Two-loop contribution of massive and massless fields to the abelian Chern-Simons term

Two-loop contributions of massive and massless fermions to the Chern-Simons term are analytically calculated in D=3 electrodynamics with exact and spontaneously broke gauge symmetry. Massless particles produce non-zero irrational corrections. Because corresponding abelian diagrams enter with independent colour weight, the integerness of the Chern-Simons coupling in the non-abelian theory is violated by renormalizations. Supersymmetry is shown to result in a partial cancellation of the contributions. (orig.)