Abstract Given any digraph D, its non-negative spectrum (or N-spectrum, shortly) consists of the eigenvalues of the matrix AA T , where A is the adjacency matrix of D. In this study, we relate the classical spectrum of undirected graphs to the N-spectrum of their oriented counterparts, permitting us to derive spectral bounds. Moreover, we study the spectral effects caused by certain modifications of a given digraph.

中文翻译：

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关于有向图的N-谱

摘要 给定任何有向图 D，其非负谱（简称 N 谱）由矩阵 A T 的特征值组成，其中 A 是 D 的邻接矩阵。 在本研究中，我们将无向图的经典谱联系起来到它们定向对应物的 N 谱，允许我们推导出谱界限。此外，我们研究了给定有向图的某些修改引起的光谱效应。