Ticket #8411 (closed defect: fixed)
Branching rule fix and doc revision
|Reported by:||bump||Owned by:||sage-combinat|
|Cc:||sage-combinat, brant@…||Work issues:|
|Report Upstream:||N/A||Reviewers:||Nicolas M. Thiéry, Brant Jones|
|Authors:||Daniel Bump||Merged in:||sage-4.4.alpha2|
Description (last modified by bump) (diff)
This corrects a minor problem with branching rules in weyl_characters.py.
Previously branching rules SO(m+n)->SO(m)xSO(n) were implemented using rule="extended", and similarly for symplectic groups. However there is one case where this does not meet the definition of the extended rule, namely SO(2n+2m+2)->SO(2n+1)xSO(2m+1). Indeed, the extended rule checks to see if the ranks are equal, which they are not in this case.
I thought the cleanest fix was to implement a new rule called "orthogonal_sum" for such cases.
I also took the chance to revise the documentation since what was said before about rule="symmetric" was misleading.
Minor bugfix in weightring: 0 in weight lattice should coerce to 1 not 0 in weight ring.
- Cc brant@… added
- Keywords Branching rules added
- Reviewers set to Nicolas M. Thiéry, Brant Jones