Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear 2+1--Dimensional Field Equations from Incomplete Lie Algebra
  Structures   We show that the nonlinear 2+1--dimensional Three--Wave Resonant Interaction
equations, describing several important physical phenomena, can be generated
starting from incomplete Lie algebras in the framework of multidimensional
prolongation structures. We make use of an {\em ansatz} involving the structure
equations of a principal prolongation connection induced by an admissible
B\"acklund map.

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The categories of this paper are: astro-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: cs
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio