Fig. 3

Supra-adjacency matrix of a multilayer network with three aspects. The first aspect consists of two layers and the others contain only one layer. The non-diagonal blocks of the supra-adjacency matrix represent the between-layer adjacency of the layers. Since we only consider the between-layer couplings, these blocks are all diagonal. The diagonal blocks record the within-layer adjacency. Since we only discuss about undirected networks, the supra-adjacency matrix is symmetric