Talk:Reducible Poincaré Complexes (Ex)
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− | 1. Let's quickly prove the mentioned theorem of Wall. Assume that $X$ is connected. The collection of top-dimensional $n$-cells $(e^{n}_{i},\phi_{i})_{i\in\{1,\ldots,k\}}$ is such that $\bigcup_{i\in\{1,\ldots,k\}} | + | 1. Let's quickly prove the mentioned theorem of Wall. Assume that $X$ is connected. The collection of top-dimensional $n$-cells $(e^{n}_{i},\phi_{i})_{i\in\{1,\ldots,k\}}$ is such that $\bigcup_{i\in\{1,\ldots,k\}} \phi_{i}(e^n_i)$ is connected - otherwise any two connected components would give two independent classes in $H_{n}(X)$. Assume that $X$ is pointed and that all attaching maps are pointed as well. We can take $X^{\bullet}$ to be the $(n-1)$-skeleton of $X$ and the unique $n$-cell to have the attaching map |
$$e^{n}\xrightarrow{}\bigvee_{i\in\{1,\ldots,k\}}e^{n}\xrightarrow{\phi_1\vee\ldots\vee\phi_k}X^{\bullet}$$ | $$e^{n}\xrightarrow{}\bigvee_{i\in\{1,\ldots,k\}}e^{n}\xrightarrow{\phi_1\vee\ldots\vee\phi_k}X^{\bullet}$$ |
Revision as of 17:58, 30 May 2012
1. Let's quickly prove the mentioned theorem of Wall. Assume that is connected. The collection of top-dimensional -cells is such that is connected - otherwise any two connected components would give two independent classes in . Assume that is pointed and that all attaching maps are pointed as well. We can take to be the -skeleton of and the unique -cell to have the attaching map
begginning with the pinching map.