简介:LetM^nbeaclosedspacelikesubmanifoldisometricallyimmersedindeSitterspaceSp^(n+p)(c),DenotebyR,HandSthenormalizedscalarcurvature,themeancurvatureandthesquareofthelengthofthesecondfundamentalformofM^n,respectively.SupposeRisconstantandR≤c.ThepinchingproblemonSisstudiedandarigiditytheoremforM^nimmersedinSp^(n+p)(c)withparallelnormalizedmeancurvaturevectorfieldisproved.Whenn≥3,thepinchingconstantisthebest.Thus,themistakeofthepaper“Space-likehypersurfacesindeSitterspacewithconstantscalarcurvature”(seeManusMath,1998,95:499-505)iscorrected.Moreover,thereductionofthecodimensionwhenM^nisacompletesubmanifoldinSp^(n+p)(c)withparallelnormalizedmeancurvaturevectorfieldisinvestigated.