normal to the horizons. The behaviour of solutions at low spatial-frequencies and their behaviour at high angular momenta are the only obstructions causing this breakdown of scattering. The breakdown follows from an analysis of a $1+1$-dimensional wave equation with exponentially decaying potential which we treat for general potentials, and we show that the breakdown is generic.