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    Supercards, sunshines and caterpillar graphs

    Brown, Paul and Fenner, Trevor (2022) Supercards, sunshines and caterpillar graphs. Journal of Combinatorics 13 (1), pp. 41-78. ISSN 2156-3527.

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    Abstract

    The vertex-deleted subgraph G−v, obtained from the graph G by deleting the vertex v and all edges incident to v, is called a card of G. The deck of G is the multiset of its unlabelled cards. The number of common cards b(G, H) of G and H is the cardinality of the multiset intersection of the decks of G and H. A supercard G+ of G and H is a graph whose deck contains at least one card isomorphic to G and at least one card isomorphic to H. We show how maximum sets of common cards of G and H correspond to certain sets of permutations of the vertices of a supercard, which we call maximum saturating sets. We apply the theory of supercards and maximum saturating sets to the case when G is a sunshine graph and H is a caterpillar graph. We show that, for large enough n, there exists some maximum saturating set that contains at least b(G, H) − 2 automorphisms of G+, and that this subset is always isomorphic to either a cyclic or dihedral group. We prove that b(G, H) ≤ 2(n+1) 5 for large enough n, and that there exists a unique family of pairs of graphs that attain this bound. We further show that, in this case, the corresponding maximum saturating set is isomorphic to the dihedral group.

    Metadata

    Item Type: Article
    School: School of Business, Economics & Informatics > Computer Science and Information Systems
    Depositing User: Trevor Fenner
    Date Deposited: 10 May 2022 15:16
    Last Modified: 10 May 2022 15:16
    URI: https://eprints.bbk.ac.uk/id/eprint/47931

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