Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: About the wording of Fermat`s principle for light propagation in media
  with negative refraction index   In this work is elaborated the wording of Fermat`s principle for
electromagnetic waves spreading in materials with negative index of refractions
(MNR). The recent experiments with such material has confirmed their main
characteristics, predicted earlier. It is shown that for MNR not applicable
wording of Fermat`s principle through minimum (or extremum) of time of
spreading the wave between two points. The correct wording for this case is a
wording through extremum of total optical length for way between two points
moreover optical length at passing of wave through MNR is taken negative. In
paper are considered some properties of original flat lenses, executed from
MNR.

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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
2
The categories of this paper are: math
1
The categories of this paper are: cs
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The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg