About Magnetic AdS Black Holes

TL;DR

This paper explores the properties of magnetically charged AdS black holes, revealing their unique electromagnetic features, stability conditions, and implications for holographic duality, especially regarding superradiant instabilities and the existence of a corona.

Contribution

It provides a detailed analysis of magnetically charged AdS black holes, highlighting their electromagnetic field configurations, stability bounds, and differences from asymptotically flat cases, advancing understanding of holographic duality.

Findings

Magnetic fields at the poles can be outside the event horizon.

Electric fields induced by rotation are significant but smaller than magnetic fields.

Superradiant instability can be avoided in magnetically charged AdS black holes.

Abstract

There has recently been a strong revival of interest in quasi-extremal magnetically charged black holes. In the asymptotically flat case, it is possible to choose the magnetic charge of such an object in such a manner that the black hole is surrounded by a corona in which electroweak symmetry is restored on macroscopic scales, a result of very considerable interest. We argue that holographic duality indicates that the asymptotically AdS analogues of these black holes have several interesting properties: the dual theory is only physical if the black hole is required to rotate; in the rotating case, the magnetic field at the poles does not attain its maximum on the event horizon, but rather somewhat outside it; the magnetic field at the equator is not a monotonically decreasing function of the magnetic charge; the electric fields induced by the rotation, while smaller than their magnetic counterparts, are by no means negligible; the maximal electric field often occurs neither at the poles nor at the equator; and so on. Most importantly, in the magnetically charged case it is possible to avoid the superradiant instability to which neutral AdS-Kerr black holes are subject; but the need to avoid this instability imposes upper bounds on the magnetic and electric fields. In some circumstances, therefore, the corona may not exist in the asymptotically AdS case.