Non-metrizable manifolds and contractibility

We investigate whether non-metrizable manifolds in various classes can be homotopy equivalent to a CW-complex (in short: heCWc),and in particular contractible. We show that a non-metrizable manifold cannot be heCWc if it has one of the following properties: it contains a countably compact non-compact subspace; it contains a copy of an ω1-compact subspace of an ω1-tree; it contains a non-Lindelöf closed subspace functionally narrow in it. (These results hold for more general spaces than just manifolds.) We also show that the positive part of the tangent bundle of the longray is never heCWc for any smoothing. These theorems follow from stabilization properties of real valued maps. On a more geometric side, we also show that the Prüfer surface, which has been shown to be contractible long ago, has an open submanifold with trivial homotopy groups which is not heCWc. On the other end of the spectrum, we show that there is a non-metrizable contractible Type I surface.

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Publication Details

Journal
Applied General Topology
Published
2025-04-01
DOI
https://doi.org/10.4995/agt.2025.21796
Primary Topic
Advanced Topology and Set Theory
Type
article
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article

Non-metrizable manifolds and contractibility

Mathieu Baillif
Applied General Topology
Advanced Topology and Set Theory
article

Non-metrizable manifolds and contractibility

Mathieu Baillif
article en

Abstract

We investigate whether non-metrizable manifolds in various classes can be homotopy equivalent to a CW-complex (in short: heCWc),and in particular contractible. We show that a non-metrizable manifold cannot be heCWc if it has one of the following properties: it contains a countably compact non-compact subspace; it contains a copy of an ω1-compact subspace of an ω1-tree; it contains a non-Lindelöf closed subspace functionally narrow in it. (These results hold for more general spaces than just manifolds.) We also show that the positive part of the tangent bundle of the longray is never heCWc for any smoothing. These theorems follow from stabilization properties of real valued maps. On a more geometric side, we also show that the Prüfer surface, which has been shown to be contractible long ago, has an open submanifold with trivial homotopy groups which is not heCWc. On the other end of the spectrum, we show that there is a non-metrizable contractible Type I surface.

Applied General TopologyVol. 26(1)
Openalex Percentile: Top 89%
Advanced Topology and Set Theory
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