Interior regularity of area minimizing currents within a $C^{2,α}$-submanifold
Stefano Nardulli, Reinaldo Resende
TL;DR
The work addresses interior regularity for area-minimizing $m$-currents $T$ in a $C^{2,\alpha}$ submanifold $\Sigma$, proving $\dim_{\mathcal{H}}(\operatorname{Sing}_{\mathrm{i}}(T))\le m-2$. Building on the De Lellis–Spadaro framework, the authors introduce an external center manifold $\mathcal{M}^{\ast}$ (potentially outside $\Sigma$) and an internal center manifold $\mathcal{M}$ (inside $\Sigma$), and develop Lipschitz approximations, $Q$-valued normal approximations $N^{\ast}$, and a Whitney decomposition to analyze branching. A PDE-based elliptic system controls the approximations on tilted cylinders, while a frequency function and a blow-up argument are used to derive a contradiction if the interior singular set were too large; this yields the desired bound and extends Allard–Allard–Almgren-type interior regularity to arbitrary codimension. The approach leverages a refined construction of $\mathcal{M}^{\ast}$ with $C^{3,\kappa}$ regularity to obtain the necessary monotonicity for the frequency, circumventing the need for $C^{3,\alpha}$-regularity of $\Sigma$ and enabling a codimension-robust interior regularity theory via Nash embedding considerations. The result sharpens the understanding of interior singularities for area-minimizing currents and provides a foundational tool for extending regularity results to Riemannian manifolds with low regularity.
Abstract
Given an area-minimizing integral $m$-current in $Σ$, we prove that the Hausdorff dimension of the interior singular set of $T$ cannot exceed $m-2$, provided that $Σ$ is an embedded $(m+\bar{n})$-submanifold of $\mathbb{R}^{m+n}$ of class $C^{2,α}$, where $α>0$. This result establishes the complete counterpart, in the arbitrary codimension setting, of the interior regularity theory for area-minimizing integral hypercurrents within a Riemannian manifold of class $C^{2,α}$.
