Hydrodynamic Modes in a Trapped Strongly Interacting Fermi Gases of   Atoms
  The zero-temperature properties of a dilute two-component Fermi gas in the BCS-BEC crossover are investigated. On the basis of a generalization of the variational Schwinger method, we construct approximate semi-analytical formulae for collective frequencies of the radial and the axial breathing modes of the Fermi gas under harmonic confinement in the framework of the hydrodynamic theory. It is shown that the method gives nearly exact solutions. 
Yeong E. Kim and Alexander L. Zubarev