$C^0$-inextendibility of a class of warped-product black hole spacetimes

Abstract

We adapt Sbierski's proof of $C^0$-inextendibility of the maximal analytic Schwarzschild spacetime to a broad class of warped-product black hole spacetimes with a static exterior region. These spacetimes are globally hyperbolic, have a codimension-two Riemannian fibre and a radial coordinate $(r)$, which serves as the warping function of the fibre. They admit a spacetime singularity as $r \to 0$, characterised by the divergence of the Kretschmann scalar. This class encompasses nonvacuum black hole models and geometries beyond spherical symmetry. Under suitable assumptions, including that the fibre is closed (compact without boundary), connected, homogeneous, and orientable, we establish future $C^0$-inextendibility for spacetimes in this class. The result further extends to spacetimes possessing more than one regular black hole horizon.