Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On extensions of completely simple semigroups by groups   An example of an extension of a completely simple semigroup U by a group H is
given which cannot be embedded into the wreath product of U by H. On the other
hand, every central extension of U by H is shown to be embeddable in the wreath
product of U by H, and any extension of U by H is proved to be embeddable in a
semidirect product of a completely simple semigroup V by H where the maximal
subgroups of V are direct powers of those of U.

24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas