Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Direct calculation of length contraction and clock retardation   For simple electromagnetic models of a rod and a clock, a change of the shape
of the rod and of the rate of the clock when they are set in uniform motion is
calculated exactly, employing the correct equation of motion of a charged
particle in the electromagnetic field and the universal boostability
assumption. Thus it is demonstrated that, for the simple system considered,
length contraction and clock retardation can be interpreted as dynamical
cause-and-effect phenomena, and not as kinematical effects as is usually
construed in conventional presentations of Special Relativity. It is argued
that the perspectival relativistic change of an object (corresponding to
observations from two inertial frames), while certainly an acausal effect, has
a dynamical content in the sense that it is {\it tantamount to} an actual
dynamical change of the object in one frame.

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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ
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The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: math
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: math-ph