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Zbl 1190.05084
Sciriha, Irene
Maximal core size in singular graphs.
(English)
[J] Ars Math. Contemp. 2, No. 2, 217-229 (2009). ISSN 1855-3966; ISSN 1855-3974/e

Summary: A graph $G$ is singular of nullity $\eta$ if the nullspace of its adjacency matrix $G$ has dimension $\eta$. Such a graph contains $\eta$ cores determined by a basis for the nullspace of $G$. These are induced subgraphs of singular configurations, the latter occurring as induced subgraphs of $G$. We show that there exists a set of $\eta$ distinct vertices representing the singular configurations. We also explore how the nullity controls the size of the singular substructures and characterize those graphs of maximal nullity containing a substructure reaching maximal size.
MSC 2000:
*05C50 Graphs and matrices
05C60 Isomorphism problems (graph theory)
05B20 (0,1)-matrices (combinatorics)

Keywords: adjacency matrix; nullity; extremal singular graphs; singular configurations; core width

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