The Stacks project

Lemma 66.24.2. Let $S$ be a scheme. Let $X$ be an algebraic space over $S$.

  1. If $X$ is locally Noetherian then $|X|$ is a locally Noetherian topological space.

  2. If $X$ is quasi-compact and locally Noetherian, then $|X|$ is a Noetherian topological space.

Proof. Assume $X$ is locally Noetherian. Choose a scheme $U$ and a surjective ├ętale morphism $U \to X$. As $X$ is locally Noetherian we see that $U$ is locally Noetherian. By Properties, Lemma 28.5.5 this means that $|U|$ is a locally Noetherian topological space. Since $|U| \to |X|$ is open and surjective we conclude that $|X|$ is locally Noetherian by Topology, Lemma 5.9.3. This proves (1). If $X$ is quasi-compact and locally Noetherian, then $|X|$ is quasi-compact and locally Noetherian. Hence $|X|$ is Noetherian by Topology, Lemma 5.12.14. $\square$

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