Scattering theories for the 1D Hubbard model
  In one-dimensional (1D) non-perturbative many-electron problems such as the 1D Hubbard model the electronic charge and spin degrees of freedom separate into exotic quantum objects. However, there are two different representations for such objects and associated scattering quantities whose relation is not well understood. Here we solve the problem by finding important information about the relation between the corresponding alternative choices for one-particle scattering states. Our study reveals why one of these representations, the {\it pseudofermion} representation, is the most suitable for the description of the unusual finite-energy spectral and dynamical properties of the model. This is a problem of physical importance, since the exotic independent charge and spin finite-energy spectral features observed by angle-resolved photoelectron spectroscopy in quasi-1D metals was found recently to correspond to the charge and spin quantum objects of the pseudofermion representation. 
J. M. P. Carmelo, K. E. Hibberd, and N. Andrei