Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Lepton pair production by a high energy photon in a strong
  electromagnetic field
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph