Einstein metrics and preserved curvature conditions for the Ricci flow
arXiv:1004.0290
Abstract
Let C be a cone in the space of algebraic curvature tensors. Moreover, let (M,g) be a compact Einstein manifold with the property that the curvature tensor of (M,g) lies in the cone C at each point on M. We show that (M,g) has constant sectional curvature if the cone C satisfies certain structure conditions.
To appear in Proceedings of CDG 2009, Hannover