A nonexistence result for rotating mean curvature flows in ℝ4

Abstract Some worrisome potential singularity models for the mean curvature flow are rotating ancient flows, i.e. ancient flows whose tangent flow at - ∞ {-\infty} is a cylinder ℝ k × S n - k {\mathbb{R}^{k}\times S^{n-k}} and that are rotating within the ℝ k {\mathbb{R}^{k}} -factor. We note that while the ℝ k {\mathbb{R}^{k}} -factor, i.e. the axis of the cylinder, is unique by the fundamental work of Colding-Minicozzi, the uniqueness of tangent flows by itself does not provide any information about rotations within the ℝ k {\mathbb{R}^{k}} -factor. In the present paper, we rule out rotating ancient flows among all ancient noncollapsed flows in ℝ 4 {\mathbb{R}^{4}} .