Dynamical correlations in the electron gas

Dynamical correlations in the homogeneous electron gas are a central issue in time-dependent density functional theory and are investigated here by evaluating exactly the leading corrections to the RPA proper polarizability. We obtain Im epsilon (k, omega) at arbitrary k and omega outside the (single) particle-hole excitation spectrum. We calculate the imaginary part of the local field factor Im G(k, omega) and compare Im epsilon (k, omega) with contributions arising from band structure effects in Al. These results are applied to Al to discuss their relative importance on plasmon damping and on the high frequency tail in the dynamical structure factor. Dynamical correlations mediated by the crystal potential contribute to the optical absorption of alkali metals below the onset of interband transitions.