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Criticality indices of 2-rainbow domination of paths and cycles

Bouchou A., Blidia M.

Opuscula Mathematica

2016

Vol. 36, no. 5

563-–574

A 2-rainbow dominating function of a graph G (V(G), E(G)) is a function ƒ that assigns to each vertex a set of colors chosen from the set {1,2} so that for each vertex with ƒ (v) = ∅ we have [formula].The weight of a 2RDF ƒ is defined as [formula] minimum weight of a 2RDF is called the 2-rainbow domination number of G, denoted by [formula].The vertex criticality index of a 2-rainbow domination of a graph G is defined as [formula] the edge removal criticality index of a 2-rainbow domination of a graph G is defined as [formula] and the edge addition of a 2-rainbow domination criticality index of G is defined as [formula] where G is the complement graph of G. In this paper, we determine the criticality indices of paths and cycles.

A note on k-Roman graphs

Bouchou A., Blidia M., Chellali M.

Opuscula Mathematica

2013

Vol. 33, no. 4

641--646

Let G = (V,E) be a graph and let k be a positive integer. A subset D of V (G) is a k-dominating set of G if every vertex in V (G) \D has at least k neighbours in D. The k-domination number Υk(G) is the minimum cardinality of a k-dominating set of G. A Roman k-dominating function on G is a function f : V (G) →{0, 1, 2} such that every vertex u for which f(u) = 0 is adjacent to at least k vertices v1, v2, . . . , vk with f(vi) = 2 for i = 1, 2, . . . , k. The weight of a Roman k-dominating function is the value [formula] and the minimum weight of a Roman k-dominating function on G is called the Roman k-domination number Υk(G) of G. A graph G is said to be a k-Roman graph if ΥkR(G) = 2Υk(G) . In this note we study k-Roman graphs.