Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Linear extensions and nilpotence for Maltsev theories   Relationship is clarified between the notions of linear extension of
algebraic theories, and central extension, in the sense of commutator calculus,
of their models. Varieties of algebras turn out to be nilpotent Maltsev
precisely when their theories may be obtained as results of iterated linear
extensions by bifunctors from the so called abelian theories. The latter
theories are described; they are slightly more general than theories of modules
over a ring.

10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: astro-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: math-ph
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The categories of this paper are: nlin
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The categories of this paper are: nucl-th
1
The categories of this paper are: cs
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The categories of this paper are: supr-con
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The categories of this paper are: cond-mat
3
The categories of this paper are: physics