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feat(CategoryTheory): Add exact sequences for Sheaf Cohomology#36218

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Brian-Nugent:coho_exact_api
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feat(CategoryTheory): Add exact sequences for Sheaf Cohomology#36218
Brian-Nugent wants to merge 33 commits intoleanprover-community:masterfrom
Brian-Nugent:coho_exact_api

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@Brian-Nugent Brian-Nugent commented Mar 5, 2026

In this PR, I add the long exact sequence for sheaf cohomology as well as prove that it is functorial. Since sheaf cohomology is defined in terms of Ext, this is done using the covariant sequence for Ext.


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Brian-Nugent and others added 16 commits February 2, 2026 18:18
@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 5, 2026
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github-actions bot commented Mar 5, 2026

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@Brian-Nugent Brian-Nugent added the WIP Work in progress label Mar 5, 2026
@github-actions github-actions 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 5, 2026
@github-actions github-actions bot added large-import Automatically added label for PRs with a significant increase in transitive imports and removed merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) labels Mar 5, 2026
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github-actions bot commented Mar 5, 2026

PR summary b301d257a1

Import changes exceeding 2%

% File
+30.22% Mathlib.Algebra.Category.Grp.ForgetCorepresentable
+31.97% Mathlib.CategoryTheory.Sites.Abelian

Import changes for modified files

Dependency changes

File Base Count Head Count Change
Mathlib.CategoryTheory.Sites.Abelian 804 1061 +257 (+31.97%)
Mathlib.Algebra.Category.Grp.ForgetCorepresentable 503 655 +152 (+30.22%)
Import changes for all files
Files Import difference
21 files Mathlib.CategoryTheory.Abelian.GrothendieckAxioms.Sheaf Mathlib.CategoryTheory.Sites.SheafCohomology.Basic Mathlib.CategoryTheory.Sites.SheafCohomology.MayerVietoris Mathlib.Condensed.AB Mathlib.Condensed.EffectiveEpi Mathlib.Condensed.Epi Mathlib.Condensed.Explicit Mathlib.Condensed.Functors Mathlib.Condensed.Light.AB Mathlib.Condensed.Light.EffectiveEpi Mathlib.Condensed.Light.Epi Mathlib.Condensed.Light.Explicit Mathlib.Condensed.Light.InternallyProjective Mathlib.Condensed.Light.Limits Mathlib.Condensed.Light.Module Mathlib.Condensed.Light.Monoidal Mathlib.Condensed.Light.Small Mathlib.Condensed.Solid Mathlib.Topology.Sheaves.Abelian Mathlib.Topology.Sheaves.AddCommGrpCat Mathlib.Topology.Sheaves.Flasque
1
Mathlib.Condensed.Limits Mathlib.Condensed.Module 22
Mathlib.Topology.Sheaves.MayerVietoris 65
Mathlib.CategoryTheory.Sites.MayerVietorisSquare 146
Mathlib.Algebra.Category.Grp.ForgetCorepresentable 152
Mathlib.CategoryTheory.Sites.Abelian 257
Mathlib.CategoryTheory.Sites.SheafCohomology.ExactSequences (new file) 1753

Declarations diff

+ AddCommGrpCat.uliftZMultiplesAddEquiv
+ H.addEquiv₀_comp
+ H.equiv₀
+ H.equiv₀_naturality
+ H.equiv₀_symm_naturality
+ H.map
+ H.map_apply
+ H.map_comp_apply
+ H.map_id_apply
+ connectingHom
+ connectingHom_naturality
+ functorH
+ instance (F : Sheaf J AddCommGrpCat.{w}) {n : ℕ} [Injective F] : Subsingleton (H F (n + 1))
+ instance (n : ℕ) : (functorH J n).Additive
+ instance : (Functor.const Cᵒᵖ : D ⥤ Cᵒᵖ ⥤ D).Additive
+ instance : (constantSheaf J D).Additive
+ longSequence
+ longSequenceFunctor
+ longSequence_equiv₀_exact₃
+ longSequence_exact
+ longSequence_exact₁
+ longSequence_exact₁'
+ longSequence_exact₂
+ longSequence_exact₂'
+ longSequence_exact₃
+ longSequence_exact₃'
+ longSequence_hom
+ uliftZMultiplesHom.add

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

Current commit 9374a27700
Reference commit b301d257a1

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).

@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 5, 2026
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This PR/issue depends on:

@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 12, 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 12, 2026
@Brian-Nugent Brian-Nugent changed the title feat: Add exact sequences for Sheaf Cohomology feat(CategoryTheory): Add exact sequences for Sheaf Cohomology Mar 31, 2026
@Brian-Nugent Brian-Nugent added t-category-theory Category theory and removed new-contributor This PR was made by a contributor with at most 5 merged PRs. Welcome to the community! labels Mar 31, 2026
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