New Pinching Estimates for Inverse Curvature Flows in Space Forms

We consider the inverse curvature flow of strictly convex hypersurfaces in the space form N of constant sectional curvature K-N with speed given by F-alpha, where alpha is an element of(0, 1] for K-N = 0, - 1 and alpha = 1 for K-N = 1, F is a smooth, symmetric homogeneous of degree one function which is inverse concave and has dual F-* approaching zero on the boundary of the positive cone Gamma(+). We show that the ratio of the largest principal curvature to the smallest principal curvature of the flow hypersurface is controlled by its initial value. This can be used to prove the smooth convergence of the flows.