Isospectral families of high‐order systems

Abstract

AbstractEarlier work of the authors concerning the generation of isospectral families of second order (vibrating) systems is generalized to higher‐order systems (with no spectrum at infinity). Results and techniques are developed first for systems without symmetries, then with Hermitian symmetry and, finally, with palindromic symmetry. The construction of linearizations which retain such symmetries is discussed. In both cases, the notion of strictly isospectral families of systems is introduced – implying that properties of both the spectrum and the sign‐characteristic are preserved. Open questions remain in the case of strictly isospectral families of palindromic systems. Intimate connections between Hermitian and unitary systems are discussed in an Appendix.