The a-function for N=2 supersymmetric gauge theories in three dimensions
  Recently, the existence of a candidate a-function for renormalisable theories in three dimensions was demonstrated for a general theory at leading order and for a scalar-fermion theory at next-to-leading order. Here we extend this work by constructing the a-function at next-to-leading order for an N=2 supersymmetric Chern-Simons theory. This increase in precision for the a-function necessitated the evaluation of the underlying renormalization-group functions at four loops. 
J. A. Gracey, I. Jack, C. Poole and Y. Schroder
hep-th