The Stacks project

Lemma 39.7.3. Let $G$ be a group scheme over a field. Then $G$ is a separated scheme.

Proof. Say $S = \mathop{\mathrm{Spec}}(k)$ with $k$ a field, and let $G$ be a group scheme over $S$. By Lemma 39.6.1 we have to show that $e : S \to G$ is a closed immersion. By Morphisms, Lemma 29.20.2 the image of $e : S \to G$ is a closed point of $G$. It is clear that $\mathcal{O}_ G \to e_*\mathcal{O}_ S$ is surjective, since $e_*\mathcal{O}_ S$ is a skyscraper sheaf supported at the neutral element of $G$ with value $k$. We conclude that $e$ is a closed immersion by Schemes, Lemma 26.24.2. $\square$

Comments (0)

There are also:

  • 5 comment(s) on Section 39.7: Properties of group schemes over a field

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Your email address will not be published.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 047L. Beware of the difference between the letter 'O' and the digit '0'.