Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: The effects of opacity on gravitational stability in protoplanetary
  discs
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
2
The categories of this paper are: math