Geodesic
Notes on the independence number in the Cartesian product of graphs
Discussiones Mathematicae. Graph Theory, Tome 31 (2011) no. 1, pp. 25-35.

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Every connected graph G with radius r(G) and independence number α(G) obeys α(G) ≥ r(G). Recently the graphs for which equality holds have been classified. Here we investigate the members of this class that are Cartesian products. We show that for non-trivial graphs G and H, α(G ☐ H) = r(G ☐ H) if and only if one factor is a complete graph on two vertices, and the other is a nontrivial complete graph. We also prove a new (polynomial computable) lower bound α(G ☐ H) ≥ 2r(G)r(H) for the independence number and we classify graphs for which equality holds.
Keywords: independence number, Cartesian product, critical independent set, radius, r-ciliate 
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Abay-Asmerom, G.; Hammack, R.; Larson, C.; Taylor, D. Notes on the independence number in the Cartesian product of graphs. Discussiones Mathematicae. Graph Theory, Tome 31 (2011) no. 1, pp. 25-35. http://geodesic.mathdoc.fr/item/DMGT_2011_31_1_a1/

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