Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Semi-discrete composite solitons in arrays of quadratically nonlinear
  waveguides   We demonstrate that an array of discrete waveguides on a slab substrate, both
featuring the $\chi^{2}$ nonlinearity, supports stable solitons composed of
discrete and continuous components. Two classes of fundamental composite
solitons are identified: ones consisting of a discrete fundamental-frequency
(FF) component in the waveguide array, coupled to a continuous second-harmonic
(SH) component in the slab waveguide, and solitons with an inverted FF/SH
structure. Twisted bound states of the fundamental solitons are found too. In
contrast with usual systems, the \emph{intersite-centered} fundamental solitons
and bound states with the twisted continuous components are stable, in an
almost entire domain of their existence.

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The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: eess
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
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The categories of this paper are: q-bio
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The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
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The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an
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The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph