Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Collective Excitations Spectrum in Density Modulated One-Dimensional
  Electron Gas in a Magnetic Field
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
16
The categories of this paper are: stat
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs