Paper detail

Regularity of minimal submanifolds and mean curvature flows with a common free boundary

Let $N$ be a smooth $(n+l)$-dimensional Riemannian manifold. We show that if $V$ is an area-stationary union of three or more $C^{1,μ}$ $n$-dimensional submanifolds-with-boundary $M_k \subset N$ with a common boundary $Γ$, then $Γ$ is smooth and each $M_k$ is smooth up to $Γ$ (real-analytic in the case $N$ is real-analytic). This extends a previous result of the author for codimension $l = 1$. We additionally show that if $\{V_t\}_{t \in (-1,1)}$ is a Brakke flow such that each time-slice $V_t$ is a union of three or more $n$-dimensional submanifolds-with-boundary $M_{k,t} \subset N$ with a common boundary $Γ_t$ and with parabolic $C^{2+μ}$ regularity in time-space, then $\{Γ_t\}_{t \in (-1,1)}$ and $\{M_{k,t}\}_{t \in (-1,1)}$ are smooth (second Gevrey with real-analytic time-slices in the case $N$ is real-analytic).