Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Breathers in PT-symmetric optical couplers   We show that the parity-time (PT) symmetric coupled optical waveguides with
gain and loss support localised oscillatory structures similar to the breathers
of the classical $\phi^4$ model. The power carried by the PT-breather
oscillates periodically, switching back and forth between the waveguides, so
that the gain and loss are compensated on the average. The breathers are found
to coexist with solitons and be prevalent in the products of the soliton
collisions. We demonstrate that the evolution of the small-amplitude breather's
envelope is governed by a system of two coupled nonlinear Schr\"odinger
equations, and employ this Hamiltonian system to show that the small-amplitude
PT-breathers are stable.

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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-lat
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: econ