On the linear stability of the extreme Kerr black hole under axially symmetric perturbations

Abstract

We prove that for axially symmetric linear gravitational perturbations of the extreme Kerr black hole, there exists a positive definite and conserved energy. This provides a basic criteria for linear stability in axial symmetry. In the particular case of Minkowski, using this energy we also prove the pointwise boundedness of the perturbation in a remarkably simple way.