Nonlinear stability of extremal Reissner-Nordstr\"om black holes in spherical symmetry

TL;DR

This paper proves the nonlinear stability of extremal Reissner-Nordström black holes in spherical symmetry, demonstrating decay of the metric and scalar field, while confirming the nonlinear manifestation of the Aretakis instability at the event horizon.

Contribution

It establishes the codimension-one nonlinear asymptotic stability of extremal Reissner-Nordström black holes within the Einstein-Maxwell-scalar field system, including the Aretakis instability effects.

Findings

Metric decays to extremal Reissner-Nordström family

Scalar field decays pointwise and in energy norm

Growth of second null derivative of scalar field along the horizon

Abstract

In this paper, we prove the codimension-one nonlinear asymptotic stability of the extremal Reissner-Nordstr\"om family of black holes in the spherically symmetric Einstein-Maxwell-neutral scalar field model, up to and including the event horizon. More precisely, we show that there exists a teleologically defined, codimension-one "submanifold" $\mathfrak M_\mathrm{stab}$ of the moduli space of spherically symmetric characteristic data for the Einstein-Maxwell-scalar field system lying close to the extremal Reissner-Nordstr\"om family, such that any data in $\mathfrak M_\mathrm{stab}$ evolve into a solution with the following properties as time goes to infinity: (i) the metric decays to a member of the extremal Reissner-Nordstr\"om family uniformly up to the event horizon, (ii) the scalar field decays to zero pointwise and in an appropriate energy norm, (iii) the first translation-invariant ingoing null derivative of the scalar field is approximately constant on the event horizon $\mathcal H^+$, (iv) for "generic" data, the second translation-invariant ingoing null derivative of the scalar field grows linearly along the event horizon. Due to the coupling of the scalar field to the geometry via the Einstein equations, suitable components of the Ricci tensor exhibit non-decay and growth phenomena along the event horizon. Points (i) and (ii) above reflect the "stability" of the extremal Reissner-Nordstr\"om family and points (iii) and (iv) verify the presence of the celebrated "Aretakis instability" for the linear wave equation on extremal Reissner-Nordstr\"om black holes in the full nonlinear Einstein-Maxwell-scalar field model.