Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Observation of Three-dimensional Photonic Dirac points and
  Spin-polarized Surface Arcs
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th