Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Conserved spin Hall conductance in two dimensional electron gas in a
  perpendicular magnetic field
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg