The Stacks project

Lemma 31.11.13. Let $X$ be an integral locally Noetherian scheme. Let $\varphi : \mathcal{F} \to \mathcal{G}$ be a map of quasi-coherent $\mathcal{O}_ X$-modules. Assume $\mathcal{F}$ is coherent, $\mathcal{G}$ is torsion free, and that for every $x \in X$ one of the following happens

  1. $\mathcal{F}_ x \to \mathcal{G}_ x$ is an isomorphism, or

  2. $\text{depth}(\mathcal{F}_ x) \geq 2$.

Then $\varphi $ is an isomorphism.

Proof. This is a translation of More on Algebra, Lemma 15.23.14 into the language of schemes. $\square$

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