Fluctuating Black Hole Horizons

TL;DR

This paper models black hole horizons as physical boundaries, deriving an effective field theory that links boundary dynamics to black hole properties, suggesting all charges are carried by the boundary and exploring Planck scale implications.

Contribution

It introduces a boundary-based effective action for black hole horizons, connecting boundary dynamics with black hole charges and entropy, and analyzes the boundary's properties at the Planck scale.

Findings

Boundary behaves like a massless Klein-Gordon field in large wave number limit.

Boundary angular momentum matches black hole's angular momentum.

Predictions on Planck scale boundary properties.

Abstract

In this paper we treat the black hole horizon as a physical boundary to the spacetime and study its dynamics following from the Gibbons-Hawking-York boundary term. Using the Kerr black hole as an example we derive an effective action that describes, in the large wave number limit, a massless Klein-Gordon field living on the average location of the boundary. Complete solutions can be found in the small rotation limit of the black hole. The formulation suggests that the boundary can be treated in the same way as any other matter contributions. In particular, the angular momentum of the boundary matches exactly with that of the black hole, suggesting an interesting possibility that all charges (including the entropy) of the black hole are carried by the boundary. Using this as input, we derive predictions on the Planck scale properties of the boundary.