Spin conductivity and spin-charge separation in the high-T-c cuprates

We address the question of how to experimentally test spin-charge separation in the high-T-c cuprates. We demonstrate that a comparison between the temperature dependences of the electrical resistivity and spin resistivity can be used for this purpose. Given the known linear in temperature dependence of the electrical resistivity, the spin resistivity should also be Linear in temperature in the absence of spin-charge separation and under conditions appropriate for the optimally doped cuprates, but is in general not so in the presence of spin-charge separation. We demonstrate the quantitative feasibility of applying the spin-injection technique to measure the electron-spin diffusion constant.