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arXiv math/0303140math.AT
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伪流形上S1-Actions的交上同调

Intersection Cohomology of S1-Actions on Pseudomanifolds

G. Padilla

摘要:

对于单位圆S1在光滑流形M上的任意光滑自由作用,M的Gysin序列是M的DeRham上同调与轨道空间M/S1的长正合序列.如果作用量不是自由的,则M/S1不是光滑流形而是一个分层伪流形,M/S1的长度取决于轨道类型的数目,并且存在一个Gysin序列与它们的相交上同调相联系. M/S1中固定层的链环是上同调的复射影空间,因此该序列的连同态是Euler类的乘法.本文将上述结果推广到S1在长度为1的分层伪流形X上的任意作用。我们使用DeRham的交叉上同调定义的展开。如果作用保持局部结构,则轨道空间X/S1又是一个长度为1的分层伪流形,并且具有开折。X和X/S1的交上同调与第三个复体$\mathcal{G}$(Gysin项)有一个长的精确序列,它的上同调依赖于两种基本的上同调数据:全局和局部。全球数据关注的欧拉类引起的行动;当地的信息取决于上同调的固定地层上的值在一些preheaves。

英文摘要:

For any smooth free action of the unit circle S1 on a smooth manifold M, the Gysin sequence of M is a long exact sequence relating the DeRham Cohomology of M and the orbit space M/S1. If the action is not free then M/S1 is not a smooth manifold but a stratified pseudomanifold, the lenght of M/S1 depending on the number of orbit types; and there is a Gysin sequence relating their intersection cohomologies. The links of the fixed strata in M/S1 are cohomological complex projective spaces, so the conecting homomorphism of this sequences is the multiplication by the Euler class. In this article we extend the above results for any action of S1 on a stratified pseudomanifold X of lenght 1. We use the DeRham-like intersection cohomology defined by means of an unfolding. If the action preserves the local structure, then the orbit space X/S1 is again a stratified pseudomanifold of lenght 1 and has an unfolding. There is a long exact sequence relating the intersection cohomology of X and X/S1 with a third complex $\mathcal{G}$, the Gysin Term, whose cohomology depends on basic cohomological data of two flavours: global and local. Global data concerns the Euler class induced by the action; local information depends on the cohomology of the fixed strata with values on some presheaves.

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