Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Electron doping evolution of the magnetic excitations in
  NaFe$_{1-x}$Co$_x$As
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph