  We show that the absorption spectrum in semiconducting nanotubes can be
determined using the bosonization technique combined with mean-field theory and
a harmonic approximation. Our results indicate that a multiple band
semiconducting nanotube reduces to a system of weakly coupled harmonic
oscillators. Additionally, the quasiparticle nature of the electron and hole
that comprise an optical exciton emerges naturally from the bosonized model.
