Separating layered treewidth and row treewidth

05/04/2021

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by   Prosenjit Bose, et al.

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Layered treewidth and row treewidth are recently introduced graph parameters that have been key ingredients in the solution of several well-known open problems. It follows from the definitions that the layered treewidth of a graph is at most its row treewidth plus 1. Moreover, a minor-closed class has bounded layered treewidth if and only if it has bounded row treewidth. However, it has been open whether row treewidth is bounded by a function of layered treewidth. This paper answers this question in the negative. In particular, for every integer k we describe a graph with layered treewidth 1 and row treewidth k. We also prove an analogous result for layered pathwidth and row pathwidth.