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Tournament pathwidth and topological containment. (English) Zbl 1301.05148
Summary: We prove that if a tournament has pathwidth \(\geq 4\theta^2+7\theta\) then it has \(\theta\) vertices that are pairwise \(\theta\)-connected. As a consequence of this and previous results, we obtain that for every set \(S\) of tournaments the following are equivalent: (1) there exists \(k\) such that every member of \(S\) has pathwidth at most \(k\), (2) there is a digraph \(H\) such that no subdivision of \(H\) is a subdigraph of any member of \(S\), (3) there exists \(k\) such that for each \(T\in S\), there do not exist \(k\) vertices of \(T\) that are pairwise \(k\)-connected. As a further consequence, we obtain a polynomial-time algorithm to test whether a tournament contains a subdivision of a fixed digraph \( H\) as a subdigraph.

MSC:
05C20 Directed graphs (digraphs), tournaments
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