Scalarized Black Hole dynamics in Einstein dilaton Gauss-Bonnet Gravity

TL;DR

This paper investigates the stability of scalarized black holes in Einstein dilaton Gauss-Bonnet gravity, revealing conditions for nonlinear stability and the formation of elliptic regions, with implications for the well-posedness of the theory.

Contribution

It provides the first numerical analysis of scalarized black hole stability in EdGB gravity, identifying regimes of stability and ill-posedness related to coupling strength.

Findings

Stable scalarized black holes for small curvature couplings.

Elliptic regions form inside black holes, remaining hidden from outside observers.

Exterior elliptic regions indicate ill-posedness in certain coupling regimes.

Abstract

We report on a numerical investigation of the stability of scalarized black holes in Einstein dilaton Gauss-Bonnet (EdGB) gravity in the full dynamical theory, though restricted to spherical symmetry. We find evidence that for sufficiently small curvature-couplings the resulting scalarized black hole solutions are nonlinearly stable. For such small couplings, we show that an elliptic region forms inside these EdGB black hole spacetimes (prior to any curvature singularity), and give evidence that this region remains censored from asymptotic view. However, for coupling values "superextremal" relative to a given black hole mass, an elliptic region forms exterior to the horizon, implying the exterior Cauchy problem is ill-posed in this regime.