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．     

李奇曲率平行的黎曼流形到欧氏空间的等距浸入

设ｆ：Ｍｎ→Ｒｎ＋ｐ为具平行李奇曲率的黎曼流形到欧氏空间的等距浸入．对ｐ＝１，本文给出了极小条件下以及平均曲率处处非零条件下该浸入的分类     

3-空间曲面上的一个重要向量场及相关结果

设 ｆ：Ｍ２（Ｃ）→ Ｎ３（ｃ）是 ２－维黎曼流形 Ｍ２到 ３维空间形式 Ｎ３（Ｃ）的等距浸入．找到一个由Ｍ２的第二基本形式确定的向量场 δ ，使得高斯曲率 Ｋ表为其散度 Ｋ＝ ｄｉｖ（δ）．在 Ｎ３（ｃ）＝ Ｅ３的情形，证明了ｆ可保持反定向高斯映射共形形变的充要条件是δ为闭向量场．对于可保持反定向高斯映射共形形变的曲面，本文给出了其形变象的表示公式     

环的自映射的最少周期点数

设Ｘ是一个紧致连通的ＡＮＲ＇ｓ，ｆ：Ｘ→Ｘ是连续映射。于是ｆ有Ｎｉｅｌｓｅｎ型数，ＮＦｎ（ｆ），它是数集｛＃Ｆｉｘ（ｇ＾ｎ）ｇ－ｆ｝的下界。本文在Ｘ是环时，给出ＮＦｎ（ｆ）是该数集的下确界，即存在连续映射ｇ＝ｆ，使得＃Ｆｉｘ（ｇ＾ｎ）＝ＮＦｎ（ｆ）的一个充分条件。     

平行三次形式的仿射超曲面

设Ａｎ 1是ｎ 1维仿射空间 ,Ｄ表示Ａｎ 1上的平坦联络 ,Ｍ是ｎ维光滑流形 ,ｘ:Ｍ→Ａｎ 1是一个非退化的仿射浸入 .对于Ｍ上的横截向量场ξ ,存在唯一的选择 ξ =1ｎ△ｘ(称为仿射法向量场 ) ,使得上述浸入是一个Ｂｌａｓｃｈｋｅ浸入 (见 [2 ]) .设 是此浸入由Ｄ在Ｍ上诱导的仿射联络 ,我们有 :ＤＸＹ= ＸＹ ｈ(Ｘ ,Ｙ) ξ　　　ＤＸξ=-ＳＸ这里Ｘ ,Ｙ ,Ｚ是Ｍ上的切向量场 ,ｈ是对称的双线性形式 ,由它可以定义Ｍ上的伪黎曼度量Ｇ(Ｇ =|Ｈ| - 1ｎ 2 ｈ ,Ｈ =ｄｅｔ(ｈｉｊ) ) ,称为Ｂｌａｓｃｈｋｅ度量 ,Ｓ称为Ｍ的形态算子 .若…     

多叶函数的Krzyz定理

设α是单叶函数ｆ（ｚ）的Ｈａｙｍａｎ指数，Ｋｒｚｙｚ证明了（１－ｒ）＾３Ｍ（ｒ，ｆ＇）→２α（ｒ→１）。本文将这个结果推广到多叶函数ｆ（ｚ）的ｎ次导数ｆ＾（ｎ）（ｚ）的情形，我们所使用的方法与Ｋｒｚｙｚ的不同。     

复射影空间的等参子流形

本文给出了复射影空间Ｐ＿ｎ（Ｃ）上的等参映射定义，并证明了等参映射ｆ在Ｈｏｐｆ主丛π：Ｓ￣（２ｎ＋１）→Ｐ＿ｎ（Ｃ）下的水平提升为Ｓ￣（２ｎ＋１）的等参映射。同时，利用对称空间的表示给出了Ｐ＿ｎ（Ｃ）上等参子流形的例子．     

实有限可除代数间保矩阵M—P逆的共变算子对

设Ｄ,Ｄ１ 和Ｄ２ 是实有限可除代数,Ｍｍｎ（Ｄ）是Ｄ上所有ｍ ×ｎ矩阵的Ｒ线性空间． 若两个Ｒ线性算子ｆ：Ｍｍ ｎ（Ｄ１）→Ｍｍｎ（Ｄ２） 和ｇ：Ｍｎｍ （Ｄ１） →Ｍｎｍ （Ｄ２）满足ｆ（Ａ）＋ ＝ ｇ（Ａ＋ ）对于一切的Ａ∈Ｍｍ ｎ（Ｄ１）均成立,则称（ｆ, ｇ） 是一个保矩阵ＭＰ逆的共变算子对． 当ｍ ｉｎ（ｍ , ｎ）２时,本文刻划了所有这种共变算子对（ｆ, ｇ） 的结构．     

关于内映射的复合

本文证明，如果Ｆ：Ｂｋ→Ｂｍ是保测度的内映射，Ｇ：Ｂｍ→Ｂｎ是内映射，则复合映射ＧＦ：Ｂｋ→Ｂｎ是内映射．这样，在较弱的条件下，肯定地回答了Ｗ．Ｒｕｄｉｎ在文［１］中提出的第５公开问题     

Hilbert模形式与一类Dirichlet级数的特殊值

在文［２］中，Ｗ．Ｋｏｈｎｎ对权为ｋ和ｌ的任意二个歧点型模形式ｆ和ｇ（其变换群是全模群ＳＬ＿２（Ｚ））定义了一类Ｄｉｒｉｃｈｌｅｔ级数Ｌ＿（ｆ，ｇ，ｎ）（ｓ），利用Ｌ＿（ｆ，ｇ；ｎ）（ｓ）（为整数），可构造一个线性映射Ｗ＿ｇ：Ｓ＿ｋ→Ｓ＿（ｋ－ｌ）．并且讨论了Ｌ＿（ｆ，ｇ；ｎ）的一些特征值．在本文中，我们将［２］中的结果推广到Ｈｉｌｂｅｒｔ模形式的情况，并得到类似的结论．     

Equiaffine immersions of general codimension and its transversal volume element map

With an equiaffine immersion of codimension 1 into the affine space with the natural equiaffine structure, the conormal map is associated. In this paper, for an equiaffine immersion of general codimension into the space, we shall define the map corresponding to the conormal map, which is called the transversal volume element map. And we shall investigate if, an equiaffine immersion of general codimension into the space is determined by its affine fundamental form and its transversal volume element map.     

A generalization of Lelieuvre’s formula to equiaffine immersions of general codimension

A non-degenerate equiaffine immersion of codimension one into an equiaffine space is locally expressed in terms of its conormal map and its affine fundamental form. The expression is called the Lelieuvre’s formula. We recently defined the notions of an equiaffine immersion of general codimension and its transversal volume element map. In this paper, we locally express a non-degenerate equiaffine immersion of general codimension into an equiaffine space in terms of its transversal volume element map and its affine fundamental form.     

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。     

HYPERSURFACES IN SPACE FORMS WITH SCALAR CURVATURE CONDITIONS

Let f : M^n→S^n 1真包含于R^n 2 be an n-dimensional complete oriented Riemannian manifold minimally immersed in an (n 1)-dimensional unit sphere S^n 1. Denote by S^n 1 the upper closed hemisphere. If f(M^n)包含于S ^n 1, then under some curvature conditions the authors can get that the isometric immersion is a totally embedding. They also generalize a theorem of Li Hai Zhong on hypersurface of space form with costant scalar curvature.     

The Center Map of an Affine Immersion

We study the center map of an equiaffine immersion which is introduced using the equiaffine support function. The center map is a constant map if and only if the hypersurface is an equiaffine sphere. We investigate those immersions for which the center map is affine congruent with the original hypersurface. In terms of centroaffine geometry, we show that such hypersurfaces provide examples of hypersurfaces with vanishing centroaffine Tchebychev operator. We also characterize them in equiaffine differential geometry using a curvature condition involving the covariant derivative of the shape operator. From both approaches, assuming the dimension is 2 and the surface is definite, a complete classification follows. Received: May 24, 2006. Revised: July 26, 2006. Accepted: July 28, 2006.     

On holomorphic immersions into K(a)hler manifolds of constant holomorphic sectional curvature

We study holomorphic immersions f: X → M from a complex manifold X into a Kahler manifold of constant holomorphic sectional curvature M, i.e. a complex hyperbolic space form, a complex Euclidean space form, or the complex projective space equipped with the Fubini-Study metric. For X compact we show that the tangent sequence splits holomorphically if and only if f is a totally geodesic immersion. For X not necessarily compact we relate an intrinsic cohomological invariant p(X) on X, viz. the invariant defined by Gunning measuring the obstruction to the existence of holomorphic projective connections, to an extrinsic cohomological invariant v(f)measuring the obstruction to the holomorphic splitting of the tangent sequence. The two invariants p(X) and v(f) are related by a linear map on cohomology groups induced by the second fundamental form.In some cases, especially when X is a complex surface and M is of complex dimension 4, under the assumption that X admits a holomorphic projective connection we obtain a sufficient condition for the holomorphic splitting of the tangent sequence in terms of the second fundamental form.     

球面上具有相对仿射共形Gauss映照的超曲面

用Moebius不变量刻画了单位球面上的子流形的共形Gauss映照为相对仿射映照的充要条件,给出了单位球面上具有相对仿射共形 Gauss映照的所有超曲面的分类.     

The Gauss map of a hypersurface in Euclidean sphere and the spherical Legendrian duality

We investigate the Gauss map of a hypersurface in Euclidean n-sphere as an application of the theory of Legendrian singularities. We can interpret the image of the Gauss map as the wavefront set of a Legendrian immersion into a certain contact manifold. We interpret the geometric meaning of the singularities of the Gauss map from this point of view.     

Another Rigidity Theorem for Affine Immersions

The theorem of Beez-Killing in Euclidean differential geometry states as follows [KN, p.46]. Let f: M ⁿ → Rⁿ⁺¹ be an isometric immersion of an n-dimensional Riemannian manifold into a Euclidean (n + l)-space. If the rank of the second fundamental form of f is greater than 2 at every point, then any isometric immersion of M ⁿ into R ^{n +} 1 is congruent to f. A generalization of this classical theorem to affine differential geometry has been given in [O] (see Theorem 1.5). We shall give in this paper another version of rigidity theorem for affine immersions.     

常曲率流形中具平行李奇曲率的超曲面

设f:M~n→M~(n+1)(c)为具平行李奇曲率的黎曼流形到常曲率流形的等距浸入,本文给出了该超曲面的分类。另外,若M~n还是极小超曲面,本文也给出了该超曲面的分类,推广了Lawson的有关结果。