  We revisit the problem of quantum localization of many-body states in a
quantum dot and the associated problem of relaxation of an excited state in a
finite correlated electron system. We determine the localization threshold for
the eigenstates in Fock space. We argue that the localization-delocalization
transition (which manifests itself, e.g., in the statistics of many-body energy
levels) becomes sharp in the limit of a large dimensionless conductance (or,
equivalently, in the limit of weak interaction). We also analyze the temporal
relaxation of quantum states of various types (a "hot-electron state", a
"typical" many-body state, and a single-electron excitation added to a "thermal
state") with energies below, at, and above the transition.
