Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Some properties of the Schur multiplier and stem covers of Leibniz
  crossed modules   In this article we investigate the interplay between stem covers, the Schur
multiplier of Leibniz crossed modules and the non-abelian exterior product of
Leibniz algebras. In concrete, we obtain a six-term exact sequence associated
to a central extension of Leibniz crossed modules, which is useful to
characterize stem covers. We show the existence of stem covers and determine
the structure of all stem covers of Leibniz crossed modules. Also, we give the
connection between the stem cover of a Lie crossed module in the categories of
Lie and Leibniz crossed modules respectively.

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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: econ
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
3
The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
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The categories of this paper are: chem-ph