Superradiance Protects Unitary Evolution on the Boundary

It has been argued that the rate at which the interior of an AdS black hole evolves is dual to the rate of unitary evolution 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 AdS₅-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 with a ``grey galaxy'' as the end state. We also argue that this claim (that unitary evolution is preserved by superradiance, and not by some other instability) might be confirmed by an experimental observation of a specific temperature-dependent upper bound on the specific angular momentum of actual strongly coupled matter -- $\,$ in particular, by the observation of such a bound in samples of the Quark-Gluon Plasma with extremely large vorticities.