  We present a Keldysh nonlinear sigma-model approach to the renormalization
group analysis of the disordered electron liquid. We include both the Coulomb
interaction and Fermi-liquid type interactions in the singlet and triplet
channels into the formalism. Based on this model, we reproduce the coupled
renormalization group equations for the diffusion coefficient, the frequency,
and interaction constants previously derived with the replica model in the
imaginary time technique. With the help of source fields coupling to the
particle-number and spin densities, we study the density-density and spin
density-spin density correlation functions in the diffusive regime. This allows
us to obtain results for the electric conductivity and the spin susceptibility
and thereby to re-derive the main results of the one-loop renormalization group
analysis of the disordered electron liquid in the Keldysh formalism.
