A spin observable for a Dirac particle
We discuss the form of the spin operator in relativistic quantum mechanics. We derive the form of the spin operator in the case when the states with negative energies are admitted. It appears that for a Dirac particle the spin operator reduces to the so called mean-spin operator introduced by Foldy and Wouthuysen. We show that the spin operator transforms under Lorentz group action according to an operator Wigner rotation, analogously as a Bloch vector describing polarization of a particle in momentum representation. - Highlights: Black-Right-Pointing-Pointer We examine the problem of a relativistic spin operator in the case of a Dirac particle. Black-Right-Pointing-Pointer We show that a proper spin operator coincides for positive energies with the operator used in quantum field theory. Black-Right-Pointing-Pointer This operator can be extended for negative energies. Black-Right-Pointing-Pointer We show that this operator is equivalent to the so called mean-spin operator introduced by Foldy and Wouthuysen. Black-Right-Pointing-Pointer The spin operator transforms under Lorentz group action according to the operator Wigner rotation.
- OSTI ID:
- 22157088
- Journal Information:
- Annals of Physics (New York), Journal Name: Annals of Physics (New York) Vol. 330; ISSN 0003-4916; ISSN APNYA6
- Country of Publication:
- United States
- Language:
- English
Similar Records
Supersymmetry, exact Foldy-Wouthuysen transformation, and gravity
Spin in stationary gravitational fields and rotating frames