Khler Manifolds with Almost Non-negative Ricci Curvature

Compact Kǎhler manifolds with semi-positive Ricci curvature have been inves-tigated by various authors. From Peternell＇s work, if M is a compact Kǎhler n-manifold with semi-positive Ricci curvature and finite fundamental group, then the universal cover has a decomposition M≌X1 χ …x Xm, where Xj is a Calabi-Yau manifold, or a hy-perKǎhler manifold, or Xj satisfies H^0（Xj,Ωp） = 0. The purpose of this paper is to generalize this theorem to almost non-negative Ricci curvature Kǎhler manifolds by us-ing the Gromov-Hansdorff convergence. Let M be a compact complex n-manifold with non-vanishing Euler number. If for any ε〉0, there exists a Kǎhler structure （Jε,gε） on M such that the volume Volgε（M） 〈 V, the sectional curvature ｜K（gε）｜〈 A^2, and the Ricci-tensor Ric（gε）〉-εgε, where V and A are two constants independent of ε. Then the fundamental group of M is finite, and M is diffeomorphic to a complex manifold X such that the universal covering of X has a decomposition, X≌X1 x … x Xs, where Xi is a Calabi-Yau manifold, or a hyperKǎhler manifold, or Xi satisfies H^0（Xi, Ωp）={0}, p 〉 0.

ON A NEW DEFINITION OF RICCI CURVATURE ON ALEXANDROV SPACES

Recently, in [49], a new definition for lower Ricci curvature bounds on Alexandrov spaces was introduced by the authors. In this article, we extend our research to summarize the geometric and analytic results under this Ricci condition. In particular, two new results, the rigidity result of Bishop-Gromov volume comparison and Lipschitz continuity of heat kernel, are obtained.

ON SHRINKING GRADIENT RICCI SOLITONS WITH POSITIVE RICCI CURVATURE AND SMALL WEYL TENSOR

We show that closed shrinking gradient Ricci solitons with positive Ricci curvature and sufficiently pinched Weyl tensor are Einstein. When Weyl tensor vanishes, this has been proved before but our proof here is much simpler.

Open Manifolds with Nonnegative Ricci Curvature and Large Volume Growth

In this paper, we prove that if M is an open manifold with nonnegativeRicci curvature and large volume growth, positive critical radius, then sup Cp = ∞.As an application, we give a theorem which supports strongly Petersen's conjecture.

Navigation Finsler metrics on a gradient Ricci soliton

In this paper,we study a class of Finsler metrics defined by a vector field on a gradient Ricci soliton.We obtain a necessary and sufficient condition for these Finsler metrics on a compact gradient Ricci soliton to be of isotropic S-curvature by establishing a new integral inequality.Then we determine the Ricci curvature of navigation Finsler metrics of isotropic S-curvature on a gradient Ricci soliton generalizing result only known in the case when such soliton is of Einstein type.As its application,we obtain the Ricci curvature of all navigation Finsler metrics of isotropic S-curvature on Gaussian shrinking soliton.

A DIFFERENTIABLE SPHERE THEOREM WITH PINCHING INTEGRAL RICCI CURVATURE

In this article, we introduce the Hausdorff convergence to derive a differentiable sphere theorem which shows an interesting rigidity phenomenon on some kind of manifolds.

Ricci Curvature of Certain Submanifolds in Kenmotsu Space Forms

In this paper, we obtain some sharp inequalities between the Ricci cur- vature and the squared mean curvature for bi-slant and semi-slant submanifolds in Kenmotsu space forms. Estimates of the scalar curvature and the k-Ricci curvature, in terms of the squared mean curvature, are also proved respectively.

梯度Ricci-Yamabe孤立子的一些刚性结果

应用散度定理及一些Riemann流形上的重要不等式,并结合几何分析的方法研究紧致梯度Ricci-Yamabe孤立子的刚性问题,在适当的条件下得到非平凡紧致梯度Ricci-Yamabe孤立子与欧氏球面等距的刚性结果.此外,在数量曲率为正的假设下,证明满足L^(n/2)-积分拼挤条件的n(4≤n≤6)维紧致梯度收缩Ricci-Yamabe孤立子一定是Einstein流形.

Complete Open Manifolds with Nonnegative Ricci Curvature

In this paper, we study complete open manifolds with nonnegative Ricci curvature and injectivity radius bounded from below. We find that this kind of manifolds are diffeomorphic to a Euclidean space when certain distance functions satisfy a reasonable condition.

The Manifolds with Ricci Curvature Decay to Zero

The paper quotes the concept of Ricci curvature decay to zero. Base on this new concept, by modifying the proof of the canonical Cheeger-Gromoll Splitting Theorem, the paper proves that for a complete non-compact Riemannian manifold M with Ricci curvature decay to zero, if there is a line in M, then the isometrically splitting M = R × N is true.

Small Excess and the Topology of Open Manifolds with Ricci Curvature Negatively Lower Bounded

In this paper, we study the relation between the excess of open manifolds and their topology by using the methods of comparison geometry. We prove that a complete open Riemmannian manifold with Ricci curvature negatively lower bounded is of finite topological type provided that the conjugate radius is bounded from below by a positive constant and its Excess is bounded by some function of its conjugate radius, which improves some results in [4].

Manifolds with Bakry-Emery Ricci Curvature Bounded Below

In this paper we show that, under some conditions, if M is a manifold with Bakry-émery Ricci curvature bounded below and with bounded potential function then M is compact. We also establish a volume comparison theorem for manifolds with nonnegative Bakry-émery Ricci curvature which allows us to prove a topolological rigidity theorem for such manifolds.

M-Eigenvalues of the Riemann Curvature Tensor of Conformally Flat Manifolds

We investigate the M-eigenvalues of the Riemann curvature tensor in the higher dimensional conformally flat manifold.The expressions of Meigenvalues and M-eigenvectors are presented in this paper.As a special case,M-eigenvalues of conformal flat Einstein manifold have also been discussed,and the conformal the invariance of M-eigentriple has been found.We also reveal the relationship between M-eigenvalue and sectional curvature of a Riemannian manifold.We prove that the M-eigenvalue can determine the Riemann curvature tensor uniquely.We also give an example to compute the Meigentriple of de Sitter spacetime which is well-known in general relativity.

COMPLETE HYPERSURFACES WITH CONSTANT MEAN CURVATURE AND FINITE INDEX IN HYPERBOLIC SPACES

In this article, we prove that any complete finite index hypersurface in the hyperbolic space H4（-1）（H5（-1）） with constant mean curvature H satisfying H2 6634 （H2 114785 respectively） must be compact. Specially, we verify that any complete and stable hypersurface in the hyperbolic space H4（-1） （resp. H5（-1）） with constant mean curvature H satisfying H2 6643 （resp. H2 114785 ） must be compact. It shows that there is no manifold satisfying the conditions of some theorems in [7, 9].

Quasi-con form ally Flat Manifolds with Constant Scalar Curvature

Goldberg and Wu studied a conformally flat manifold M with constant scalar curvature. When the Ricci curvature of M is of bounded below or positive,the conditions of M becoming a constant curvature manifold are obtained. In this paper,we consider conharmonically flat manifolds and quasi conformally flat manifolds with constant saclar curvature. The corresponding results are generalized.

射影Ricci曲率及其射影不变性

研究了芬斯勒几何中一类新的几何量,即射影Ricci曲率.刻划了两个射影等价的芬斯勒度量的射影Ricci曲率的关系.特别地,在一个给定体积形式的流形上,如果两个芬斯勒度量F和F是射影等价的,那么它们的射影Ricci曲率是相等的,即此时的射影Ricci曲率是射影不变量.

射影Ricci平坦的Kropina度量

本文研究和刻画了射影Ricci平坦的Kropina度量.利用Kropina度量的S-曲率和Ricci曲率的公式,得到了Kropina度量的射影Ricci曲率公式.在此基础上得到了Kropina度量是射影Ricci平坦度量的充分必要条件.进一步,作为自然的应用,本文研究和刻画了由一个黎曼度量和一个具有常数长度的Killing 1-形式定义的射影Ricci平坦的Kropina度量,也刻画了具有迷向S-曲率的射影Ricci平坦的Kropina度量.在这种情形下,Kropina度量是Ricci平坦度量.

一类椭圆方程的梯度估计

通过计算与推导,得到了n维完备黎曼流形上椭圆方程Δ_(g)u+au^(q)(ln u)^(p)+bu=0正解的梯度估计,其不依赖于解的界和距离函数的拉普拉斯(Laplace)算子;将文献[1]中对正调和函数的梯度估计推广到更一般的情形;将文献[10]中对一类椭圆方程正解的梯度估计进行了拓展,得到了更具一般性的结果.

黎曼流形上度量的Ricci流的一个定理

利用Huisken的热流方法 ,推广了Hamilton的 3维Ricci流的著名结果 .证明了一个球面定理 :如果黎曼曲率张量的模长和它的数量曲率分量U的模长的比接近于 1,则M容许一个正的常曲率的度量 .

具有非负Ricci曲率和次大体积增长的完备流形(英文)

本文研究了具有非负Ricci曲率和次大体积增长的完备黎曼流形的拓扑结构问题.利用Toponogov型比较定理及临界点理论,获得了流形具有有限拓扑型的结果,推广了H.Zhan和Z.Shen的定理,并且还证明了该流形的基本群是有限生成的.