SPECTRAL-FUNCTION OF 2-DIMENSIONAL FERMI LIQUIDS

We show that the spectral function for single-particle excitations in a two-dimensional Fermi liquid has a Lorentzian shape in the low-energ y limit. Landau quasiparticles have a uniquely defined spectral weight and a decay rate which is much smaller than the quasiparticle energy. By contrast, perturbation theory and the T-matrix approximation yield spurious deviations from Fermi-liquid behavior, which are particularl y pronounced for a linearized dispersion relation. [S0163-1829(98)0021 5-X].