Superconductivity and ferromagnetism in the Hubbard model

In the framework of the Hubbard model at $U\to\infty$, the phase transitions related to the lower underfilled subband are studied. The self-consistent equations determining the superconducting and ferromagnetic order parameters are derived in the one-loop approximation. The phase boundaries within which ferromagnetic and superconducting phenomena can coexist are discussed.