Pathwidth, trees, and random embeddings

On constant multi-commodity flow-cut gaps for directed minor-free graphs

The multi-commodity flow-cut gap is a fundamental parameter that affects the performance of several divide & conquer algorithms, and has been extensively studied for various classes of undirected graphs. It has been shown by Linial, London and Rabinovich [15] and by Aumann and Rabani [3] that for general n-vertex graphs it is bounded by Oplog nq and the GuptaNewman-Rabinovich-Sinclair conjectur...

On self duality of pathwidth in polyhedral graph embeddings

Let G be a 3-connected planar graph and G∗ be its dual. We show that the pathwidth of G∗ is at most 6 times the pathwidth of G. We prove this result by relating the pathwidth of a graph with the cut-width of its medial graph and we extend it to bounded genus embeddings. We also show that there exist 3-connected planar graphs such that the pathwidth of such a graph is at least 1.5 times the path...

CSP duality and trees of bounded pathwidth

We study non-uniform constraint satisfaction problems definable in monadic Datalog stratified by the use of non-linearity. We show how such problems can be described in terms of homomorphism dualities involving trees of bounded pathwidth and in algebraic terms. For this, we introduce a new parameter for trees that closely approximates pathwidth and can be characterised via a hypergraph searchin...

Pathwidth is NP-Hard for Weighted Trees

The pathwidth of a graph G is the minimum clique number of H minus one, over all interval supergraphs H of G. We prove in this paper that the PATHWIDTH problem is NP-hard for particular subclasses of chordal graphs, and we deduce that the problem remains hard for weighted trees. We also discuss subclasses of chordal graphs for which the problem is polynomial.

Randomized Algorithms 2017A - Lecture 10 Metric Embeddings into Random Trees