Opened 6 years ago

Closed 6 years ago

#18005 closed defect (duplicate)

Group algebra of nonstandard symmetric groups broken

Reported by: darij Owned by:
Priority: major Milestone: sage-duplicate/invalid/wontfix
Component: combinatorics Keywords: symmetric group, group algebra, permutations
Cc: sage-combinat, tscrim, virmaux, nthiery Merged in:
Authors: Reviewers: Travis Scrimshaw
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: #16926 Stopgaps:

Description (last modified by darij)

I have found and recorded the problem in #16926, although it predates said ticket. Quoting src/sage/groups/perm_gps/permgroup_named.py:

    def algebra(self, base_ring):
        """
        Return the symmetric group algebra associated to ``self``.

        .. WARNING::

            This is broken!

                sage: S = SymmetricGroup([2,3,5])
                sage: S.an_element()
                (2,3,5)
                sage: S.algebra(QQ)(_)
                Traceback (most recent call last):
                ...
                ValueError: The permutation has length 3 but its maximal element is 5. Some
                 element may be repeated, or an element is missing, but there is something
                 wrong with its length.

            Best make it a usual group algebra with none of the bells and whistles
            of the SGA but with functioning methods.

        EXAMPLES::

            sage: S4 = SymmetricGroup(4)
            sage: S4.algebra(QQ)
            Symmetric group algebra of order 4 over Rational Field
        """
        from sage.combinat.symmetric_group_algebra import SymmetricGroupAlgebra
        return SymmetricGroupAlgebra(base_ring, self)

Change History (6)

comment:1 Changed 6 years ago by darij

  • Description modified (diff)

comment:2 Changed 6 years ago by nthiery

I just implemented that in #16926; this ticket can probably be closed as duplicate.

comment:3 Changed 6 years ago by darij

Great job! Can I ask you to review my doctests? (probably half a minute of work, thanks!)

comment:4 Changed 6 years ago by tscrim

  • Milestone changed from sage-6.6 to sage-duplicate/invalid/wontfix
  • Reviewers set to Travis Scrimshaw
  • Status changed from new to needs_review

Done.

comment:5 Changed 6 years ago by tscrim

  • Status changed from needs_review to positive_review

comment:6 Changed 6 years ago by vbraun

  • Resolution set to duplicate
  • Status changed from positive_review to closed
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