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prabau committed Dec 5, 2024
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6 changes: 3 additions & 3 deletions properties/P000088.md
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name: Baireness of $C_k(X)$ for locally compact $X$ (Gruenhage & Ma)
---

For every discrete family $(F_i)_{i \in I}$ of closed subsets of $X$, there exists a pairwise disjoint family of open sets $(U_i)_{i \in I}$, such that $F_i \subseteq U_i$ for all $i$.
For every discrete family $(F_i)_{i \in I}$ of closed subsets of $X$, there exists a pairwise disjoint family of open sets $(U_i)_{i \in I}$ with $F_i \subseteq U_i$ for all $i$.

Equivalently, for every discrete family $(F_i)_{i \in I}$ of closed subsets of $X$, there exists a discrete family of open sets $(U_i)_{i \in I}$, such that $F_i \subseteq U_i$ for all $i$.
Equivalently, for every discrete family $(F_i)_{i \in I}$ of closed subsets of $X$, there exists a discrete family of open sets $(U_i)_{i \in I}$ with $F_i \subseteq U_i$ for all $i$.

Terminology:
- A *discrete family* is a family of subsets such that each point of $X$ has a neighborhood meeting at most one of the subsets.
- In the first definition, the family of open sets $(U_i)_i$ is sometimes called a *disjoint open expansion* of the family $(F_i)_i$. (REFERENCE ?)
- In the first definition, the family of open sets $(U_i)_i$ is sometimes called a *disjoint open expansion* of the family $(F_i)_i$.
- In the second definition, the family of open sets $(U_i)_i$ is sometimes called a *discrete open expansion* of the family $(F_i)_i$. (See for example {{doi:10.1016/S0166-8641(96)00163-0}}.)

The equivalence between the two definitions is Theorem 5.1.17 of {{zb:0684.54001}}.
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3 changes: 2 additions & 1 deletion spaces/S000082/properties/P000021.md
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---

Every non-empty set has a limit point, since every non-empty subset of
{S42} has a limit point (e.g. any lesser point).
{S42} has a limit point
(e.g. any point smaller than a point in the set).
2 changes: 1 addition & 1 deletion theorems/T000657.md → theorems/T000661.md
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---
uid: T000657
uid: T000661
if:
and:
- P000197: true
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2 changes: 1 addition & 1 deletion theorems/T000658.md → theorems/T000662.md
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---
uid: T000658
uid: T000662
if:
and:
- P000198: true
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