All nodes are in their own community

If all nodes are in their own community, then δ(c_i, c_j) is always 0 since c_i is always different from c_j, except in the cases where i=j. Since our graph does not have a self-loop (a node connected to itself), A_ii is always equal to zero and only the negative term in the sum remains. So in that particular case, the modularity Q is negative. In the following, we will write it as Q_diag and its value for our graph is Q_diag=-0.148.