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[Merged by Bors] - feat: sum of a locally finite collection of C^n sections is C^n#27349

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[Merged by Bors] - feat: sum of a locally finite collection of C^n sections is C^n#27349
grunweg wants to merge 3 commits intoleanprover-community:masterfrom
grunweg:cnsections-locallyfinite

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@grunweg grunweg commented Jul 22, 2025

This can be used to golf #26875 (and is nice API anyway).
As such, it is necessary to prove the existence of a Riemannian metric (hence of a Levi-Civita connection).
One could say it's on the path towards the Levi-Civita connection.

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@github-actions github-actions bot added the t-differential-geometry Manifolds etc label Jul 22, 2025
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github-actions bot commented Jul 22, 2025 •
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PR summary f1a92a38b2

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference

Declarations diff

+ ContMDiff.sum_section_of_locallyFinite
+ ContMDiffAt.sum_section_of_locallyFinite
+ ContMDiffOn.sum_section_of_locallyFinite
+ ContMDiffWithinAt.sum_section_of_locallyFinite

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).

@grunweg grunweg mentioned this pull request Jul 22, 2025
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sgouezel
sgouezel reviewed Jul 22, 2025
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bors d+
Thanks!

Mathlib/Geometry/Manifold/VectorBundle/SmoothSection.lean
/-- The sum of a locally finite collection of sections is `C^k` iff each section is.
Version at a point within a set. -/
lemma ContMDiffWithinAt.sum_section_of_locallyFinite {ι : Type*} {t : ι → (x : M) → V x}
(ht : LocallyFinite fun i ↦ {x : M | t i x ≠ 0})
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could you use support (t i) instead, here and below?

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That was the first thing I tried --- it doesn't work since t i is a dependent function.

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mathlib-bors bot commented Jul 22, 2025

✌️ grunweg can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

@ghost ghost added the delegated This pull request has been delegated to the PR author (or occasionally another non-maintainer). label Jul 22, 2025
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grunweg commented Jul 22, 2025

Thanks for the quick review!
bors merge

mathlib-bors bot pushed a commit that referenced this pull request Jul 22, 2025
@grunweg
feat: sum of a locally finite collection of C^n sections is C^n (#27349)
3bfbd0e 
This can be used to golf #26875 (and is nice API anyway).
As such, it is necessary to prove the existence of a Riemannian metric (hence of a Levi-Civita connection).
One could say it's on the path towards the Levi-Civita connection.
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mathlib-bors bot commented Jul 22, 2025

Pull request successfully merged into master.

Build succeeded:

@mathlib-bors mathlib-bors bot changed the title feat: sum of a locally finite collection of C^n sections is C^n [Merged by Bors] - feat: sum of a locally finite collection of C^n sections is C^n Jul 22, 2025
@mathlib-bors mathlib-bors bot closed this Jul 22, 2025
@grunweg grunweg deleted the cnsections-locallyfinite branch July 23, 2025 09:59
callesonne pushed a commit to callesonne/mathlib4 that referenced this pull request Jul 24, 2025
@grunweg @callesonne
feat: sum of a locally finite collection of C^n sections is C^n (lean…
28be132 
…prover-community#27349)

This can be used to golf leanprover-community#26875 (and is nice API anyway).
As such, it is necessary to prove the existence of a Riemannian metric (hence of a Levi-Civita connection).
One could say it's on the path towards the Levi-Civita connection.
hrmacbeth pushed a commit to szqzs/mathlib4 that referenced this pull request Jul 28, 2025
@grunweg @hrmacbeth
feat: sum of a locally finite collection of C^n sections is C^n (lean…
bce66a9 
…prover-community#27349)

This can be used to golf leanprover-community#26875 (and is nice API anyway).
As such, it is necessary to prove the existence of a Riemannian metric (hence of a Levi-Civita connection).
One could say it's on the path towards the Levi-Civita connection.
@grunweg grunweg mentioned this pull request Aug 6, 2025
Closed
mathlib-bors bot pushed a commit that referenced this pull request Aug 6, 2025
@grunweg
feat: locally finite finsums of C^n sections are C^n (#28048)
2e65cf9 
This may seem redundant in light of #27349, but is not: `finsum`s are more convenient for use with partitions of unity:
when using them for constructing new objects, one takes a convex combination
Equilibris pushed a commit to Equilibris/mathlib4 that referenced this pull request Aug 7, 2025
@grunweg
feat: sum of a locally finite collection of C^n sections is C^n (lean…
82e794c 
…prover-community#27349)

This can be used to golf leanprover-community#26875 (and is nice API anyway).
As such, it is necessary to prove the existence of a Riemannian metric (hence of a Levi-Civita connection).
One could say it's on the path towards the Levi-Civita connection.
staroperator pushed a commit to staroperator/mathlib4 that referenced this pull request Aug 8, 2025
@grunweg @staroperator
feat: locally finite finsums of C^n sections are C^n (leanprover-comm…
fa2df54 
…unity#28048)

This may seem redundant in light of leanprover-community#27349, but is not: `finsum`s are more convenient for use with partitions of unity:
when using them for constructing new objects, one takes a convex combination
Paul-Lez pushed a commit to Paul-Lez/mathlib4 that referenced this pull request Aug 23, 2025
@grunweg @Paul-Lez
feat: locally finite finsums of C^n sections are C^n (leanprover-comm…
9294204 
…unity#28048)

This may seem redundant in light of leanprover-community#27349, but is not: `finsum`s are more convenient for use with partitions of unity:
when using them for constructing new objects, one takes a convex combination
Paul-Lez pushed a commit to Paul-Lez/mathlib4 that referenced this pull request Aug 23, 2025
@grunweg @Paul-Lez
feat: locally finite finsums of C^n sections are C^n (leanprover-comm…
4f5c052 
…unity#28048)

This may seem redundant in light of leanprover-community#27349, but is not: `finsum`s are more convenient for use with partitions of unity:
when using them for constructing new objects, one takes a convex combination
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