Opened 2 years ago

Closed 23 months ago

#29808 closed defect (fixed)

fix left and right actions of permutations on matrices

Reported by: gh-mwageringel Owned by:
Priority: minor Milestone: sage-9.2
Component: group theory Keywords:
Cc: tscrim Merged in:
Authors: Markus Wageringel Reviewers: Travis Scrimshaw
Report Upstream: N/A Work issues:
Branch: a9dd308 (Commits, GitHub, GitLab) Commit: a9dd3081e05e858e9a19dca973d51968130ec2db
Dependencies: Stopgaps:

Status badges

Description

As observed in #29553, permutations incorrectly act on matrices via a left action on the rows when multiplying on the right. This ticket fixes the left action to act on the left, and also adds the missing right action on the columns. 

sage: S = SymmetricGroup(6)
sage: p, q = S('(1,2,3,4,5,6)'), S('(1,2)(3,4)(5,6)')
sage: M = matrix.diagonal([1..6])
sage: (M * p.matrix()) * q.matrix() == M * (p.matrix() * q.matrix())  # correct
True
sage: (M * p) * q == M * (p * q)  # should be True
False

Change History (3)

comment:1 Changed 2 years ago by gh-mwageringel

  • Authors set to Markus Wageringel
  • Branch set to u/gh-mwageringel/29808
  • Cc tscrim added
  • Commit set to a9dd3081e05e858e9a19dca973d51968130ec2db
  • Status changed from new to needs_review

New commits:

​a9dd30829808: fix left/right permutation actions on matrices

comment:2 Changed 2 years ago by tscrim

  • Reviewers set to Travis Scrimshaw
  • Status changed from needs_review to positive_review

LGTM.

comment:3 Changed 23 months ago by vbraun

  • Branch changed from u/gh-mwageringel/29808 to a9dd3081e05e858e9a19dca973d51968130ec2db
  • Resolution set to fixed
  • Status changed from positive_review to closed
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