On the computation of extremal trees of Harmonic index with given edge-vertex domination number
Abstract
Let v1,v2 be vertices of a graph G with degree of the vertices being d(v1) and d(v2), respectively. First, let us define the weight of the edge v1v2 as twice the value of 1d(v1)+d(v2) in G. Let us define H(G), the harmonic index of the graph G, as the sum obtained by adding the weight assigned to every edge of G. In this paper, for the class of trees, we shall obtain an upper bound for the harmonic index H(G) in terms of the edge-vertex domination number and the order of G. Also, we shall ascertain that the equality is true by characterizing the collection of all extremal trees attaining this bound.