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[Merged by Bors] - chore: refactor Lie algebra weight spaces #7210

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@ocfnash ocfnash commented Sep 16, 2023

The key change is the new definition LieModule.weightSpaceOf which shows that the eigenspaces of the action of a single element of a Lie algebra on a representation are Lie submodules. I need to use this fact to develop the theory further.


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The key change is the new definition `LieModule.weightSpaceOf` which shows that
the eigenspaces of the action of a single element of a Lie algebra on a representation
are Lie submodules. I need to use this fact to develop the theory further.
@ocfnash ocfnash added awaiting-review awaiting-CI t-algebra Algebra (groups, rings, fields, etc) labels Sep 16, 2023
exact LieAlgebra.iInf_max_gen_zero_eigenspace_eq_top_of_nilpotent R L }
#align lie_module.weight_space LieModule.weightSpace
exact lie_mem_maxGenEigenspace_toEndomorphism (by simp) hm }

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Would it be possible to change the meaning of 𝕎 M χ x, so that it now denotes a weight space? Or do you think that's not a good idea?

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I'd be very reluctant to have the same notation mean different things in this way.

I claim the notation for (toEndomorphism R L M x).maximalGeneralizedEigenspace χ is useful because it's such a mouthful and we will never care about it (in statements anyway) once we define weightSpaceOf M χ x.

However I think weightSpace M χ is perfectly fine and not in need of notation.

Of course I'm open to suggestions but as I say, I'd be reluctant to overload notation depending on context.

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Fair enough, makes a lot of sense

@jcommelin jcommelin added awaiting-author A reviewer has asked the author a question or requested changes and removed awaiting-review labels Sep 18, 2023
@ocfnash ocfnash added awaiting-review and removed awaiting-author A reviewer has asked the author a question or requested changes labels Sep 18, 2023
@ocfnash ocfnash requested a review from jcommelin September 18, 2023 15:42
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Thanks 🎉

bors merge

@leanprover-community-mathlib4-bot leanprover-community-mathlib4-bot added ready-to-merge This PR has been sent to bors. and removed awaiting-review labels Sep 18, 2023
bors bot pushed a commit that referenced this pull request Sep 18, 2023
The key change is the new definition `LieModule.weightSpaceOf` which shows that the eigenspaces of the action of a single element of a Lie algebra on a representation are Lie submodules. I need to use this fact to develop the theory further.
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@bors bors bot changed the title chore: refactor Lie algebra weight spaces [Merged by Bors] - chore: refactor Lie algebra weight spaces Sep 18, 2023
@bors bors bot closed this Sep 18, 2023
@bors bors bot deleted the ocfnash/killing_cartan branch September 18, 2023 18:51
kodyvajjha pushed a commit that referenced this pull request Sep 22, 2023
The key change is the new definition `LieModule.weightSpaceOf` which shows that the eigenspaces of the action of a single element of a Lie algebra on a representation are Lie submodules. I need to use this fact to develop the theory further.
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