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feat(RingTheory/AdicCompletion): AdicCompletion of Noetherian ring is Noetherian#38331

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feat(RingTheory/AdicCompletion): AdicCompletion of Noetherian ring is Noetherian#38331
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Thmoas-Guan:AdicCompletion-IsNoetherian

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@Thmoas-Guan

@Thmoas-Guan Thmoas-Guan commented Apr 21, 2026

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For I an ideal of R, if R/I is Noetherian and I is finitely generated, the the completion of R wrt I is Noetherian.


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@mathlib-dependent-issues mathlib-dependent-issues Bot removed the blocked-by-other-PR This PR depends on another PR (this label is automatically managed by a bot) label May 31, 2026
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mathlib-dependent-issues Bot commented May 31, 2026

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This PR/issue depends on:

Comment thread Mathlib/RingTheory/AdicCompletion/Noetherian.lean Outdated
Comment thread Mathlib/RingTheory/AdicCompletion/Noetherian.lean Outdated
Comment thread Mathlib/RingTheory/AdicCompletion/Noetherian.lean Outdated
Comment thread Mathlib/RingTheory/AdicCompletion/Noetherian.lean Outdated

@faenuccio faenuccio left a comment

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I left some comments.


variable {R : Type u} [CommRing R] (I : Ideal R)

section

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I think that this section should rather live in Mathlib.Topology.Algebra.Ring.Ideal, no?

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This is also what I am not very sure about, should I add adic completion of Noetherian ring is Noetherian here?

Comment thread Mathlib/RingTheory/AdicCompletion/Noetherian.lean Outdated
· simp [degle, coeff']
· simp [coeff', hi]

lemma isNoetherianRing_of_isAdicComplete_of_fg [IsNoetherianRing (R ⧸ I)] (fg : I.FG)

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These are almost 70 lines of proof, can't you factor some results?

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I'll try, but I probably need to explain about the proof itself first: by the lemma above using associated graded, it finds series of coefficients forming Cauchy sequence to approximate the final element step by step, this is just complicated by itself, or else we might need some auxilary defs...

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OK, thanks!! You might have a look at the proof of LaurentSeries.Cauchy.limit (or friends around there) because it might give you an idea both on how to conceptualise the proof and on how to factor it.

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awaiting-author

@@ -1,3 +1,3 @@
/-
Copyright (c) 2024 Andrew Yang. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.

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I guess you need to add your name here.

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I added two more stylistic comments

Comment thread Mathlib/RingTheory/AdicCompletion/Noetherian.lean Outdated
Comment thread Mathlib/RingTheory/AdicCompletion/Noetherian.lean Outdated
@faenuccio faenuccio added the awaiting-author A reviewer has asked the author a question or requested changes. label Jul 9, 2026
@Thmoas-Guan Thmoas-Guan removed the awaiting-author A reviewer has asked the author a question or requested changes. label Jul 10, 2026
@mathlib-dependent-issues mathlib-dependent-issues Bot added the blocked-by-other-PR This PR depends on another PR (this label is automatically managed by a bot) label Jul 10, 2026
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Also, can I ask why you removed the awaiting-author tag? I see you factored out the part concerning Rees algebras but the "long proof" still requires some look from you, no?

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