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First example of non-normal extremally disconnected space is $\mathbb{N}\cup \{p_A: A\in\mathcal{A}\}$, $\mathcal{A}$ maximal almost disjoint family, $p_A\in \text{cl}_{\beta\mathbb{N}} A\setminus\mathbb{N}$. It's the space witnessing that $\beta\mathbb{N}$ is not $T_5$ so name probably should reflect that.
Second example of non-normal $P$-space is $X^2\setminus \{(\omega_2, \omega_2)\}$ where $X = \omega_2+1$ has topology letting $U\subseteq X$ be open iff its a $G_\delta$-set in the order topology. I would like to call it Dow plank since it's a space that appears in the article On F-spaces and F'-spaces by Dow, clearly analogous to something like the Tychonoff plank.
Rationale
First example is in Engelking, second I mentioned the article already.
Relationship to other spaces and properties
They provide searches for non-normal extremally disconnected and non-normal P-spaces.
The text was updated successfully, but these errors were encountered:
@yhx-12243 oh sorry I forgot that existed, since it was sitting there for so long.
Not quite, but it's similar. And also showing that $\beta\mathbb{N}$ is non-normal. Moreover it's more specific
Space Suggestion
First example of non-normal extremally disconnected space is$\mathbb{N}\cup \{p_A: A\in\mathcal{A}\}$ , $\mathcal{A}$ maximal almost disjoint family, $p_A\in \text{cl}_{\beta\mathbb{N}} A\setminus\mathbb{N}$ . It's the space witnessing that $\beta\mathbb{N}$ is not $T_5$ so name probably should reflect that.
Second example of non-normal$P$ -space is $X^2\setminus \{(\omega_2, \omega_2)\}$ where $X = \omega_2+1$ has topology letting $U\subseteq X$ be open iff its a $G_\delta$ -set in the order topology. I would like to call it Dow plank since it's a space that appears in the article On F-spaces and F'-spaces by Dow, clearly analogous to something like the Tychonoff plank.
Rationale
First example is in Engelking, second I mentioned the article already.
Relationship to other spaces and properties
They provide searches for non-normal extremally disconnected and non-normal P-spaces.
The text was updated successfully, but these errors were encountered: