Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Liouville theorem for Beltrami flow   We prove that the Beltrami flow of ideal fluid in $R^3$ of a finite energy is
zero.

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The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex
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The categories of this paper are: adap-org
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph