A decimation method for studying transport properties of disordered systems

We present a numerical decimation method for the study of transport propert ies of disordered tight-binding systems. We demonstrate this method by cons idering two situations: 1) the problem of two interacting particles (TIP) i n a quasi-one dimensional random potential and 2) the conductance of disord ered normal - superconducting structures. For case 1) we compute the two pa rticle localisation length lambda(2) presenting results for its dependence on disorder, interaction strength and system width. For case 2) we illustra te the method by presenting results for the sub-gap conductance of a normal wire connected to one normal and one superconducting reservoir and the cas e of a normal region in contact with two superconductors.