Supercards, sunshines and caterpillar graphs
Brown, Paul and Fenner, Trevor (2022) Supercards, sunshines and caterpillar graphs. Journal of Combinatorics 13 (1), pp. 4178. ISSN 21563527.

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Abstract
The vertexdeleted 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:  Birkbeck Faculties and Schools > Faculty of Science > School of Computing and Mathematical Sciences 
Depositing User:  Trevor Fenner 
Date Deposited:  10 May 2022 15:16 
Last Modified:  24 Jul 2024 18:03 
URI:  https://eprints.bbk.ac.uk/id/eprint/47931 
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