Optical conductivity in model with anisotropic inelastic scattering

Inelastic scattering is very strong in the oxides and large momentum space anisotropies exist in models in which the effective interaction is strongly peaked at (pi,pi) in the 2-dimensional Brillouin zone. This situation is favourable to d-wave superconductivity and may apply to the oxides. We calculate the normal state optical conductivity and describe the relationship of the derived optical-scattering rates and effective masses to the underlying self energies with emphasis on frequency dependence and on anisotropy. Comparison with experiments is made. It is found that anisotropy leads to an energy dependence in the optical rate even when the scattering is elastic.