  The Bose-Hubbard model is well-defined description of a Bose solid which may
be realistic for cold atoms in a periodic optical lattice. We show that
contrary to accepted theories it can never have as a ground state a perfect
Mott insulator solid and that it has a low-energy spectrum of vortex-like phase
fluctuations. Whether the ground state is necessarily commensurate remains an
open question.
