The Anderson Model is a Hamiltonian model that is often used to describe Heavy Fermion systems. The model contains a narrow resonance between a magnetic impurity state and a conduction electron state. The model also contains a short range U repulsion term as found in the Hubbard model between localized electrons. For a single impurity, the Hamiltonian takes the form
where the f operator corresponds to an impurity, and c corresponds to a conduction electron, and σ labels the spin. In heavyfermion systems, we find we have a lattice of impurities. The relevant model is then the periodic Anderson model.
Bibliography P.W. Anderson, Phys. Rev. 124 (1961), p. 41 Retrieved from "http://en.wikipedia.org/" 
