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The Stacks project

Lemma 51.5.5. Let A be a Noetherian ring. Let T \subset \mathop{\mathrm{Spec}}(A) be a subset stable under specialization. If \dim (A) < \infty , then functor D(\text{Mod}_{A, T}) \to D_ T(A) is an equivalence.

Proof. Say \dim (A) = d. Then we see that H^ i_ Z(M) = 0 for i > d for every closed subset Z of \mathop{\mathrm{Spec}}(A), see Lemma 51.4.7. By Lemma 51.5.3 we find that H^0_ T has bounded cohomological dimension.

Let K \in D_ T(A). We claim that RH^0_ T(K) \to K is an isomorphism. We know this is true when K is bounded below, see Lemma 51.5.4. However, since H^0_ T has bounded cohomological dimension, we see that the ith cohomology of RH_ T^0(K) only depends on \tau _{\geq -d + i}K and we conclude. Thus D(\text{Mod}_{A, T}) \to D_ T(A) is an equivalence with quasi-inverse RH^0_ T. \square


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