Spectra of corona products of digraphs

Two types of corona products for simple directed graphs are introduced, extending the classical notions from the undirected setting: the vertex-corona and the arc-corona. Their structural and spectral properties are investigated through the use of digraph coronals, with particular emphasis on the adjacency, Laplacian, and signless Laplacian spectra. Finally, the coronals corresponding to these three matrices are computed for several families of digraphs.