2025-03-01 14:26:36 +01:00

12 lines
554 B
Markdown

# Definition
Given $F \subset \wp(X)$. The **weakest topology** on $X$ that contains $F$ is the intersection of all the [[Topology|topologies]] that contains $F$. This is a [[Topology|topology]], and consists of $\emptyset$, $X$, and all unions of finite intersections of members from $F$.
> [!example]
> $F \subset \tau$
> $\textvisiblespace \cap \tau \ni U_{i} \implies U_{i} \in \tau$
> $\implies \cap_{i \in F} \; U_{i} \in \tau \implies \cap U_{i} \in \cap_{F \in \tau} \;\tau$
>
> $x_{i} \to x$
> $\exists j$ such that $x_{i} = x, \; i \geq j$.