The paper is concerned with singular Hamiltonian systems of arbitrary order with arbitrary equal defect indices. It is proved that the minimal operator generated by the Hamiltonian system is simple. As a consequence, a sufficient condition is obtained for the continuous spectrum of every self-adjoint extension of the minimal operator to be empty in some interval and for the spectrum to be nowhere dense in this interval in terms of the numbers of linearly independent square integrable solutions.
"Simplicity and Spectrum of Singular Hamiltonian Systems of Arbitrary Order." Abstr. Appl. Anal. 2013 1 - 6, 2013. https://doi.org/10.1155/2013/202851