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[Merged by Bors] - feat(ring_theory/jacobson): Generalize proofs about Jacobson rings and polynomials #5520

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@dtumad dtumad commented Dec 28, 2020

These changes are meant to make deriving the classical nullstellensatz from the generalized version about Jacobson rings much easier and much more direct.

is_integral_localization_map_polynomial_quotient already exists in the proof of a previous theorem, and this just pulls it out into an independent lemma.

polynomial.quotient_mk_comp_C_is_integral_of_jacobson and mv_polynomial.quotient_mk_comp_C_is_integral_of_jacobson are the two main new statements, most of the rest of the changes are just generalizations and reorganizations of the existing theorems.


@dtumad dtumad changed the title feat(ring_theory/jacobson): Generalize proofs feat(ring_theory/jacobson): Generalize proofs about Jacobson rings and polynomials Dec 28, 2020
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First comments. I haven't looked at the longer proofs yet.

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The code looks good!

I'm wondering how easy it would be to "generalize" your results from "for all maximal ideals, the quotient map ..." to "for all ring homs that are surjective onto a field, ...". (Even though they should be equivalent, the latter contains more free variables in its conclusion: it might be easier to use in practice.) Have you considered the surjective map case already?

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Co-authored-by: Anne Baanen <Vierkantor@users.noreply.github.com>
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dtumad commented Jan 8, 2021

The code looks good!

I'm wondering how easy it would be to "generalize" your results from "for all maximal ideals, the quotient map ..." to "for all ring homs that are surjective onto a field, ...". (Even though they should be equivalent, the latter contains more free variables in its conclusion: it might be easier to use in practice.) Have you considered the surjective map case already?

I think this is possible to do, but the trouble I had is that the proof needs to derive that certain other rings are actually fields by pulling across the homomorphisms, and the interface for is_field isn't as expansive as for is_maximal, map, and comap. I think this is something that could be derived in another PR with a bit of work though.

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I'm hqppy with merging this as it currently stands, and deriving the "surjective to a field" conclusion later, since it needs more work in other parts.

@jcommelin, what do you think?

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dtumad commented Jan 13, 2021

@Vierkantor I realized there are much simpler proofs to the field surjection versions of the lemmas than the proofs I was picturing. I've just added them to this PR since they don't actually require many other changes elsewhere.

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Fantastic 😄

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Fantastic! Thanks for adding the variants for surjecive maps. 🎉

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 Jan 16, 2021
bors bot pushed a commit that referenced this pull request Jan 16, 2021
…d polynomials (#5520)

These changes are meant to make deriving the classical nullstellensatz from the generalized version about Jacobson rings much easier and much more direct.

`is_integral_localization_map_polynomial_quotient` already exists in the proof of a previous theorem, and this just pulls it out into an independent lemma.

`polynomial.quotient_mk_comp_C_is_integral_of_jacobson` and `mv_polynomial.quotient_mk_comp_C_is_integral_of_jacobson` are the two main new statements, most of the rest of the changes are just generalizations and reorganizations of the existing theorems.



Co-authored-by: Devon Tuma <dtumad@gmail.com>
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bors bot commented Jan 16, 2021

Build failed (retrying...):

bors bot pushed a commit that referenced this pull request Jan 16, 2021
…d polynomials (#5520)

These changes are meant to make deriving the classical nullstellensatz from the generalized version about Jacobson rings much easier and much more direct.

`is_integral_localization_map_polynomial_quotient` already exists in the proof of a previous theorem, and this just pulls it out into an independent lemma.

`polynomial.quotient_mk_comp_C_is_integral_of_jacobson` and `mv_polynomial.quotient_mk_comp_C_is_integral_of_jacobson` are the two main new statements, most of the rest of the changes are just generalizations and reorganizations of the existing theorems.



Co-authored-by: Devon Tuma <dtumad@gmail.com>
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bors bot commented Jan 16, 2021

Build failed (retrying...):

bors bot pushed a commit that referenced this pull request Jan 16, 2021
…d polynomials (#5520)

These changes are meant to make deriving the classical nullstellensatz from the generalized version about Jacobson rings much easier and much more direct.

`is_integral_localization_map_polynomial_quotient` already exists in the proof of a previous theorem, and this just pulls it out into an independent lemma.

`polynomial.quotient_mk_comp_C_is_integral_of_jacobson` and `mv_polynomial.quotient_mk_comp_C_is_integral_of_jacobson` are the two main new statements, most of the rest of the changes are just generalizations and reorganizations of the existing theorems.



Co-authored-by: Devon Tuma <dtumad@gmail.com>
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bors bot commented Jan 16, 2021

Pull request successfully merged into master.

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@bors bors bot changed the title feat(ring_theory/jacobson): Generalize proofs about Jacobson rings and polynomials [Merged by Bors] - feat(ring_theory/jacobson): Generalize proofs about Jacobson rings and polynomials Jan 16, 2021
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@bors bors bot deleted the ggnss branch January 16, 2021 13:21
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