Willmore子流形的共形高斯映射

本文研究球空间中子流形的共形高斯映射,用Moebius不变量刻划了该映射 为调和映射的条件.作为特例,指出球空间的2维子流形的共形高斯映射是调和映射 当且仅当该子流形是Willmore子流形.     

复射影空间中子流形的Gauss映照

本文利用复射影空间到欧氏空间的第一标准嵌入，对于复射影空间的子流形建立了一种广义的Ｇａｕｓｓ映照，并给出了这种广义的Ｇａｕ８ｓ映照是调和映照和相对仿射映照的条件。     

The Gauss Map and Second Fundamental Form of Surfaces in \mathbb{R}^3

Given a surface S, a map N from S to and a conformal structure on S, we solve the problem of the existence and uniqueness of an immersion with a Gauss map N such that the conformal structure on S is the induced by the second fundamental form.     

On the Structure of Submanifolds with Degenerate Gauss Maps

An n-dimensional submanifold X of a projective space P ^N (C) is called tangentially degenerate if the rank of its Gauss mapping gamma;; X G(n, N) satisfies 0 < rank < n. The authors systematically study the geometry of tangentially degenerate submanifolds of a projective space P ^N (C). By means of the focal images, three basic types of submanifolds are discovered: cones, tangentially degenerate hypersurfaces, and torsal submanifolds. Moreover, for tangentially degenerate submanifolds, a structural theorem is proven. By this theorem, tangentially degenerate submanifolds that do not belong to one of the basic types are foliated into submanifolds of basic types. In the proof the authors introduce irreducible, reducible, and completely reducible tangentially degenerate submanifolds. It is found that cones and tangentially degenerate hypersurfaces are irreducible, and torsal submanifolds are completely reducible while all other tangentially degenerate submanifolds not belonging to basic types are reducible.     

集值Superpramart的上鞅逼近

文中讨论了可积随机集条件期望的若干性质,在此基础上,给出了集值Superpramart的上鞅逼近.同时,证明了集值Superpramart在Kuratowski-Mosco意义下的收敛定理.     

Rigidity and mean curvature flow via harmonic Gauss maps

We investigate properties of harmonic Gauss maps and their applications to Lawson-Osserman’s problem, to the rigidity of space-like submanifolds in a pseudo-Euclidean space and to the mean curvature flow.     

3维双曲空间中曲面的双曲Gauss映照和法Gauss映照

本文导出了3维双曲空间中曲面的双曲Gauss映照和法Gauss映照的关系,发现了一般的曲面由双曲Gauss映照和平均曲率函数唯一确定,并证明了双曲Gauss映照所满足的二阶线性椭圆方程,给出了两种形式的关于双曲Gauss映照的三阶非线性偏微分方程(组)的一个解.     

法联络平坦子流形与第二基本张量

本文首先将常曲率黎曼流形中Ｂ．Ｙ．Ｃｈｅｎ和Ｍ．Ｏｋｕｍｕｒａ关于数量曲率和截面曲率关系间的一个著名不等式推广到环绕空间是局部对称共形平坦黎曼流形的情形．作为应用，较简捷地将Ｍ．Ｏｋｕｍｕｒａ在［２］，［３］中的结果推广到这种环绕空间中法联络是平坦的子流形上去．     

保持高斯映射的仿射形变

给定Ｒｉｅｍａｎｎ流形到欧氏空间的仿射浸入ｆ：　Ｍｎ→ＲＮ　　，我们建立存在另一个与ｆ有相同高斯映射的仿射浸入ｆ：Ｍｎ→ＲＮ　　的条件，进一步利用这个条件，解答了仿射浸入的高斯映射将其确定到何种程度的问题．     

欧氏空间中具有共形Gauss映照的曲面

本文考虑欧氏空间中具有共形Ｇａｕｓｓ映照的曲面．从Ｇａｕｓｓ映照的观点给出了 ｖｅｒｏｎｅｓｅ曲面的一个新特征．     

Stability of Frobenius pull-backs of tangent bundles and generic injectivity of Gauss maps in positive characteristic

For a smooth projective variety X of dimension n in a projective space defined over an algebraically closed field k, the Gauss mapis a morphism from X to the Grassmannian of n-plans in sending to the embedded tangent space .The purpose of this paper is to prove the generic injectivity of Gauss mapsin positive characteristic for two cases; (1) weighted complete intersectionsof dimension of general type; (2) surfaces or 3-folds with -semistable tangent bundles; based on a criterion of Kaji by looking atthe stability of Frobenius pull-backs of their tangent bundles. The first result implies that a conjecture of Kleiman--Piene is true in case X is of general type of dimension . The second result is a generalization of the injectivity for curves.     

Minkowski空间中保高斯映射的共形形变

设Ｍｎ为Ｒｉｅｍａｎｎ流形，给定类空浸入：Ｍｎ→Ｒｎ，ｐ，如果存在另一个类空浸入：Ｍｎ→Ｒｎ，ｐ，使与在共形对应之下且对应点的地空间平行，则称类空子流形是可保高斯映射共形形变的．本文给出可保高斯映射共形形变的充要条件．对ｎ＝２，ｐ＝１的情形，如果上述形变是同向的，我们分类了曲面；如果是反向的，我们用主曲率满足的方程来描述．     

开平面C上的亚纯函数与完备极小曲面的Gauss映射

设■:D→R~3确定了以等温参数表示的极小曲面M,其中D是全平面R~2的开子区域,那么极小曲面的Gauss映射g(z)是D上的亚纯函数.Xavier与Chao提出了一个尚未解决的问题:任意给定区域■上的亚纯函数g(z),它是否是某完备极小曲面的Gauss映射?本文证明了若开平面C上的亚纯函数g(z)的零点列或极点列的收敛指数小于1/2,则g(z)—定是某完备极小曲面的Gauss映射.     

Sasakian空间形式中具有平行平均曲率向量的C-全实子流形

本文讨论了Sasakian空间形式中具有平行平均曲率向量的C-全实子流形,得到了一个Simons型公式并且改进了S.Yamaguchi等的一个结果.     

四维Minkowski空间中类空超曲面的双曲高斯映射的奇点

介绍了四维Minkowski空间中类空超曲面的局部理论,定义了类空超曲面上的双曲高斯映射,双曲高度函数及距离平方函数,给出了一些定理的详细证明.介绍了一种证明高度函数是Morse族的新方法并应用Arnold等建立的Lagrange奇点理论对类空超曲面的双曲高斯映射的奇点进行了分类.     

关于单位球面的子流形的一个Pinching定理

设Ｍ是单位球面的一个浸入子流形，ＵＭ＝∪ＵＭｘ是Ｍ的单位切丛.本文研究函数ｆ（ｘ）＝ｍａｘ－Ｂ（ｕ，ｕ）－Ｂ（ｖ，ｖ）２。其中Ｂ是Ｍ的第二基本形式．当Ｍ具平行平均曲率时，我们给出关于第二基本形式的一个Ｐｉｎｃｈｉｎｇ定理．对Ｍ是极小的情形，我们有相同的讨论．     

不定复空间型中具有平行平均曲率向量的完备全实类空子流形

利用活动标架法和广义极大值原理研究了不定复射影空间中完备的具有平行平均曲率向量的全实类空子流形,得到这类子流形的Pinching定理.     

Complete Space－like Submanifolds in a de Sitter Space with Parallel Mean CurvatureVector

ＣｏｍｐｌｅｔｅＳｐａｃｅ－ｌｉｋｅＳｕｂｍａｎｉｆｏｌｄｓｉｎａｄｅＳｉｔｔｅｒＳｐａｃｅｗｉｔｈＰａｒａｌｌｅｌＭｅａｎＣｕｒｖａｔｕｒｅＶｅｃｔｏｒＳｈｕＳｈｉｃｈａｎｇ（ＸｉａｎｙａｎｇＴｅａｃｈｅｒｓＣｏｌｌｅｇｅ，Ｘｉａｎｙａｎｇ，７１２...     

指标为2的半四维欧氏空间中三维Lorentzian子流形的Anti de Sitter高斯映射的奇点

作为R_(2~4)空间中子流形研究的补充工作,试图利用Lagrange奇点理论对R_(2~4)空间中三维Lorentzian子流形的微分几何性质及奇异性进行研究.     

The separability of the Gauss map and the reflexivity for a projective surface

It is known that if a projective variety X in P ^N is reflexive with respect to the projective dual, then the Gauss map of X defined by embedded tangent spaces is separable, and moreover that the converse is not true in general. We prove that the converse holds under the assumption that X is of dimension two. Explaining the subtleness of the problem, we present an example of smooth projective surfaces in arbitrary positive characteristic, which gives a negative answer to a question raised by S. Kleiman and R. Piene on the inseparability of the Gauss map.