  Recent experiments on imbalanced Fermi gases have raised interest in the
physics of an impurity immersed in a Fermi sea, the so-called Fermi polaron. In
this letter, a simple theory is devised to describe dilute Fermi-polaron
ensembles corresponding to the normal phase of an imbalanced Fermi gas. An
exact formula is obtained for the dominant interaction between polarons,
expressed solely in terms of a single polaron parameter. The physics of this
interaction is identified as a signature of the Pauli exclusion principle.
