Slave Boson Formulation for Interacting Boson Systems and the   Superfluid-Insulator Transition
  A new formulation for the study of interacting bosons on a lattice is introduced. This approach is used to give analytical expressions for the Mott insulating lobes in the phase diagram and to calculate the density-density correlation function. It is also shown that, at mean-field level, this newly introduced slave boson theory coincides with mean-field theory of a suitably introduced order parameter. 
Raymond Fresard (Institut fuer Theorie der Kondensierten Materie, U.   Karlsruhe)