文摘
Let T be a rooted tree, G a connected graph, x, y ?V(G) be fixed and G i ’s be |V(T)| disjoint copies of G with x i and y i denoting the corresponding copies of x and y in G i , respectively. We define the T-repetition of G to be the graph obtained by joining y i to x j for each i ?V(T) and each child j of i. In this paper, we compute the Kirchhoff index of the T-repetition of G in terms of parameters of T and G. Also we study how Kf(G) behaves under some graph operations such as joining vertices or subdividing edges.