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Single-Particle Electrodynamics - Assassination Science

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A.8.25<br />

Nonrelativistic and pre-relativistic limits<br />

There are two distinct low-velocity limits of special relativity that are recognised<br />

throughout this thesis, and they are not equivalent.<br />

We call the prerelativistic limit of the motion of a classical particle that<br />

limit obtained by only retaining terms up to first order in the three-velocity<br />

of the particle or any of its lab-time derivatives, i.e., any of v, ˙v, ¨v, . . . ,<br />

but discarding any terms jointly proportional to more than one of these<br />

quantities. Note carefully that the acceleration, jerk, etc. (i.e., ˙v, ¨v, etc.)<br />

may not be replaced in any way (such as by using equations of motion) before<br />

taking the prerelativistic limit.<br />

The prerelativistic limit only achieves its full power in the CACS of the<br />

particle. Under these conditions, the prerelativistic equations of motion, if<br />

obtainable by first principles, may be used to uniquely and rigorously obtain<br />

the fully covariant equations of motion for the particle.<br />

We call the nonrelativistic limit that limit obtained by replacing the acceleration,<br />

jerk, etc. (i.e., ˙v, ¨v, etc.) by expressions possibly involving v<br />

(but no time-derivatives of v) wherever they appear in the fully relativistic<br />

equations, by using the equations of motion, together with any constitutive<br />

equations available, and then retaining only terms up to first order in v. It<br />

should be noted that this is not equivalent to the prerelativistic limit defined<br />

above. (Most famously, the Thomas precession of the prerelativistic limit is<br />

converted to a numerical “Thomas factor” in the nonrelativistic limit.) The<br />

nonrelativistic limit is less powerful than the prerelativistic limit.<br />

See Section 2.6.12 for a more detailed discussion of these issues.<br />

A.8.26<br />

C, P, T<br />

In any Lorentz frame with coördinates (t, x), the operation<br />

x → −x<br />

(A.64)<br />

357

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