  We consider a dilute spin-polarized Fermi gas at positive temperature in
dimensions $d\in\{1,2,3\}$. We show that the pressure of the interacting gas is
bounded from below by that of the free gas plus, to leading order, an explicit
term of order $a^d\rho^{2+2/d}$, where $a$ is the $p$-wave scattering length of
the repulsive interaction and $\rho$ is the particle density. The results are
valid for a wide range of repulsive interactions, including that of a hard
core, and uniform in temperatures at most of the order of the Fermi
temperature. A central ingredient in the proof is a rigorous implementation of
the fermionic cluster expansion of Gaudin, Gillespie and Ripka (Nucl. Phys. A,
176.2 (1971), pp. 237--260).
