9 research outputs found
On the metric dimension of corona product graphs
Given a set of vertices of a connected graph , the
metric representation of a vertex of with respect to is the vector
, where ,
denotes the distance between and . is a resolving set for if
for every pair of vertices of , . The metric
dimension of , , is the minimum cardinality of any resolving set for
. Let and be two graphs of order and , respectively. The
corona product is defined as the graph obtained from and by
taking one copy of and copies of and joining by an edge each
vertex from the -copy of with the -vertex of . For any
integer , we define the graph recursively from
as . We give several results on the metric
dimension of . For instance, we show that given two connected
graphs and of order and , respectively, if the
diameter of is at most two, then .
Moreover, if and the diameter of is greater than five or is
a cycle graph, then $dim(G\odot^k H)=n_1(n_2+1)^{k-1}dim(K_1\odot H).
Boundary powerful k-alliances in graphs
A global boundary defensive k-alliance in a graph G = (V, E) is a dominating set S of vertices of G with the property that every vertex in 5 has fc more neighbors in 5 than it has outside of S. A global boundary offensive fc-alliance in a graph G is a set S of vertices of G with the property that every vertex in V - S has fc more neighbors in S than it has outside of S. We define a global boundary powerful fc-alliance as a set 5 of vertices of G, which is both global boundary defensive kalliance and global boundary offensive (k + 2)-alliance. In this paper we study mathematical properties of boundary powerful k-alliances. In particular, we obtain several bounds (closed formulas for the case of regular graphs) on the cardinality of every global boundary powerful k-alliance. In addition, we consider the case in which the vertex set of a graph G can be partitioned' into two boundary powerful fcalliances, showing that, in such a case, k = - 1 and, if G is amp;d-regular, its algebraic connectivity is equal to amp;d +1