Radio-frequency spectroscopy of trapped Fermi gases with population imbalance

Motivated by recent experiments, we address the behavior and evolution of radio-frequency (RF) spectra as temperature and polarization are varied in population-imbalanced Fermi gases from above to below T-c. We discuss a series of scenarios for the experimentally observed zero-temperature pseudogap phase and show how present and future RF experiments may help in its elucidation. We conclude that the experiments of Zwierlein and co-workers at the lowest T may well reflect ground-state properties, but take issue with their claim that the pairing gap survives up to temperatures of the order of the degeneracy temperature T-F at unitarity.