Nonrenormalization Theorem for Gauge Coupling in 2+1D
  We prove that $\be$-function of the gauge coupling in $2+1D$ gauge theory coupled to any renormalizable system of spinor and scalar fields is zero. This result holds both when the gauge field action is the Chern-Simons action and when it is the topologically massive action. 
A.N.Kapustin, P.I.Pronin