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Various improvements to Weyl character rings#35186

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vbraun merged 1 commit intosagemath:developfrom
tscrim:algebras/improvements_weyl_char_ring
Mar 26, 2023
Merged

Various improvements to Weyl character rings#35186
vbraun merged 1 commit intosagemath:developfrom
tscrim:algebras/improvements_weyl_char_ring

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@tscrim tscrim commented Feb 24, 2023 •
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📚 Description

We provide a number of improvements to the Weyl character ring:

  1. We make it know that it is commutative (along with its ambient ring).
  2. We speedup the _demazure_helper method by only doing operations based upon the support of the simple roots. 
    sage: F = FusionRing(['B',10], 2, base_ring=QQ)
sage: dd = {(1,0,0,1,0,0,0,0,0,0): 1}
sage: %time X = F._demazure_helper(dd)
CPU times: user 3.1 s, sys: 12 ms, total: 3.11 s
Wall time: 3.11 s
    Previously took ~6s.
  3. We don't set the FusionRing as a subobject of the WeightRing.

📝 Checklist

  • I have made sure that the title is self-explanatory and the description concisely explains the PR.
  • I have linked an issue or discussion.
  • I have created tests covering the changes.
  • I have updated the documentation accordingly.

⌛ Dependencies

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tscrim commented Feb 24, 2023 •
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@dwbump @willieab Here are some improvements to the WCR which also improves the fusion rings.

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github-actions bot commented Feb 24, 2023

Documentation preview for this PR is ready! 🎉
Built with commit: d008a9c

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dwbump commented Feb 26, 2023

I built the commit and verified the speedup, which is pretty good if the rank is moderately large. The Demazure character formula is used to compute characters, which also underly the calculations of tensor products. The exception is that for reductive groups that are not semisimple such as GL(r), the Demazure character formula is not used, in lieu of the Freudenthal multiplicity formula. Because of this here is no speedup for WeylCharacterRings in Type A unless you make the WeylCharacterRing with style="coroots" but this is the default for FusionRings.

Nothing in the patch would require doctest revisions. I can recommend a positive review.

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tscrim commented Feb 27, 2023

Someone with sufficient powers (e.g., @mkoeppe @dimpase) needs to approve the PR request (and also upgrade @dwbump to the triage team since he is a long-term contributor).

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dimpase approved these changes Feb 27, 2023
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as requested by @tscrim

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dimpase commented Feb 27, 2023

@dwbump is a member of triage team

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tscrim commented Feb 28, 2023

Thank you @dimpase!

@vbraun vbraun merged commit 88a9ab8 into sagemath:develop Mar 26, 2023
@tscrim tscrim deleted the algebras/improvements_weyl_char_ring branch April 28, 2023 05:31
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@dimpase dimpase dimpase approved these changes

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c: algebra p: major / 3 t: enhancement

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sage-10.0

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@tscrim @dwbump @dimpase @vbraun @kwankyu @mkoeppe