title: Purely imaginary eigenvalues of Zakharov-Shabat systems.
abstract: Zakharov-Shabat systems with single-hump and real, but not necessarily symmetric, potentials are shown to have purely imaginary eigenvalues only. Coupled with examples of double-hump potentials with nonimaginary eigenvalues, this establishes that confinement of Zakharov-Shabat eigenvalues to the imaginary axis is a characteristic of potentials whose energy is concentrated in a single region of the time axis.
authors.affiliation: Department of Mathematics, Virginia Tech, Blacksburg, Virginia 24061-0123, USA.
authors.forename: M
authors.initials: M
authors.lastname: Klaus
authors.forename: J K
authors.initials: JK
authors.lastname: Shaw