Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravitational Lensing of Pregalactic 21 cm Radiation   Low-frequency radio observations of neutral hydrogen during and before the
epoch of cosmic reionization will provide hundreds of quasi-independent source
planes, each of precisely known redshift, if a resolution of ~ 1 arcminutes or
better can be attained. These planes can be used to reconstruct the projected
mass distribution of foreground material. A wide-area survey of 21 cm lensing
would provide very sensitive constraints on cosmological parameters, in
particular on dark energy. These are up to 20 times tighter than the
constraints obtainable from comparably sized, very deep surveys of galaxy
lensing although the best constraints come from combining data of the two
types. Any radio telescope capable of mapping the 21cm brightness temperature
with good frequency resolution (~ 0.05 MHz) over a band of width ~> 10 MHz
should be able to make mass maps of high quality. If the reionization epoch is
at z ~ 9 very large amounts of cosmological information will be accessible. The
planned Square Kilometer Array (SKA) should be capable of mapping the mass with
a resolution of a few arcminutes depending on the reionization history of the
universe and how successfully foreground sources can be subtracted. The
Low-Frequency Array (LOFAR) will be able to measure an accurate matter power
spectrum if the same conditions are met.

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The categories of this paper are: cmp-lg
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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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: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th