Eigenvalues of rank one perturbations of unstructured matrices
  Let $A$ be a fixed complex matrix and let $u,v$ be two vectors. The eigenvalues of matrices $A+\tau uv^\top $ $(\tau\in\mathbb{R})$ form a system of intersecting curves. The dependence of the intersections on the vectors $u,v$ is studied. 
A.C.M. Ran, M. Wojtylak
math.FA math.CV