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feat(Analysis/Calculus/FDeriv): continuous differentiability from continuous partial derivatives on an open domain in a product space#25304

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feat(Analysis/Calculus/FDeriv): continuous differentiability from continuous partial derivatives on an open domain in a product space#25304
igorkhavkine wants to merge 44 commits intomasterfrom
igorkhavkine/fderiv_of_partial

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@igorkhavkine igorkhavkine commented May 29, 2025

If a function f : E × F → G is continuously differentiable, then its partial derivatives along E and F are also continuous. The non-trivial converse implication holds when the partial derivatives are continuous on an open domain, and they can be added together to give the total derivative of f. See this #mathlib4 > Partial derivatives @ 💬 and the containing thread for some discussion. The PR creates a new import (Mathlib.Analysis.Calculus.FDeriv.Partial), where other results about partial derivatives could go in the future.


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@igorkhavkine igorkhavkine added the new-contributor This PR was made by a contributor with at most 5 merged PRs. Welcome to the community! label May 29, 2025
@github-actions github-actions bot added the t-analysis Analysis (normed *, calculus) label May 29, 2025
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github-actions bot commented May 29, 2025

PR summary bd82942c80

Import changes for modified files

No significant changes to the import graph

Import changes for all files
Files Import difference
Mathlib.Analysis.Calculus.FDeriv.Partial (new file) 1744

Declarations diff

+ Continuous.continuousLinearMapCoprod
+ ContinuousOn.continuousLinearMapCoprod
+ HasFDerivWithinAt.partial_fst
+ HasFDerivWithinAt.partial_snd
+ coprod_comp_prodComm
+ hasFDerivWithinAt_continuousOn_of_partial_continuousOn_open
+ hasFDerivWithinAt_of_partial_fst_continuousOn_prod_open
+ hasFDerivWithinAt_of_partial_snd_continuousOn_prod_open

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 added the awaiting-CI This PR does not pass CI yet. This label is automatically removed once it does. label May 30, 2025
@github-actions github-actions bot removed the awaiting-CI This PR does not pass CI yet. This label is automatically removed once it does. label May 30, 2025
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Thank you for the PR! Here are a few preliminary comments.

@YaelDillies YaelDillies added the awaiting-author A reviewer has asked the author a question or requested changes. label May 31, 2025
@igorkhavkine igorkhavkine added the WIP Work in progress label Jun 4, 2025
@igorkhavkine igorkhavkine added the awaiting-CI This PR does not pass CI yet. This label is automatically removed once it does. label Jun 11, 2025
@github-actions github-actions bot removed the awaiting-CI This PR does not pass CI yet. This label is automatically removed once it does. label Jun 11, 2025
mathlib-bors bot pushed a commit that referenced this pull request Jun 12, 2025
…nearEquiv.prodComm (#25564)

`ContinuousLinearMap.coprod_comp_prodComm` shows that pre-composition of a coproduct with prodComm swaps the terms in the coproduct. A dependency of #25304.



Co-authored-by: igorkhavkine <133780155+igorkhavkine@users.noreply.github.com>
mathlib-bors bot pushed a commit that referenced this pull request Jun 12, 2025
…nearEquiv.prodComm (#25564)

`ContinuousLinearMap.coprod_comp_prodComm` shows that pre-composition of a coproduct with prodComm swaps the terms in the coproduct. A dependency of #25304.



Co-authored-by: igorkhavkine <133780155+igorkhavkine@users.noreply.github.com>
pfaffelh pushed a commit to pfaffelh/mathlib4 that referenced this pull request Jun 15, 2025
…nearEquiv.prodComm (leanprover-community#25564)

`ContinuousLinearMap.coprod_comp_prodComm` shows that pre-composition of a coproduct with prodComm swaps the terms in the coproduct. A dependency of leanprover-community#25304.



Co-authored-by: igorkhavkine <133780155+igorkhavkine@users.noreply.github.com>
pfaffelh pushed a commit to pfaffelh/mathlib4 that referenced this pull request Jun 15, 2025
…nearEquiv.prodComm (leanprover-community#25564)

`ContinuousLinearMap.coprod_comp_prodComm` shows that pre-composition of a coproduct with prodComm swaps the terms in the coproduct. A dependency of leanprover-community#25304.



Co-authored-by: igorkhavkine <133780155+igorkhavkine@users.noreply.github.com>
@mathlib4-dependent-issues-bot mathlib4-dependent-issues-bot removed the blocked-by-other-PR This PR depends on another PR (this label is automatically managed by a bot) label Jun 22, 2025
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Has been migrated to new workflow at #26300.

@YaelDillies YaelDillies deleted the igorkhavkine/fderiv_of_partial branch June 24, 2025 08:16
callesonne pushed a commit to callesonne/mathlib4 that referenced this pull request Jul 24, 2025
…nearEquiv.prodComm (leanprover-community#25564)

`ContinuousLinearMap.coprod_comp_prodComm` shows that pre-composition of a coproduct with prodComm swaps the terms in the coproduct. A dependency of leanprover-community#25304.



Co-authored-by: igorkhavkine <133780155+igorkhavkine@users.noreply.github.com>
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