A Derivation of Vector and Momentum Matrices
  Given standard angular momentum and boost matrices, the commutation rules for vector and momentum matrices are solved. The resulting matrix components are displayed as detailed functions of spin with factors such as the square root of (2A+1). For comparison and as an alternative, Lyubarskii's formulas in terms of Clebsch-Gordan coefficients are recalled from the literature and displayed. A set of these momentum matrices combined with the corresponding set of six angular momentum and boost matrices form the generators of a nonunitary finite dimensional representation of the Poincare group of translations, rotations and boosts. A problem set is included.   PACS: 11.30.Cp Lorentz and Poincare invariance 
Richard Shurtleff