Edge-disjoint spanning trees

[ncohen]

The theorem from Nash-Williams on the existence of k edge-disjoint spanning trees in a graph is both important, useful, and polynomial to compute. This could be implemented using the short proof described in the following article :

​http://arxiv.org/abs/0911.2809

Or, if we achieve to eventually define in Sage a class Matroid, this could be done through the Matroid Union Theorem as presented in Schrijver's book.