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arXiv 1707.09618math.DG
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环与正曲率同调类的临界值

Critical values of homology classes of loops and positive curvature

Hans-Bert Rademacher

摘要:

本文研究了具有正截面曲率的紧致单连通黎曼流形$K\ge 1.$.对于以点$p$为基的环空间或自由环空间中的最低维非平凡同调类,可以分别定义一个临界长度${\sf crl}_p\left(M,g\right)$.那么${\sf crl}\left(M,g\right).$等于测地线环的长度,而${\sf crl}\left(M,g\right)$等于闭合测地线的长度。这是想法的证明存在一个封闭的测地线的积极长度提出的伯克霍夫的情况下,一个领域和Lusternik和费特在一般情况下。本文的主要结果是:数${\sf crl}_p\left(M,g\right)$分别为. ${\sf crl}\left(M,g\right)$仅对$n$ -球面上的轮度量达到其最大值$2π$。在额外的假设$K \le 4$下,${\sf crl}\left(M,g\right)$的这个结果来自Sugimoto在偶数维和Ballmann,Thorbergsson和Ziller在奇数维的结果。

英文摘要:

We study compact and simply-connected Riemannian manifolds with positive sectional curvature $K\ge 1.$ For a non-trivial homology class of lowest dimension in the space of loops based at a point $p$ or in the free loop space one can define a critical length ${\sf crl}_p\left(M,g\right)$ resp. ${\sf crl}\left(M,g\right).$ Then ${\sf crl}_p\left(M,g\right)$ equals the length of a geodesic loop and ${\sf crl}\left(M,g\right)$ equals the length of a closed geodesic. This is the idea of the proof of the existence of a closed geodesic of positive length presented by Birkhoff in case of a sphere and by Lusternik and Fet in the general case. It is the main result of the paper that the numbers ${\sf crl}_p\left(M,g\right)$ resp. ${\sf crl}\left(M,g\right)$ attain its maximal value $2π$ only for the round metric on the $n$-sphere. Under the additional assumption $K \le 4$ this result for ${\sf crl}\left(M,g\right)$ follows from results by Sugimoto in even dimensions and Ballmann, Thorbergsson and Ziller in odd dimensions.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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