The Stacks project

Lemma 101.4.8. Let $\mathcal{T}$ be an algebraic stack. Let $g : \mathcal{X} \to \mathcal{Y}$ be a morphism of algebraic stacks over $\mathcal{T}$. Consider the graph $i : \mathcal{X} \to \mathcal{X} \times _\mathcal {T} \mathcal{Y}$ of $g$. Then

  1. $i$ is representable by algebraic spaces and locally of finite type,

  2. if $\mathcal{Y} \to \mathcal{T}$ is DM, then $i$ is unramified,

  3. if $\mathcal{Y} \to \mathcal{T}$ is quasi-DM, then $i$ is locally quasi-finite,

  4. if $\mathcal{Y} \to \mathcal{T}$ is separated, then $i$ is proper, and

  5. if $\mathcal{Y} \to \mathcal{T}$ is quasi-separated, then $i$ is quasi-compact and quasi-separated.

Proof. This is a special case of Lemma 101.4.7 applied to the morphism $\mathcal{X} = \mathcal{X} \times _\mathcal {Y} \mathcal{Y} \to \mathcal{X} \times _\mathcal {T} \mathcal{Y}$. $\square$


Comments (0)

There are also:

  • 2 comment(s) on Section 101.4: Separation axioms

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Your email address will not be published.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 050I. Beware of the difference between the letter 'O' and the digit '0'.