Topological approach to Luttinger's theorem and the Fermi surface of a   Kondo lattice
  A non-perturbative proof of Luttinger's theorem, based on a topological argument, is given for Fermi liquids in arbitrary dimensions. Application to the Kondo lattice shows that even the completely localized spins do contribute to the Fermi sea volume as electrons, whenever the system can be described as a Fermi liquid. 
Masaki Oshikawa (Tokyo Inst. Tech.)