Ward identity in noncommutative QED
  Although noncommutative QED presents a nonabelian structure, it does not present structure constants. In view of this we investigate how Ward identity is satisfied in pair annihilation process and $\gamma \gamma \to \gamma \gamma$ scattering in noncommutative QED. 
T. Mariz, C. A. de S. Pires, and R. F. Ribeiro