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arXiv 1306.1617math.DGmath.GT
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关于T^n、RP ^n和M^3的等收缩不等式

On Isosystolic Inequalities for T^n, RP^n, and M^3

Kei Nakamura

摘要:

若闭光滑n-流形M有一个有限复盖,其Z/2 Z-上同调具有最大杯长,则对M上的任意黎曼度量g,我们证明了收缩Sys(M,g)与黎曼流形(M,g)的体积Sys(M,g)之间存在如下的等收缩不等式:Sys(M,g)^n \leq n!(M,g).该不等式可以看作是Burago和Hebda关于闭本质曲面的不等式的推广,也可以看作是Guth关于Z/2 Z-上同调具有最大杯长的闭n-流形的不等式的改进。我们也建立了同样的不等式的背景下,可能非紧流形下类似的上同调条件。这个不等式适用于(i)T^n和所有其他紧致欧几里得空间形式,(ii)RP^n和包括庞加莱十二面体空间在内的许多其他球面空间型,以及(iii)包括所有闭非球面三维流形在内的大多数闭本质三维流形。

英文摘要:

If a closed smooth n-manifold M admits a finite cover whose Z/2Z-cohomology has the maximal cup-length, then for any riemannian metric g on M, we show that the systole Sys(M,g) and the volume Vol(M,g) of the riemannian manifold (M,g) are related by the following isosystolic inequality: Sys(M,g)^n \leq n! Vol(M,g). The inequality can be regarded as a generalization of Burago and Hebda's inequality for closed essential surfaces and as a refinement of Guth's inequality for closed n-manifolds whose Z/2Z-cohomology has the maximal cup-length. We also establish the same inequality in the context of possibly non-compact manifolds under a similar cohomological condition. The inequality applies to (i) T^n and all other compact euclidean space forms, (ii) RP^n and many other spherical space forms including the Poincaré dodecahedral space, and (iii) most closed essential 3-manifolds including all closed aspherical 3-manifolds.

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