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The Stacks project

Lemma 36.13.1. Let X be a scheme and let j : U \to X be a quasi-compact open immersion. The functors

D_\mathit{QCoh}(\mathcal{O}_ X) \to D_\mathit{QCoh}(\mathcal{O}_ U) \quad \text{and}\quad D^+_\mathit{QCoh}(\mathcal{O}_ X) \to D^+_\mathit{QCoh}(\mathcal{O}_ U)

are essentially surjective. If X is quasi-compact, then the functors

D^-_\mathit{QCoh}(\mathcal{O}_ X) \to D^-_\mathit{QCoh}(\mathcal{O}_ U) \quad \text{and}\quad D^ b_\mathit{QCoh}(\mathcal{O}_ X) \to D^ b_\mathit{QCoh}(\mathcal{O}_ U)

are essentially surjective.

Proof. The argument preceding the lemma applies for the first case because Rj_* maps D_\mathit{QCoh}(\mathcal{O}_ U) into D_\mathit{QCoh}(\mathcal{O}_ X) by Lemma 36.4.1. It is clear that Rj_* maps D^+_\mathit{QCoh}(\mathcal{O}_ U) into D^+_\mathit{QCoh}(\mathcal{O}_ X) which implies the statement on bounded below complexes. Finally, Lemma 36.4.1 guarantees that Rj_* maps D^-_\mathit{QCoh}(\mathcal{O}_ U) into D^-_\mathit{QCoh}(\mathcal{O}_ X) if X is quasi-compact. Combining these two we obtain the last statement. \square


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