Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Base de Helicidad y Paridad   We study the theory of the Lorentz group (1/2,0)+(0,1/2) representation in
the helicity basis of the corresponding 4-spinors. As Berestetski, Lifshitz and
Pitaevskii mentioned, the helicity eigenstates are not the parity eigenstates.
Relations with the Gelfand-Tsetlin-Sokolik-type quantum field theory are
discussed. Finally, a new form of the parity operator (which commutes with the
Hamiltonian) is proposed in the Fock space.

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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
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The categories of this paper are: cs
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The categories of this paper are: ao-sci
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The categories of this paper are: astro-ph
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ph