Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Almost para-Hermitian and almost paracontact metric structures induced
  by natural Riemann extensions
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci