Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The $R_\infty$ property for free groups, free nilpotent groups and free
  solvable groups   Let $F$ be either a free nilpotent group of a given class and of finite rank
or a free solvable group of a certain derived length and of finite rank. We
show precisely which ones have the $R_{\infty}$ property. Finally, we also show
that the free group of infinite rank does not have the $R_{\infty}$ property.

20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin