Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Comment on "Spin and Orbital Angular Momentum in Gauge Theories" by X.
  S. Chen et. al. (PRL100, 232002 (2008))
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
19
The categories of this paper are: eess
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int