Partition energy of complete product of circulant graphs and some new class of graphs

Abstract

Let G = (V,E) be a graph and Pk = {V1, V2, ..., Vk} be a partition of V . The L-matrix with respect to a partition Pk of the vertex set V of graph G of order n is the unique square symmetric matrix Pk(G) = [aij ] with zero diagonal, whose entries aij with i 6≠ j are defined as follows: (i) If vi, vj ∈ Vr, then aij = 2 or −1 according as vivj is an edge or not. (ii) If vi ∈ Vr and vj ∈ Vs for r 6≠s, then aij = 1 or 0 according as vivj is an edge or not. For all Vi and Vj in Pk, i 6≠j remove the edges between vertices of Vi and Vj and add the edges between the vertices of Vi and Vj which are not in G, the resulting graph is called k-complement of G and is denoted by (G)k. For each set Vr in Pk, remove the edges of G joining the vertices within Vr and add the edges of G (complement of G) joining the vertices of Vr, the graph obtained is called k(i)-complement and is denoted by (G)k(i). The k-partition energy of a graph G with respect to partition Pk is denoted by EPk (G) and is defined as the sum of the absolute values of k-partition eigenvalues of Pk(G). In this paper we construct some graphs such that the graph and its 2-complement are equienergetic with respect to a given partition. We also determine partition energy of complete product of m copies of a circulant graph G and its subgraph, their k-complement and k(i)-complement.