© 1995 by London Mathematical Society
© The London Mathematical Society
An Oscillation Theorem for Self-Adjoint Differential Systems and the Rayleigh Principle for Quadratic Functionals
Abteilung Mathematik V, Universität Ulm Helmholtzstrasse 18, D-89069 Ulm, Germany
Received 18 February 1993.
In this note an oscillation theorem on self-adjoint differential systems of the form
= Ax + Bu,
= (C –
C0)x – ATu is obtained, complementing, in particular, results of M. Morse. The application of this oscillation result yields the Rayleigh principle for quadratic functionals, respectively, the existence theorem for corresponding self-adjoint eigenvalue problems, under the central assumptions that the pair (A, B) is controllable (or identically normal) and the triple (A, B, C0) is strongly observable.