@article{3063490, title = "Cutwidth: Obstructions and Algorithmic Aspects", author = "Giannopoulou, A.C. and Pilipczuk, M. and Raymond, J.-F. and Thilikos, D.M. and Wrochna, M.", journal = "Algorithmica (New York)", year = "2019", volume = "81", number = "2", pages = "557-588", publisher = "Springer New York LLC", doi = "10.1007/s00453-018-0424-7", keywords = "Algorithms, Algorithmic aspects; AS graph; Combinatorics; Cutwidths; Fixed-parameter algorithms; Fixed-parameter tractability; Immersions; Obstructions, Computer science", abstract = "Cutwidth is one of the classic layout parameters for graphs. It measures how well one can order the vertices of a graph in a linear manner, so that the maximum number of edges between any prefix and its complement suffix is minimized. As graphs of cutwidth at most k are closed under taking immersions, the results of Robertson and Seymour imply that there is a finite list of minimal immersion obstructions for admitting a cut layout of width at most k. We prove that every minimal immersion obstruction for cutwidth at most k has size at most 2O(k3logk). As an interesting algorithmic byproduct, we design a new fixed-parameter algorithm for computing the cutwidth of a graph that runs in time 2O(k2logk)·n, where k is the optimum width and n is the number of vertices. While being slower by a log k-factor in the exponent than the fastest known algorithm, given by Thilikos et al. (J Algorithms 56(1):1–24, 2005; J Algorithms 56(1):25–49, 2005), our algorithm has the advantage of being simpler and self-contained; arguably, it explains better the combinatorics of optimum-width layouts. © 2018, The Author(s)." }