  We consider a fibrillar medium with a continuous distribution of two-level
atoms coupled to quantized electromagnetic fields. Perturbation theory is
developed based on the current algebra satisfied by the atomic operators. The
one-loop corrections to the dispersion relation for the polaritons and the
dielectric constant are computed. Renormalization group equations are derived
which demonstrate a screening of the two-level splitting at higher energies.
Our results are compared with known results in the slowly varying envelope and
rotating wave approximations. We also discuss the quantum sine-Gordon theory as
an approximate theory.
