Comment on `Dirac theory in spacetime algebra'

  title={Comment on `Dirac theory in spacetime algebra'},
  author={William E. Baylis},
  journal={Journal of Physics A},
  • W. E. Baylis
  • Published 11 February 2002
  • Physics
  • Journal of Physics A
In contrast to formulations of the Dirac theory by Hestenes and by the present author, the formulation recently presented by Joyce (Joyce W P 2001 J. Phys. A: Math. Gen. 34 1991-2005) is equivalent to the usual Dirac equation only in the case of vanishing mass. For nonzero mass, solutions to Joyce's equation can be solutions either of the Dirac equation in the Hestenes form or of the same equation with the sign of the mass reversed, and in general they are mixtures of the two possibilities… 

COMMENT: Reply to Comment on `Dirac theory in spacetime algebra'

The Dirac theory formulated by Joyce (Joyce W P 2001 J. Phys. A: Math. Gen. 34 1991-2005) is equivalent to two copies of the usual Dirac formulation. The comment of Baylis (Baylis W E 2002 J. Phys.

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