Field dependent quasiparticles in a strongly correlated local system II

We extend the renormalized quasiparticle description of the symmetric Anderson model in a magnetic field $H$, developed in earlier work, to the non-symmetric model. The renormalized parameters are deduced from the low energy NRG fixed point for arbitrary field values. We find quasiparticle resonance widths, ${\tilde{\mathrm{\Delta }}}_{\sigma }(H)$, which depend in general on the spin $\sigma$ as well as $H$. The low temperature static properties can be expressed completely in terms of these parameters, which can also be used as inputs for a renormalized perturbation theory. We show that taking into account repeated quasiparticle scattering gives results for the longitudinal and transverse dynamic spin susceptibilities which are in very good agreement with those obtained from direct NRG calculations.