ABSTRACT
Our goal in this section will be to provide an overview of the NRG method pioneered by Wilson (1973, 1975) for the ordinary Kondo model. We shall stress the results obtained from this approach which provide insight into the two-channel Kondo model and the influence of symmetry-breaking fields on that model. Specifically, we shall consider the effects of exchange anisotropy J (1) ≠ J (2) = J (3)), the influence of local and bulk fields which couple to the spin, and the influence of a channel field which splits the exchange integrals for the electrons in the two different channels. We shall also discuss a simple ‘shell model' approach which works remarkably well for characterizing the lowest few states of the non-trivial fixed point and appears to generalize to more complex models not treatable by the NRG.
