Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravitational waves in preheating   We study the evolution of gravitational waves through the preheating era that
follows inflation. The oscillating inflaton drives parametric resonant growth
of scalar field fluctuations, and although super-Hubble tensor modes are not
strongly amplified, they do carry an imprint of preheating. This is clearly
seen in the Weyl tensor, which provides a covariant description of
gravitational waves.

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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: q-bio
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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: math
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: supr-con