Colliding clouds of strongly interacting spin-polarized fermions
  Motivated by a recent experiment at MIT, we consider the collision of two clouds of spin-polarized atomic Fermi gases close to a Feshbach resonance. We explain why two dilute gas clouds, with underlying attractive interactions between their constituents, bounce off each other in the strongly interacting regime. Our hydrodynamic analysis, in excellent agreement with experiment, gives strong evidence for a metastable many-body state with effective repulsive interactions. 
Edward Taylor, Shizhong Zhang, William Schneider, Mohit Randeria
cond-mat.quant-gas