A NEW 3-PARAMETER CURVATURE CONDITION PRESERVED BY RICCI FLOW

Abstract. In this paper, we firstly establish a family of curvature in-variant conditions lying between the well-known 2-nonnegative curvature operator and nonnegative curvature operator along the Ricci flow. These conditions are defined by a set of inequalities involving the first four eigenvalues of the curvature operator, which are named as 3-parameter λ-nonnegative curvature conditions. Then a related rigidity property of manifolds with 3-parameter λ-nonnegative curvature operators is also de-rived. Based on these, we also obtain a strong maximum principle for the 3-parameter λ-nonnegativity along Ricci flow. 1. Introduction an