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The integral closure of a Dedekind domain in a finite separable extension is finite #202

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kbuzzard opened this issue Nov 7, 2024 · 6 comments
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@kbuzzard
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kbuzzard commented Nov 7, 2024

Is it true that if A is a Dedekind domain with field of fractions K, and if L/K is a finite separable extension, then the integral closure B of A in L is a finite A-module? I'm assuming so but was reluctant to add it as an assumption if it was not true in this generality. This is

example : Module.Finite A B := by sorry -- I assume this is correct

in FLT.DedekindDomain.FiniteAdeleRing.BaseChange .

@github-project-automation github-project-automation bot moved this to Unclaimed in FLT Project Nov 7, 2024
@4hma4d
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4hma4d commented Nov 7, 2024

It seems to be true by this

@4hma4d
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4hma4d commented Nov 7, 2024

claim

@kbuzzard kbuzzard moved this from Unclaimed to Claimed in FLT Project Nov 7, 2024
@alreadydone
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alreadydone commented Nov 7, 2024

I also found a reference to Milne, and a reference to a counterexample in the inseparable case. (Krull--Akizuki implies the integral closure is a Dedekind domain even in the inseparable case.)
This paper is also tangentially relevant (a Japanese domain is one whose integral closure in any finite extension of its field of fractions is finite).

@4hma4d
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4hma4d commented Nov 8, 2024

propose #211

@kbuzzard kbuzzard moved this from Claimed to In Progress in FLT Project Nov 8, 2024
@Ruben-VandeVelde
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This is done in 2473f61

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kbuzzard commented Dec 1, 2024

Thanks!

@kbuzzard kbuzzard closed this as completed Dec 1, 2024
@github-project-automation github-project-automation bot moved this from In Progress to Completed in FLT Project Dec 1, 2024
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4 participants