[Merged by Bors] - feat(RepresentationTheory/*): prerequisites for the bar resolution#25546
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101damnations wants to merge 9 commits intomasterfrom
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[Merged by Bors] - feat(RepresentationTheory/*): prerequisites for the bar resolution#25546101damnations wants to merge 9 commits intomasterfrom
101damnations wants to merge 9 commits intomasterfrom
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June 4, 2025 21:46
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PR summary 031a816291
|
| File | Base Count | Head Count | Change |
|---|---|---|---|
| Mathlib.RepresentationTheory.Rep | 1616 | 1618 | +2 (+0.12%) |
| Mathlib.RepresentationTheory.GroupCohomology.Resolution | 1713 | 1712 | -1 (-0.06%) |
| Mathlib.RepresentationTheory.GroupCohomology.Basic | 1714 | 1713 | -1 (-0.06%) |
Import changes for all files
| Files | Import difference |
|---|---|
5 filesMathlib.RepresentationTheory.GroupCohomology.Basic Mathlib.RepresentationTheory.GroupCohomology.Functoriality Mathlib.RepresentationTheory.GroupCohomology.Hilbert90 Mathlib.RepresentationTheory.GroupCohomology.LowDegree Mathlib.RepresentationTheory.GroupCohomology.Resolution |
-1 |
8 filesMathlib.RepresentationTheory.Character Mathlib.RepresentationTheory.Coinduced Mathlib.RepresentationTheory.Coinvariants Mathlib.RepresentationTheory.FDRep Mathlib.RepresentationTheory.Induced Mathlib.RepresentationTheory.Invariants Mathlib.RepresentationTheory.Rep Mathlib.RepresentationTheory.Tannaka |
2 |
Declarations diff
+ Rep.standardComplex
+ diagonalOneIsoLeftRegular
+ diagonal_succ_projective
+ free_projective
+ leftRegular_projective
+ ofMulActionSubsingletonIsoTrivial
+ partialProd_contractNth
+ standardResolution
+ standardResolution.extIso
+ trivial_projective_of_subsingleton
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.
Decrease in tech debt: (relative, absolute) = (1.00, 0.00)
| Current number | Change | Type |
|---|---|---|
| 852 | -1 | erw |
Current commit 031a816291
Reference commit c448abd10a
You can run this locally as
./scripts/technical-debt-metrics.sh pr_summary
- The
relativevalue is the weighted sum of the differences with weight given by the inverse of the current value of the statistic. - The
absolutevalue is therelativevalue divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).
Member
|
This PR LGTM: it gives a great refactor to quite a nasty proof (and removes an |
mathlib-bors bot
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Jun 7, 2025
…25546) The second of 3 PRs refactoring group cohomology to use the bar resolution. Given a comm ring `k` and a group `G`, this is the projective resolution of `k` as a trivial `G`-representation whose `n`th object is `Gⁿ →₀ k[G]` with representation defined pointwise by the left regular representation on k[G], and whose differentials send `(g₀, ..., gₙ)` to `g₀·(g₁, ..., gₙ) + ∑ (-1)ʲ⁺¹·(g₀, ..., gⱼgⱼ₊₁, ..., gₙ) + (-1)ⁿ⁺¹·(g₀, ..., gₙ₋₁)` for `j = 0, ... , n - 1`. The refactor means we can reuse this material to set up group homology. In #21736 we defined an isomorphism `Rep.diagonalSuccIsoFree` between the objects in the standard resolution and bar resolution. In the next PR, #21738, we show that this isomorphism defines a commutative square with the respective differentials, and thus conclude that the bar resolution differential squares to zero and that the 2 complexes are isomorphic. We carry the exactness properties across this isomorphism to conclude the bar resolution is a projective resolution too, in `Rep.barResolution`. In this PR we factor out some material from #21738, to make it easier to review.
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Pull request successfully merged into master. Build succeeded: |
joelriou
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Jun 8, 2025
…25546) The second of 3 PRs refactoring group cohomology to use the bar resolution. Given a comm ring `k` and a group `G`, this is the projective resolution of `k` as a trivial `G`-representation whose `n`th object is `Gⁿ →₀ k[G]` with representation defined pointwise by the left regular representation on k[G], and whose differentials send `(g₀, ..., gₙ)` to `g₀·(g₁, ..., gₙ) + ∑ (-1)ʲ⁺¹·(g₀, ..., gⱼgⱼ₊₁, ..., gₙ) + (-1)ⁿ⁺¹·(g₀, ..., gₙ₋₁)` for `j = 0, ... , n - 1`. The refactor means we can reuse this material to set up group homology. In #21736 we defined an isomorphism `Rep.diagonalSuccIsoFree` between the objects in the standard resolution and bar resolution. In the next PR, #21738, we show that this isomorphism defines a commutative square with the respective differentials, and thus conclude that the bar resolution differential squares to zero and that the 2 complexes are isomorphic. We carry the exactness properties across this isomorphism to conclude the bar resolution is a projective resolution too, in `Rep.barResolution`. In this PR we factor out some material from #21738, to make it easier to review.
TOMILO87
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Jun 8, 2025
…25546) The second of 3 PRs refactoring group cohomology to use the bar resolution. Given a comm ring `k` and a group `G`, this is the projective resolution of `k` as a trivial `G`-representation whose `n`th object is `Gⁿ →₀ k[G]` with representation defined pointwise by the left regular representation on k[G], and whose differentials send `(g₀, ..., gₙ)` to `g₀·(g₁, ..., gₙ) + ∑ (-1)ʲ⁺¹·(g₀, ..., gⱼgⱼ₊₁, ..., gₙ) + (-1)ⁿ⁺¹·(g₀, ..., gₙ₋₁)` for `j = 0, ... , n - 1`. The refactor means we can reuse this material to set up group homology. In #21736 we defined an isomorphism `Rep.diagonalSuccIsoFree` between the objects in the standard resolution and bar resolution. In the next PR, #21738, we show that this isomorphism defines a commutative square with the respective differentials, and thus conclude that the bar resolution differential squares to zero and that the 2 complexes are isomorphic. We carry the exactness properties across this isomorphism to conclude the bar resolution is a projective resolution too, in `Rep.barResolution`. In this PR we factor out some material from #21738, to make it easier to review.
callesonne
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Jul 24, 2025
…eanprover-community#25546) The second of 3 PRs refactoring group cohomology to use the bar resolution. Given a comm ring `k` and a group `G`, this is the projective resolution of `k` as a trivial `G`-representation whose `n`th object is `Gⁿ →₀ k[G]` with representation defined pointwise by the left regular representation on k[G], and whose differentials send `(g₀, ..., gₙ)` to `g₀·(g₁, ..., gₙ) + ∑ (-1)ʲ⁺¹·(g₀, ..., gⱼgⱼ₊₁, ..., gₙ) + (-1)ⁿ⁺¹·(g₀, ..., gₙ₋₁)` for `j = 0, ... , n - 1`. The refactor means we can reuse this material to set up group homology. In leanprover-community#21736 we defined an isomorphism `Rep.diagonalSuccIsoFree` between the objects in the standard resolution and bar resolution. In the next PR, leanprover-community#21738, we show that this isomorphism defines a commutative square with the respective differentials, and thus conclude that the bar resolution differential squares to zero and that the 2 complexes are isomorphic. We carry the exactness properties across this isomorphism to conclude the bar resolution is a projective resolution too, in `Rep.barResolution`. In this PR we factor out some material from leanprover-community#21738, to make it easier to review.
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The second of 3 PRs refactoring group cohomology to use the bar resolution. Given a comm ring
kand a groupG, this is the projective resolution ofkas a trivialG-representation whosenth object isGⁿ →₀ k[G]with representation defined pointwise by the left regular representation on k[G], and whose differentials send(g₀, ..., gₙ)tog₀·(g₁, ..., gₙ) + ∑ (-1)ʲ⁺¹·(g₀, ..., gⱼgⱼ₊₁, ..., gₙ) + (-1)ⁿ⁺¹·(g₀, ..., gₙ₋₁)forj = 0, ... , n - 1.The refactor means we can reuse this material to set up group homology.
In #21736 we defined an isomorphism
Rep.diagonalSuccIsoFreebetween the objects in the standard resolution and bar resolution. In the next PR, #21738, we show that this isomorphism defines a commutative square with the respective differentials, and thus conclude that the bar resolution differential squares to zero and that the 2 complexes are isomorphic. We carry the exactness properties across this isomorphism to conclude the bar resolution is a projective resolution too, inRep.barResolution.In this PR we factor out some material from #21738, to make it easier to review.