On Kippenhahn curves of low rank partial isometries
arXiv:2601.12923 · doi:10.1007/s00020-026-02846-w
Abstract
Conditions are established for rank three partial isometries to have circular components contained in their Kippenhahn curves. In particular, such matrices with circular numerical ranges are described. It is also established that the Gau-Wang-Wu conjecture holds for matrices under consideration.