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feat(Algebra): projective dimension of quotient regular sequence#31644

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Thmoas-Guan:projective-dimension-of-quotSMulTop
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feat(Algebra): projective dimension of quotient regular sequence#31644
Thmoas-Guan wants to merge 139 commits intoleanprover-community:masterfrom
Thmoas-Guan:projective-dimension-of-quotSMulTop

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@Thmoas-Guan Thmoas-Guan commented Nov 15, 2025

In this PR, we proved that for finitely generated module over Noetherian local ring, quotient by regular sequence increase the projective dimension by exactly its length.


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@github-actions github-actions bot added the t-ring-theory Ring theory label Nov 15, 2025
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github-actions bot commented Nov 15, 2025

PR summary 4ec5d95aa6

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference
Mathlib.RingTheory.Regular.ProjectiveDimension (new file) 2210

Declarations diff

+ add_one_le_iff'
+ add_one_le_natCast_iff
+ add_one_le_zero_iff
+ coe_eq_natCast
+ ext_vanish_of_for_all_finite
+ lt_zero_iff_eq_bot
+ projectiveDimension_eq_zero_of_projective
+ projectiveDimension_quotSMulTop_eq_succ_of_isSMulRegular
+ projectiveDimension_quotient_eq_length
+ projectiveDimension_quotient_regular_sequence

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.


Increase in tech debt: (relative, absolute) = (2.00, 0.00)
Current number Change Type
6897 2 backward.isDefEq.respectTransparency

Current commit 99365ae914
Reference commit 4ec5d95aa6

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).

Comment on lines +126 to +128
lemma ext_vanish_of_for_all_finite (M : ModuleCat.{v} R) (n : ℕ) [Module.Finite R M]
(h : ∀ L : ModuleCat.{v} R, Module.Finite R L → Subsingleton (Ext.{w} M L n)) :
∀ N : ModuleCat.{v} R, Subsingleton (Ext.{w} M N n) := by
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Suggested change
lemma ext_vanish_of_for_all_finite (M : ModuleCat.{v} R) (n : ℕ) [Module.Finite R M]
(h : ∀ L : ModuleCat.{v} R, Module.Finite R L → Subsingleton (Ext.{w} M L n)) :
N : ModuleCat.{v} R, Subsingleton (Ext.{w} M N n) := by
lemma subsingleton_ext_of_forall_finite (M : ModuleCat.{v} R) (n : ℕ) [Module.Finite R M]
(h : ∀ L : ModuleCat.{v} R, Module.Finite R L → Subsingleton (Ext.{w} M L n))
(N : ModuleCat.{v} R) : Subsingleton (Ext.{w} M N n) := by

Comment on lines +111 to +112
have : Subsingleton (Ext S.X₂ M (n + 1)) :=
subsingleton_of_forall_eq 0 Ext.eq_zero_of_projective
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This should be its own instance.
(arguably should replace Ext.eq_zero_of_projective)

@erdOne erdOne added the awaiting-author A reviewer has asked the author a question or requested changes. label Nov 15, 2025
@mathlib4-merge-conflict-bot mathlib4-merge-conflict-bot added the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Nov 19, 2025
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This pull request has conflicts, please merge master and resolve them.

@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 Feb 24, 2026
@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 Mar 6, 2026
@mathlib-merge-conflicts mathlib-merge-conflicts bot added the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Mar 6, 2026
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This pull request has conflicts, please merge master and resolve them.

@github-actions github-actions bot removed the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Mar 7, 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 Mar 21, 2026
@Thmoas-Guan Thmoas-Guan removed the awaiting-author A reviewer has asked the author a question or requested changes. label Mar 21, 2026
@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 Apr 2, 2026
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This PR/issue depends on:

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