Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Nature of Low-Density Star Formation   How do stars manage to form within low-density, HI-dominated gas? Such
environments provide a laboratory for studying star formation with physical
conditions distinct from starbursts and the metal-rich disks of spiral galaxies
where most effort has been invested. Here we outline fundamental open questions
about the nature of star formation at low-density. We describe the wide-field,
high-resolution UV-optical-IR-radio observations of stars, star clusters and
gas clouds in nearby galaxies needed in the 2020's to provide definitive
answers, essential for development of a complete theory of star formation.

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The categories of this paper are: quant-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
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The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: adap-org
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The categories of this paper are: math
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ph