For mean curvature
flows in Euclidean spaces, Brian White proved a regularity theorem which
gives C2,α estimates in regions of spacetime where the Gaussian density
is close enough to 1. This is proved by applying Huisken’s monotonicity
formula. Here we will consider mean curvature flows in semi-Euclidean spaces,
where each spatial slice is an m-dimensional graph in ℝnm+n satisfying a
gradient bound stronger than the spacelike condition. By defining a suitable
quantity to replace the Gaussian density ratio, we prove monotonicity theorems
similar to Huisken’s and use them to prove a regularity theorem similar to
White’s.