Screening an extremal black hole with a thin shell of exotic matter

TL;DR

This paper explores the theoretical possibility of shielding an extremal black hole using a thin shell of exotic matter, analyzing the shell's properties and stability conditions.

Contribution

It introduces a model for black hole shielding with a thin shell of exotic matter and derives the shell's physical properties using junction conditions.

Findings

Surface energy density is negative on the shell.

Tangential pressures are positive and finite near the horizon.

Stability conditions are briefly analyzed.

Abstract

We study the possibility of shielding a regular extremal black hole by means of a matter thin-shell. While the surface energy density $\sigma$ on the static shell is negative, the tangential pressures $p$ are positive, both of them being finite when the shell approaches the black hole horizon. The Darmois-Israel junction conditions are used to find $\sigma$ and $p$ in terms of the radius $a$ of the shell. The surface gravitational energy $E_{S}$ is computed, keeping track of the pressure contribution. The stability conditions are briefly investigated.