The normal ΔH-matrices with connection to some Jacobi-like methods

AbstractThe ΔH-matrices appear in the context of certain maximization and minimization problems. The following purely algebraic problem, arising in connection with certain norm-reducing Jacobi-type algorithms is treated: When is a normal ΔH-matrix diagonal? Final results are obtained in the cases n = 3 and n = 4, and in general for the attractive normal ΔH-matrices