EIGEN-FUNCTIONAL METHOD AND EIKONAL-TYPE EQUATIONS IN ONE-DIMENSIONAL STRONGLY CORRELATED ELECTRON SYSTEMS

Using eigen-functional method, we study one-dimensional strongly correlated electron systems with large momentum (2k_F and/or 4k_F) transfer term(s), and demonstrate that this kind of problems ends in to solve the Eikonal-type equations, and these equations are universal, and independent of whether or not the system is integrable. In contrast to usual perturbation theory, this method is valid not only for weak electron interaction, but also for strong electron interaction. Comparing with exact solution of some integrable models, it can give correct results in linearization approximation. This method can also be used to study electron-phonon interaction systems, and two coupled spin chain (or quantum wire) systems.