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Implement the Schur functors applied to semigroup representations #37830

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merged 3 commits into from
Jun 22, 2024

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@tscrim tscrim commented Apr 19, 2024

The Schur functor is an important part of the representation theory of $GL_n$, but it can be defined generically for any representation of a semigroup (well, really for any vector space, but the utility is for representation theory). We provide an implementation, realizing the natural representation structure. To help with examples, we also implement the natural representation of any matrix (semi)group.

Along the way, we clean up some stuff with the sign representations.

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  • The description explains in detail what this PR is about.
  • I have linked a relevant issue or discussion.
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  • I have updated the documentation and checked the documentation preview.

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Documentation preview for this PR (built with commit ee80187; changes) is ready! 🎉
This preview will update shortly after each push to this PR.

@tscrim tscrim force-pushed the lie_algebras/schur_functors branch 4 times, most recently from 4767055 to 5cf0111 Compare April 22, 2024 04:23
@tscrim tscrim force-pushed the lie_algebras/schur_functors branch from 5cf0111 to eac63fb Compare May 7, 2024 03:53
@tscrim tscrim removed the v: large label May 10, 2024
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Otherwise LGTM

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tscrim commented Jun 4, 2024

I am planning to rebase this over #37871 since that reworks the class hierarchy that this code depends on. I am going to try to do that today before going home, but it might have to wait until tomorrow.

@tscrim tscrim force-pushed the lie_algebras/schur_functors branch from eac63fb to b75d1b4 Compare June 4, 2024 07:44
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tscrim commented Jun 4, 2024

It went much more smoothly than I thought (which is a good thing).

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mkoeppe commented Jun 10, 2024

rebase again?

@tscrim tscrim force-pushed the lie_algebras/schur_functors branch from b75d1b4 to ee80187 Compare June 10, 2024 00:26
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tscrim commented Jun 10, 2024

I didn't need to do it locally it seems, but I have done so.

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LGTM.

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tscrim commented Jun 10, 2024

Thank you.

vbraun pushed a commit to vbraun/sage that referenced this pull request Jun 16, 2024
…epresentations

    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

The Schur functor is an important part of the representation theory of
$GL_n$, but it can be defined generically for any representation of a
semigroup (well, really for any vector space, but the utility is for
representation theory). We provide an implementation, realizing the
natural representation structure. To help with examples, we also
implement the natural representation of any matrix (semi)group.

Along the way, we clean up some stuff with the sign representations.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [x] I have created tests covering the changes.
- [x] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->

- sagemath#37871 - Uses the `Subrepresentation` class implemented here.
    
URL: sagemath#37830
Reported by: Travis Scrimshaw
Reviewer(s): Matthias Köppe
vbraun pushed a commit to vbraun/sage that referenced this pull request Jun 16, 2024
…epresentations

    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

The Schur functor is an important part of the representation theory of
$GL_n$, but it can be defined generically for any representation of a
semigroup (well, really for any vector space, but the utility is for
representation theory). We provide an implementation, realizing the
natural representation structure. To help with examples, we also
implement the natural representation of any matrix (semi)group.

Along the way, we clean up some stuff with the sign representations.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [x] I have created tests covering the changes.
- [x] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->

- sagemath#37871 - Uses the `Subrepresentation` class implemented here.
    
URL: sagemath#37830
Reported by: Travis Scrimshaw
Reviewer(s): Matthias Köppe
@vbraun vbraun merged commit 19a6233 into sagemath:develop Jun 22, 2024
21 checks passed
@tscrim tscrim deleted the lie_algebras/schur_functors branch July 1, 2024 02:34
@mkoeppe mkoeppe added this to the sage-10.4 milestone Jul 8, 2024
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3 participants