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[Merged by Bors] - feat(RingTheory/FiniteType): generalize some results to non-commutative rings #6681

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@eric-wieser eric-wieser commented Aug 19, 2023

I was hoping to use this in combination with #6680 to show the TensorAlgebra is finitely generated, where I needed to generalize FiniteType.equiv; but it turns out that the FiniteType instance on MonoidAlgebra also isn't generalized!

The summary here is:

  • Move Algebra.adjoin_algebraMap from Mathlib/RingTheory/Adjoin/Tower.lean to Mathlib/RingTheory/Adjoin/Basic.lean and golf the proof to oblivion
  • Provide an alternative statement of adjoin_union_eq_adjoin_adjoin, adjoin_algebraMap_image_union_eq_adjoin_adjoin, which works in non-commutative rings, and use it along with a new adjoin_top lemma to prove Algebra.fg_trans' more generally.
  • Introduce a new S variable throughout, with the convention that R and S are commutative, A and B remain not-necessarily-commutative, and A/S/R is a tower of algebras.
  • Apply some zero-effort generalizations to semirings.

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@eric-wieser eric-wieser added awaiting-review The author would like community review of the PR awaiting-CI t-algebra Algebra (groups, rings, fields etc) labels Aug 19, 2023
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ocfnash commented Aug 23, 2023

Thanks!

bors merge

@github-actions github-actions 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 Aug 23, 2023
bors bot pushed a commit that referenced this pull request Aug 23, 2023
…ve rings (#6681)

I was hoping to use this in combination with #6680 to show the `TensorAlgebra` is finitely generated, where I needed to generalize `FiniteType.equiv`; but it turns out that the `FiniteType` instance on `MonoidAlgebra` also isn't generalized!

The summary here is:
* Move `Algebra.adjoin_algebraMap` from `Mathlib/RingTheory/Adjoin/Tower.lean` to `Mathlib/RingTheory/Adjoin/Basic.lean` and golf the proof to oblivion
* Provide an alternative statement of `adjoin_union_eq_adjoin_adjoin`, `adjoin_algebraMap_image_union_eq_adjoin_adjoin`, which works in non-commutative rings, and use it along with a new `adjoin_top` lemma to prove `Algebra.fg_trans'` more generally.
* Introduce a new `S` variable throughout, with the convention that `R` and `S` are commutative, `A` and `B` remain not-necessarily-commutative, and `A/S/R` is a tower of algebras.
* Apply some zero-effort generalizations to semirings.
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bors bot commented Aug 23, 2023

Pull request successfully merged into master.

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@bors bors bot changed the title feat(RingTheory/FiniteType): generalize some results to non-commutative rings [Merged by Bors] - feat(RingTheory/FiniteType): generalize some results to non-commutative rings Aug 23, 2023
@bors bors bot closed this Aug 23, 2023
@bors bors bot deleted the eric-wieser/FiniteType-noncomm branch August 23, 2023 12:45
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