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feat(MeasureTheory.VectorMeasure) : add a definition of total variation for VectorMeasure#25442

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feat(MeasureTheory.VectorMeasure) : add a definition of total variation for VectorMeasure#25442
oliver-butterley wants to merge 88 commits intomasterfrom
oliver-butterley/Variation

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@oliver-butterley oliver-butterley commented Jun 4, 2025

This PR adds variation for any VectorMeasure using a supremum definition. Currently mathlib has TotalVariation defined for a signed measure using the Hahn-Jordan decomposition, but this doesn't generalise.

Includes the result showing that for SignedMeasures the two definitions coincide.

Motivation: generally this is an important concept but specifically as a step for proving RMK in the complex case which in turn is a step to prove the spectral theorem.

Co-authored-by: @yoh-tanimoto


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@oliver-butterley oliver-butterley added RFC Request for comment and removed WIP Work in progress labels Jun 9, 2025
@oliver-butterley oliver-butterley marked this pull request as ready for review June 9, 2025 09:31
@oliver-butterley oliver-butterley changed the title feat(MeasureTheory.VectorMeasure) : add a definition of variation / total variation for VectorMeasure feat(MeasureTheory.VectorMeasure) : add a definition of total variation for VectorMeasure Jun 9, 2025
@oliver-butterley oliver-butterley added the t-measure-probability Measure theory / Probability theory label Jun 10, 2025
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This PR has been migrated to a fork-based workflow: #26140

@YaelDillies YaelDillies deleted the oliver-butterley/Variation branch August 15, 2025 16:43
mathlib-bors bot pushed a commit that referenced this pull request Feb 10, 2026
…n for VectorMeasure (#26156)

This PR adds variation for any `VectorMeasure` using a supremum definition. Currently mathlib has `TotalVariation` defined for a signed measure using the Hahn-Jordan decomposition, but this doesn't generalise.

Motivation: generally this is an important concept but specifically as a step for proving RMK in the complex case which in turn is a step to prove the spectral theorem.


This PR was migrated from #25442. PR divided into smaller pieces, this is just the definition without additional lemmas. PRs adding further results related to variation are:
* #26160
* #26165 
* #26168 (shows that for `SignedMeasures` the two definitions of variation coincide)

Co-authored-by: @yoh-tanimoto
Co-authored-by: Yoh Tanimoto <[email protected]>
Co-authored-by: Yoh Tanimoto <[email protected]>
rao107 pushed a commit to rao107/mathlib4 that referenced this pull request Feb 18, 2026
…n for VectorMeasure (leanprover-community#26156)

This PR adds variation for any `VectorMeasure` using a supremum definition. Currently mathlib has `TotalVariation` defined for a signed measure using the Hahn-Jordan decomposition, but this doesn't generalise.

Motivation: generally this is an important concept but specifically as a step for proving RMK in the complex case which in turn is a step to prove the spectral theorem.


This PR was migrated from leanprover-community#25442. PR divided into smaller pieces, this is just the definition without additional lemmas. PRs adding further results related to variation are:
* leanprover-community#26160
* leanprover-community#26165 
* leanprover-community#26168 (shows that for `SignedMeasures` the two definitions of variation coincide)

Co-authored-by: @yoh-tanimoto
Co-authored-by: Yoh Tanimoto <[email protected]>
Co-authored-by: Yoh Tanimoto <[email protected]>
Maldooor pushed a commit to Maldooor/mathlib4 that referenced this pull request Feb 25, 2026
…n for VectorMeasure (leanprover-community#26156)

This PR adds variation for any `VectorMeasure` using a supremum definition. Currently mathlib has `TotalVariation` defined for a signed measure using the Hahn-Jordan decomposition, but this doesn't generalise.

Motivation: generally this is an important concept but specifically as a step for proving RMK in the complex case which in turn is a step to prove the spectral theorem.


This PR was migrated from leanprover-community#25442. PR divided into smaller pieces, this is just the definition without additional lemmas. PRs adding further results related to variation are:
* leanprover-community#26160
* leanprover-community#26165 
* leanprover-community#26168 (shows that for `SignedMeasures` the two definitions of variation coincide)

Co-authored-by: @yoh-tanimoto
Co-authored-by: Yoh Tanimoto <[email protected]>
Co-authored-by: Yoh Tanimoto <[email protected]>
pfaffelh pushed a commit to pfaffelh/mathlib4 that referenced this pull request Mar 2, 2026
…n for VectorMeasure (leanprover-community#26156)

This PR adds variation for any `VectorMeasure` using a supremum definition. Currently mathlib has `TotalVariation` defined for a signed measure using the Hahn-Jordan decomposition, but this doesn't generalise.

Motivation: generally this is an important concept but specifically as a step for proving RMK in the complex case which in turn is a step to prove the spectral theorem.


This PR was migrated from leanprover-community#25442. PR divided into smaller pieces, this is just the definition without additional lemmas. PRs adding further results related to variation are:
* leanprover-community#26160
* leanprover-community#26165 
* leanprover-community#26168 (shows that for `SignedMeasures` the two definitions of variation coincide)

Co-authored-by: @yoh-tanimoto
Co-authored-by: Yoh Tanimoto <[email protected]>
Co-authored-by: Yoh Tanimoto <[email protected]>
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migrated-to-fork new-contributor This PR was made by a contributor with at most 5 merged PRs. Welcome to the community! RFC Request for comment t-measure-probability Measure theory / Probability theory

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