Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Transient Cherenkov radiation from an inhomogeneous string excited by an
  ultrashort laser pulse at superluminal velocity   An optical response of one-dimensional string made of dipoles with a
periodically varying density excited by a spot of light moving along the string
at the superluminal (sub-luminal) velocity is theoretically studied. The
Cherenkov radiation in such system is rather unusual, possessing both transient
and resonant character. We show that under certain conditions, in addition to
the resonant Cherenkov peak another Doppler-like frequency appears in the
radiation spectrum. Both linear (small-signal) and nonlinear regimes as well as
different string topologies are considered.

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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: math
11
The categories of this paper are: hep-lat
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The categories of this paper are: chao-dyn
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The categories of this paper are: eess
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The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: patt-sol