Anisotropic expansion of a thermal dipolar Bose gas
  We report on the anisotropic expansion of ultracold bosonic dysprosium gases at temperatures above quantum degeneracy and develop a quantitative theory to describe this behavior. The theory expresses the post-expansion aspect ratio in terms of temperature and microscopic collisional properties by incorporating Hartree-Fock mean-field interactions, hydrodynamic effects, and Bose-enhancement factors. Our results extend the utility of expansion imaging by providing accurate thermometry for dipolar thermal Bose gases, reducing error in expansion thermometry from tens of percent to only a few percent. Furthermore, we present a simple method to determine scattering lengths in dipolar gases, including near a Feshbach resonance, through observation of thermal gas expansion. 
Yijun Tang, Andrew G. Sykes, Nathaniel Q. Burdick, Jack M. DiSciacca,   Dmitry S. Petrov, and Benjamin L. Lev
cond-mat.quant-gas physics.atom-ph quant-ph