1/(N-1) expansion for a finite-U Anderson model away from half-filling

We apply recently developed 1/(N - 1) expansion to a particle-hole asymmetric SU(N) Anderson model with finite Coulomb interaction U. To leading order in 1/(N - 1) it describes the Hartree-Fock random-phase approximation (HF-RPA), and the higher-order corrections describe systematically the fluctuations beyond the HF-RPA. We show that the next-leading-order results of the renormalized parameters for the local Fermi-liquid state agree closely with the numerical renormalization group results at N = 4. This ensures the reliability of the next-leading-order results for N >= 4, and we examine the N dependence of the local Fermi-liquid parameters. Our expansion scheme uses the standard Feynman diagrams and has wide potential applications.