Reciprocal complementary distance polynomial and energy of join of two graphs. (English) Zbl 1533.05168
Summary: For a connected graph \(G\) with diameter \(D\), the reciprocal complementary distance matrix is defined as, \(RCD(G)=[rc_{ij}]\) in which \(rc_{ij}=\frac{1}{1+D-d_{ij}}\) if \(i\ne j\) and 0 otherwise, where \(d_{ij}\) is distance between the vertices \(v_i\) and \(v_j\). In literature, \(RCD\)-polynomial has been studied for the join of two regular graphs when both the graphs are of diameter less than or equal to 2. In the present work, we study the \(RCD\)-polynomial for join of any two graphs and hence construct a pair of \(RCD\)-equienergetic graphs by joining a regular graph (which is among a pair of \(RCD\)-equienergetic graphs of same order and degree) with a non regular graph. Further, \(RCD\)-eigenvalues for these structures are studied in terms of adjacency eigenvalues of \(G_1\) and \(G_2\) when both of them are regular.
MSC:
05C50 | Graphs and linear algebra (matrices, eigenvalues, etc.) |
05C76 | Graph operations (line graphs, products, etc.) |
15A18 | Eigenvalues, singular values, and eigenvectors |
05C40 | Connectivity |
05C12 | Distance in graphs |