The Stacks project

Lemma 70.23.3. In Situation 70.23.1. Let $X \to B$ be a quasi-separated and finite type morphism of algebraic spaces. Given $i \in I$ and a diagram

\[ \vcenter { \xymatrix{ X \ar[r] \ar[d] & W \ar[d] \\ B \ar[r] & B_ i } } \]

as in (70.23.2.1) for $i' \geq i$ let $X_{i'}$ be the scheme theoretic image of $X \to B_{i'} \times _{B_ i} W$. Then $X = \mathop{\mathrm{lim}}\nolimits _{i' \geq i} X_{i'}$.

Proof. Since $X$ is quasi-compact and quasi-separated formation of the scheme theoretic image of $X \to B_{i'} \times _{B_ i} W$ commutes with étale localization (Morphisms of Spaces, Lemma 67.16.3). Hence we may and do assume $W$ is affine and maps into an affine $U_ i$ étale over $B_ i$. Then

\[ B_{i'} \times _{B_ i} W = B_{i'} \times _{B_ i} U_ i \times _{U_ i} W = U_{i'} \times _{U_ i} W \]

where $U_{i'} = B_{i'} \times _{B_ i} U_ i$ is affine as the transition morphisms are affine. Thus the lemma follows from the case of schemes which is Limits, Lemma 32.22.3. $\square$


Comments (0)


Post a comment

Your email address will not be published. Required fields are marked.

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).

Unfortunately JavaScript is disabled in your browser, so the comment preview function will not work.

All contributions are licensed under the GNU Free Documentation License.




In order to prevent bots from posting comments, we would like you to prove that you are human. You can do this by filling in the name of the current tag in the following input field. As a reminder, this is tag 0CP9. Beware of the difference between the letter 'O' and the digit '0'.