ABSTRACT
For interacting electrons the electron self-energy is introduced:
In this way we find
and a new quasiparticle spectrum renormalised by the interaction is given near the Fermi level by:
where
and fl = fi + ^(kp, 0) is the renormalised Fermi energy. The spectrum is assumed to be isotropic and the spin and band quantum numbers are deleted for simplicity, vp and kp are the Fermi velocity and momentum respectively.
