[Merged by Bors] - feat(Algebra/Category/Ring): Under.pushout preserves finite limits for properties with stable equalizers#39572
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PR summary 783b2a40cb
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| File | Base Count | Head Count | Change |
|---|---|---|---|
| Mathlib.Algebra.Category.Ring.Under.Property | 2072 | 2074 | +2 (+0.10%) |
Import changes for all files
| Files | Import difference |
|---|---|
Mathlib.Algebra.Category.Ring.Under.Property |
2 |
Declarations diff
+ CommRingCat.preservesLimit_parallelPair_tensorProd_iff_tensorEqualizer_bijective
+ HasStableEqualizers
+ Over.pullbackCompForgetIso
+ RingHom.HasFiniteProducts.preservesFiniteProducts_pushout
+ RingHom.HasStableEqualizers.preservesEqualizers_pushout
+ RingHom.HasStableEqualizers.preservesFiniteLimits_pushout
+ RingHom.HasStableEqualizers.preservesLimit_parallelPair_tensorProd
+ Under.pushoutCompForgetIso
+ instance {X Y : C} (f : X ⟶ Y) [HasPullbacksAlong f] : P.HasPullbacksAlong f
+ instance {X Y : C} (f : X ⟶ Y) [HasPushoutsAlong f] : P.HasPushoutsAlong f
+ preservesColimit_iff_of_iso_diagram
+ preservesLimit_iff_of_iso_diagram
You can run this locally as follows
## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>
## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.
No changes to strong technical debt.
No changes to weak technical debt.
dagurtomas
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May 21, 2026
dagurtomas
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… variants of `preservesLimits_of_natIso` (#39667) ... as well as `preservesLimit_iff_isLimit_mapCone`: a functor preserves a limit if and only if it preserves some limit cone This PR was automatically created from PR #39572 by @chrisflav via a [review comment](#39572 (comment)) by @dagurtomas. Co-authored-by: chrisflav <136261474+chrisflav@users.noreply.github.com>
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… variants of `preservesLimits_of_natIso` (leanprover-community#39667) ... as well as `preservesLimit_iff_isLimit_mapCone`: a functor preserves a limit if and only if it preserves some limit cone This PR was automatically created from PR leanprover-community#39572 by @chrisflav via a [review comment](leanprover-community#39572 (comment)) by @dagurtomas.
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Under.pushout preserves finite coproducts for properties with stable equalizersUnder.pushout preserves finite limits for properties with stable equalizers
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Thanks! bors merge |
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…for properties with stable equalizers (#39572) We introduce a predicate `RingHom.HasStableEqualizers` for properties of ring homomorphisms: This is satisfied for `P` if base change along *arbitrary* ring homomorphisms preserves the equalizer of any two algebra maps between algebras satisfying `P`. In a follow-up PR we will show that finite étale ring homomorphisms satisfy this predicate. We relate `RingHom.HasStableEqualizers` to preservation of finite limits in `P.Under R` for `R : CommRingCat`. From Pi1.
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Pull request successfully merged into master. Build succeeded: |
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Under.pushout preserves finite limits for properties with stable equalizersUnder.pushout preserves finite limits for properties with stable equalizers
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May 25, 2026
The merge of master in 76b190c lost four lemmas added by master PR leanprover-community#39667 (commit 27850fe): `preservesLimit_iff_isLimit_mapCone`, `preservesLimitsOfSize_iff_of_natIso`, `preservesColimit_iff_isColimit_mapCocone`, and `preservesColimitsOfSize_iff_of_natIso`. PR leanprover-community#39572's new file `Algebra/Category/Ring/Under/Property.lean` uses the first of these, so it failed to elaborate. Restore them and add the now-standard `set_option backward.defeqAttrib.useBackward true in` scope to the ported `CommRingCat.preservesLimit_parallelPair_tensorProd_iff_tensorEqualizer_bijective`. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
b-mehta
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… variants of `preservesLimits_of_natIso` (leanprover-community#39667) ... as well as `preservesLimit_iff_isLimit_mapCone`: a functor preserves a limit if and only if it preserves some limit cone This PR was automatically created from PR leanprover-community#39572 by @chrisflav via a [review comment](leanprover-community#39572 (comment)) by @dagurtomas. Co-authored-by: chrisflav <136261474+chrisflav@users.noreply.github.com>
b-mehta
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Jun 2, 2026
…for properties with stable equalizers (leanprover-community#39572) We introduce a predicate `RingHom.HasStableEqualizers` for properties of ring homomorphisms: This is satisfied for `P` if base change along *arbitrary* ring homomorphisms preserves the equalizer of any two algebra maps between algebras satisfying `P`. In a follow-up PR we will show that finite étale ring homomorphisms satisfy this predicate. We relate `RingHom.HasStableEqualizers` to preservation of finite limits in `P.Under R` for `R : CommRingCat`. From Pi1.
Bergschaf
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Jun 3, 2026
… variants of `preservesLimits_of_natIso` (leanprover-community#39667) ... as well as `preservesLimit_iff_isLimit_mapCone`: a functor preserves a limit if and only if it preserves some limit cone This PR was automatically created from PR leanprover-community#39572 by @chrisflav via a [review comment](leanprover-community#39572 (comment)) by @dagurtomas. Co-authored-by: chrisflav <136261474+chrisflav@users.noreply.github.com>
Bergschaf
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Jun 3, 2026
…for properties with stable equalizers (leanprover-community#39572) We introduce a predicate `RingHom.HasStableEqualizers` for properties of ring homomorphisms: This is satisfied for `P` if base change along *arbitrary* ring homomorphisms preserves the equalizer of any two algebra maps between algebras satisfying `P`. In a follow-up PR we will show that finite étale ring homomorphisms satisfy this predicate. We relate `RingHom.HasStableEqualizers` to preservation of finite limits in `P.Under R` for `R : CommRingCat`. From Pi1.
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We introduce a predicate
RingHom.HasStableEqualizersfor properties of ring homomorphisms: This is satisfied forPif base change along arbitrary ring homomorphisms preserves the equalizer of any two algebra maps between algebras satisfyingP. In a follow-up PR we will show that finite étale ring homomorphisms satisfy this predicate.We relate
RingHom.HasStableEqualizersto preservation of finite limits inP.Under RforR : CommRingCat.From Pi1.