Rewriting Lie subalgebras and ideals to always do computations in the ambient Lie algebra #40137
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@fchapoton Can you review this? It is a bit subtle of an issue, but it fixes a pretty bad bug with incorrect quotients. |
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there seems to be broken doctests |
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Indeed, those are real failures. I will fix them tomorrow. |
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Okay, I have fixed the problem. It took a bit of work to make sure all of the indices are handled correctly. As a by-product, the Lie subalgebras and ideals have their basis naturally indexed by the leading monomial of the ambient. This is a backwards incompatible change in a sense, but it was essentially necessary to fix the bug. (I could revert that portion, but it will take a bit more care.) |
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…bras and quotient algebras.
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Documentation preview for this PR (built with commit 5a0f7bd; changes) is ready! 🎉 |
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Tests now seem to pass. |
fchapoton
approved these changes
Jun 6, 2025
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Merci! I appreciate it; this fixes a subtle-but-important bug. |
vbraun
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Jun 8, 2025
sagemathgh-40137: Rewriting Lie subalgebras and ideals to always do computations in the ambient Lie algebra <!-- ^ 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". --> Currently, ideals $A$ of a Lie subalgebra $B$ of an ambient Lie algebra $L$ do a number of computations in $B$. However, they are more attuned to working in $L$. This causes problems for constructing quotients $B / A$ as there can be mismatches in the indices. We fix these problems by making sure that $A$ always does computations in $L$ whether it is constructed as an ideal of $B$ or of $L$. ### 📝 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: ... --> URL: sagemath#40137 Reported by: Travis Scrimshaw Reviewer(s): Frédéric Chapoton
vbraun
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Jun 9, 2025
sagemathgh-40137: Rewriting Lie subalgebras and ideals to always do computations in the ambient Lie algebra <!-- ^ 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". --> Currently, ideals $A$ of a Lie subalgebra $B$ of an ambient Lie algebra $L$ do a number of computations in $B$. However, they are more attuned to working in $L$. This causes problems for constructing quotients $B / A$ as there can be mismatches in the indices. We fix these problems by making sure that $A$ always does computations in $L$ whether it is constructed as an ideal of $B$ or of $L$. ### 📝 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: ... --> URL: sagemath#40137 Reported by: Travis Scrimshaw Reviewer(s): Frédéric Chapoton
vbraun
pushed a commit
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that referenced
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Jun 9, 2025
sagemathgh-40137: Rewriting Lie subalgebras and ideals to always do computations in the ambient Lie algebra <!-- ^ 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". --> Currently, ideals $A$ of a Lie subalgebra $B$ of an ambient Lie algebra $L$ do a number of computations in $B$. However, they are more attuned to working in $L$. This causes problems for constructing quotients $B / A$ as there can be mismatches in the indices. We fix these problems by making sure that $A$ always does computations in $L$ whether it is constructed as an ideal of $B$ or of $L$. ### 📝 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: ... --> URL: sagemath#40137 Reported by: Travis Scrimshaw Reviewer(s): Frédéric Chapoton
vbraun
pushed a commit
to vbraun/sage
that referenced
this pull request
Jun 9, 2025
sagemathgh-40137: Rewriting Lie subalgebras and ideals to always do computations in the ambient Lie algebra <!-- ^ 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". --> Currently, ideals $A$ of a Lie subalgebra $B$ of an ambient Lie algebra $L$ do a number of computations in $B$. However, they are more attuned to working in $L$. This causes problems for constructing quotients $B / A$ as there can be mismatches in the indices. We fix these problems by making sure that $A$ always does computations in $L$ whether it is constructed as an ideal of $B$ or of $L$. ### 📝 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: ... --> URL: sagemath#40137 Reported by: Travis Scrimshaw Reviewer(s): Frédéric Chapoton
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Currently, ideals$A$ of a Lie subalgebra $B$ of an ambient Lie algebra $L$ do a number of computations in $B$ . However, they are more attuned to working in $L$ . This causes problems for constructing quotients $B / A$ as there can be mismatches in the indices. We fix these problems by making sure that $A$ always does computations in $L$ whether it is constructed as an ideal of $B$ or of $L$ .
📝 Checklist
⌛ Dependencies