On the regularity of stationary points of a nonlocal isoperimetric problem
Dorian Goldman, Alexander Volkmann · arXiv (Cornell University) · 2014
In this article we establish $C^{3,α}$-regularity of the reduced boundary of stationary points of a nonlocal isoperimetric problem in a domain $Ω\subset \mathbb{R}^n$. In particular, stationary points satisfy the corresponding Euler-Lagrange equation classically on the reduced boundary. Moreover, we show that the singular set has zero $(n-1)$-dimensional Hausdorff measure. This complements the results in Choksi & Sternberg, in which the Euler-Lagrange equation was derived under the assumption of $C^2$-regularity of the topological boundary and the results in Sternberg & Topaloglu in which the authors assume local minimality. In case $Ω$ has non-empty boundary, we show that stationary points meet the boundary of $Ω$ orthogonally in a weak sense, unless they have positive distance to it.