Computing Planar Intertwines
نویسندگان
چکیده
The proof of Wagner's Conjecture by Robertson and Seymour gives a nite description of any family of graphs which is closed under the minor ordering. This description is a nite set of graphs called the obstructions of the family. Since the intersection and the union of two minor closed graph families is again a minor closed graph family, an interesting question is that of computing the obstructions of the new family given the obstructions for the original two families. It is easy to compute the obstructions of the intersection but, until very recently, it was an open problem to compute the obstructions of the union. We show that if the original families are planar then the obstructions of the union are no larger than n O(n 2) where n is the size of the largest obstruction of the original family.
منابع مشابه
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