#14913: Add GroupMixinLibGAP as a base class for finitely presented groups
---------------------------------------+--------------------------------
Reporter: dshurbert | Owner:
Type: enhancement | Status: positive_review
Priority: minor | Milestone:
Component: group theory | Resolution:
Keywords: group presentations | Merged in:
Authors: Davis Shurbert | Reviewers: Volker Braun
Report Upstream: N/A | Work issues:
Branch: | Dependencies:
Stopgaps: |
---------------------------------------+--------------------------------
Comment (by dshurbert):
I discovered the following behavior while writing doctests for a
direct_product function for finitely presented groups.
{{{
sage: from sage.groups.finitely_presented import wrap_FpGroup
sage: F = FreeGroup("a")
sage: G = FreeGroup("b")
sage: C4 = F / [F.0^4]
sage: C3 = G / [G.0^3]
sage: C12 = wrap_FpGroup(libgap.DirectProduct([C3.gap(), C4.gap()]))
sage: C12
Finitely presented group < f1, f2 | f1^3, f2^4, f1^-1*f2^-1*f1*f2 >
sage: C12.is_isomorphic(F / [F.0^12])
False
sage: C12.as_permutation_group().is_isomorphic(CyclicPermutationGroup(12))
True
# Again, constructing C12 by hand as C3 x C4.
sage: K = FreeGroup(2)
sage: C_12 = K / [K.0^4, K.1^3, K([-1,-2,1,2])]
sage: C_12
Finitely presented group < x0, x1 | x0^4, x1^3, x0^-1*x1^-1*x0*x1 >
sage: C_12.is_isomorphic(F / [F.0^12])
False
sage:
C_12.as_permutation_group().is_isomorphic(CyclicPermutationGroup(12))
True
}}}
To replicate this behavior you must apply the patch attached to this
ticket, #14913.
This failure of the {{{is_isomorphic}}} call seems to recur in similar
instances of cyclic groups being constructed as a direct product. I'm not
sure if I should make a new ticket for this apparent bug, but at the very
least it seems as though it should halt this ticket.
--
Ticket URL: <http://trac.sagemath.org/ticket/14913#comment:8>
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 http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/groups/opt_out.
