Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Approximate Analytical Description of the Underdense Short Plasma Lens   The perturbative approach for describing the underdense
plasma--ultrarelativistic electron bunch system is developed, using the ratio
$\frac{n_0}{n_b}$ as a small parameter ($n_b$--bunch,$n_0$--plasma electron
densities). Focusing of the electron bunch emerged in the first approximation
of the perturbative procedure as a result of the plasma electrons
redistribution. Focusing gradient and strength for ultrarelativistic, flat,
uniform and short bunch are obtained and compared with the previous results.

11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph