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feat(RingTheory): Grassmannian functor#34705

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mpenciak wants to merge 14 commits intoleanprover-community:masterfrom
mpenciak:grassmannian
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feat(RingTheory): Grassmannian functor#34705
mpenciak wants to merge 14 commits intoleanprover-community:masterfrom
mpenciak:grassmannian

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@mpenciak mpenciak commented Feb 2, 2026

This PR shows that the association A → G(k, (A ⊗[R] M); A) for an R-algebra A and R-module M forms a functor.

(AI disclosure: an early version of this PR was prepared with the help of Claude)


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github-actions bot commented Feb 2, 2026

PR summary c71d2faa1b

Import changes exceeding 2%

% File
+3.28% Mathlib.LinearAlgebra.TensorProduct.Quotient

Import changes for modified files

Dependency changes

File Base Count Head Count Change
Mathlib.LinearAlgebra.TensorProduct.Quotient 1127 1164 +37 (+3.28%)
Mathlib.RingTheory.Grassmannian 2114 2130 +16 (+0.76%)
Import changes for all files
Files Import difference
Mathlib.RingTheory.Finiteness.NilpotentKer 1
Mathlib.RingTheory.Grassmannian 16
Mathlib.LinearAlgebra.TensorProduct.Quotient 37

Declarations diff

+ baseChange_comp_cancelBaseChange_symm_self
+ baseChange_mkQ_surjective
+ cancelBaseChange_self_eq_lid
+ functor
+ ker_baseChange_comp_cancelBaseChange_symm
+ map
+ map_comp
+ map_id

You can run this locally as follows
## summary with just the declaration names:
./scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh contains some details about this script.


No changes to technical debt.

You can run this locally as

./scripts/reporting/technical-debt-metrics.sh pr_summary
  • The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
  • The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

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@robin-carlier robin-carlier left a comment

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As a general comment, the code has the classic AI-generated code issue that there are way too many lets/have that are making things unnecessarily long.

@robin-carlier robin-carlier added the awaiting-author A reviewer has asked the author a question or requested changes. label Feb 6, 2026
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mpenciak commented Feb 14, 2026

Thanks for the review! I think I addressed your comments, incorporated your changes, and cleaned up the Claude's first pass of the proofs so they should be more clear now.

@mpenciak mpenciak removed awaiting-author A reviewer has asked the author a question or requested changes. labels Feb 14, 2026
@mathlib-merge-conflicts mathlib-merge-conflicts bot added the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Feb 27, 2026
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This pull request has conflicts, please merge master and resolve them.

@github-actions github-actions bot removed the merge-conflict The PR has a merge conflict with master, and needs manual merging. (this label is managed by a bot) label Mar 2, 2026
@grunweg grunweg added the LLM-generated PRs with substantial input from LLMs - review accordingly label Mar 16, 2026
@mariainesdff mariainesdff removed their assignment Mar 20, 2026
@chrisflav chrisflav added the awaiting-author A reviewer has asked the author a question or requested changes. label Mar 21, 2026
@chrisflav chrisflav changed the title feat(AlgebraicGeometry): Grassmannian functor feat(RingTheory): Grassmannian functor Mar 21, 2026
@mpenciak mpenciak removed the awaiting-author A reviewer has asked the author a question or requested changes. label Mar 25, 2026
@chrisflav chrisflav added the awaiting-author A reviewer has asked the author a question or requested changes. label Apr 1, 2026
@github-actions github-actions bot added the large-import Automatically added label for PRs with a significant increase in transitive imports label Apr 3, 2026
@mpenciak mpenciak force-pushed the grassmannian branch 3 times, most recently from efe2b89 to 9b6bfa2 Compare April 3, 2026 16:55
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mpenciak commented Apr 3, 2026

I think I fixed up your comments, let me know how it looks!

  1. I got rid of the changes in the file. Things got a little more verbose at the end of the proof of map_comp, but otherwise it got cleaner
  2. I got rid of the erw. I needed to add a couple API lemmas relating baseChange and cancelBaseChange on A -> A, so I moved those to Mathlib/LinearAlgebra/TensorProduct/Tower.lean
  3. I moved baseChange_mkQ_surjective to Mathlib/LinearAlgebra/TensorProduct/Quotient.lean. It seemed like the spot where it was most relevant, but also minimized the need to modify the dependencies of the file.

@mpenciak mpenciak removed the awaiting-author A reviewer has asked the author a question or requested changes. label Apr 3, 2026
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