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Automated testing and interactive construction of unavoidable sets for graph classes of small path‐width

Bachtler, Oliver ; Heinrich, Irene (2023)
Automated testing and interactive construction of unavoidable sets for graph classes of small path‐width.
In: Journal of Graph Theory, 104 (2)
doi: 10.1002/jgt.22964
Artikel, Bibliographie

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Kurzbeschreibung (Abstract)

Let G be a class of graphs with a membership test, k∈N , and let Gk be the class of graphs in G of path-width at most k. We present an interactive framework that finds an unavoidable set for Gk, which is a set of graphs U such that any graph in Gk contains an isomorphic copy of a graph in U. At the core of our framework is an algorithm that verifies whether a set of graphs is, indeed, unavoidable for Gk. While obstruction sets are well-studied, so far there is no general theory or algorithm for finding unavoidable sets. In general, it is undecidable whether a finite set of graphs is unavoidable for a given graph class. However, we give a criterion for termination: our algorithm terminates whenever G is locally checkable of bounded maximum degree and U is a finite set of connected graphs. For example, l-regular graphs, l-colourable graphs, and H-free graphs are locally checkable classes. We put special emphasis on the case that G is the class of cubic graphs and tailor the algorithm to this case. In particular, we introduce the new concept of high-degree-first path-decompositions, which enables highly efficient pruning techniques. We exploit our framework to prove a new lower bound on the path-width of cubic graphs. Moreover, we determine the extremal girth values of cubic graphs of path-width for all and all smallest graphs which take on these extremal girth values. Further, we present a new constructive characterisation of the extremal cubic graphs of path-width 3 and girth 4.

Typ des Eintrags: Artikel
Erschienen: 2023
Autor(en): Bachtler, Oliver ; Heinrich, Irene
Art des Eintrags: Bibliographie
Titel: Automated testing and interactive construction of unavoidable sets for graph classes of small path‐width
Sprache: Englisch
Publikationsjahr: 2023
Ort: New York
Verlag: Wiley
Titel der Zeitschrift, Zeitung oder Schriftenreihe: Journal of Graph Theory
Jahrgang/Volume einer Zeitschrift: 104
(Heft-)Nummer: 2
DOI: 10.1002/jgt.22964
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Kurzbeschreibung (Abstract):

Let G be a class of graphs with a membership test, k∈N , and let Gk be the class of graphs in G of path-width at most k. We present an interactive framework that finds an unavoidable set for Gk, which is a set of graphs U such that any graph in Gk contains an isomorphic copy of a graph in U. At the core of our framework is an algorithm that verifies whether a set of graphs is, indeed, unavoidable for Gk. While obstruction sets are well-studied, so far there is no general theory or algorithm for finding unavoidable sets. In general, it is undecidable whether a finite set of graphs is unavoidable for a given graph class. However, we give a criterion for termination: our algorithm terminates whenever G is locally checkable of bounded maximum degree and U is a finite set of connected graphs. For example, l-regular graphs, l-colourable graphs, and H-free graphs are locally checkable classes. We put special emphasis on the case that G is the class of cubic graphs and tailor the algorithm to this case. In particular, we introduce the new concept of high-degree-first path-decompositions, which enables highly efficient pruning techniques. We exploit our framework to prove a new lower bound on the path-width of cubic graphs. Moreover, we determine the extremal girth values of cubic graphs of path-width for all and all smallest graphs which take on these extremal girth values. Further, we present a new constructive characterisation of the extremal cubic graphs of path-width 3 and girth 4.

Freie Schlagworte: cubic graph, girth, path‐width, unavoidable structure
Sachgruppe der Dewey Dezimalklassifikatin (DDC): 500 Naturwissenschaften und Mathematik > 510 Mathematik
Fachbereich(e)/-gebiet(e): 04 Fachbereich Mathematik
04 Fachbereich Mathematik > Didaktik
04 Fachbereich Mathematik > Optimierung
Hinterlegungsdatum: 12 Mär 2024 07:55
Letzte Änderung: 12 Mär 2024 07:55
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