Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options not deleted user 121225

Commutative rings, modules, ideals, homological algebra, computational aspects, invariant theory, connections to algebraic geometry and combinatorics.

11 votes

Does any derivation of commutative algebra preserve its nil-radical?

Here is another cute argument (I don't remember where I learned it, I think it is folklore). Let $P\subset A$ be an arbitrary prime ideal. We claim it contains a $D$-stable prime ideal. For this, cons …
Marc's user avatar
  • 374
4 votes
Accepted

Etale map has image whose complement is the vanishing locus of a finitely generated ideal

Let $U$ be the image of $\operatorname{Spec} B$ in $\operatorname{Spec} A$. Since the map $\operatorname{Spec} B \to \operatorname{Spec} A$ is open, $U$ is open. And since $\operatorname{Spec} B$ is q …
Marc's user avatar
  • 374