Expanding the two-particle Green’s functions determines the self-energy and the polarization as well as the
response function on the same footing. The correlation energy is calculated with the help of the extended
quasiparticle picture, which accounts for off-shell effects. The corresponding response function leads to the same
correlation energy as the self-energy in agreement with perturbation theory, provided one works in the extended
quasiparticle picture. A one-dimensional quantum wire of fermions is considered and ground-state properties
are calculated in the high-density regime within the extended quasiparticle picture and Born approximation.
While the on-shell selfenergies are strictly zero due to Pauli-blocking of elastic scattering, the off-shell behavior
shows a rich structure of a gap in the damping of excitation, which is closed when the momentum approaches
the Fermi one. The consistent spectral function is presented, completing the first two energy-weighted sum
rules. The excitation spectrum shows a splitting due to holons and antiholons as non-Fermi liquid behavior.
A renormalization procedure is proposed by subtracting an energy constant to render the Fock exchange
energy finite. The effective mass derived from meanfield approximation shows a dip analogous to the onset
of Peierls instability. The reduced density matrix or momentum distribution is calculated with the help of a
Padé regularization repairing deficiencies of the perturbation theory. A seemingly finite step at the Fermi energy
indicating Fermi-liquid behavior is repaired in this way.