Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Primordial helium recombination I: feedback, line transfer, and
  continuum opacity
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci