Adiabatic sweep theorem for three-dimensional dipolar Bose gases

The variational theorem for the scattering length in the presence of the dipole-dipole interaction is developed. The theorem is applied to the spinless dipolar Bose gas in three dimensions. We calculated analytically the long-range tails of the single-particle momentum distribution and static structure factor, and the pair distribution function at short distances. The momentum distribution is inversely proportional to $q^4$ with the anisotropic prefactor. In the absence of the dipole-dipole interaction, Tan's adiabatic sweep theorem is reproduced as a particular case. For the homogeneous dilute Bose gas, all the relations are calculated analytically.