Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unbreakable PT-symmetry of solitons supported by inhomogeneous
  defocusing nonlinearity   We consider bright solitons supported by a symmetric inhomogeneous defocusing
nonlinearity growing rapidly enough toward the periphery of the medium,
combined with an antisymmetric gain-loss profile. Despite the absence of any
symmetric modulation of the linear refractive index, which is usually required
to establish a PT-symmetry in the form of a purely real spectrum of modes, we
show that the PT-symmetry is never broken in the present system, and that the
system always supports stable bright solitons, fundamental and multi-pole ones.
Such phenomenon is connected to non-linearizability of the underlying evolution
equation. The increase of the gain-losses strength results, in lieu of the
PT-symmetry breaking, in merger of pairs of different soliton branches, such as
fundamental and dipole, or tripole and quadrupole ones. The fundamental and
dipole solitons remain stable for all values of the gain-loss coefficient.

25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs