Fermi Liquid Theory for Nonlinear Transport through a Multilevel Anderson Impurity

We present a microscopic Fermi liquid view on the low-energy transport through an Anderson impurity with $N$ discrete levels, at arbitrary electron filling ${N}_{d}$. It is applied to nonequilibrium current fluctuations, for which the two-quasiparticle collision integral and the three-body correlations that determine the quasiparticle energy shift play important roles. Using the numerical renormalization group up to $N=6$, we find that for strong interactions the three-body fluctuations are determined by a single parameter other than the Kondo energy scale in a wide filling range $1\ensuremath{\lesssim}{N}_{d}\ensuremath{\lesssim}N\ensuremath{-}1$. It significantly affects the current noise for $Ng2$ and the behavior of noise in magnetic fields.