Bethe Ansatz and thermodynamic limit of affine quantum group invariant extensions of the t-J model

We have constructed a one-dimensional exactly solvable model, which is based on the t-J model of strongly correlated electrons, but which has additional quantum group symmetry, ensuring the degeneration of states. We use Bethe Ansatz technique to investigate this model. The thermodynamic limit of the model is considered and equations for different density functions written down. These equations demonstrate that the additional color degrees of freedom of the model behave as in a gauge theory, namely, an arbitrary distribution of color indices over particles leave invariant the energy of the ground state and the excitations. The S-matrix of the model is shown to be the product of the ordinary t-J model S-matrix and the unity matrix in the color space. (C) 1999 American Institute of Physics. [S0022-2488(99)02411-1].