Dynamics of Extremal Black Holes

TL;DR

This paper studies the scattering and radiation processes near extremal magnetically charged dilatonic black holes, revealing a connection to two-dimensional black hole physics and discussing implications for unitarity and quantum properties.

Contribution

It demonstrates that near the extremal limit, black hole horizon physics can be effectively described by a two-dimensional theory, introducing the concept of 'quantum whiskers' for black hole characterization.

Findings

Scattering near extremal black holes can be modeled by 2D effective field theory.

Particle capture and Hawking re-emission processes are analyzed.

Backreaction effects may restore unitarity in scattering processes.

Abstract

Particle scattering and radiation by a magnetically charged, dilatonic black hole is investigated near the extremal limit at which the mass is a constant times the charge. Near this limit a neighborhood of the horizon of the black hole is closely approximated by a trivial product of a two-dimensional black hole with a sphere. This is shown to imply that the scattering of long-wavelength particles can be described by a (previously analyzed) two-dimensional effective field theory, and is related to the formation/evaporation of two-dimensional black holes. The scattering proceeds via particle capture followed by Hawking re-emission, and naively appears to violate unitarity. However this conclusion can be altered when the effects of backreaction are included. Particle-hole scattering is discussed in the light of a recent analysis of the two-dimensional backreaction problem. It is argued that the quantum mechanical possibility of scattering off of extremal black holes implies the potential existence of additional quantum numbers - referred to as ``quantum whiskers'' - characterizing the black hole.