Alternate proofs for the \(n\)-dimensional resolution theorems (Q2052568)
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| Language | Label | Description | Also known as |
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| English | Alternate proofs for the \(n\)-dimensional resolution theorems |
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Alternate proofs for the \(n\)-dimensional resolution theorems (English)
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26 November 2021
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In this paper the authors give alternative new unified proofs for the following resolution theorems in cohomological dimension theory: 1) (Cell-like resolution theorem) Let \(n\in\mathbb{N}\) and \(X\) be a nonempty metrizable compactum with \(\dim_{\mathbb{Z}}X\leq n\). Then there exists a metrizable compactum \(Z\) with \(\dim Z \leq n\) and a surjective cell-like map \(\pi: Z\to X\). 2) (\(\mathbb{Z}/p\)-resolution theorem) Let \(n\in\mathbb{N}\), \(p\in\mathbb{N}\) with \(p\geq 2\), and \(X\) be a nonempty metrizable compactum with \(\dim_{\mathbb{Z}/p}X\leq n\). Then there exists a metrizable compactum \(Z\) with \(\dim Z \leq n\) and a surjective \(\mathbb{Z}/p\)-acyclic map \(\pi: Z\to X\). 3) (\(\mathbb{Q}\)-resolution theorem) Let \(n\in\mathbb{N}\) with \(n\geq 2\), and \(X\) be a nonempty metrizable compactum with \(\dim_{\mathbb{Q}}X\leq n\). Then there exists a metrizable compactum \(Z\) with \(\dim Z \leq n\) and a surjective \(\mathbb{Q}\)-acyclic map \(\pi: Z\to X\). The original proofs for the theorems can be found in [\textit{J. J. Walsh}, Lect. Notes Math. 870, 105--118 (1981; Zbl 0474.55002); \textit{M. Levin}, Algebr. Geom. Topol. 5, 219--235 (2005; Zbl 1081.55001)]. The authors use extensions (of maps) that are much simpler than those used by the previous proofs, which employed more complicated extensions such as Edward-Walsh resolutions [\textit{J. J. Walsh}, loc. cit.].
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absolute co-extensor
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absolute neighborhood retract
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cell-like
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cohomological dimension
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compactum
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CW-complex
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dimension
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Eilenberg-MacLane CW-complex
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\(G\)-acyclic
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inverse sequence
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