Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On a reduction of nonlinear evolution and wave type equations via
  non-point symmetry method   We study the symmetry reduction of nonlinear evolution and wave type
differential equations by using operators of non-point symmetry. In our
approach we use both operators of classical and conditional symmetry. It
appears that the combination of non-point and conditional symmetry enables us
to construct not only solutions but B\"acklund transformations too for the
equation under study. We show that the method can be applied to nonevolutionary
partial differential equations.

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The categories of this paper are: physics
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The categories of this paper are: cond-mat
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The categories of this paper are: nlin
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-th
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The categories of this paper are: cs
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
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The categories of this paper are: ao-sci
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The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
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The categories of this paper are: adap-org