Convexity Estimates for High Codimension Mean Curvature Flow

Abstract

We consider the evolution by mean curvature of smooth $n$-dimensional submanifolds in ${\mathbb{R}}^{n+k}$ which are compact and quadratically pinched. We will be primarily interested in flows of high codimension, the case $k\ge 2$. We prove that our submanifold is asymptotically convex, that is the first eigenvalue of the second fundamental form in the principal mean curvature direction blows up at a strictly slower rate than the mean curvature vector. We use this convexity estimate to show that at a singular time of the flow, there exists a rescaling that converges to a smooth codimension-one limiting flow which is convex and moves by translation.