The outflying singularity inside fast spinning black holes

Marolf and Ori proposed a shock wave singularity along the outgoing segment of the inner horizon (OIH) of black holes. Previous evidence stems mostly from spherical charged toy models with scalar fields or scalar fields in addition to null fluids, or from a scalar field model for a rotating black hole (but with initial data that are not well motivated astrophysically, specifically external perturbations). We consider linearized perturbations of fast rotating Kerr black holes, for either scalar field or vacuum, gravitational perturbations. The perturbation fields are the fields that result from the collapse of an isolated black hole (“Price tails”). We show the occurrence of a Marolf-Ori like singularity at the OIH (“outflying singularity”) as experienced by either null or timelike observers. This singularity joins a null, weak singularity (“mass inflation”, “infalling”) at the ingoing leg. We then study in detail the quantitative features of the outflying singularity, specifically the shock sharpening effect of the scalar field for scalar field perturbations, and the Weyl scalars ψ₀ and ψ₄ (scaled appropriately by the horizon function Δ), and the Kretschmann curvature scalar K for gravitational perturbations, and show that in all cases its rate agrees with expectations. .