  We calculate the imaginary part of the frequency-dependent dielectric
function of bulk silicon by applying time-dependent density-functional theory
based on the exact-exchange (EXX) Kohn-Sham (KS) band structure and the
adiabatic local-density approximation (ALDA) kernel. The position of the E2
absorption peak calculated with the EXX band structure at the
independent-particle level is in excellent agreement with experiments, which
demonstrates the good quality of EXX `KS quasiparticles'. The excitonic E1 peak
that is missing at the independent-particle level remains absent if
two-particle interaction effects are taken into account within the
time-dependent LDA, demonstrating the incapability of the ALDA kernel to
describe excitonic effects.
