EXCHANGE AND CORRELATION CORRECTIONS TO THE RESPONSE FUNCTIONS OF A SPIN-POLARIZED ELECTRON-GAS

We analyze the spin and charge responses induced in a spin-polarized e lectron gas by a weak electromagnetic field. The coupled spin-charge r esponse is derived from the equation of motion of the particle distrib ution function in the presence of the perturbation. To obtain the corr ect frequency and the wave-vector dependence we introduce the spin-dep endent local-field factors, G(sigma)(+/-) = G(sigma)(X) +/- G(sigma)(C ), which give the exchange (x) and correlation (c) corrections to the random phase approximation. For an arbitrary degree of polarization of the electron gas, we derive the exact analytical expressions for G(si gma)(+/-) ((q) over right arrow,pi) in the limit of high frequency or large wavevectors. The results for (q) over right arrow -->infinity ar e expressed in terms of the two-particle correlation function, g((r) o ver right arrow) at r = O.