Generic Metrics on $S^{n+1}$ Preclude Linearly Stable Singular Tangent Cones of Area-Minimizing Boundaries

Abstract

We prove that for a residual (and hence dense) subset $\mathcal{G}$ of Riemannian metrics on $S^{n+1}$ in the $C^{3}$ topology, no area-minimizing integral $n$-current that is a boundary admits a singular tangent cone which is linearly stable in the Euclidean sense. The proof proceeds in three stages. First, we develop a perturbation theorem: given any area-minimizer possessing an isolated singularity whose unique tangent cone $C$ is linearly stable, we construct an explicit $C^{3}$-small metric perturbation that destroys the compatibility conditions required for $C$ to persist as a tangent cone. The construction rests on the Hardt--Simon asymptotic expansion near isolated singularities, the spectral theory of the Jacobi operator on the cross-section of $C$, and a surjectivity argument showing that the map from compactly supported metric variations to forcing terms in the linearised minimal-surface equation on $C$ has dense range. Second, we establish that the set of metrics admitting no area-minimizer with a prescribed cone type as tangent cone is open, using compactness of integral currents and upper-semicontinuity of the density function. Third, we assemble these ingredients via a Baire category argument, intersecting countably many open dense sets to obtain the residual set $\mathcal{G}$. An extension to non-isolated singularities is outlined using Federer--Almgren dimension reduction.