A Lie-Algebra model for a noncommutative space time geometry
  We propose a Lie-algebra model for noncommutative coordinate and momentum space . Based on a rigid commutation relation for the commutators of space time operators the model is quite constrained if one tries to keep Lorentz invariance as much as possible. We discuss the question of invariants esp. the definition of a mass. 
Bernd-Dietrich Doerfel