Gap theorem on K\"ahler manifold with nonnegative orthogonal bisectional curvature

In this paper we prove a gap theorem for K"ahler manifolds with nonnegative orthogonal bisectional curvature and nonnegative Ricci curvature, which generalizes an earlier result of the first author. We also prove a Liouville theorem for plurisubharmonic functions on such a manifolds, which generalizes a previous result of L.-F. Tam and the first author.