Lemma 21.21.2 (0FN5)—The Stacks project

Processing math: 100%

Table of contents
Part 1: Preliminaries
Chapter 21: Cohomology on Sites
Section 21.21: Localization and cohomology
Lemma 21.21.2 (cite)

previous lemma

numberstags

Lemma 21.21.2. Let $(\mathcal{C}, \mathcal{O})$ be a ringed site. Let

$\xymatrix{ X' \ar[d] \ar[r] & X \ar[d] \\ Y' \ar[r] & Y }$

be a cartesian diagram of $\mathcal{C}$ . Then we have $j_{Y'/Y}^* \circ Rj_{X/Y, *} = Rj_{X'/Y', *} \circ j_{X'/X}^*$ as functors $D(\mathcal{O}_ X) \to D(\mathcal{O}_{Y'})$ .

Proof. Since $j_{Y'/Y}^{-1}\mathcal{O}_ Y = \mathcal{O}_{Y'}$ we have $j_{Y'/Y}^* = Lj_{Y'/Y}^* = j_{Y'/Y}^{-1}$ . Similarly we have $j_{X'/X}^* = Lj_{X'/X}^* = j_{X'/X}^{-1}$ . Thus by Lemma 21.20.7 it suffices to prove the result on derived categories of abelian sheaves which we did in Lemma 21.21.1. $\square$

Comments (0)

In your comment you can use Markdown and LaTeX style mathematics (enclose it like $\pi$ ). A preview option is available if you wish to see how it works out (just click on the eye in the toolbar).

Comments (0)

Post a comment