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[Axiom-developer] Re: [Aldor-l] operations working in general, but not i
From: |
Martin Rubey |
Subject: |
[Axiom-developer] Re: [Aldor-l] operations working in general, but not in special cases -- help needed |
Date: |
05 Apr 2006 11:05:25 +0200 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.4 |
"Christian Aistleitner" <address@hidden> writes:
> I am not familiar with matroids, so let me get this straightened out.
>
> 1. Graphic non-planar matroids do not provide a way to compute a dual
> element.
Well, no. The dual of a graphic non-planar matroids is not a graphic matroid
again. It is perfectly well defined on the level of matroids.
Consider the rationals versus the integers. Then only units are invertible in
the integers, but all non-zero elements are invertible in the rationals.
> 2. Graphic planar matroids are able to compute duals for all elements.
yes.
> 3. Graphic non-planar three-connected Matroids do not have duals at all.
no. See 1.
> 4. Graphic three-connected Matroids allow recovering of vertices.
yes.
> 5. Planar graphic matroids are called "matroids".
yes.
I think that William Sit got it right -- and his solution is simple, too -- but
I don't have time right now to check the details. He sent his mail also to
Aldor-l, so you should have gotten it...
Are we going to meet on the workshop?
Martin
- Re: [Aldor-l] Re: [Axiom-developer] operations working in general, but not in special cases -- help needed, (continued)