Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Magnetism-induced massive Dirac spectra and topological defects in the
  surface state of Cr-doped Bi$_2$Se$_3$-bilayer topological insulators
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex