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arXiv 0908.1465math.KTmath.GT
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等变嵌入定理与拓扑指数映射

Equivariant embedding theorems and topological index maps

Ralf Meyer, Heath Emerson

摘要:

构造等变Dirac算子族的拓扑指数映射需要通过一种非常简单的映射来分解一个一般光滑映射:向量丛的零截面、开嵌入和向量丛投影。粗略地说,一个正常非奇异映射是一个带有这样一个因子分解的映射。这些因式分解是拓扑指数映射的模型。在一些关于等变向量丛存在的假设下,任何光滑映射都有一个正规因子分解,并且两个正规因子分解在某种等价概念下是唯一的。为了证明这一点,我们推广的Mostow嵌入定理配备适当的广群行动的空间。我们还讨论了正常非奇异映射的方向上同调理论,并表明,定向正常非奇异映射诱导错误的方式选择上同调理论的映射。对于K-定向正规非奇异映射,我们也得到了Kasparov等变KK-理论的函子。我们解释这个函子作为一个拓扑指数映射。

英文摘要:

The construction of topological index maps for equivariant families of Dirac operators requires factoring a general smooth map through maps of a very simple type: zero sections of vector bundles, open embeddings, and vector bundle projections. Roughly speaking, a normally non-singular map is a map together with such a factorisation. These factorisations are models for the topological index map. Under some assumptions concerning the existence of equivariant vector bundles, any smooth map admits a normal factorisation, and two such factorisations are unique up to a certain notion of equivalence. To prove this, we generalise the Mostow Embedding Theorem to spaces equipped with proper groupoid actions. We also discuss orientations of normally non-singular maps with respect to a cohomology theory and show that oriented normally non-singular maps induce wrong-way maps on the chosen cohomology theory. For K-oriented normally non-singular maps, we also get a functor to Kasparov's equivariant KK-theory. We interpret this functor as a topological index map.

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