Complete Pseudoparticle Representation and the Conductivity Spectrum of   the Hubbard Chain
  We use a complete pseudoparticle operator representation to study the explicit form of the finite-frequency conductivity for the Hubbard chain. Our study reveals that the spectral weight is mostly concentrated at the \omega =0 Drude peak (except at density n=1) and at an absorption starting just below twice the value of the chemical potential whose \omega-dependence we evaluate exactly. We also obtain the exact \omega dependence of the higher-energy, less-pronounced absorption edges, whose weights vanish for large on-site interaction U. 
J.M.P. Carmelo, N.M.R. Peres, and D.K. Campbell