Brewer, S. Adv. Appl. Clifford Algebras (2013) 23: 1. doi:10.1007/s00006-012-0335-7
The paper presents a new cross-ratio of hypercomplex numbers based on projective geometry. We discuss the essential properties of the projective cross-ratio, notably its invariance under Möbius transformations. Applications to the geometry of conic sections and Möbiusinvariant metrics on the upper half-plane are also given.
Cross-ratio Projective linear group Möbius transformation Cycles SL(2,R) Special linear group Clifford algebra dual numbers double numbers