The Heisenberg-Lorentz quantum group
  In this article we present a new C*-algebraic deformation of the Lorentz group. It is obtained by means of the Rieffel deformation applied to SL(2,C). We give a detailed description of the resulting quantum group in terms of generators - the quantum counterparts of the matrix coefficients of the fundamental representation of SL(2,C). In order to construct the most involved of four generators, we first define it on the quantum Borel subgroup, then on the quantum complement of the Borel subgroup and finally we perform the gluing procedure. In order to classify representations of the C*-algebra of the Heisenberg-Lorentz quantum group and to analyze the action of the comultiplication on the generators we employ the duality in the theory of locally compact quantum groups. 
P. Kasprzak