Lost equivalence of nonlinear sigma and $CP^{1}$ models on   noncommutative space
  We show that the equivalence of nonlinear sigma and $CP^{1}$ models which is valid on the commutative space is broken on the noncommutative space. This conclusion is arrived at through investigation of new BPS solitons that do not exist in the commutative limit. 
H. Otsu, T. Sato, H. Ikemori, S. Kitakado