Null-plane Quantum Universal $R$-matrix
  A non-linear map is applied onto the (non-standard) null-plane deformation of (3+1) Poincar\'e algebra giving rise to a simpler form of this triangular quantization. A universal $R$-matrix for the null plane quantum algebra is then obtained from a universal $T$-matrix corresponding to a Hopf subalgebra. Finally, the associated Poincar\'e Poisson--Lie group is quantized by using the FRT approach. 
A. Ballesteros, F.J. Herranz and C.M. Pere\~na