We consider population-imbalanced two-component Fermi gases under external harmonic confinement interacting through short-range two-body potentials with diverging $s$-wave scattering length. Using the fixed-node diffusion Monte Carlo method, the energies of the “normal state” are determined as functions of the population imbalance and the number of particles. The energies of the trapped system follow, to a good approximation, a universal curve even for fairly small systems. A simple parametrization of the universal curve is presented and related to the equation of state of the bulk system.

• Received 14 May 2008

DOI:https://doi.org/10.1103/PhysRevA.78.013635