Direct calculation of conductance and conductance fluctuations in a disordered Fermi liquid

We derive a formalism by which it is possible to calculate directly the conductance and conductance fluctuations for disordered interacting electrons. With this formalism, we explicitly calculate the conductance and conductance fluctuations to lowest nontrivial order in the disorder. Our conductance results agree with previous indirect calculations and confirm the Einstein relation for diffusion. We also calculate conductance fluctuations to one-loop order. We find the fluctuations to be interaction independent and still universal. Higher moments of the conductance are also found to be interaction independent to one-loop order, therefore restricting the possible form of the conductance distribution function.