On the topology of stable minimal hypersurfaces in a homeomorphic $S^4$
Chao Li, Boyu Zhang
TL;DR
This work develops a framework to control the topology of stable minimal hypersurfaces in PSC 4-manifolds with boundary that embed in a space homeomorphic to $S^4$. By combining a White-inspired extremal-position minimization with covering-space arguments and 4-manifold topology, the authors show that minimal hypersurfaces homologous to a boundary component have constrained topology, ruling out nontrivial spherical space-forms in their prime decomposition. They derive a black-hole topology theorem: the outermost horizons in suitable asymptotically flat 4-manifolds are diffeomorphic to unions of $S^3$ or connected sums of $S^2\times S^1$, with stronger results under positive bi-Ricci curvature. The paper also extends these ideas to Plateau problems in homeomorphic $D^4$, constructs PSC embeddings involving lens spaces, and discusses the Dahl–Larsson horizon examples, highlighting both geometric-analytic methods and topological obstructions with potential applications to general relativity.
Abstract
We construct stable minimal hypersurfaces with simple topology in certain compact $4$-manifolds $X$ with boundary, where $X$ embeds into a smooth manifold homeomorphic to $S^4$. For example, if $X$ is equipped with a Riemannian metric $g$ with positive scalar curvature, we prove the existence of a stable minimal hypersurface $M$ that is diffeomorphic to either $S^3$ or a connected sum of $S^2\times S^1$'s, ruling out spherical space forms in its prime decomposition. These results imply new theorems on the topology of black holes in four dimensions. The proof involves techniques from geometric measure theory and $4$-manifold topology.
