  We use exact diagonalization to determine the spectrum of reduced
Hamiltonians based on renormalization group flows to strong coupling. For the
half-filled two-leg Hubbard ladder we reproduce the known insulating d-Mott
groundstate with spin and charge gaps. For the saddle point regions of the
two-dimensional Hubbard model near half-filling we find a crossover to a
similar strong coupling state, which truncates the Fermi surface near the
saddle points. At lower scales d-wave superconductivity appears on the
remaining Fermi surface.
