title: Exact dynamical exchange-correlation kernel of a weakly inhomogeneous electron gas.
abstract: The dynamical exchange-correlation kernel f{xc} of a nonuniform electron gas is an essential input for the time-dependent density-functional theory of electronic systems. The long-wavelength behavior of this kernel is known to be of the form f{xc}=alpha/q{2} where q is the wave vector and alpha is a frequency-dependent coefficient. We show that in the limit of weak nonuniformity the coefficient alpha has a simple and exact expression in terms of the ground-state density and the frequency-dependent kernel of a uniform electron gas at the average density. We present an approximate evaluation of this expression for Si and discuss its implications for the theory of excitonic effects.
authors.affiliation: Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan.
authors.forename: V U
authors.initials: VU
authors.lastname: Nazarov
authors.forename: G
authors.initials: G
authors.lastname: Vignale
authors.forename: Y-C
authors.initials: YC
authors.lastname: Chang