The Pauli spin matrices , and are central to the representation of spin-particles in quantum mechanics. Their matrix products are given by =where I is the 2⨯2 identity matrix and , the Levi-Civita permutation symbol. These products lead to the commutation and anticommutation relations = and , respectively. The Pauli matrices transform as a 3-dimensional pseuodovector (axial vector) related to the angular-momentum operators for spin- by . These, in turn, obey the canonical commutation relations .