Journal of Operator Theory, Vol. 58, No. 2 (Fall 2007), pp. 415-440 (26 pages) In this paper the well-known result that a definitizable operator in a Krein space remains definitizable after a finite ...

A wide class of problems in the study of the spectral and orbital stability of dispersive waves in Hamiltonian systems can be reduced to understanding the so-called "energy spectrum", that is, the ...