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arXiv 1209.2785math.GT
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关于3-流形梳化的同伦不变量

On homotopy invariants of combings of 3-manifolds

Christine Lescop

AI总结:

本文研究了定向紧3-流形梳化的同伦不变量,给出了Gompf挠梳化不变量的替代定义并以链环数表示其变化,同时为有边流形定义了$p_1$不变量,并证明$Θ$-不变量自然是有理同调球梳化的不变量。

摘要:

定向紧3-流形的梳化是这些流形中处处非零向量场的同伦类。梳化的第一个已知不变量是其Euler类,即3-流形$M$的切丛中梳化代表的法丛的Euler类。它仅依赖于梳化所代表的Spin$^c$-结构。当此Euler类是$H^2(M;Z)$的挠元素时,我们称该梳化为挠梳化。Gompf引入了闭3-流形挠梳化的$Q$值不变量$θ_G$,它区分了代表给定Spin$^c$-结构的所有梳化。该不变量为配备了挠Spin$^c$-结构的流形的Heegaard Floer同调$\hat{HF}$提供了分次。我们给出了Gompf不变量的另一种定义,并将其变化表示为链环数。我们还为以$S^2$为边界的流形的梳化定义了类似的不变量$p_1$。我们证明,$Θ$-不变量,即有理同调球的最简构型空间积分不变量,自然是有理同调球梳化的不变量,其值为$(\frac14p_1 + 6 λ)$,其中$λ$是Casson-Walker不变量。本文还包含了对梳化的一个基本自洽的介绍。

英文摘要:

Combings of oriented compact 3-manifolds are homotopy classes of nowhere zero vector fields in these manifolds. A first known invariant of a combing is its Euler class, that is the Euler class of the normal bundle to a combing representative in the tangent bundle of the 3-manifold $M$. It only depends on the Spin$^c$-structure represented by the combing. When this Euler class is a torsion element of $H^2(M;Z)$, we say that the combing is a torsion combing. Gompf introduced a $Q$-valued invariant $θ_G$ of torsion combings of closed 3-manifolds that distinguishes all combings that represent a given Spin$^c$-structure. This invariant provides a grading of the Heegaard Floer homology $\hat{HF}$ for manifolds equipped with torsion Spin$^c$-structures. We give an alternative definition of the Gompf invariant and we express its variation as a linking number. We also define a similar invariant $p_1$ for combings of manifolds bounded by $S^2$. We show that the $Θ$-invariant, that is the simplest configuration space integral invariant of rational homology spheres, is naturally an invariant of combings of rational homology balls, that reads $(\frac14p_1 + 6 λ)$ where $λ$ is the Casson-Walker invariant. The article also includes a mostly self-contained presentation of combings.

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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