Density and Spin Response of a Fermi Gas in the Attractive and Quasi-Repulsive
Regime 
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Recent experimental advances in ultracold Fermi gases allow
for exploring response functions under different dynamical conditions. In
particular, the issue of obtaining a quasirepulsive regime starting from a
Fermi gas with an attractive interparticle interaction while avoiding the
formation of the two-body bound state is currently debated. Here, we provide a
calculation of the density and spin response for a wide range of temperature and
coupling both in the attractive and quasirepulsive regime, whereby the system is
assumed to evolve nonadiabatically toward the upper branch of the Fermi gas.
A comparison is made with the available experimental data for these two
quantities.