Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The rationality of Sol manifolds   Let $\Gamma$ be the fundamental group of a manifold modeled on three
dimensional Sol geometry. We prove that $\Gamma$ has a finite index subgroup
$G$ which has a rational growth series with respect to a natural generating
set. We do this by enumerating $G$ by a regular language. However, in contrast
to most earlier proofs of this sort our regular language is not a language of
words in the generating set, but rather reflects a different geometric
structure in $G$.

16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol