Noncommutative Sine-Gordon Model
  As I briefly review, the sine-Gordon model may be obtained by dimensional and algebraic reduction from 2+2 dimensional self-dual U(2) Yang-Mills through a 2+1 dimensional integrable U(2) sigma model. I argue that the noncommutative (Moyal) deformation of this procedure should relax the algebraic reduction from U(2)->U(1) to U(2)->U(1)xU(1). The result are novel noncommutative sine-Gordon equations for a pair of scalar fields. The dressing method is outlined for constructing its multi-soliton solutions. Finally, I look at tree-level amplitudes to demonstrate that this model possesses a factorizable and causal S-matrix in spite of its time-space noncommutativity. 
Olaf Lechtenfeld