We discuss the 2D Mott insulator (MI) state of a 2D array of coupled finite
size 1D Bose gases. It is shown that the momentum distribution in the lattice
plane is very sensitive to the interaction regime in the 1D tubes. In
particular, we find that the disappearance of the interference pattern in time
of flight experiments will not be a signature of the MI phase, but a clear
consequence of the strongly interacting Tonks-Girardeau regime along the tubes.Comment: 4 pages, 3 figure