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arXiv 0901.4019math.DG
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模型曲面的全曲率控制了具有下界径向曲率的完备开流形的拓扑。II

Total curvatures of model surfaces control topology of complete open manifolds with radial curvature bounded below. II

Kei Kondo, Minoru Tanaka

摘要:

作为我们的主要定理,我们证明了具有一个基点$p \in M$的完全开黎曼流形$M$的拓扑型的有限性,该基点$p \in M$在$p$处的径向曲率是由一个非紧模型旋转曲面$\tilde{M}$的径向曲率从下面有界的,该旋转曲面具有有限的全曲率并且在一个扇区中没有一对割点.根据定义,这里的扇区是由从基点$\tilde{p} \in \tilde{M}$发出的两条子午线切断的域。注意,我们的模型$\tilde{M}$并不总是满足Abresch和Gromoll引入的直径增长条件。为了证明主要定理,我们需要一个新的Toponogov比较定理。作为主要定理的一个应用,我们给出了关于完备开流形的基本群的Milnor开猜想的部分答案。

英文摘要:

We prove, as our main theorem, the finiteness of topological type of a complete open Riemannian manifold $M$ with a base point $p \in M$ whose radial curvature at $p$ is bounded from below by that of a non-compact model surface of revolution $\tilde{M}$ which admits a finite total curvature and has no pair of cut points in a sector. Here a sector is, by definition, a domain cut off by two meridians emanating from the base point $\tilde{p} \in \tilde{M}$. Notice that our model $\tilde{M}$ does not always satisfy the diameter growth condition introduced by Abresch and Gromoll. In order to prove the main theorem, we need a new type of the Toponogov comparison theorem. As an application of the main theorem, we present a partial answer to Milnor's open conjecture on the fundamental group of complete open manifolds.

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