Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: RX J0720.4--3125 as a Possible Example of the Magnetic Field Decay of
  Neutron Stars
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
18
The categories of this paper are: econ
19
The categories of this paper are: eess