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feat(RingTheory/UniqueFactorizationDomain): UFD iff height one primes are principal#36781

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feat(RingTheory/UniqueFactorizationDomain): UFD iff height one primes are principal#36781
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@hommmmm hommmmm commented Mar 18, 2026

We prove that a Noetherian integral domain is a UFD if and only if every prime ideal of height one is principal (UniqueFactorizationMonoid.iff_height_one_prime_principal).

New declarations

  • UniqueFactorizationMonoid.exists_height_one_le_of_finite_height: given a prime of finite height ≥ 1, there exists a height one prime contained in it.
  • UniqueFactorizationMonoid.ne_bot_of_height_one: an ideal of height one is nonzero.
  • UniqueFactorizationMonoid.height_ge_one_of_prime_ne_bot: the height of a nonzero prime ideal in a domain is at least one.
  • UniqueFactorizationMonoid.height_one_prime_principal: in a UFD, every height one prime is principal.
  • UniqueFactorizationMonoid.of_height_one_prime_principal: every height one prime being principal implies UFD (Noetherian case).
  • UniqueFactorizationMonoid.iff_height_one_prime_principal: the full iff statement.

References

See https://stacks.math.columbia.edu/tag/0AFT

AI Disclosure

This code is written without AI, then uses Claude Code with cameronfreer's Lean4-skills (specifically, the review, refactor, and golf workflow) for style changes, refactoring and golfing.


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hommmmm added 4 commits March 17, 2026 15:26
This is a new fork of mathlib 4 for PR on the factoriality criterion. Original edits were made in https://github.com/uw-math-ai/auslander-buchsbaum
Shorten proof significantly. Clean up comments. Refactor `ne_bot_of_height_one`.
Fix <= 1 and add attribution to doc string.
@github-actions github-actions bot added the new-contributor This PR was made by a contributor with at most 5 merged PRs. Welcome to the community! label Mar 18, 2026
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Welcome new contributor!

Thank you for contributing to Mathlib! If you haven't done so already, please review our contribution guidelines, as well as the style guide and naming conventions. In particular, we kindly remind contributors that we have guidelines regarding the use of AI when making pull requests.

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@github-actions github-actions bot added the large-import Automatically added label for PRs with a significant increase in transitive imports label Mar 18, 2026
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github-actions bot commented Mar 18, 2026

PR summary 316a0377d0

Import changes exceeding 2%

% File
+66.58% Mathlib.RingTheory.UniqueFactorizationDomain.Kaplansky

Import changes for modified files

Dependency changes

File Base Count Head Count Change
Mathlib.RingTheory.UniqueFactorizationDomain.Kaplansky 1113 1854 +741 (+66.58%)
Import changes for all files
Files Import difference
Mathlib.RingTheory.PowerSeries.Ideal 409
Mathlib.RingTheory.UniqueFactorizationDomain.Kaplansky 741

Declarations diff

+ exists_height_one_le_of_finite_height
+ height_one_prime_principal
+ ne_bot_of_height_one
+ of_height_one_prime_principal

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

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

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


No changes to technical debt.

You can run this locally as

./scripts/reporting/technical-debt-metrics.sh pr_summary
  • The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
  • The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

@github-actions github-actions bot added the t-ring-theory Ring theory label Mar 18, 2026
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tb65536 commented Mar 20, 2026

Note #36739

@Thmoas-Guan
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Thmoas-Guan commented Mar 20, 2026

Note #36739

I believe this also partly overlaps with your #36785 :(
This definitely need some rearrangement.

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Welcome! Could you please clarify if and how you used AI for (parts of) this pull request? Note that our contribution guidelines require disclosure of any AI assistance.
Please note that this message does not say anything about your PR in particular, this is just a regular question we ask on PRs by new contributors.

@chrisflav chrisflav added the awaiting-author A reviewer has asked the author a question or requested changes. label Mar 22, 2026
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hommmmm commented Mar 22, 2026

Welcome! Could you please clarify if and how you used AI for (parts of) this pull request? Note that our contribution guidelines require disclosure of any AI assistance. Please note that this message does not say anything about your PR in particular, this is just a regular question we ask on PRs by new contributors.

Updated PR message with AI disclosure

-awaiting-author

@github-actions github-actions bot removed the awaiting-author A reviewer has asked the author a question or requested changes. label Mar 22, 2026
@mariainesdff mariainesdff removed their assignment Mar 31, 2026
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