Black hole uniqueness and magnetic shear

TL;DR

This paper explores the possibility that realistic black holes possess a magnetic shear component in their gravitational field, which challenges the traditional black hole uniqueness conjecture by suggesting non-stationary effects at large distances.

Contribution

It introduces the idea that black holes generically have a magnetic shear component, influenced by processes like Blandford-Znajek and gravitational gyrotropy, affecting their long-range gravitational fields.

Findings

Black holes may have a magnetic shear component.

Magnetic effects become significant near null infinity.

Black-hole uniqueness may not hold at large distances.

Abstract

A series of tantalizing results led to the black hole uniqueness conjecture: isolated, realistic black holes should settle down to states characterized by their spin, mass and charge. I argue that generically real black holes will also possess a `magnetic' shear; equivalently, that the dominant contribution to their long-range gravitational field should have a `magnetic' (odd-parity) component. In fact, the Blandford-Znajek process, combined with the axial anomaly and gravitational gyrotropy, would tend to leave a black hole in such a state. It seems that the black-hole uniqueness conjecture may apply in a regime around the hole, but as one approaches future null infinity the `magnetic' effects become significant. In this far-field regime, the space-time will be non-stationary, but there will be no radiation.