a1 Department of Applied Mathematics, Xidian University, Xi'an 710071, Shaanxi, Peoples Republic of China, e-mail: xysxssc@yahoo.com.cn
a2 Department of Mathematics, Xianyang Teachers' University, Xianyang 712000, Shaanxi, Peoples Republic of China
In this paper, we consider n (n ≥ 3)-dimensional compact oriented connected hypersurfaces with constant scalar curvature n(n − 1)r in the unit sphere Sn+1(1). We prove that, if r ≥ (n − 2)/(n − 1) and S ≤ (n − 1)(n(r − 1) + 2)/(n − 2) + (n − 2)/(n(r − 1) + 2), then either M is diffeomorphic to a spherical space form if n = 3; or M is homeomorphic to a sphere if n ≥ 4; or M is isometric to the Riemannian product
, where c2 = (n − 2)/(nr) and S is the squared norm of the second fundamental form of M.
(Received September 30 2003)