  A Hubbard-like model with SU(4) symmetry for electrons with two-fold orbital
degeneracy is studied extensively. Exact solution in one dimension is derived
by means of Bethe ansatz, where the sites are supposed to be occupied by at
most two electrons. The features of ground state and excited states for
repulsive coupling are shown. For finite N number of electrons, the
configurations of quantum numbers are given explicitly and the spectra of
excitations are obtained by solving the Bethe-ansatz equation numerically. For
infinite N, the ground state and various kinds of low-lying excitations are
obtained on the basis of thermodynamics limit.
