Lorentz invariance of scalar field action on $\kappa$-Minkowski   space-time
  We construct field theory on noncommutative $\kappa$-Minkowski space-time. Having the Lorentz action on the noncommutative space-time coordinates we show that the field lagrangian is invariant. We show that noncommutativity requires replacing the Leibnitz rule with the coproduct one. 
Sebastian Nowak