Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stabilization of Spatial Solitons by Gain Diffusion   It is shown, that diffusion of saturated gain (e.g. diffusion of population
inversion in lasers) causes, and/or enhances a modulational instability of
generated light field. In case of a subcritical system (e.g. a laser with
saturable absorber) the enhancement of the modulational instability stabilizes
spatial solitons. These predictions are made for general nonlinear optical
systems, and are illustrated by numerical simulation of lasers with saturable
absorber.

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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: q-bio
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph
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The categories of this paper are: adap-org
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The categories of this paper are: math
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The categories of this paper are: solv-int
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The categories of this paper are: alg-geom
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The categories of this paper are: eess