On the ground-state energy of a mixture of two different oppositely polarized fermionic gases

We report the results of the computation of the order $(k_{\rm F}a_0)^2$ correction, where $k_{\rm F}=3\pi^2\rho$ is the Fermi wave vector and $a_0$ the $s$-wave scattering length of the repulsive interaction, to the ground-state energy of a mixture of oppositely polarized $N_a$ spin $1/2$ fermions $a$ of masses $m_a$ and $N_b$ spin $1/2$ fermions $b$ of masses $m_b$ ($\rho=N/V$, $N=N_a+N_b$). It is shown that the results of the paper \cite{FraPil} in which the same correction has been computed entirely numerically, using a more traditional approach, can be easily and semianalytically reproduced using the effective field theory technique.