Rigidity theorems of complete K\"ahler-Einstein manifolds and complex   space forms
  We derive some elliptic differential inequalities from the Weitzenb\"ock formulas for the traceless Ricci tensor of a K\"ahler manifold with constant scalar curvature and the Bochner tensor of a K\"ahler-Einstein manifold respectively. Using elliptic estimates and maximum principle, some $L^p$ and $L^\infty $ pinching results are established to characterize K\"ahler-Einstein manifolds among K\"ahler manifolds with constant scalar curvature, and others are given to characterize complex space forms among K\"ahler-Einstein manifolds. Finally, these pinching results may be combined to characterize complex space forms among K\"ahler manifolds with constant scalar curvature. 
Tian Chong, Yuxin Dong, Hezi Lin and Yibin Ren
math.DG