Multigrid method for the random-resistor problem

We discuss the problem of solving large linear systems of equations that arise in lattice systems with disorder. Three examples of this kind of problem are (i) computing currents in a random-resistor network, (ii) computing the fermion (quark) propagator in lattice quantum chromodynamics, and (iii) the discrete Schrödinger operator with a random potential (the Anderson model of localization). We show that the algebraic multigrid is a very effective way to compute currents in a random-resistor network. It is likely that similar techniques will apply to the other problems.