Lemma 15.111.2. Let $A \subset B$ be an extension of discrete valuation rings with fraction fields $K \subset L$. If the extension $L/K$ is finite, then the residue field extension is finite and we have $ef \leq [L : K]$.

**Proof.**
Finiteness of the residue field extension is Algebra, Lemma 10.119.10. The inequality follows from Algebra, Lemmas 10.119.9 and 10.52.12.
$\square$

## 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Your email address will not be published.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.

## Comments (0)