Two-Dimensional Compact N=(2,2) Lattice Super Yang-Mills Theory with   Exact Supersymmetry
  We construct two-dimensional N=(2,2) lattice super Yang-Mills theory, where the gauge and Higgs fields are all represented by U(N) compact variables, with keeping one exact supercharge along the line of the papers [1,2,3]. Interestingly, requirements of the exact supersymmetry as well as of the compact gauge and Higgs fields lead to the gauge group U(N) rather than SU(N). As a result of the perturbative renormalization argument, the model is shown to flow to the target continuum theory without any fine-tuning. Different from the case of noncompact Higgs fields, the path integral along the flat directions is well-defined in this model. 
Fumihiko Sugino