Hadamard difference sets in groups of order 64
We determine the groups \(G\) of order 64 which contain 4 pairwise disjoint subgroups of order 8. We show that \(G\) must be either elementary abelian or isomorphic to a group \(G_ 0\) of nilpotence class two. \(G_ 0\) is the semidirect product \(\langle t\rangle V\), where \(V\) is elementary abelian of order 32 and \(t\) is an involution which acts on \(V\) with two nontrivial Jordan blocks.
scientific article; zbMATH DE number 3698