Properties of low-lying states in a diffusive quantum dot and Fock-space localization

Motivated by an experiment by Sivan er nl. [Europhys. Lett. 25, 605 (1994)] and by subsequent theoretical work on localization in Fock space, we study numerically a hierarchical model for a finite many-body system of fermions moving in a disordered potential and coupled by a two-body interaction. We focus attention on the low-lying states close to the Fermi energy. Both th e spreading width and the participation number depend smoothly on excitatio n energy. This behavior is in keeping with naive expectations and does not display Anderson localization. We show that the model reproduces essential features of the experiment by Sivan et al. [S0031-9007(98)07906-X].