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feat(AlgebraicTopology/ModelCategory): a trick by Joyal#20224

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feat(AlgebraicTopology/ModelCategory): a trick by Joyal#20224
joelriou wants to merge 52 commits intomasterfrom
jriou-joyal-trick

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@joelriou joelriou commented Dec 24, 2024

In order to construct a model category, we may sometimes have basically proven all the axioms with the exception of the left lifting property of cofibrations with respect to trivial fibrations. A trick by Joyal allows to obtain this lifting property under suitable assumptions, namely that cofibrations are stable under composition and cobase change.


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@joelriou joelriou added the t-category-theory Category theory label Dec 24, 2024
@mathlib4-dependent-issues-bot mathlib4-dependent-issues-bot added the blocked-by-other-PR This PR depends on another PR (this label is automatically managed by a bot) label Dec 24, 2024
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mathlib4-dependent-issues-bot commented Dec 24, 2024

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PR summary eecc0d927c

Import changes exceeding 2%

% File
+10.24% Mathlib.AlgebraicTopology.ModelCategory.Basic

Import changes for modified files

Dependency changes

File Base Count Head Count Change
Mathlib.AlgebraicTopology.ModelCategory.Basic 586 646 +60 (+10.24%)
Import changes for all files
Files Import difference
Mathlib.AlgebraicTopology.ModelCategory.Basic 60
Mathlib.AlgebraicTopology.ModelCategory.JoyalTrick (new file) 640
Mathlib.CategoryTheory.MorphismProperty.WeakFactorizationSystem (new file) 643
Mathlib.AlgebraicTopology.ModelCategory.Instances (new file) 645

Declarations diff

+ IsWeakFactorizationSystem
+ cofibrations_isStableUnderCoproductsOfShape
+ cofibrations_rlp
+ fibrations_isStableUnderProductsOfShape
+ fibrations_llp
+ hasLiftingProperty_of_wfs
+ instance : (cofibrations C).IsMultiplicative := by
+ instance : (cofibrations C).IsStableUnderCobaseChange := by
+ instance : (fibrations C).IsMultiplicative := by
+ instance : (fibrations C).IsStableUnderBaseChange := by
+ instance : (trivialCofibrations C).IsMultiplicative := by
+ instance : (trivialCofibrations C).IsStableUnderCobaseChange := by
+ instance : (trivialFibrations C).IsMultiplicative := by
+ instance : (trivialFibrations C).IsStableUnderBaseChange := by
+ instance : MorphismProperty.IsWeakFactorizationSystem (cofibrations C) (trivialFibrations C)
+ instance : MorphismProperty.IsWeakFactorizationSystem (trivialCofibrations C) (fibrations C)
+ instance [(cofibrations C).IsStableUnderCobaseChange] [hf : Cofibration f] :
+ instance [(cofibrations C).IsStableUnderCobaseChange] [hg : Cofibration g] :
+ instance [(cofibrations C).IsStableUnderComposition]
+ instance [(fibrations C).IsStableUnderComposition]
+ instance [(weakEquivalences C).IsStableUnderComposition]
+ instance [CategoryWithWeakEquivalences C] [CategoryWithCofibrations C]
+ instance [CategoryWithWeakEquivalences C] [CategoryWithFibrations C]
+ instance [IsWeakFactorizationSystem (cofibrations C) (trivialFibrations C)] :
+ instance [IsWeakFactorizationSystem (cofibrations C) (trivialFibrations C)] [IsIso f] :
+ instance [IsWeakFactorizationSystem (trivialCofibrations C) (fibrations C)] :
+ instance [IsWeakFactorizationSystem (trivialCofibrations C) (fibrations C)] [IsIso f] :
+ joyal_trick
+ llp_eq_of_wfs
+ mk'.cm3a_aux
+ rlp_eq_of_wfs
+ trivialCofibrations_isStableUnderCoproductsOfShape
+ trivialCofibrations_rlp
+ trivialFibrations_isStableUnderProductsOfShape
+ trivialFibrations_llp
+ weakEquivalence_of_postcomp
+ weakEquivalence_of_postcomp_of_fac
+ weakEquivalence_of_precomp
+ weakEquivalence_of_precomp_of_fac
++ instance [(fibrations C).IsStableUnderBaseChange]
++ instance [(trivialCofibrations C).IsStableUnderCobaseChange]
++ instance [(trivialFibrations C).IsStableUnderBaseChange]
++ instance [IsWeakFactorizationSystem (cofibrations C) (trivialFibrations C)]
++ mk'
+++++ instance [IsWeakFactorizationSystem (trivialCofibrations C) (fibrations C)]

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

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

The doc-module for script/declarations_diff.sh contains some details about this script.


No changes to technical debt.

You can run this locally as

./scripts/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).

@leanprover-community-bot-assistant leanprover-community-bot-assistant added the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Jan 11, 2025
@github-actions github-actions bot added the large-import Automatically added label for PRs with a significant increase in transitive imports label Jan 12, 2025
@leanprover-community-bot-assistant leanprover-community-bot-assistant removed the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Jan 12, 2025
@leanprover-community-bot-assistant leanprover-community-bot-assistant added the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Jan 22, 2025
@leanprover-community-bot-assistant leanprover-community-bot-assistant 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 17, 2025
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This pull request has conflicts, please merge master and resolve them.

@leanprover-community-bot-assistant leanprover-community-bot-assistant added the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Apr 8, 2025
@joneugster joneugster changed the title AlgebraicTopology(ModelCategory): a trick by Joyal feat(AlgebraicTopology/ModelCategory): a trick by Joyal Apr 17, 2025
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This PR has been migrated to a fork-based workflow: #26169

@joelriou joelriou closed this Jun 19, 2025
@YaelDillies YaelDillies deleted the jriou-joyal-trick branch August 17, 2025 11:43
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