Lemma 5.18.2 (005V)—The Stacks project

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Lemma 5.18.2. Let $X$ be a topological space. Let $X_0$ be the set of closed points of $X$ . Suppose that for every point $x\in X$ the intersection $X_0 \cap \overline{\{ x\} }$ is dense in $\overline{\{ x\} }$ . Then $X$ is Jacobson.

Proof. Let $Z$ be closed subset of $X$ and $U$ be and open subset of $X$ such that $U\cap Z$ is nonempty. Then for $x\in U\cap Z$ we have that $\overline{\{ x\} }\cap U$ is a nonempty subset of $Z\cap U$ , and by hypothesis it contains a point closed in $X$ as required. $\square$

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