1Nexpansion for the degenerate Anderson model in the mixed-valence regime

The $\frac{1}{N}$ expansion method for the degenerate Anderson model is formulated. $N$ is the degeneracy factor of one of the $f$-electron configurations. Various ground-state properties are calculated. Excellent agreement with the result of Bethe ansatz for $N=6\mathrm{}$ is shown. The rate of convergence of the series is analyzed. The merit and inadequacy of the method are discussed. At zero temperature the ratio of the magnetic susceptibility and the specific-heat linear coefficient is shown to lie within a range of 1 and $1+{\mathrm{}(N-1\mathrm{})\mathrm{}}^{-1\mathrm{}}$.