Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Algebraic theory of abelian groups   This document aims to give a self-contained account of the parts of abelian
group theory that are most relevant for algebraic topology. It is almost purely
expository, although there are some slightly unusual features in the treatment
of tensor products, torsion products and $\text{Ext}$ groups.

29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin