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.