Nonuniversal transmission phase lapses through a quantum dot: An   exact-diagonalization of the many-body transport problem
  Systematic trends of nonuniversal behavior of electron transmission phases through a quantum dot, with no phase lapse for the transition N=1 -> N=2 and a lapse of pi for the N=2 -> N=3 transition, are predicted, in agreement with experiments, from many-body transport calculations involving exact diagonalization of the dot Hamiltonian. The results favor shape anisotropy of the dot and strong e-e repulsion with consequent electron localization, showing dependence on spin configurations and the participation of excited doorway transmission channels. 
Leslie O. Baksmaty, Constantine Yannouleas, Uzi Landman