Special relativity is reformulated as a symmetry property of space-time: space-time exchange invariance. The additional hypothesis of spatial homogeneity is then sufficient to derive the Lorentz transformation without reference to the traditional form of the Principle of Special Relativity. The kinematical version of the latter is shown to be a consequence of the Lorentz transformation. As a dynamical application, the laws of electrodynamics and magnetodynamics are derived from those of electrostatics and magnetostatics respectively. The four-vector nature of the electromagnetic potential plays a crucial role in the last two derivations.

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7.
That is, all laws applying to physical systems where the curvature of space-time may be neglected, so that general relativistic effects are unimportant, and may be neglected.
8.
See, for example, A. Einstein, Relativity, the Special and General Theory (Routledge, London, 1994).
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The positive sign for γ is taken in solving Eq. (2.12). Evidently γ→1 as β→0.
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See, for example, I. J. R. Aitchison and A. J. G. Hey Gauge Theories in Particle Physics (Hilger, London, 1982), Appendix C.
18.
See, for example, S. Weinberg, Gravitation and Cosmology (Wiley, New York, 1972), p. 36.
19.
See, for example, Eq. (2.36) of Ref. 6.
20.
For a recent discussion of the physical meaning of the three-vector magnetic potential see
M. D.
Semon
and
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21.
It is often stated in the literature that the potentials φ, A⃗ are introduced only for “reasons of mathematical simplicity” and “have no physical meaning.” See, for example: F. Röhrlich, Classical Charged Particles (Addison-Wesley, Reading, MA, 1990), pp. 65–66. Actually, the underlying space-time symmetries of Maxwell’s equations can only be expressed by using the four-vector character of Aμ. Also the minimal electromagnetic interaction in the covariant formulation of relativistic quantum mechanics, which is the dynamical basis of quantum electrodynamics, requires the introduction of a quantum field for the photon that has the same four-vector nature as the electromagnetic potential.
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