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[Merged by Bors] - feat: additivize equivariance of morphisms of actions#19171

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[Merged by Bors] - feat: additivize equivariance of morphisms of actions#19171
AntoineChambert-Loir wants to merge 11 commits intomasterfrom
ACL/AddEquiv

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@AntoineChambert-Loir AntoineChambert-Loir commented Nov 17, 2024

Additivize the definition of equivariant morphisms with respect to multiplicative actions.
The notation introduced is X →ₑᵥ[φ] Y for equivariant morphisms, and X →ᵥ[M] Y when the
underlying map is identity.

The goal is to be able to fully additivize the properties of blocks for actions and the definition
of primitive actions in #12052


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@AntoineChambert-Loir AntoineChambert-Loir added the t-algebra Algebra (groups, rings, fields, etc) label Nov 17, 2024
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github-actions bot commented Nov 17, 2024

PR summary 41ce244be7

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference

Declarations diff

+ AddActionHom
+ AddActionSemiHomClass

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).

@YaelDillies YaelDillies changed the title Feat: additivize equivariant of morphisms of actions feat: additivize equivariance of morphisms of actions Nov 17, 2024
@YaelDillies YaelDillies self-assigned this Nov 17, 2024
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Thanks! This is really necessary work

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bot fix style


/-- `φ`-equivariant functions `X → Y`,
where `φ : M → N`, where `M` and `N` act additively on `X` and `Y` respectively -/
notation:25 (name := «AddActionHomLocal≺») X " →ₑ[" φ:25 "] " Y:0 => AddActionHom φ X Y
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This notation is the same as the multiplicative one, right? Surely that's not desirable!

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(and if it is, it should come with a comment explaining why this isn't an issue)

I think you run into trouble when φ = id (PUnit), for instance; but maybe these cases are rare enough that you can make people use the AddActionHom spelling in that case.

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The issue is:

  • finding a new notation (and I don't know which one to choose, that would be remembered and make sense at first sight, and is not too heavy), I had proposed _ev which Yaël didn't like so much.
  • having a duplicate notation which will rarely lead into confusion.

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Can you add a comment explaining that the notation is actually the same? Personally I think it is OK, and we can at least give a try.

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it is said so in the header of the file, but I will add something here.

@eric-wieser eric-wieser added the awaiting-author A reviewer has asked the author a question or requested changes. label Nov 19, 2024
@AntoineChambert-Loir AntoineChambert-Loir removed the awaiting-author A reviewer has asked the author a question or requested changes. label Nov 19, 2024
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bot fix style

AntoineChambert-Loir and others added 2 commits November 22, 2024 10:30
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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LGTM, @eric-wieser what do you think?

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Looks good to me, thanks! @Eric Wieser ?

maintainer merge?

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🚀 Pull request has been placed on the maintainer queue by YaelDillies.

@github-actions github-actions bot added the maintainer-merge A reviewer has approved the changed; awaiting maintainer approval. label Nov 23, 2024
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Let's merge this, we can always change the notation if we realize it is a bad idea.

bors merge

@ghost ghost added the ready-to-merge This PR has been sent to bors. label Nov 25, 2024
mathlib-bors bot pushed a commit that referenced this pull request Nov 25, 2024
Additivize the definition of equivariant morphisms with respect to multiplicative actions.
The notation introduced is `X →ₑᵥ[φ] Y` for equivariant morphisms, and `X →ᵥ[M] Y` when the
underlying map is identity.

The goal is to be able to fully additivize the properties of blocks for actions and the definition
of primitive actions in #12052 



Co-authored-by: leanprover-community-mathlib4-bot <leanprover-community-mathlib4-bot@users.noreply.github.com>
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mathlib-bors bot commented Nov 25, 2024

Pull request successfully merged into master.

Build succeeded:

@mathlib-bors mathlib-bors bot changed the title feat: additivize equivariance of morphisms of actions [Merged by Bors] - feat: additivize equivariance of morphisms of actions Nov 25, 2024
@mathlib-bors mathlib-bors bot closed this Nov 25, 2024
@mathlib-bors mathlib-bors bot deleted the ACL/AddEquiv branch November 25, 2024 13:12
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