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Families of pairs of graphs with a large number of common cards

Bowler, Andrew and Brown, Paul and Fenner, Trevor (2010) Families of pairs of graphs with a large number of common cards. Journal of Graph Theory 63 (2), pp. 146-163. ISSN 0364-9024.

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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 vertex-deleted subgraphs. The number of common cards of G and H (or between G and H) is the cardinality of the multiset intersection of the decks of G and H. In this article, we present infinite families of pairs of graphs of order n ≥ 4 that have at least equation image common cards; we conjecture that these, along with a small number of other families constructed from them, are the only pairs of graphs having this many common cards, for sufficiently large n. This leads us to propose a new stronger version of the Reconstruction Conjecture. In addition, we present an infinite family of pairs of graphs with the same degree sequence that have equation image common cards, for appropriate values of n, from which we can construct pairs having slightly fewer common cards for all other values of n≥10. We also present infinite families of pairs of forests and pairs of trees with equation image and equation image common cards, respectively. We then present new families that have the maximum number of common cards when one graph is connected and the other disconnected. Finally, we present a family with a large number of common cards, where one graph is a tree and the other unicyclic, and discuss how many cards are required to determine whether a graph is a tree.

Item Type: Article
Keyword(s) / Subject(s): reconstruction conjecture, reconstruction number, card, vertex-deleted subgraph, examples, counter-examples
School or Research Centre: Birkbeck Schools and Research Centres > School of Business, Economics & Informatics > Computer Science and Information Systems
Depositing User: Administrator
Date Deposited: 08 Feb 2011 08:51
Last Modified: 11 Oct 2016 15:26

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