3维单位球面中保主曲率的曲面的变形

在[1]中,陈省身大师讨论了欧氏空间 E~3保主曲率的曲面的变形,本文,考虑了维单位球面 S~3中相同的问题,并给出了分类定理。     

单位球面中极小子流形的曲率拼挤

本文证明了单位球面中极小子流形的一些拼挤定理,特别注意到单位球面中的极小超曲面、给出了截曲率的拼挤常数,我们也改进了由Ｎ．Ｅｊｉｒｉ得到的Ｒｉｃｃｉ曲率拼挤常数。     

S4(1)中常数量曲率的完备超曲面

本文把[1]的结论推广到超曲面是完备的情形,即我们证明了:设M³是单位球面S⁴(1)中常平均曲率及常数量曲率的完备超曲面。若S≤H²+6,则S只能等于1/3H²,3/4H²—1/4(H⁴+8H²)^1/2+3,(3/4)H²+1/4(H⁴+8H²)^{1/2相似文献}   

Lorentz空间中常平均曲率类空超曲面

本文证明了ｎ＋１维Ｌｏｒｅｎｔｚ空Ｌｎ＋１中以Ｓｎ－１（ｒ）为边界的紧致常平均曲率类空超曲面只有 Ｂｎ（ｒ）和超伪球面盖．对于 Ｒｎ＋１中的紧致常平均曲率超曲面，当高斯映照像落在一个半球面内时，得到相应的唯一性结果．     

球面2型超曲面

本文在无先念条件下,证明了Ｃｈｅｎ［１］关于２型超曲面的一个定理．     

球面中具有常平均曲率超曲面的谱特征

本文中，我们研究了一类Schroedinger算子的第一特征值，给出了S^n 1中一类常平均曲率超曲面的特征，并得到了这种超曲面的谱几何，从而推广了第二作者的有关结果。     

单位球面中具平行单位平均曲率向量的子流形

设M是n-维闭黎曼流形,等距浸入(n+p)-维单位球空间S^n+p,具有平行的单位平均曲率向量。若S≤min{2n/3,2(n-1)^1/2},其中S是M的第二基本形式长度的平方,则M是S^n+p的一个(n+1)-维全测地子流形Sⁿ⁺¹中的超曲面。     

球面2型超曲面

本文在无先念条件下,证明了Chen     

子流形与拓扑球面定理

本文建立了球面Sn p(c) (c>0 )中的完备子流形的一个拓扑球面定理 ,结果表明完备子流形的拓扑是受其内在和外在曲率不变量满足的某些条件所影响的     

球面上紧超曲面的等谱问题

本文讨论了球面上全脐超曲面与全测地超曲面的等谱问题。     

A Rigidity Theorem for Compact Hypersurfaces with an Upper Bound for the Ricci Curvature

We focus our attention on compact hypersurfaces with Ricci curvature bounded from above and we give a sufficient condition for them to be spherical. This generalizes and completes previous results.     

Unit Tangent Sphere Bundles with Constant Scalar Curvature

As a first step in the search for curvature homogeneous unit tangent sphere bundles we derive necessary and sufficient conditions for a manifold to have a unit tangent sphere bundle with constant scalar curvature. We give complete classifications for low dimensions and for conformally flat manifolds. Further, we determine when the unit tangent sphere bundle is Einstein or Ricci-parallel.     

The Hypersurfaces in a Unit Sphere with Nonnegative Mobius Sectional Curvature

Let x ： M→S^n＋1 be a hypersurface in the （n ＋ 1）-dimensional unit sphere S^n＋1 without umbilic point. The Mobius invariants of x under the Mobius transformation group of S^n＋1 are Mobius metric, Mobius form, Mobius second fundamental form and Blaschke tensor. In this paper, we prove the following theorem： Let x ： M→S^n＋1 （n≥2） be an umbilic free hypersurface in S^n＋1 with nonnegative Mobius sectional curvature and with vanishing Mobius form. Then x is locally Mobius equivalent to one of the following hypersurfaces： （i） the torus S^k（a） × S^n-k（√1- a^2） with 1 ≤ k ≤ n - 1; （ii） the pre-image of the stereographic projection of the standard cylinder S^k × R^n-k belong to R^n＋1 with 1 ≤ k ≤ n- 1; （iii） the pre-image of the stereographic projection of the Cone in R^n＋1 ： -↑x（u, v, t） = （tu, tv）, where （u,v, t）∈S^k（a） × S^n-k-1（ √1-a^2）× R^＋.     

Rigidity Theorem of Hypersurfaces with Constant Scalar Curvature in a Unit Sphere

In this paper, we give a characterization of tori S^1 （ √ nr＋2-n/nr）×S^n-1（√ n-2/nr） and S^m （ √n/m ） ×S^n-m （√n-m/n）. Our result extends the result due to Li （1996）on the condition that M is an n-dimensional complete hypersurface in Sn＋1 with two distinct principal curvatures. Keywords principal curvature, Clifford torus, Gauss equations     

单位球面上具有非负M bius截面曲率的超曲面

Let x:M→S~(n 1)be a hypersurface in the (n 1)-dimensional unit sphere S~(n 1)without umbilic point. The M(?)bius invariants of x under the M(?)bius transformation group of S~(n 1) are M(?)bius metric,M(?)bius form,M(?)bius second fundamental form and Blaschke tensor.In this paper,we prove the following theorem: Let x:M→S~(n 1)(n＞2)be an umbilic free hypersurface in S~(n 1) with nonnegative M(?)bius sectional curvature and with vanishing M(?)bius form.Then x is locally M(?)bius equivalent to one of the following hypersurfaces:(i)the torus S~k(a)×S~(n-k)((1-a~2)~(1/2))with 1≤k≤n-1;(ii)the pre-image of the stereographic projection of the standard cylinder S~k×R~(n-k)(?)R~(n 1) with 1≤k≤n-1;(iii)the pre-image of the stereographic projection of the cone in R~(n 1):(?)(u,v,t)=(tu,tv), where(u,v,t)∈S~k(a)×S~(n-k-1)((1-a~2)~(1/2))×R~ .     

Mean Curvature and Volume of Extrinsic Spheres in Hypersurfaces of Real Space Forms

Given a hypersurface P^n-1 in a real space form of constantcurvature b, , we have obtained a lower bound for the norm of the mean curvature normal vector field of extrinsicspheres in P^n-1 in terms of the mean curvature of the geodesic spheres in , with the same radius, and the meancurvature of P^n-1, characterizing too the equality.     

Minimizing Constant Mean Curvature Hypersurfaces in Hyperbolic Space

We study the constant mean curvature (CMC) hypersurfaces in whose asymptotic boundaries are closed codimension-1 submanifolds in . We consider CMC hypersurfaces as generalizations of minimal hypersurfaces. We naturally generalize some notions of minimal hypersurfaces like being area-minimizing, convex hull property, exchange roundoff trick to CMC hypersurface context. We also give a generic uniqueness result for CMC hypersurfaces in hyperbolic space.     

The Isometry of Riemannian Manifold to a Sphere

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