On the Hubbard model with boundaries

The magnetization and the electron number at the edge site are analytically calculated in the repulsive Hubbard model with a small magnetic field near the half-filling. Such quantities in the strong-coupling limit are evaluated. The relationship between the repulsive and the attractive Hubbard models with boundary fields is discussed. The magnetization and the electron number at the edge site are also derived in the attractive Hubbard model.