Mass-Centered GCM Framework in Perturbations of Kerr(-Newman)
Allen Juntao Fang, Elena Giorgi, Jingbo Wan
TL;DR
The paper addresses nonlinear stability for charged black holes by extending the GCM gauge to perturbations of Reissner–Nordström and Kerr–Newman spacetimes. It replaces the vacuum transport-based control of the center-of-mass mode with a sphere-by-sphere vanishing condition on a renormalized $m{C}_{\ell=1}$ quantity, yielding mass-centered GCM spheres and a mass-centered GCM hypersurface. The construction relies on fixing an effective canonical $\,\ell=1$ basis via uniformization and solving a determined elliptic-transport system to propagate the gauge consistently from spheres to a hypersurface. This gauge design preserves the structural advantages of GCM methods while accommodating electromagnetic coupling, providing a foundation for nonlinear stability results in the electrovacuum regime and potential applicability to broader matter models.
Abstract
The nonlinear stability problem for black hole solutions of the Einstein equations critically depends on choosing an appropriate geometric gauge. In the vacuum setting, the use of Generally Covariant Modulated (GCM) spheres and hypersurfaces has played a central role in the proof of stability for slowly rotating Kerr spacetime. In this work, we develop an alternative GCM framework, that we call mass-centered, designed to overcome the breakdown of the standard GCM construction in the charged case, where electromagnetic-gravitational coupling destroys the exceptional behavior of the $\ell=1$ mode of the center-of-mass quantity used in the vacuum analysis. This construction is aimed at the nonlinear stability of Reissner-Nordström and Kerr-Newman spacetimes. Our approach replaces transport-based control of the center-of-mass quantity with a sphere-wise vanishing condition on a renormalized $\ell=1$ mode, yielding mass-centered GCM hypersurfaces with modified gauge constraints. The resulting elliptic-transport system remains determined once an $\ell=1$ basis is fixed via effective uniformization and provides an alternative construction in vacuum in the uncharged limit.
