Induced interaction in a spin-polarized Fermi gas

We study the effect of the induced interaction on the superfluid transition temperature of a spin-polarized Fermi gas. In the BCS limit, the polarization is very small in the superfluid state, and the effect of the induced interaction is almost the same as in the spin-balanced case. The temperature T-t and the polarization P-t of the tricritical point are both reduced from mean-field results by a factor about 2.22. This reduction is also significant beyond the BCS limit. In the unitary limit, we find (P-t, T-t/T-F) = (0.42,0.16), in comparison with mean-field and experimental results.