Janus Configurations, Chern-Simons Couplings, And The Theta-Angle in N=4   Super Yang-Mills Theory
  We generalize the half-BPS Janus configuration of four-dimensional N=4 super Yang-Mills theory to allow the theta-angle, as well as the gauge coupling, to vary with position. We show that the existence of this generalization is closely related to the existence of novel three-dimensional Chern-Simons theories with N=4 supersymmetry. Another closely related problem, which we also elucidate, is the D3-NS5 system in the presence of a four-dimensional theta-angle. 
Davide Gaiotto and Edward Witten