  We study electronic transport through a strongly interacting quantum dot by
using the finite temperature extension of Wilson's numerical renormalization
group (NRG) method. This allows the linear conductance to be calculated at all
temperatures and in particular at very low temperature where quantum
fluctuations and the Kondo effect strongly modify the transport. The quantum
dot investigated has one active level for transport and is modeled by an
Anderson impurity model attached to left and right electron reservoirs. The
predictions for the linear conductance are compared to available experimental
data for quantum dots in heterostructures. The spin-resolved conductance is
calculated as a function of gate voltage, temperature and magnetic field
strength and the spin-filtering properties of quantum dots in a magnetic field
are described.
