where a, b, c, d are real numbers, and ad - bc =\= 0. It is an automorphism of the Riemann sphere, and the set of all Möbius transformations on the Riemann sphere forms the automorphism group. | where a, b, c, d are real numbers, and ad - bc =\= 0. It is an automorphism of the Riemann sphere, and the set of all Möbius transformations on the Riemann sphere forms the automorphism group. |