  The propagation of the electromagnetic field of a laser through a dense Bose
gas is examined and nonlinear operator equations for the motion of the center
of mass of the atoms are derived. The goal is to present a self-consistent set
of coupled Maxwell-Bloch equations for atomic and electromagnetic fields
generalized to include the atomic center-of-mass motion. Two effects are
considered: The ultracold gas forms a medium for the Maxwell field which
modifies its propagation properties. Combined herewith is the influence of the
dipole-dipole interaction between atoms which leads to a density dependent
shift of the atomic transition frequency. It is expressed in a position
dependent detuning and is the reason for the nonlinearity. This results in a
direct and physically transparent way from the quantum field theoretical
version of the local-field approach to electrodynamics in quantum media. The
equations for the matter fields are general. Previously published nonlinear
equations are obtained as limiting cases. As an atom optical application the
scattering of a dense beam of a Bose gas is studied in the Raman-Nath regime.
The main conclusion is that for increasing density of the gas the dipole-dipole
interaction suppresses or enhances the scattering depending on the sign of the
detuning.
