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feat (LocalRing/MaximalIdeal/Basic): add LocalRing.not_mem_maximalIdeal and nilradmax_localization_IsSelf #17549

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@maddycrim maddycrim commented Oct 8, 2024

For theorem LocalRing.not_mem_maximalIdeal: An element x of a commutative local semiring is not contained in the maximal ideal if and only if it is a unit.

For noncomputable def nilradmax_localization_IsSelf: Let S be the localization of a commutative semiring R at a submonoid M that does not contain 0. If the nilradical of R is maximal then there is a ring isomorphism between R and S.

As discussed on Zulip here: https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/PR.20Permission/near/472582165


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@github-actions github-actions bot added the new-contributor This PR was made by a contributor with fewer than 5 merged PRs. Welcome to the community! label Oct 8, 2024
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github-actions bot commented Oct 8, 2024

PR summary 3bf55718c2

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference

Declarations diff

+ nilradmaxlocalizationIsSelf
+ not_mem_maximalIdeal

You can run this locally as follows
## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

@github-actions github-actions bot added the t-algebra Algebra (groups, rings, fields, etc) label Oct 8, 2024
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Thanks for the contribution!
Some suggestions:

Let `S` be the localization of a commutative semiring `R` at a submonoid `M` that does not
contain 0. If the nilradical of `R` is maximal then there is a ring isomorphism between `R` and `S`.
-/
noncomputable def nilradmax_localization_IsSelf (h : (nilradical R).IsMaximal) (h' : (0 : R) ∉ M)
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The naming convention requires defs to be in lowerCamelCase, i.e., nilradMaxLocalizationIsSelf in this case.

Mathlib/RingTheory/LocalRing/MaximalIdeal/Basic.lean Outdated Show resolved Hide resolved
Mathlib/RingTheory/LocalRing/MaximalIdeal/Basic.lean Outdated Show resolved Hide resolved
An element `x` of a commutative local semiring is not contained in the maximal ideal
iff it is a unit.
-/
theorem LocalRing.not_mem_maximalIdeal [LocalRing R] (x : R) :
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I think maybe this theorem should be moved to immediately follow the theorem mem_maximalIdeal.

@mbkybky mbkybky added the awaiting-author A reviewer has asked the author a question or requested changes label Oct 9, 2024
@maddycrim maddycrim requested a review from mbkybky October 9, 2024 18:05
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