The spectral determinations of the multicone graphs Kw+mCn (1703.08728v2)

Abstract: The main goal of the paper is to characterize new classes of multicone graphs which are determined by both adjacency and Laplacian spectra. A multicone graph is defined to be the join of a clique and a regular graph. A wheel graph obtained from the join of a complete graph on a vertex with a cycle. A question about when wheel graphs are determined by their adjacency spectra is still unsolved. So, any indication about the determinations of these graphs with respect to their adjacency spectra can be an interesting and important problem. In [Y. Zhang, X. Liu, and X. Yong: Which wheel graphs are determined by their Laplacian spectra?. Comput. Math. Appl., 58 (2009) 1887{1890] and [M.-H. Liu: Some graphs determined by their (signless) Laplacian spectra. Czech. Math. J., 62, (2012) 1117{1134] it have been shown that except for, the wheel graph of order seven, all wheel graphs are determined by their Laplacian spectra and wheel graphs are determined by their signless Laplacian spectra, respectively. In this study, we present new classes of connected multicone graphs which are a natural generalization of wheel graphs and we show that these graphs are determined by their adjacency spectra as well as their Laplacian spectra. Also, we show that complement of some of these graphs are determined by their adjacency spectra. In addition, we give a necessary and sufficient condition for perfecting graphs cospectral with presented graphs in the paper. Finally, we pose two problems for further work.