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arXiv · 1812.03382

Irredundance Graphs

Kieka Mynhardt·Riana Roux
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Abstract

A set D of vertices of a graph G=(V,E) is irredundant if each v of D satisfies (a) v is isolated in the subgraph induced by D, or (b) v is adjacent to a vertex in V-D that is nonadjacent to all other vertices in D. The upper irredundance number IR(G) is the largest cardinality of an irredundant set of G; an IR(G)-set is an irredundant set of cardinality IR(G). The IR-graph of G has the IR(G)-sets as vertex set, and sets D and D' are adjacent if and only if D' is obtained from D by exchanging a single vertex of D for an adjacent vertex in D'. We study the realizability of graphs as IR-graphs and show that all disconnected graphs are IR-graphs, but some connected graphs (e.g. stars of order three or more, the paths of order 4 or 5, the 5-cycle) are not.

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Kieka Mynhardt, Riana Roux. 2018-12-08. Irredundance Graphs. https://arxiv.org/abs/1812.03382

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