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feat(RingTheory): Ideal.span corollaries of Krull's height theorem - #41401

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feat(RingTheory): Ideal.span corollaries of Krull's height theorem#41401
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vlad902:krull-corollaries

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@vlad902 vlad902 commented Jul 6, 2026

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Currently we have statements bounding the height of minimal primes of Ideal.span S. Add the obvious corollaries to bound the height of Ideal.span S directly.

Also add a Set.encard-valued statement of Krull's height theorem. In a Noetherian ring we know the bound should always be finite, but this is useful in downstream applications that are using ENat.


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@github-actions github-actions Bot added the t-ring-theory Ring theory label Jul 6, 2026
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github-actions Bot commented Jul 6, 2026

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PR summary a53dcb7feb

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference

Declarations diff (regex)

+ Ideal.height_le_encard_of_mem_minimalPrimes_span
+ Ideal.height_le_ncard_of_mem_minimalPrimes_span
+ Ideal.height_span_le_card_of_span_ne_top
+ Ideal.height_span_le_encard_of_span_ne_top
+ Ideal.height_span_le_ncard_of_span_ne_top

You can run this locally as follows
## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>

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

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

Declarations diff (Lean)

Lean-aware diff — post-build, computed from the Lean environment (commit a53dcb7).

  • +5 new declarations
  • −0 removed declarations
+Ideal.height_le_encard_of_mem_minimalPrimes_span
+Ideal.height_le_ncard_of_mem_minimalPrimes_span
+Ideal.height_span_le_card_of_span_ne_top
+Ideal.height_span_le_encard_of_span_ne_top
+Ideal.height_span_le_ncard_of_span_ne_top

No changes to strong technical debt.

No changes to weak technical debt.

Current commit a53dcb7feb
Reference commit 85ce110e6b

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/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).

Currently we have statements bounding the height of minimal primes of
`Ideal.span s`. Add the obvious corollaries to bound the height of
`Ideal.span s` directly.

Also add a `Set.encard`-valued statement of Krulls' height theorem for
`Ideal.span`s. In a Noetherian ring we know the bound should always be
finite, but this is useful in downstream applications that are using
ENats.
@vlad902
vlad902 force-pushed the krull-corollaries branch from e900534 to 4ee7bec Compare July 6, 2026 08:55
@joneugster joneugster removed their assignment Sep 4, 2026

@robin-carlier robin-carlier left a comment

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The only question I’d have is whether or not we should just add the Set + Finite version and drop the Finset ones. Otherwise, LGTM.

Comment thread Mathlib/RingTheory/Ideal/KrullsHeightTheorem.lean
@robin-carlier robin-carlier added the awaiting-author Reply -awaiting-author to remove the label on your PR once you have addressed all comments. label Sep 5, 2026
@vlad902 vlad902 removed the awaiting-author Reply -awaiting-author to remove the label on your PR once you have addressed all comments. label Sep 5, 2026

@robin-carlier robin-carlier left a comment

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Thanks!

maintainer merge

Comment thread Mathlib/RingTheory/Ideal/KrullsHeightTheorem.lean
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github-actions Bot commented Sep 6, 2026

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🚀 Pull request has been placed on the maintainer queue by robin-carlier.

@mathlib-triage mathlib-triage Bot added the maintainer-merge A reviewer has approved the changed; awaiting maintainer approval. label Sep 6, 2026
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3 participants