Position Operators for Systems Exhibiting the Special Relativistic Relation Between Momentum and Velocity

  • R. F. O’Connell
  • E. P. Wigner
Part of the The Scientific Papers book series (WIGNER, volume A / 3)


We have previously shown [1] that if the position operator is defined as in ref. [21, the movement of the mean position of a free particle obeys the classical equation υ = P/P 0 where P0 is the total energy, including the rest mass. Conversely, it will be demonstrated here that the validity of this equation implies that, for spinless particles, the position operator is that of ref. [2]. For spin 1/2 particles, however, another choice is also possible (eq. (7)). The corresponding value of the orbital angular momentum in the latter case is unity, whereas for the state of ref. [2] it is zero.


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  1. [1]
    R.F. O’Connell and E.P. Wigner, Phys. Lett. 61A (1977) 353.CrossRefGoogle Scholar
  2. [2]
    T.D. Newton and E.P. Wigner, Rev. Mod. Phys. 21 (1949) 400.ADSCrossRefzbMATHGoogle Scholar
  3. [3]
    G.N. Fleming, Phys. Rev. 139 (1975) B963.CrossRefGoogle Scholar
  4. [4]
    G.C. Hegerfeldt, Phys. Rev. D10 (1974) 3320.ADSGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • R. F. O’Connell
  • E. P. Wigner
    • 1
  1. 1.Department of Physics, Joseph Henry LaboratoryPrinceton UniversityPrincetonUSA

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