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We study the effects of dynamic correlations on the ground-state
properties of a double-layer two-dimensional electron gas within
the quantum Singwi-Tosi-Land-Sj?lander theory (STLS). The
intralayer and interlayer static structure factors, the
pair-correlation functions, and the wave vector and
frequency-dependent local-field factors have been calculated for a
range of electron densities and layer separations. We find that
the local-field factors have an oscillatory frequency dependence
and the magnitude of interlayer local-field factors is about an
order of magnitude smaller than that of the intralayer. Our
results are compared with the random-phase approximation and the
static STLS approximation to assess the importance of dynamical
correlations. We also calculate the dispersion relations for the
optical and acoustic plasmons and the damping of these modes to
compare them with other mean-field theories, and we comment on the
relevance of our results to the recent experiments.
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