Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear separate spin evolution in degenerate electron-positron-ion
  plasmas   The non-linear evolution of spin-electron acoustic, positron-acoustic, and
spin-electron-positron acoustic waves is considered. It is demonstrated that
weakly nonlinear dynamics of each wave leads to the soliton formation.
Altogether, we report on existence of three different solitons. The
spin-electron acoustic soliton known for electron-ion plasmas is described for
electron-positron-ion plasmas for the first time. The existence of the
spin-electron-positron acoustic soliton is reported for the first time. The
positron-acoustic soliton and the spin-electron-positron acoustic soliton arise
as the areas of a positive electric potential. The spin-electron acoustic
soliton behaves as the area of a negative electric potential at the relatively
small positron imbalance $n_{0p}/n_{0e}=0.1$ and as the area of a positive
electric potential at the relatively large positron imbalance
$n_{0p}/n_{0e}=0.5$.

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The categories of this paper are: cs
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
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The categories of this paper are: eess
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The categories of this paper are: hep-ph
18
The categories of this paper are: econ
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The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin