  We consider a quasi-one-dimensional model of a two-component Fermi gas at
zero temperature on one, two and three-leg attractive-U Hubbard ladders. We
construct the grand canonical phase diagram of a two-component spin-polarized
gas. We find that the structure of the phase diagram of the attractive-U
Hubbard model for two and three leg ladders significantly differs q from the
structure of the phase diagram of a single chain. We argue that the single
chain model is a special case, and that multichain ladders display qualitative
features of the 1D-to-3D crossover, observed in experiments with trapped
ultracold gases.
