[Merged by Bors] - feat(RepresentationTheory/Homological): generalization of the vanishing of inflation/restriction

[joelriou]

We show that the map in group cohomology induced by a trivial morphism of groups vanishes in nonzero degrees (because it factors through the cohomology of the trivial group). This allows to generalize the "inflation/restriction" short complex to arbitrary nonzero degrees.

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[github-actions]

PR summary 3c82b32c1d

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff (regex)

+ HInfRes
+ map_eq_zero

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.

Declarations diff (Lean)

✅ Lean-aware diff — post-build, computed from the Lean environment (commit 3c82b32).

• +7 new declarations
• −5 removed declarations

-groupCohomology.H1InfRes_X₁
-groupCohomology.H1InfRes_X₂
-groupCohomology.H1InfRes_X₃
-groupCohomology.H1InfRes_f
-groupCohomology.H1InfRes_g
+groupCohomology.HInfRes
+groupCohomology.HInfRes_X₁
+groupCohomology.HInfRes_X₂
+groupCohomology.HInfRes_X₃
+groupCohomology.HInfRes_f
+groupCohomology.HInfRes_g
+groupCohomology.map_eq_zero

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Decrease in strong tech debt: (relative, absolute) = (2.00, 0.00)

Current number	Change	Type (strong)
backward.defeqAttrib.useBackward	4307	-2
backward.isDefEq.respectTransparency	4866	-2

No changes to weak technical debt.

Current commit 3c82b32c1d
Reference commit dbb8420388

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/scripts/reporting/technical-debt-metrics.py 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).

[Whysoserioushah]

Also (completely irrelavent), I have this PR toCFT that also does the same job :)

[Whysoserioushah]

Thanks!

maintainer merge

[github-actions]

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

[jcommelin]

Thanks 🎉

bors merge

[mathlib-bors]

Pull request successfully merged into master.

Build succeeded:

• ci (staging) / Lint style
• ci (staging) / Build
• ci (staging) / Post-Build Step
• ci (staging) / Test and lint
• ci (staging) / Post-CI job