,
Carla Groenland
Creative Commons Attribution 4.0 International license
We study the trade-off between (average) spread and width in tree decompositions, answering several questions from Wood [arXiv:2509.01140]. The spread of a vertex v in a tree decomposition is the number of bags that contain v. Wood asked for which c > 0, there exists c' such that each graph G has a tree decomposition of width ctw(G) in which each vertex v has spread at most c'(d(v)+1). We show that c ≥ 2 is necessary and that c > 3 is sufficient. Moreover, we answer a second question fully by showing that near-optimal average spread can be achieved simultaneously with width O(tw(G)).
@InProceedings{bodlaender_et_al:LIPIcs.WG.2026.9,
author = {Bodlaender, Hans L. and Groenland, Carla},
title = {{Trade-Off Between Spread and Width for Tree Decompositions}},
booktitle = {52nd International Workshop on Graph-Theoretic Concepts in Computer Science (WG 2026)},
pages = {9:1--9:16},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-430-7},
ISSN = {1868-8969},
year = {2026},
volume = {376},
editor = {Goedgebeur, Jan and Rz\k{a}\.{z}ewski, Pawe{\l}},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.WG.2026.9},
URN = {urn:nbn:de:0030-drops-261753},
doi = {10.4230/LIPIcs.WG.2026.9},
annote = {Keywords: Tree decomposition, spread, domino treewidth}
}