Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Towards an open set of regular cosmological models   The possibility of obtaining an open set of regular cosmological models is
discussed. Cylindrical stiff perfect fluid cosmologies are studied in detail.
The condition for geodesic completeness is easy to check. A large family of
non-singular models is found therein.

17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con