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

9 votes
3 answers
1k views

Quasi-compact maps in Number Theory

Can someone give me an example of a non-quasi-compact morphism of schemes which arises naturally in the field of Algebraic Number Theory?
Andrew Stout's user avatar
6 votes

Does smoothness descend along flat morphisms?

Your second question is answered affirmatively by EGA IV_2 Corollary 6.5.2, which references EGA IV_1 $\S0$ 17.3.3(i). Here you only need to assume that $f: X \rightarrow Y$ is a flat morphism of loca …
Andrew Stout's user avatar
5 votes

algebraic multivariate power series over a field

I am not sure if this is what the OP really wants, but this is the proof I had in mind. Theorem. Let $(A,m)$ be a local ring which is obtained by localizing a finitely generated $k$-algebra where $k$ …
Andrew Stout's user avatar
3 votes
0 answers
191 views

What are the enforceable models of local artinian rings?

I was reading Hodges' "Model Theory" Chapter 8 a propos existentially closed models of $\forall_2$ theories in a countable first order language $L$. He extends the proof of the omitting type theorem …
2 votes
0 answers
133 views

quasi-ordinary singularities on a versal deformation?

Let $V$ be a variety over $\mathbb{C}$ and suppose $O$ is a singular point of $V$. Are there conditions on $(V,O)$ such that a versal deformation $W$ of $(V,O)$ has only quasi-ordinary singularities. …
Andrew Stout's user avatar
2 votes
2 answers
490 views

Model Theoretic Localization

This is a re-post on a previous question I asked. My first question was too vague to warrant detailed responses. Really, I have two specific questions to ask. 1) Let $\sigma = (A; \{0,1\}; +, \times …
Andrew Stout's user avatar
1 vote

finite global dimension vs integral Domain

No, but Serre proved that for noetherian local rings having finite global dimension is the same as being regular. So, choose any non-regular local ring which at the same time an integral domain such …
Andrew Stout's user avatar
1 vote
1 answer
478 views

formally étale morphisms which are also universally closed

A morphism of schemes which is formally unramified, universally closed, and a monomorphism is a closed immersion. Is it possible to characterize morphisms which are formally etale and universally clos …
Andrew Stout's user avatar