Infrared behavior of dipolar Bose systems at low temperatures

Abstract: We rigorously discuss the infrared behavior of the uniform three dimensional dipolar Bose systems. In particular, it is shown that low-temperature physics of the system is controlled by two parameters, namely isothermal compressibility and intensity of the dipole-dipole interaction. By using hydrodynamic approach we calculate the spectrum and damping of low-lying excitations and analyze infrared behavior of the one-particle Green's function. The low-temperature corrections to the anisotropic superfluid density as well as condensate depletion are found. Additionally we derive equations of the two-fluid hydrodynamics for dipolar Bose systems and calculate velocities of first and second sound.