Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Adding cellular bases for the SymmetricGroupAlgebra over general fields #36718

Merged
merged 4 commits into from
Dec 10, 2023

Conversation

tscrim
Copy link
Collaborator

@tscrim tscrim commented Nov 14, 2023

Currently the SymmetricGroupAlgebra uses the seminormal basis for computing a cell basis, but this only is guaranteed to work over a field where Maschke's theorem holds. However, it is known that the Kazhdan-Lusztig C' basis at q = 1 for the type A Hecke algebra is a cell basis, We implement that as the fallback when we cannot use the seminormal basis.

We also fix a few typos in the doc that were noticed.

📝 Checklist

  • The title is concise, informative, and self-explanatory.
  • The description explains in detail what this PR is about.
  • I have linked a relevant issue or discussion.
  • I have created tests covering the changes.
  • I have updated the documentation accordingly.

⌛ Dependencies

@tscrim
Copy link
Collaborator Author

tscrim commented Nov 14, 2023

@fchapoton I hope you can do the review for this. Mathematically it is just implementing the KL $C'$ basis at $q=1$. Everything else is handled by the general framework for cellular algebras already implemented.

@fchapoton
Copy link
Contributor

there are a few failing doctests, some trivial and other less so

@tscrim
Copy link
Collaborator Author

tscrim commented Nov 15, 2023

This should fix all of the failing doctests. They were all trivial coming from the fact that the cell poset was in the reverse order.

@fchapoton
Copy link
Contributor

testing wihtout coxeter3 does not work:

KLG = SymmetricGroup(self.n)
    UnboundLocalError: local variable 'SymmetricGroup' referenced before assignment

@tscrim
Copy link
Collaborator Author

tscrim commented Nov 16, 2023

Good catch. This should fix it.

Copy link

Documentation preview for this PR (built with commit 2e492e9; changes) is ready! 🎉

Copy link
Contributor

@fchapoton fchapoton left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

works with and without coxeter3, ok

@tscrim
Copy link
Collaborator Author

tscrim commented Nov 16, 2023

Merci

@tscrim tscrim mentioned this pull request Nov 30, 2023
5 tasks
@vbraun vbraun merged commit 5b1eea4 into sagemath:develop Dec 10, 2023
19 of 20 checks passed
@mkoeppe mkoeppe added this to the sage-10.3 milestone Dec 10, 2023
@tscrim tscrim deleted the algebra/sga_cellular branch December 12, 2023 01:03
vbraun pushed a commit to vbraun/sage that referenced this pull request Dec 21, 2023
    
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes sagemath#1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->

We implement the Murphy basis of the symmetric group algebra (as defined
by Dipper-James-Mathas) and make this the default cellular basis over
positive characteristic since it is (significantly) faster to compute
the change of basis necessary.

<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes sagemath#12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->

- [x] The title is concise, informative, and self-explanatory.
- [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 accordingly.

### ⌛ Dependencies

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

- sagemath#36718 Uses the KL basis implementation

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: sagemath#36790
Reported by: Travis Scrimshaw
Reviewer(s): Frédéric Chapoton
vbraun pushed a commit to vbraun/sage that referenced this pull request Dec 22, 2023
    
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes sagemath#1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->

We implement the Murphy basis of the symmetric group algebra (as defined
by Dipper-James-Mathas) and make this the default cellular basis over
positive characteristic since it is (significantly) faster to compute
the change of basis necessary.

<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes sagemath#12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->

- [x] The title is concise, informative, and self-explanatory.
- [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 accordingly.

### ⌛ Dependencies

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

- sagemath#36718 Uses the KL basis implementation

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: sagemath#36790
Reported by: Travis Scrimshaw
Reviewer(s): Frédéric Chapoton
vbraun pushed a commit to vbraun/sage that referenced this pull request Dec 23, 2023
    
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes sagemath#1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->

We implement the Murphy basis of the symmetric group algebra (as defined
by Dipper-James-Mathas) and make this the default cellular basis over
positive characteristic since it is (significantly) faster to compute
the change of basis necessary.

<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes sagemath#12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->

- [x] The title is concise, informative, and self-explanatory.
- [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 accordingly.

### ⌛ Dependencies

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

- sagemath#36718 Uses the KL basis implementation

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: sagemath#36790
Reported by: Travis Scrimshaw
Reviewer(s): Frédéric Chapoton
vbraun pushed a commit to vbraun/sage that referenced this pull request Dec 24, 2023
    
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes sagemath#1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->

We implement the Murphy basis of the symmetric group algebra (as defined
by Dipper-James-Mathas) and make this the default cellular basis over
positive characteristic since it is (significantly) faster to compute
the change of basis necessary.

<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes sagemath#12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->

- [x] The title is concise, informative, and self-explanatory.
- [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 accordingly.

### ⌛ Dependencies

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

- sagemath#36718 Uses the KL basis implementation

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: sagemath#36790
Reported by: Travis Scrimshaw
Reviewer(s): Frédéric Chapoton
vbraun pushed a commit to vbraun/sage that referenced this pull request Dec 26, 2023
    
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes sagemath#1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->

We implement the Murphy basis of the symmetric group algebra (as defined
by Dipper-James-Mathas) and make this the default cellular basis over
positive characteristic since it is (significantly) faster to compute
the change of basis necessary.

<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes sagemath#12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->

- [x] The title is concise, informative, and self-explanatory.
- [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 accordingly.

### ⌛ Dependencies

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

- sagemath#36718 Uses the KL basis implementation

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: sagemath#36790
Reported by: Travis Scrimshaw
Reviewer(s): Frédéric Chapoton
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Projects
None yet
Development

Successfully merging this pull request may close these issues.

None yet

4 participants