Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On a `time' reparametrization in relativistic electrodynamics with
  travelling waves   We briefly report on our method [Fiore JPA 2017] of simplifying the equations
of motion of charged particles in an electromagnetic field that is the sum of a
plane travelling wave and a static part; it is based on changes of the
dependent variables and the independent one (light-like coordinate instead of
time t). We sketch its application to a few cases of extreme laser-induced
accelerations, both in vacuum and in plane problems at the vacuum-plasma
interface, where we are able to reduce the system of the (Lorentz-Maxwell and
continuity) partial differential equations into a family of decoupled systems
of Hamilton equations in 1 dimension. Since Fourier analysis plays no role, the
method can be applied to all kind of travelling waves, ranging from almost
monochromatic to socalled "impulse".

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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: eess
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The categories of this paper are: q-bio
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The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph