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arXiv · 2409.09998

Constructing cospectral graphs via regular rational orthogonal matrix with level two and three

Lihuan Mao·Fu Yan
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Abstract

Two graphs $G$ and $H$ are \emph{cospectral} if the adjacency matrices share the same spectrum. Constructing cospectral non-isomorphic graphs has been studied extensively for many years and various constructions are known in the literature, e.g. the famous GM-switching method. In this paper, we shall construct cospectral graphs via regular rational orthogonal matrix $Q$ with level two and three. We provide two straightforward algorithms to characterize with adjacency matrix $A$ of graph $G$ such that $Q^TAQ$ is again a (0,1)-matrix, and introduce two new switching methods to construct families of cospectral graphs which generalized the GM-switching to some extent.

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Lihuan Mao, Fu Yan. 2024-09-16. Constructing cospectral graphs via regular rational orthogonal matrix with level two and three. https://arxiv.org/abs/2409.09998

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