Local and band approaches to actinide systems

We investigate two models of interest in the context of actinide and rare earth systems. We extend previous work on the Anderson model for two magnetic configurations and obtain the singlet quasiparticle energy to next leading order in the 1/N expansion. We prove that the appropriate Ward identity and perturbative scaling results are reproduced in this theory. We also prove the opposite limit in which there is significant f-f overlap using the infinite U Hubbard model. Working to second order in the 1/N expansion, we study the quasiparticle scattering amplitudes and find a large enhancement in the Landau parameter f0a near half filling which varies as the cube of the mass enhancement. For a free-electron-like dispersion relation, this implies a transition to a ferromagnetic state for small hole concentrations. (orig.)