Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Gapped energy spectra around the Dirac node at the surface of a 3D
  topological insulator in the presence of the time-reversal symmetry
2
The categories of this paper are: math
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol