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The Stacks project

Lemma 52.15.4. Let I \subset \mathfrak a be ideals of a Noetherian ring A. Let U = \mathop{\mathrm{Spec}}(A) \setminus V(\mathfrak a). Assume

  1. A is I-adically complete and has a dualizing complex,

  2. for any associated prime \mathfrak p \subset A with \mathfrak p \not\in V(I) and V(\mathfrak p) \cap V(I) \not\subset V(\mathfrak a) and \mathfrak q \in V(\mathfrak p) \cap V(\mathfrak a) we have \dim ((A/\mathfrak p)_\mathfrak q) > \text{cd}(A, I) + 1,

  3. for \mathfrak p \subset A with \mathfrak p \not\in V(I) and V(\mathfrak p) \cap V(I) \subset V(\mathfrak a) we have \text{depth}(A_\mathfrak p) \geq 2.

Then the completion functor

\textit{Coh}(\mathcal{O}_ U) \longrightarrow \textit{Coh}(U, I\mathcal{O}_ U), \quad \mathcal{F} \longmapsto \mathcal{F}^\wedge

is fully faithful on the full subcategory of finite locally free objects.

Proof. By Lemma 52.15.1 it suffices to show that

\Gamma (U, \mathcal{O}_ U) = \mathop{\mathrm{lim}}\nolimits \Gamma (U, \mathcal{O}_ U/I^ n\mathcal{O}_ U)

This follows immediately from Lemma 52.12.4. \square


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