  We introduce an efficient method to solve the Mott-Hubbard model. The
Schr\"{o}dinger equation is solved by the successive construction of doorway
states. The ground state wavefunction derived by this method contains all
relevant many-body correlations introduced by the hamiltonian, but the
dimensionality of the Hilbert space is greatly reduced. We apply the doorway
method to obtain the chemical potential, the on-site fluctuations and the
visibility of the interference pattern arising from atoms in a one-dimensional
periodic lattice. Excellent agreement with exact numerical calculations as well
as recent experimental observations is found.
