Three Dimensional N=2 Gauge Theories and Degenerations of Calabi-Yau   Four-Folds
  Three dimensional N=2 gauge theories with arbitrary gauge group and fundamental flavors are engineered from degenerations of Calabi-Yau four-folds. We show how Coulomb and Higgs branches emerge in the geometric picture. The analysis of instanton generated superpotentials unravels interesting aspects of the five-brane effective action in M theory. 
Duiliu-Emanuel Diaconescu, Sergei Gukov