Extracting the energy and angular momentum of a Kerr black hole

TL;DR

This paper explains how rotating black holes can transfer their energy and angular momentum to surrounding particles through electromagnetic processes in magnetic fields, without relying on the ergosphere.

Contribution

It introduces a novel electromagnetic mechanism for energy extraction from Kerr black holes involving external magnetic fields and ionized matter, bypassing the ergosphere.

Findings

Electromagnetic fields induce particle acceleration around Kerr black holes.

Energy and angular momentum are extracted via particles with negative energy states.

The process does not depend on the black hole ergosphere.

Abstract

It has been thought for decades that rotating black holes (BHs) power the energetic gamma-ray bursts (GRBs) and active galactic nuclei (AGNs), but the mechanism that extracts the BH energy has remained elusive. We here show that the solution to this problem arises when the BH is immersed in an external magnetic field and ionized low-density matter. For a magnetic field parallel to the BH spin, the induced electric field accelerates electrons outward and protons inward in a conical region, centered on the BH rotation axis, and of semi-aperture angle $\theta \approx 60^\circ$ from the BH rotation axis. For an antiparallel magnetic field, protons and electrons exchange their roles. The particles that are accelerated outward radiate off energy and angular momentum to infinity. The BH powers the process by reducing its energy and angular momentum by capturing polar protons and equatorial electrons with net negative energy and angular momentum. The electric potential allows for negative energy states outside the BH ergosphere, so the latter does not play any role in this electrodynamical BH energy extraction process.