Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Periodic Geodesics and Geometry of Compact Lorentzian Manifolds with a
  Killing Vector Field
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex