Monday, 21 December 2015

at.algebraic topology - Noncompact homology spheres?

If $M$ is a connected, non-compact $n$-manifold, then $H_i(M;R)=0$ for $igeq n$. For a proof, see Proposition 3.29 in Hatcher's Algebraic Topology book.



So, if you are going to have $H_n(M;R)=R$, $M$ had better be compact.



EDIT (to answer about homology $n$-manifolds):



A homology $n$-manifold is a finite dimensional, locally contractible space $X$ whose local homology groups $H_*(X, X-{x})$ are the local homology groups for $mathbb{R}^n$ for every $xin X$. In particular, $mathbb{R}^n$ is a non-compact homology $n$-manifold.

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