#16678 closed defect (fixed)
Fix coercions for descent and symmetric group algebras
Reported by:  tscrim  Owned by:  tscrim 

Priority:  major  Milestone:  sage6.3 
Component:  coercion  Keywords:  symmetric group algebra, descent algebra 
Cc:  darij  Merged in:  
Authors:  Travis Scrimshaw  Reviewers:  Darij Grinberg 
Report Upstream:  N/A  Work issues:  
Branch:  d8ea764 (Commits)  Commit:  
Dependencies:  Stopgaps: 
Description (last modified by )
This splits off the first issue of #15475 (which has already been reviewed by Darij). This will also address the issues noted on https://groups.google.com/forum/#!topic/sagedevel/rXobHQXrCck.
Change History (12)
comment:1 Changed 3 years ago by
 Branch set to public/coercion/fix_sga_coercions16678
 Commit set to e1ff76939b42bd0c0bd20af1ea365b5b7f1aa5f8
 Description modified (diff)
 Status changed from new to needs_review
comment:2 Changed 3 years ago by
 Commit changed from e1ff76939b42bd0c0bd20af1ea365b5b7f1aa5f8 to 30e769e05e76d19b2057c7bb1f32a3f1f80c72f4
Branch pushed to git repo; I updated commit sha1. New commits:
30e769e  Removed erroneous character in permgroup.py.

comment:3 Changed 3 years ago by
 Commit changed from 30e769e05e76d19b2057c7bb1f32a3f1f80c72f4 to 3fa802d270a0d6f560ecd845132c22a85add33ee
Branch pushed to git repo; I updated commit sha1. New commits:
3fa802d  a couple doctests and a blunder of my own

comment:4 Changed 3 years ago by
Thanks for the split, which was rather appropriate. Positive_review on my side.
comment:6 Changed 3 years ago by
 Status changed from positive_review to needs_work
sage t long src/sage/categories/groups.py ********************************************************************** File "src/sage/categories/groups.py", line 531, in sage.categories.groups.Groups.Algebras.example Failed example: GroupAlgebras(QQ).example(SymmetricGroup(4)) Expected: Group algebra of Symmetric group of order 4! as a permutation group over Rational Field Got: Symmetric group algebra of order 4 over Rational Field ********************************************************************** File "src/sage/categories/groups.py", line 578, in sage.categories.groups.Groups.Algebras.ParentMethods.algebra_generators Failed example: GroupAlgebras(QQ).example(SymmetricGroup(10)).algebra_generators() Expected: Finite family {(1,2): B[(1,2)], (1,2,3,4,5,6,7,8,9,10): B[(1,2,3,4,5,6,7,8,9,10)]} Got: [[2, 1, 3, 4, 5, 6, 7, 8, 9, 10], [2, 3, 4, 5, 6, 7, 8, 9, 10, 1]] ********************************************************************** sage t long src/sage/combinat/root_system/hecke_algebra_representation.py ********************************************************************** File "src/sage/combinat/root_system/hecke_algebra_representation.py", line 81, in sage.combinat.root_system.hecke_algebra_representation.HeckeAlgebraRepresentation.__init__ Failed example: HeckeAlgebraRepresentation(domain, action, CartanType(["A",2]), 1, 1) Expected: A representation of the (1, 1)Hecke algebra of type ['A', 2] on Group algebra of Symmetric group of order 3! as a permutation group over Rational Field Got: A representation of the (1, 1)Hecke algebra of type ['A', 2] on Symmetric group algebra of order 3 over Rational Field ********************************************************************** File "src/sage/combinat/root_system/hecke_algebra_representation.py", line 229, in sage.combinat.root_system.hecke_algebra_representation.HeckeAlgebraRepresentation.on_basis Failed example: rho.on_basis(W.one(), (1,2,1)) Expected: B[(1,3)] Got: (1,3) **********************************************************************
comment:7 Changed 3 years ago by
 Commit changed from 3fa802d270a0d6f560ecd845132c22a85add33ee to d8ea76401d64a798f3d1d6cf7a0d7e0dbdd7c099
comment:8 Changed 3 years ago by
 Status changed from needs_work to positive_review
Trivial failures due to SGA's being returned from SymmetricGroup(n).algebra()
.
comment:9 Changed 3 years ago by
 Branch changed from public/coercion/fix_sga_coercions16678 to d8ea76401d64a798f3d1d6cf7a0d7e0dbdd7c099
 Resolution set to fixed
 Status changed from positive_review to closed
comment:10 Changed 3 years ago by
 Commit d8ea76401d64a798f3d1d6cf7a0d7e0dbdd7c099 deleted
See followup #16625. Sorry I did not spot this earlier; it's too bad the change was released in 6.3, since now we are reverting a backward incompatible change, making it compabible back to <=6.2 but not 6.3 ...
comment:11 followup: ↓ 12 Changed 3 years ago by
I'm seeing it right that only the SymmetricGroup?.Algebra part of this ticket will be reverted?
comment:12 in reply to: ↑ 11 Changed 3 years ago by
Replying to darij:
Oops, I am updown dislexic apparently :)
I'm seeing it right that only the SymmetricGroup?.Algebra part of this ticket will be reverted?
Definitely.
Last 10 new commits:
Implemented _coerce_map_from_ for SGA.
More fixes and doctests.
Fixed the issue...finally... Also some other minor cleanup.
Added comment about register_embedding.
Changed to use _coerce_map_from_ and made it more robust/general.
documentation fixes to canonical_embedding of symmetric group algebra (yes, these maps aren't always embeddings, and the inequality was backwards)
oops, another doc fix
Merge commit 'ff4e546a838e9e9a4be86b3a89d8596658beb3f4' into public/coercions/fix_sga_coercions16678
Additional fixes noted on sagedevel thread.
Fixed stupid mistake.