正平均曲率的一个注记

设Ω是R~n(n≥2)中的单连通有界开集,其边界骪Ω是无限可微的封闭超曲面。设H(S)是Ω的平均曲率(n=2,H(s)是曲率)。假定s∈Ω,H(s)>0。记 则我们证明 ii)H_0/H_1≤(1-1/n)~2|Ω|/|Ω|~2 integral from n=Ω to (ds)/(H(s))~2, iii)|Ω|≤(1-1/n)integral from n=Ω to (ds)/H(s), 我们有如下未解决问题:是否成立不等式     

De Sitter空间的2-调和超曲面

设M是de sitter空间S1^n 1(1)的紧致2－调和类空超曲面，获得了关于M的第二基本形式模长平方的Pinching结果。     

关于《2型球面超曲面》一文的注记

本文证明了2型球面紧致超曲面是1型的，因而是质量对称的．换言之，不存在2型球面紧致超曲面，推广了文［2，3，4，5」中的结论．     

de Sitter空间中第二基本形式模长平方为常数的类空超曲面

设Mn是de Sitter空间S1n+1+1(c)中具有第二基本形式模长平方‖h‖2是常数的类空超曲面,利用极大值原理得到了Mn是全脐超曲面的三个充分条件.     

Sn+1(1)内凸超曲面为边界的区域的第一特征值估计

M是Sn+1(1)内紧致嵌入凸超曲面.M分Sn+1(1)为两个连通区域Ω1和Ω2. Ω1=M和Ω1是凸的.本文估计了Ω1的Laplace算子的第一特征值的下界.     

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。     

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流形中的类空超曲面

1.引言在[1]中,Calabi证明了n+1(n≤4)维Minkowski空间中的完备极大类空超曲面是全测地的。在[2]中 , Cheng-Yau对所有的n证明了这一结论。在[3]中,对于某一类Lorentz流形,Nishikawa证明了类似的结果。并且在[2]中,Cheng-Yau还证明了当具有常数平均曲率的类空超曲面M是Minkowski空间的闭子集时,有     

常曲率空间的半平行超曲面和高阶平行超曲面的分类

本文给出了非欧氏常曲率空间Ｎ＾ｎ＋１（Ｃ）的半平行超曲面的分类，并利用此分类定理证明了非欧氏常曲率空间的高阶平行超曲面与平行超曲面的等价性，从而也给出了非欧氏常曲率空间的高阶平行超曲面的分类；     

Null screen quasi-conformal hypersurfaces in semi-Riemannian manifolds and applications

We introduce a class of null hypersurfaces of a semi-Riemannian manifold, namely, screen quasi-conformal hypersurfaces, whose geometry may be studied through the geometry of its screen distribution. In particular, this notion allows us to extend some results of previous works to the case in which the sectional curvature of the ambient space is different from zero. As applications, we study umbilical, isoparametric and Einstein null hypersurfaces in Lorentzian space forms and provide several classification results.     

Semi-parallel real hypersurfaces in complex two-plane Grassmannians

We prove that there does not exist any semi-parallel real hypersurface in complex two-plane Grassmannians. With this result, the nonexistence of recurrent real hypersurfaces in complex two-plane Grassmannians can also be proved.     

共形空间${\mathbb Q}^{n+1}_1$中类空超曲面的拼挤问题

通过对第二共形基本形式的模长平方作拼挤,给出Clifford超柱面的一个共形特征.     

Compact embedded rotation hypersurfaces of <Emphasis Type="Italic">S</Emphasis><Superscript><Emphasis Type="Italic">n</Emphasis>+1</Superscript>

In this paper, we prove that and round geodesic spheres are the only n-dimensional compact embedded rotation hypersurfaces with H_m = 0 (1 ≤ m ≤ n − 1) in a unit sphere Sⁿ⁺¹(1). When m = 1, our result reduces to the result of T. Otsuki [O1], [O2], Brito and Leite [BL]. The project is supported by the grant No. 10531090 of NSFC.     

Hopf hypersurfaces in space forms

Some geometrical properties of Hopf hypersurfaces of Kähler manifolds are introduced and a special attention is given to the case of hypersurfaces in complex projective spaces.     

Hopf hypersurfaces in pseudo-Riemannian complex and para-complex space forms

The study of real hypersurfaces in pseudo-Riemannian complex space forms and para-complex space forms, which are the pseudo-Riemannian generalizations of the complex space forms, is addressed. It is proved that there are no umbilic hypersurfaces, nor real hypersurfaces with parallel shape operator in such spaces. Denoting by J be the complex or para-complex structure of a pseudo-complex or para-complex space form respectively, a non-degenerate hypersurface of such space with unit normal vector field N is said to be Hopf if the tangent vector field JN is a principal direction. It is proved that if a hypersurface is Hopf, then the corresponding principal curvature (the Hopf curvature) is constant. It is also observed that in some cases a Hopf hypersurface must be, locally, a tube over a complex (or para-complex) submanifold, thus generalizing previous results of Cecil, Ryan and Montiel.     

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．