A unified description is presented for internal space‐time symmetries of photons and neutrinos. Lorentz‐boosted Dirac equation for a massive spin‐1/2 particle is discussed in the Weyl representation. In the large‐momentum/small‐mass limit, the resulting large component of the Dirac spinor becomes invariant under transformations of the E(2)‐like little group, and the small component is not invariant under the E(2)‐like transformation. The gauge dependence of the photon four‐potential can thus be derived from a direct product of the gauge‐independent large component and the gauge‐dependent small component.
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© 1986 American Association of Physics Teachers.
1986
American Association of Physics Teachers
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