"Christian Aistleitner" <[EMAIL PROTECTED]> 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 _______________________________________________ Axiom-developer mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/axiom-developer
