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[Merged by Bors] - feat(CategoryTheory/Sites): discrete sheaves#13947

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dagur/PreservesDiscrete
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[Merged by Bors] - feat(CategoryTheory/Sites): discrete sheaves#13947
dagurtomas wants to merge 17 commits intomasterfrom
dagur/PreservesDiscrete

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@dagurtomas dagurtomas commented Jun 19, 2024

This PR defines the property of discreteness for sheaves. A discrete sheaf in this context is a sheaf F such that the counit (F(*))^cst ⟶ F is an isomorphism. Here * denotes a particular chosen terminal object of the defining site, and cst denotes the constant sheaf.

We also prove that this property is invariant under equivalence of categories and that certain well-behaved "forgetful" functors preserve and reflect the property.


This will be used in a future PR (#14027) to characterise discrete (light) condensed sets and modules.
The two lemmas sheafComposeNatIso_app_counit and constantCommuteComposeApp_comp_counit added here are not used in this PR, but will be useful in the characterisation of discrete condensed modules.

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@dagurtomas dagurtomas added the WIP Work in progress label Jun 19, 2024
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github-actions bot commented Jun 19, 2024

PR summary ad6c09d123

Import changes

No significant changes to the import graph


Declarations diff

+ constantCommuteCompose
+ constantCommuteComposeApp_comp_counit
+ constantSheafAdj_counit_app
+ equivCommuteConstant
+ equivCommuteConstant'
+ instance [h : F.IsDiscrete J ht] :
+ isDiscrete_iff_forget
+ isDiscrete_iff_isIso_counit_app
+ isDiscrete_iff_mem_essImage
+ isDiscrete_iff_mem_essImage'
+ isDiscrete_iff_of_equivalence
+ isDiscrete_of_iso
+ sheafComposeNatIso_app_counit
+ sheafCompose_reflects_discrete

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>

@dagurtomas dagurtomas added awaiting-review awaiting-CI This PR does not pass CI yet. This label is automatically removed once it does. t-category-theory Category theory and removed WIP Work in progress labels Jun 19, 2024
@github-actions github-actions bot removed the awaiting-CI This PR does not pass CI yet. This label is automatically removed once it does. label Jun 19, 2024
@dagurtomas dagurtomas added awaiting-author A reviewer has asked the author a question or requested changes. WIP Work in progress and removed awaiting-review awaiting-author A reviewer has asked the author a question or requested changes. labels Jun 19, 2024
@dagurtomas dagurtomas added awaiting-review awaiting-CI This PR does not pass CI yet. This label is automatically removed once it does. and removed WIP Work in progress labels Jul 2, 2024
@dagurtomas dagurtomas changed the title feat(CategoryTheory/Sites): reflecting and preserving discreteness of sheaves feat(CategoryTheory/Sites): discrete sheaves Jul 2, 2024
@github-actions github-actions bot removed the awaiting-CI This PR does not pass CI yet. This label is automatically removed once it does. label Jul 2, 2024
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kim-em commented Jul 15, 2024

bors merge

@github-actions github-actions bot added the ready-to-merge This PR has been sent to bors. label Jul 15, 2024
mathlib-bors bot pushed a commit that referenced this pull request Jul 15, 2024
This PR defines the property of discreteness for sheaves. A discrete sheaf in this context is a sheaf `F` such that the counit `(F(*))^cst ⟶ F` is an isomorphism. Here `*` denotes a particular chosen terminal object of the defining site, and `cst` denotes the constant sheaf. 

We also prove that this property is invariant under equivalence of categories and that certain well-behaved "forgetful" functors preserve and reflect the property.
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mathlib-bors bot commented Jul 15, 2024

Build failed (retrying...):

mathlib-bors bot pushed a commit that referenced this pull request Jul 15, 2024
This PR defines the property of discreteness for sheaves. A discrete sheaf in this context is a sheaf `F` such that the counit `(F(*))^cst ⟶ F` is an isomorphism. Here `*` denotes a particular chosen terminal object of the defining site, and `cst` denotes the constant sheaf. 

We also prove that this property is invariant under equivalence of categories and that certain well-behaved "forgetful" functors preserve and reflect the property.
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mathlib-bors bot commented Jul 15, 2024

This PR was included in a batch that was canceled, it will be automatically retried

mathlib-bors bot pushed a commit that referenced this pull request Jul 15, 2024
This PR defines the property of discreteness for sheaves. A discrete sheaf in this context is a sheaf `F` such that the counit `(F(*))^cst ⟶ F` is an isomorphism. Here `*` denotes a particular chosen terminal object of the defining site, and `cst` denotes the constant sheaf. 

We also prove that this property is invariant under equivalence of categories and that certain well-behaved "forgetful" functors preserve and reflect the property.
mathlib-bors bot pushed a commit that referenced this pull request Jul 15, 2024
This PR defines the property of discreteness for sheaves. A discrete sheaf in this context is a sheaf `F` such that the counit `(F(*))^cst ⟶ F` is an isomorphism. Here `*` denotes a particular chosen terminal object of the defining site, and `cst` denotes the constant sheaf. 

We also prove that this property is invariant under equivalence of categories and that certain well-behaved "forgetful" functors preserve and reflect the property.
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mathlib-bors bot commented Jul 15, 2024

Pull request successfully merged into master.

Build succeeded:

@mathlib-bors mathlib-bors bot changed the title feat(CategoryTheory/Sites): discrete sheaves [Merged by Bors] - feat(CategoryTheory/Sites): discrete sheaves Jul 15, 2024
@mathlib-bors mathlib-bors bot closed this Jul 15, 2024
@mathlib-bors mathlib-bors bot deleted the dagur/PreservesDiscrete branch July 15, 2024 21:06
@adomani adomani mentioned this pull request Aug 1, 2024
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