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[Merged by Bors] - feat(linear_algebra/invariant_basis_number): strong_rank_condition_iff_succ #9128

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@riccardobrasca riccardobrasca commented Sep 10, 2021

We add strong_rank_condition_iff_succ: a ring satisfies the strong rank condition if and only if, for all n : ℕ, there are no
injective linear maps (fin (n + 1) → R) →ₗ[R] (fin n → R). This will be used to prove that any commutative ring satisfies the strong rank condition.

The proof is simple and it uses the natural inclusion R^n → R^m, for n ≤ m (adding zeros at the end). We provide this in general as extend_by_zero.linear_map : (ι → R) →ₗ[R] (η → R) where ι and η are types endowed with a function ι → η.


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@riccardobrasca riccardobrasca added the awaiting-review The author would like community review of the PR label Sep 10, 2021
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I think this should go in invariant_basis_number.lean, right after strong_rank_condition is defined.

@semorrison semorrison added awaiting-author A reviewer has asked the author a question or requested changes and removed awaiting-review The author would like community review of the PR labels Sep 11, 2021
@jcommelin jcommelin changed the title feat(src/linear_algebra/invariant_basis_number.lean): add strong_rank_condition_iff feat(linear_algebra/invariant_basis_number): add strong_rank_condition_iff Sep 11, 2021
riccardobrasca and others added 2 commits September 13, 2021 12:56
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
riccardobrasca and others added 4 commits September 15, 2021 13:56
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
@riccardobrasca riccardobrasca changed the title feat(linear_algebra/invariant_basis_number): add strong_rank_condition_iff feat(linear_algebra/invariant_basis_number): strong_rank_condition_iff_succ Sep 15, 2021
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bors merge

@github-actions github-actions bot added ready-to-merge All that is left is for bors to build and merge this PR. (Remember you need to say `bors r+`.) and removed awaiting-review The author would like community review of the PR labels Sep 22, 2021
bors bot pushed a commit that referenced this pull request Sep 22, 2021
…f_succ (#9128)

We add `strong_rank_condition_iff_succ`: a ring satisfies the strong rank condition if and only if, for all `n : ℕ`, there are no
injective linear maps `(fin (n + 1) → R) →ₗ[R] (fin n → R)`. This will be used to prove that any commutative ring satisfies the strong rank condition.

The proof is simple and it uses the natural inclusion `R^n → R^m`, for `n ≤ m` (adding zeros at the end). We provide this in general as `extend_by_zero.linear_map : (ι → R) →ₗ[R] (η → R)` where `ι` and `η` are types endowed with a function `ι → η`.
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bors bot commented Sep 23, 2021

Build failed (retrying...):

bors bot pushed a commit that referenced this pull request Sep 23, 2021
…f_succ (#9128)

We add `strong_rank_condition_iff_succ`: a ring satisfies the strong rank condition if and only if, for all `n : ℕ`, there are no
injective linear maps `(fin (n + 1) → R) →ₗ[R] (fin n → R)`. This will be used to prove that any commutative ring satisfies the strong rank condition.

The proof is simple and it uses the natural inclusion `R^n → R^m`, for `n ≤ m` (adding zeros at the end). We provide this in general as `extend_by_zero.linear_map : (ι → R) →ₗ[R] (η → R)` where `ι` and `η` are types endowed with a function `ι → η`.
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bors bot commented Sep 23, 2021

Build failed:

@Vierkantor
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Looks like it was a transient error.

bors merge

bors bot pushed a commit that referenced this pull request Sep 23, 2021
…f_succ (#9128)

We add `strong_rank_condition_iff_succ`: a ring satisfies the strong rank condition if and only if, for all `n : ℕ`, there are no
injective linear maps `(fin (n + 1) → R) →ₗ[R] (fin n → R)`. This will be used to prove that any commutative ring satisfies the strong rank condition.

The proof is simple and it uses the natural inclusion `R^n → R^m`, for `n ≤ m` (adding zeros at the end). We provide this in general as `extend_by_zero.linear_map : (ι → R) →ₗ[R] (η → R)` where `ι` and `η` are types endowed with a function `ι → η`.
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bors bot commented Sep 23, 2021

Build failed:

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@bryangingechen
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Let's try one more time.
bors r+

bors bot pushed a commit that referenced this pull request Sep 23, 2021
…f_succ (#9128)

We add `strong_rank_condition_iff_succ`: a ring satisfies the strong rank condition if and only if, for all `n : ℕ`, there are no
injective linear maps `(fin (n + 1) → R) →ₗ[R] (fin n → R)`. This will be used to prove that any commutative ring satisfies the strong rank condition.

The proof is simple and it uses the natural inclusion `R^n → R^m`, for `n ≤ m` (adding zeros at the end). We provide this in general as `extend_by_zero.linear_map : (ι → R) →ₗ[R] (η → R)` where `ι` and `η` are types endowed with a function `ι → η`.
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bors bot commented Sep 23, 2021

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title feat(linear_algebra/invariant_basis_number): strong_rank_condition_iff_succ [Merged by Bors] - feat(linear_algebra/invariant_basis_number): strong_rank_condition_iff_succ Sep 23, 2021
@bors bors bot closed this Sep 23, 2021
@bors bors bot deleted the strong_rank_iff branch September 23, 2021 19:19
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5 participants