Superradiance in the Bulk Protects Quantum State Evolution of Rapidly Rotating Matter on the Boundary

TL;DR

This paper explores how superradiant instabilities in rotating black holes impose an upper limit on angular momentum, which in turn constrains the quantum state evolution rate of boundary matter in holographic duality, with implications for observable phenomena.

Contribution

It introduces the concept that superradiant instabilities prevent black holes from exceeding a critical angular momentum, affecting the dual boundary matter's evolution rate and providing a new perspective on holographic dynamics.

Findings

Superradiant instability causes black holes to shed excess angular momentum.

An upper bound on specific angular momentum exists due to superradiance.

This bound influences the quantum state evolution rate of boundary matter.

Abstract

It has been argued that the rate at which the interior of an AdS black hole evolves is dual to the rate of evolution of the (quantum state of the) strongly coupled matter on the boundary which, according to holography, is dual to the black hole. However, we have shown elsewhere that it seems to be possible, by adjusting the specific angular momentum of an AdS$_5$-Kerr black hole, to reduce this rate to (effectively) zero. We argue that this is unphysical, and that it is prevented by the intervention of a superradiant instability, which causes the black hole to shed angular momentum when the angular velocity exceeds a certain critical value. The precise way in which this works has recently been explained by the ``grey galaxy'' model of the end state, in which the angular momentum is transferred to a ``galactic disc.'' Thus, the black hole itself cannot sustain a specific angular momentum beyond a critical value: there is an effective upper bound. The holographic interpretation is that, beyond a certain limiting specific angular momentum, strongly coupled matter (corresponding to the black hole) will spontaneously shed angular momentum to some other, confined, form of matter (corresponding to the disc). This idea is supported by recent numerical work on ultra-vortical plasmas. Such an upper bound on specific angular momentum would prevent arbitrarily small rates of quantum state evolution on the boundary. We give a tentative discussion of the relevant observational data in the case of the vortical Quark-Gluon Plasma, and suggest a way in which such an upper bound might appear in future observations.