,
Simon Raßmann
Creative Commons Attribution 4.0 International license
The twin-width of a graph measures its distance to co-graphs and generalizes classical width concepts such as tree-width or rank-width. Since its introduction in 2020 [Édouard Bonnet et al., 2022; Édouard Bonnet et al., 2020], a mass of new results has appeared relating twin width to group theory, model theory, combinatorial optimization, and structural graph theory. We take a detailed look at the interplay between the twin-width of a graph and the twin-width of its components under tree-structured decompositions: We prove that the twin-width of a graph is at most twice its strong tree-width, contrasting nicely with the result of [Édouard Bonnet and Hugues Déprés, 2023; Édouard Bonnet and Hugues Déprés, 2022], which states that twin-width can be exponential in tree-width. Further, we employ the fundamental concept from structural graph theory of decomposing a graph into highly connected components, in order to obtain optimal linear bounds on the twin-width of a graph given the widths of its biconnected components. For triconnected components we obtain a linear upper bound if we add red edges to the components indicating the splits which led to the components. Extending this approach to quasi-4-connectivity, we obtain a quadratic upper bound. Finally, we investigate how the adhesion of a tree decomposition influences the twin-width of the decomposed graph.
@InProceedings{heinrich_et_al:LIPIcs.IPEC.2023.25,
author = {Heinrich, Irene and Ra{\ss}mann, Simon},
title = {{Twin-Width of Graphs with Tree-Structured Decompositions}},
booktitle = {18th International Symposium on Parameterized and Exact Computation (IPEC 2023)},
pages = {25:1--25:17},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-305-8},
ISSN = {1868-8969},
year = {2023},
volume = {285},
editor = {Misra, Neeldhara and Wahlstr\"{o}m, Magnus},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.IPEC.2023.25},
URN = {urn:nbn:de:0030-drops-194449},
doi = {10.4230/LIPIcs.IPEC.2023.25},
annote = {Keywords: twin-width, quasi-4 connected components, strong tree-width}
}