STRONGLY CORRELATED BOSONS ON A LATTICE - A SLAVE-BOSON APPROACH

The grand canonical system of hard-core bosons, subject to thermal flu ctuations, is studied on a lattice. Starting from the slave-boson, rep resentation we derive an effective Ginzburg-Landau functional for the superfluid order parameter. The order parameter field is a collective field constructed from the slave-boson fields for empty and singly occ upied sites. We find two phase transitions; one from a normal fluid at high density to a superfluid and another one from the superfluid to a normal fluid at low density.