Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Twisted conjugacy classes of the unit element   We study twisted conjugacy classes of the unit element in different groups.
Fel'shtyn and Troitsky showed that the twisted conjugacy class of the unit
element of an abelian group is a subgroup for every automorphism. The structure
is investigated of a group whose twisted conjugacy class of the unit element is
a subgroup for every automorphism (inner automorphism).

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The categories of this paper are: atom-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: econ
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The categories of this paper are: hep-th
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The categories of this paper are: eess
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The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: cs
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The categories of this paper are: hep-ph
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The categories of this paper are: acc-phys