Variational study of hard-core bosons in a 2-D optical lattice using   Projected Entangled Pair States (PEPS)
  We have studied the system of hard-core bosons on a 2-D optical lattice using a variational algorithm based on projected entangled-pair states (PEPS). We have investigated the ground state properties of the system as well as the responses of the system to sudden changes in the parameters. We have compared our results to mean field results based on a Gutzwiller ansatz. 
V. Murg, F. Verstraete, J. I. Cirac