Comment on "Novel Superfluidity in a Trapped Gas of Fermi Atoms with   Repulsive Interaction Loaded on an Optical Lattice"
  In a recent letter Machida et al. [Phys. Rev. Lett. 93, 200402 (2004)] concluded that in a trapped gas of fermions with repulsive interactions a superfluid phase appears around the Mott-insulator at the center of the trap. They base their conclusion on a negative binding energy, and a large weight for a singlet formed by particles located at opposite sides of the Mott-insulator. We show here that the observed effects are not related to superfluidity. 
M. Rigol, S. R. Manmana, A. Muramatsu, R. T. Scalettar, R. R. P.   Singh, and S. Wessel