ABSTRACT. Suppose G is a graph, A(G) its adjacency matrix and f(G, x)=x^n+a_(n-1)x^(n-1)+... is the characteristic polynomial of G. The matching polynomial of G is defined as M(G, x) = x^n-m(G,1)x^(n-2) + ... where m(G,k) is the number of k-matchings in G. In this paper, we determine the relationship between 2k-th coefficient of characteristic polynomial, a_(2k), and k-th coefficient of matchin...

This study deals with the forcing subsets of a minimum connected co-independent hop dominating sets in graphs. Bounds or exact values domination numbers graphs resulting from some binary operations such asjoin and corona are determined.Some main results generated this include characterization sets, for these types bounds join

In this paper, we provide an upper bound for the intersection number in join and corona of graphs. Moreover, give formulas Kn ◦G, Pn Cn ◦G Crn.

In an earlier paper, I showed that the classes of pentagon-free two-graphs and of pentagon-and-hexagon-free two-graphs could be represented in terms of trees. This paper gives formulae for the numbers of labelled objects in each of these classes, as well as the numbers of labelled reduced two-graphs in each class. The proofs use various enumeration results for trees. At least some of these resu...

In this paper we determine when the join of two graphs is locally homogeneous. It is shown that the Cartesian product of a locally H1 graph and a locally H2 graph is locally (H1∪ H2). All graphs H of order at most 4 for which there are no locally H graphs are determined.