Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamic conductivity of semiconducting manganites approaching the
  metal-insulator transition   We report the frequency-dependent conductivity of the manganite system
La1-xSrxMnO3 (x <= 0.2) when approaching the metal-insulator transition from
the insulating side. Results from low-frequency dielectric measurements are
combined with spectra in the infrared region. For low doping levels the
behavior is dominated by hopping transport of localized charge carriers at low
frequencies and by phononic and electronic excitations in the infrared region.
For the higher Sr contents the approach of the metallic state is accompanied by
the successive suppression of the hopping contribution at low frequencies and
by the development of polaronic excitations in the infrared region, which
finally become superimposed by a strong Drude contribution in the fully
metallic state.

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The categories of this paper are: physics
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
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The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph