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arXiv 0908.1447math.DG
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黎曼空间上闭共形向量场的几何

The geometry of closed conformal vector fields on Riemannian spaces

A. Caminha

摘要:

本文研究了黎曼流形上闭共形向量场几何的不同方面。首先给出了完备流形上具有非正里奇曲率的闭共形非平行向量场存在的障碍,从而推广了T. K.锅然后,我们解释为什么它是如此困难,找到的例子,比平凡的,空间至少有两个封闭的,共形和位似向量场。然后,我们专注于等距浸入,首先推广的定理J.西蒙斯锥平行中曲率的空间配备了一个封闭的,里奇零共形向量场,然后我们证明一般伯恩斯坦型定理某些完整的,不一定CMC,超曲面的黎曼流形配备了封闭共形向量场。特别地,我们得到了J.Jellett和A. Barros和P.Sousa关于黎曼空间型的删余测地球面上的完全cmc径向图的结果。

英文摘要:

In this paper we examine different aspects of the geometry of closed conformal vector fields on Riemannian manifolds. We begin by getting obstructions to the existence of closed conformal and nonparallel vector fields on complete manifolds with nonpositive Ricci curvature, thus generalizing a theorem of T. K. Pan. Then we explain why it is so difficult to find examples, other than trivial ones, of spaces having at least two closed, conformal and homothetic vector fields. We then focus on isometric immersions, firstly generalizing a theorem of J. Simons on cones with parallel mean curvature to spaces furnished with a closed, Ricci null conformal vector field; then we prove general Bernstein-type theorems for certain complete, not necessarily cmc, hypersurfaces of Riemannian manifolds furnished with closed conformal vector fields. In particular, we obtain a generalization of theorems J. Jellett and A. Barros and P. Sousa for complete cmc radial graphs over finitely punctured geodesic spheres of Riemannian space forms.

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