Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spontaneous localization in self-focusing of ultrashort light pulses   This is a summary directed to PhD students of the research work conducted on
the problem of the production of "light bullets", or multidimensional wave
packets that propagate without distortion in unbounded, homogeneous, nonlinear
media, and on the actual nature of the self-localized light wave packets
spontaneously generated in self-focusing experiments with ultrashort pulses.

10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org