Abstract
A defensive (offensive) k-alliance in Γ = (V,E) is a set S ⊆ V such that every υ in S (in the boundary of S) has at least k more neighbors in S than it has in V / S. A set X ⊆ V is defensive (offensive) k-alliance free, if for all defensive (offensive) k-alliance S, S/X ≠ ∅, i.e., X does not contain any defensive (offensive) k-alliance as a subset. A set Y ⊆ V is a defensive (offensive) k-alliance cover, if for all defensive (offensive) k-alliance S, S ∩ Y ≠ ∅, i.e., Y contains at least one vertex from each defensive (offensive) k-alliance of Γ. In this paper we show several mathematical properties of defensive (offensive) k-alliance free sets and defensive (offensive) k-alliance cover sets, including tight bounds on their cardinality.
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Supported by the Spanish Ministry of Science and Innovation through projects TSI2007-65406-C03-01 “EAEGIS”, CONSOLIDER INGENIO 2010 CSD2007-0004 “ARES” and MTM2009-09501, and by the Junta de Andalucía, ref. FQM-260 and ref. P06-FQM-02225
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Rodriguez-Velazquez, J.A., Sigarreta, J.M., Gonzalez Yero, I. et al. Alliance free and alliance cover sets. Acta. Math. Sin.-English Ser. 27, 497–504 (2011). https://doi.org/10.1007/s10114-011-0056-1
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DOI: https://doi.org/10.1007/s10114-011-0056-1