EFFECT OF VERTEX CORRECTIONS ON THE CHARGE AND SPIN RESPONSES OF THE FERMI-LIQUID

The effects of vertex corrections on the charge and spin responses of the Fermi liquid are considered. It is shown that the interaction in t he particle-hole channel induces virtual pair excitations (Cooper pair like) in both the charge and the spin channels. It leads to the appea rance of an anomalous Fermi-liquid term Im <(chi)over tilde> similar t o - omega/T in both the charge and the spin responses of the Fermi liq uid in addition to the normal response similar to - omega/nu(F)k. Such a contribution of the anomalous term to the charge and spin responses is in agreement with the marginal Fermi-liquid hypothesis proposed by Varma et al to explain the universal anomalies in the normal state of cuprate high-T-c superconductors.