Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Retarded/Advanced Correlation Functions and Soft Photon Production in
  the Hard Loop Approximation
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin