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[Merged by Bors] - feat(Order/Hom): prove disjoint from order embedding #12223

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This adds 3 lemmas which state that if you have an order embedding f such that f a₁ and f a₂ are disjoint/codisjoint/complements, then the same holds for a₁ and a₂.

Motivation: For a project described here, I wanted to know that if two Lie ideals are complements as submodules, then they are complements as Lie ideals too. I realized that the correct level of generality was probably in the Order.Hom.Basic file.

Caveats: I am very much open to golfing/naming/redesign suggestions. Within the modified file, there was already a Disjoint.map_orderIso result, but it requires an OrderIso (not just a one-way embedding) and it requires a SemilatticeInf (whereas my version just uses PartialOrder).

@frederic-marbach frederic-marbach added awaiting-review The author would like community review of the PR t-order Order hierarchy labels Apr 17, 2024
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urkud commented Apr 18, 2024

I golfed your proofs (I hope, without loss of readability). LGTM
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🚀 Pull request has been placed on the maintainer queue by urkud.

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Thanks 🎉

bors merge

@leanprover-community-mathlib4-bot leanprover-community-mathlib4-bot added ready-to-merge This PR has been sent to bors. and removed awaiting-review The author would like community review of the PR labels Apr 18, 2024
mathlib-bors bot pushed a commit that referenced this pull request Apr 18, 2024
This adds 3 lemmas which state that if you have an order embedding `f` such that `f a₁` and `f a₂` are disjoint/codisjoint/complements, then the same holds for `a₁` and `a₂`.

*Motivation*: For a project described [here](https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/Derivations.20on.20Lie.20algebras), I wanted to know that if two Lie ideals are complements as submodules, then they are complements as Lie ideals too. I realized that the correct level of generality was probably in the `Order.Hom.Basic` file.

*Caveats*: I am very much open to golfing/naming/redesign suggestions. Within the modified file, there was already a `Disjoint.map_orderIso` result, but it requires an `OrderIso` (not just a one-way embedding) and it requires a `SemilatticeInf` (whereas my version just uses `PartialOrder`).

Co-authored-by: Yury G. Kudryashov <urkud@urkud.name>
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mathlib-bors bot commented Apr 18, 2024

Pull request successfully merged into master.

Build succeeded:

@mathlib-bors mathlib-bors bot changed the title feat(Order/Hom): prove disjoint from order embedding [Merged by Bors] - feat(Order/Hom): prove disjoint from order embedding Apr 18, 2024
@mathlib-bors mathlib-bors bot closed this Apr 18, 2024
@mathlib-bors mathlib-bors bot deleted the fm_lie_derivations_killing branch April 18, 2024 05:39
@frederic-marbach
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Thank you very much for the golfing and the fast merging. The proofs indeed look much better.

uniwuni pushed a commit that referenced this pull request Apr 19, 2024
This adds 3 lemmas which state that if you have an order embedding `f` such that `f a₁` and `f a₂` are disjoint/codisjoint/complements, then the same holds for `a₁` and `a₂`.

*Motivation*: For a project described [here](https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/Derivations.20on.20Lie.20algebras), I wanted to know that if two Lie ideals are complements as submodules, then they are complements as Lie ideals too. I realized that the correct level of generality was probably in the `Order.Hom.Basic` file.

*Caveats*: I am very much open to golfing/naming/redesign suggestions. Within the modified file, there was already a `Disjoint.map_orderIso` result, but it requires an `OrderIso` (not just a one-way embedding) and it requires a `SemilatticeInf` (whereas my version just uses `PartialOrder`).

Co-authored-by: Yury G. Kudryashov <urkud@urkud.name>
callesonne pushed a commit that referenced this pull request Apr 22, 2024
This adds 3 lemmas which state that if you have an order embedding `f` such that `f a₁` and `f a₂` are disjoint/codisjoint/complements, then the same holds for `a₁` and `a₂`.

*Motivation*: For a project described [here](https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/Derivations.20on.20Lie.20algebras), I wanted to know that if two Lie ideals are complements as submodules, then they are complements as Lie ideals too. I realized that the correct level of generality was probably in the `Order.Hom.Basic` file.

*Caveats*: I am very much open to golfing/naming/redesign suggestions. Within the modified file, there was already a `Disjoint.map_orderIso` result, but it requires an `OrderIso` (not just a one-way embedding) and it requires a `SemilatticeInf` (whereas my version just uses `PartialOrder`).

Co-authored-by: Yury G. Kudryashov <urkud@urkud.name>
Jun2M pushed a commit that referenced this pull request Apr 24, 2024
This adds 3 lemmas which state that if you have an order embedding `f` such that `f a₁` and `f a₂` are disjoint/codisjoint/complements, then the same holds for `a₁` and `a₂`.

*Motivation*: For a project described [here](https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/Derivations.20on.20Lie.20algebras), I wanted to know that if two Lie ideals are complements as submodules, then they are complements as Lie ideals too. I realized that the correct level of generality was probably in the `Order.Hom.Basic` file.

*Caveats*: I am very much open to golfing/naming/redesign suggestions. Within the modified file, there was already a `Disjoint.map_orderIso` result, but it requires an `OrderIso` (not just a one-way embedding) and it requires a `SemilatticeInf` (whereas my version just uses `PartialOrder`).

Co-authored-by: Yury G. Kudryashov <urkud@urkud.name>
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4 participants