Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electron laser acceleration in vacuum by a quadratically chirped laser
  pulse   Single MeV electrons subjected in vacuum to single high-intensity
quadratically-chirped laser pulses are shown to gain multi-GeV energies. The
laser pulses are modeled by finite-duration trapezoidal and $\cos^2$
pulse-shapes and the equations of motion are solved numerically. It is found
that, typically, the maximum energy gain from interaction with a quadratic
chirp is about half of what would be gained from a linear chirp.

9
The categories of this paper are: nlin
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The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
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The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex