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An upper bound on the Laplacian spectral radius of the signed graphs

Hong-Hai Li, Jiong-Sheng Li (2008)

Discussiones Mathematicae Graph Theory

In this paper, we established a connection between the Laplacian eigenvalues of a signed graph and those of a mixed graph, gave a new upper bound for the largest Laplacian eigenvalue of a signed graph and characterized the extremal graph whose largest Laplacian eigenvalue achieved the upper bound. In addition, an example showed that the upper bound is the best in known upper bounds for some cases.

Asymptotic spectral analysis of generalized Erdős-Rényi random graphs

Song Liang, Nobuaki Obata, Shuji Takahashi (2007)

Banach Center Publications

Motivated by the Watts-Strogatz model for a complex network, we introduce a generalization of the Erdős-Rényi random graph. We derive a combinatorial formula for the moment sequence of its spectral distribution in the sparse limit.

Asymptotic spectral analysis of growing graphs: odd graphs and spidernets

Daisuke Igarashi, Nobuaki Obata (2006)

Banach Center Publications

Two new examples are given for illustrating the method of quantum decomposition in the asymptotic spectral analysis for a growing family of graphs. The odd graphs form a growing family of distance-regular graphs and the two-sided Rayleigh distribution appears in the limit of vacuum spectral distribution of the adjacency matrix. For a spidernet as well as for a growing family of spidernets the vacuum distribution of the adjacency matrix is the free Meixner law. These distributions are calculated...

Asymptotic spectral distributions of distance-k graphs of Cartesian product graphs

Yuji Hibino, Hun Hee Lee, Nobuaki Obata (2013)

Colloquium Mathematicae

Let G be a finite connected graph on two or more vertices, and G [ N , k ] the distance-k graph of the N-fold Cartesian power of G. For a fixed k ≥ 1, we obtain explicitly the large N limit of the spectral distribution (the eigenvalue distribution of the adjacency matrix) of G [ N , k ] . The limit distribution is described in terms of the Hermite polynomials. The proof is based on asymptotic combinatorics along with quantum probability theory.

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