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18 changes: 14 additions & 4 deletions spaces/S000171/README.md
Original file line number Diff line number Diff line change
@@ -1,10 +1,20 @@
---
uid: S000171
name: Brian's Example
name: Brian's stack of Bernstein sets
refs:
- mo: 416331
name: Example of an uncountable scattered space with some properties
- mo: 416752
name: Answer to "Example of an uncountable scattered space with some properties"
- wikipedia: Bernstein_set
name: Bernstein set on Wikipedia
---

In {{mo:416331}} Will Brian provides an example in ZFC for an uncountable, Hausdorff,
Let $X = \mathbb{R}$ and let $(X_i)_{i\in \omega}$ be a countably infinite partition of $X$ into
[Bernstein sets](https://en.wikipedia.org/wiki/Bernstein_set) (for the Euclidean topology).
Given $x \in X$, let $n \in \omega$ be such that $x \in X_n$.
Then basic open neighbourhoods of $x$ are given by the sets $\{x\} \cup (U \cap \bigcup_{i<n}X_i)$,
with $U$ (basic) open neighbourhood of $x$ in the Euclidean topology.

This topology is finer than {S25}.

This space was constructed in {{mo:416752}} by Will Brian, providing an example in ZFC for an uncountable, Hausdorff,
first-countable, scattered, Lindelöf space.
7 changes: 7 additions & 0 deletions spaces/S000171/properties/P000022.md
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---
space: S000171
property: P000022
value: false
---

{S25} has a coarser topology than $X$, but {S25|P22}.
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