  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.
