#19830: Classification of finite and affine Coxeter groups
---------------------------+-----------------------------------------------
Reporter: stumpc5 | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.0
Component: | Keywords: coxeter system, root system
combinatorics | Authors:
Merged in: | Report Upstream: N/A
Reviewers: | Branch:
Work issues: | Dependencies:
Commit: |
Stopgaps: |
---------------------------+-----------------------------------------------
The bug here is two-fold:
1. The roots for a {{{CoxeterGroup}}} are constructed as in Humphreys "in
the Coxeter sense, that all have the same norm". Therefore it seems more
natural to not at all introduce a type C and to follow Humphrey's
classification of finite Coxeter groups given on page 32.
2. The current implementation of types B/C (which I suggest to remove and
to only keep type B) is also broken:
* First Sage start
{{{
sage: W = CoxeterGroup(['B',4])
sage: W.coxeter_matrix().coxeter_type()
Coxeter type of ['B', 4]
sage: W = CoxeterGroup(['C',4])
sage: W.coxeter_matrix().coxeter_type()
Coxeter type of ['B', 4]
}}}
* Second Sage start
{{{
sage: W = CoxeterGroup(['C',4])
sage: W.coxeter_matrix().coxeter_type()
Coxeter type of ['C', 4]
sage: W = CoxeterGroup(['B',4])
sage: W.coxeter_matrix().coxeter_type()
Coxeter type of ['C', 4]
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/19830>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
