Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Propagation of instability fronts in modulationally unstable systems   We study evolution of pulses propagating through focusing nonlinear media.
Small disturbance on the smooth initial non-uniform background leads to
formation of the region of strong nonlinear oscillations. We develop here an
asymptotic method for finding the law of motion of the front of this region.
The method is applied to the focusing nonlinear Schroedinger equation for the
particular cases of Talanov and Akhmanov-Sukhorukov-Khokhlov initial
distributions with zero initial phase. The approximate analytical results agree
well with the exact numerical solutions for these two problems.

27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex