  We examine the problem of finite Fermi systems having a degenerate
single-particle spectrum and show that the Landau approach, applied to such a
system, admits the possibility of merging single-particle levels. It is
demonstrated that the opportunity for this behavior is widespread in quantum
many-body systems. The salient feature of the phenomenon is the occurrence of
nonintegral quasiparticle occupation numbers, leading to a radical alteration
of the standard quasiparticle picture. Implications of this alteration are
considered for nuclear, atomic, and solid-state systems.
