Field Configurations and the SU(2) Haar Measure in QCD
  We characterise a class of SU(2) gluonic field configurations in the modified axial gauge where a zero mode component vanishes at some space point but the global Haar measure remains non-zero. The consequence of this is that gluonic wavefunctionals need not vanish at the boundary of the fundamental modular domain, which itself permits $\theta$ dependence in QCD(3+1). 
Harald W. Griesshammer and Alex C. Kalloniatis (Institute for   Theoretical Physics III, University Erlangen - N\"urnberg, G...