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9 changes: 6 additions & 3 deletions spaces/S000125/README.md
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Expand Up @@ -10,11 +10,14 @@ refs:
- wikipedia: Knaster-Kuratowski_fan
name: Knaster-Kuratowski fan
---
For any $a \in [0,1]$, let $L(a)$ be the line segment from $(a,0)$ to $p = (\frac{1}{2}, \frac{1}{2})$. Let $\mathcal{C}$ be the middle-thirds Cantor set in the unit interval, $\mathcal{E}$ the endpoints of the removed intervals and $\mathcal{F} = \mathcal{C} \setminus \mathcal{E}$. Define $A = \{(x,y) \in L(c)\ |\ c \in \mathcal{E}, y \in \mathbb{Q}\}$ and $B = \{(x,y) \in L(c)\ |\ c \in \mathcal{F}, y \not\in \mathbb{Q}\}$. This space is $X = A \cup B \subset \mathbb{R}^2$ with the subspace topology.

$X$ is a subspace of {S176} defined as follows.
For any $a \in [0,1]$, let $L(a)$ be the closed line segment from $(a,0)$ to $p = (\frac{1}{2}, \frac{1}{2})$.
Let $C$ be the middle-thirds Cantor set in the unit interval, $E$ the set of endpoints of the removed intervals and $F = C\setminus E$.
Define $A = \{(x,y) \in L(c):c \in E, y \in \mathbb Q\}$ and $B = \{(x,y) \in L(c):c \in F, y \not\in \mathbb Q\}$.
Then take $X = A \cup B\subseteq\mathbb R^2$ with the subspace topology.

The subspace $X\setminus\{p\}$ obtained by removing the apex point is {S126}.

Defined as counterexample #128 ("Cantor's Leaky Tent")
in {{zb:0386.54001}}.

<!-- ![](http://i.imgur.com/P36Jx0z.png?1) -->
11 changes: 0 additions & 11 deletions spaces/S000125/properties/P000022.md

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11 changes: 0 additions & 11 deletions spaces/S000125/properties/P000023.md

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7 changes: 2 additions & 5 deletions spaces/S000125/properties/P000041.md
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space: S000125
property: P000041
value: false
refs:
- zb: "0386.54001"
name: Counterexamples in Topology
---

Asserted in the General Reference Chart for space #128 in
{{zb:0386.54001}}.
{S126} is an open subset of $X$,
and {S126|P41}.
9 changes: 9 additions & 0 deletions spaces/S000125/properties/P000055.md
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---
space: S000125
property: P000055
value: false
---

Take some $c\in E$.
The closed set $L(c)\cap X\subseteq X$ contains a closed set homeomorphic to {S27}.
And {S27|P55}.
9 changes: 9 additions & 0 deletions spaces/S000125/properties/P000066.md
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---
space: S000125
property: P000066
value: false
---

Take some $c\in F$.
The closed set $L(c)\cap X\subseteq X$ contains a closed set homeomorphic to {S28}.
And {S28|P66}.
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