Singular Gauge Transformation in Non-Commutative U(2) Gauge Theory
  A method developed by Polychronakos to study singular gauge transformations in 1+2 dimensional non-commutative Chern-Simons gauge theory is generalized from U(1) group to U(2) group. The method clarifies the singular behavior of topologically non-trivial gauge transformations in non-commutative gauge theory, which appears when the gauge transformations are viewed from the commutative gauge theory equivalent to the commutative theory. 
Yuko Kobashi, Akio Sugamoto