is a homomorphism of classical matrix Lie groups. The lefthand group consists of 2 × 2 complex matrices with determinant 1. The righthand group consists of 4× 4 real matrices with determinant 1 which preserve some fixed real quadratic form Q of signature (1, 3). This map is alternately called the spinor map and variations. The image of this map is the identity component of SO1,3(R), denoted SO1...