Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exactly solvable model for nonlinear pulse propagation in optical fibers   The nonlinear Schr\"odinger (NLS) equation is a fundamental model for the
nonlinear propagation of light pulses in optical fibers. We consider an
integrable generalization of the NLS equation which was first derived by means
of bi-Hamiltonian methods in [A. S. Fokas, {\it Phys. D} {\bf 87} (1995),
145--150]. The purpose of the present paper is threefold: (a) We show how this
generalized NLS equation arises as a model for nonlinear pulse propagation in
monomode optical fibers when certain higher-order nonlinear effects are taken
into account; (b) We show that the equation is equivalent, up to a simple
change of variables, to the first negative member of the integrable hierarchy
associated with the derivative nonlinear Schr\"odinger equation; (c) We analyze
traveling-wave solutions.

29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph