Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear wave propagation through cold plasma   Electromagnetic wave propagation through cold collision free plasma is
studied using the nonlinear perturbation method. It is found that the equations
can be reduced to the modified Kortweg-de Vries equation.

9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th