Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NP Stokes fields for radio astronomy   The spin weighted spherical harmonic (SWSH) description of angular functions
typically is associated with the Newman-Penrose (NP) null tetrad formalism.
Recently the SWSH description, but not the NP formalism, has been used in the
study of the polarization anisotropy of the cosmic microwave background. Here
we relate this application of SWSHs to a description of electromagnetic
radiation and polarization in the NP formalism. In particular we introduce NP
Stokes fields that are the NP equivalent of the Stokes parameters. In addition
to giving a more coherent foundation for the recent cosmological SWSH
application, the NP formalism aids in the computation of the Lorentz
transformation properties of polarization.

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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: atom-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: nlin
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
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The categories of this paper are: solv-int
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The categories of this paper are: eess
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The categories of this paper are: q-bio
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The categories of this paper are: funct-an
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The categories of this paper are: ao-sci
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The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph