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[Merged by Bors] - feat(CategoryTheory): (co)limits in the category of coalgebras#14236

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[Merged by Bors] - feat(CategoryTheory): (co)limits in the category of coalgebras#14236
mckoen wants to merge 20 commits intomasterfrom
mckoen/comonadic_limits

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@mckoen mckoen commented Jun 28, 2024

Shows that the forgetful functor forget T : Coalgebra T ⥤ C for a comonad T : C ⥤ C creates colimits and creates any limits which T preserves. This is used to show that Coalgebra T has any colimits which C has, and any limits which C has and T preserves. This is generalised to the case of a comonadic functor D ⥤ C.

Dualises everything currently in Mathlib.CategoryTheory.Monad.Limits.

This contribution was created as part of the AIM workshop "Formalizing Algebraic Geometry" in June 2024.


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@mckoen mckoen added t-category-theory Category theory workshop-AIM-AG-2024 This PR is associated with the 2024 AIM workshop on formalization of algebraic geometry labels Jun 28, 2024
@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 Jun 28, 2024
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github-actions bot commented Jun 28, 2024

PR summary cf2493aad9

Import changes for modified files

Dependency changes

File Base Count Head Count Change
Mathlib.CategoryTheory.Limits.Preserves.Shapes.Equalizers 381 382 +1 (+0.26%)
Import changes for all files
Files Import difference
Too many changes (271)!

Declarations diff

+ coconePoint
+ commuting
+ comonadicCreatesColimits
+ comonadicCreatesLimitOfPreservesLimit
+ comonadicCreatesLimitsOfPreservesLimits
+ comonadicCreatesLimitsOfShapeOfPreservesLimitsOfShape
+ comp_comparison_forget_hasColimit
+ comp_comparison_hasColimit
+ comparison_essSurj
+ comparison_full
+ conePoint
+ forgetCreatesColimit
+ forgetCreatesLimit
+ forgetCreatesLimits
+ forgetCreatesLimitsOfShape
+ forget_creates_limits_of_comonad_preserves
+ hasColimit_of_comp_forget_hasColimit
+ hasColimit_of_coreflective
+ hasColimitsOfShape_of_coreflective
+ hasColimits_of_coreflective
+ hasLimitsOfShape_of_coreflective
+ hasLimits_of_coreflective
+ instance (priority := 1) preservesSplitEqualizers (f g : X ⟶ Y) [HasSplitEqualizer f g] :
+ instance (priority := 100) comonadicOfCoreflective [Coreflective R] :
+ instance [Coreflective R] (X : (coreflectorAdjunction R).toComonad.Coalgebra) :
+ instance δ_iso_of_coreflective [Coreflective R] : IsIso (coreflectorAdjunction R).toComonad.δ := by
+ liftedCocone
+ liftedCoconeIsColimit
+ liftedCone
+ liftedConeIsLimit
+ newCocone
+ newCone
+ rightAdjointPreservesInitialOfCoreflective
++ γ

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

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

@ghost ghost added the blocked-by-other-PR This PR depends on another PR (this label is automatically managed by a bot) label Jun 28, 2024
@ghost ghost removed the blocked-by-other-PR This PR depends on another PR (this label is automatically managed by a bot) label Jul 2, 2024
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ghost commented Jul 2, 2024

This PR/issue depends on:

@ghost ghost added the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Jul 2, 2024
@ghost ghost removed the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Jul 4, 2024
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Thanks 🎉

bors merge

mathlib-bors bot pushed a commit that referenced this pull request Jul 10, 2024
Shows that the forgetful functor `forget T : Coalgebra T ⥤ C` for a comonad `T : C ⥤ C` creates colimits and creates any limits which `T` preserves. This is used to show that `Coalgebra T` has any colimits which `C` has, and any limits which `C` has and `T` preserves. This is generalised to the case of a comonadic functor `D ⥤ C`.

Dualises everything currently in [Mathlib.CategoryTheory.Monad.Limits](https://leanprover-community.github.io/mathlib4_docs/Mathlib/CategoryTheory/Monad/Limits.html).

This contribution was created as part of the AIM workshop "Formalizing Algebraic Geometry" in June 2024.



Co-authored-by: dagurtomas <dagurtomas@gmail.com>
Co-authored-by: adamtopaz <github@adamtopaz.com>
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mathlib-bors bot commented Jul 10, 2024

Pull request successfully merged into master.

Build succeeded:

@mathlib-bors mathlib-bors bot changed the title feat(CategoryTheory): (co)limits in the category of coalgebras [Merged by Bors] - feat(CategoryTheory): (co)limits in the category of coalgebras Jul 10, 2024
@mathlib-bors mathlib-bors bot closed this Jul 10, 2024
@mathlib-bors mathlib-bors bot deleted the mckoen/comonadic_limits branch July 10, 2024 18:10
@adomani adomani mentioned this pull request Aug 1, 2024
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5 participants