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Space Suggestion: (R × (0, +∞)) ∪ (Q × {0}) #1234

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yhx-12243 opened this issue Feb 10, 2025 · 1 comment
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Space Suggestion: (R × (0, +∞)) ∪ (Q × {0}) #1234

yhx-12243 opened this issue Feb 10, 2025 · 1 comment
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@yhx-12243
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I have not decided and found the name of this space yet. 😂

Space Suggestion

Let $X = \bigl( \mathbb R \times (0, + \infty) \bigr) \cup \bigl( \mathbb Q \times {0} \bigr)$ with subspace topology of $\mathbb R^2$.

Rationale

This space appears in https://math.stackexchange.com/questions/3003649, https://math.stackexchange.com/questions/3260430, and Wikipedia Baire_space.

Relationship to other spaces and properties

This space provides an example of a (nontrivial) Baire space that is not Strongly Choquet.

π-Base, Search for Baire + ~Empty + ~Strongly Choquet

@pzjp
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pzjp commented Feb 10, 2025

I would call it the rational edge halfplane.
Or a fringed carpet space if aiming for something whimsy.

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