Universal phase diagram of a strongly interacting Fermi gas with unbalanced spin populations

We present a theoretical interpretation of a recent experiment presented by Zwierlein [Nature (London) 442, 54 (2006)] on the density profile of Fermi gases with unbalanced spin populations. We show that in the regime of strong interaction, the boundaries of the three phases observed by Zwierlein can be characterized by two dimensionless numbers eta(alpha) and eta(beta). Using a combination of a variational treatment and a study of the experimental results, we infer rather precise bounds for these two parameters.