Advances in Applied Clifford Algebras

, Volume 21, Issue 4, pp 721–756

On Conformal Infinity and Compactifications of the Minkowski Space


DOI: 10.1007/s00006-011-0285-5

Cite this article as:
Jadczyk, A. Adv. Appl. Clifford Algebras (2011) 21: 721. doi:10.1007/s00006-011-0285-5


Using the standard Cayley transform and elementary tools it is reiterated that the conformal compactification of the Minkowski space involves not only the “cone at infinity” but also the 2-sphere that is at the base of this cone. We represent this 2-sphere by two additionally marked points on the Penrose diagram for the compactified Minkowski space. Lacks and omissions in the existing literature are described, Penrose diagrams are derived for both, simple compactification and its double covering space, which is discussed in some detail using both the U(2) approach and the exterior and Clifford algebra methods. Using the Hodge \({\star}\) operator twistors (i.e. vectors of the pseudo-Hermitian space H2,2) are realized as spinors (i.e., vectors of a faithful irreducible representation of the even Clifford algebra) for the conformal group SO(4, 2)/Z2. Killing vector fields corresponding to the left action of U(2) on itself are explicitly calculated. Isotropic cones and corresponding projective quadrics in Hp,q are also discussed. Applications to flat conformal structures, including the normal Cartan connection and conformal development has been discussed in some detail.


Compactification Minkowski space-time Conformal spinors Twistors SU(2) SU(2,2) U(2) SO(4,2) Null geodesics Penrose diagram Conformal infinity Conformal group Conformal inversion Hodge star bivectors Grassmann manifold Clifford algebra Cℓ(4, 2) 

Copyright information

© Springer Basel AG 2011

Authors and Affiliations

  1. 1.Center CAIROS, Institut de Mathématiques de ToulouseUniversité Paul SabatierToulouse Cedex 9France

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