Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A survey for large image-separation lensed quasars   The statistics of gravitationally lensed quasars with multiple images in the
0.1''-7'' range have been measured in various surveys. Little is known,
however, about lensed-quasar statistics at larger image separations, which
probe masses on the scale of galaxy clusters. We extend the results of the HST
Snapshot Survey for Lensed Quasars to the 7''-50'' range for a sub-sample of 76
quasars that is free of known selection effects. Using a combination of
multicolor photometry and spectroscopy, we show that none of the point sources
in the entire field of view of the HST observations of these quasars are lensed
images. Large-separation quasar lensing is therefore not common. We carry out a
detailed calculation of the expected statistics of large-separation lensing for
this quasar sample, incorporating realistic input for the mass profiles and
mass function of galaxy clusters. We find that the observational null results
are consistent with the expected effect of galaxy clusters, even if these have
existed in their present form and number since z of about 2. The rarity of
large-separation lensed quasars can rule out some extreme scenarios, e.g. that
the mass-function of clusters has been severely underestimated, or that large
mass concentrations that are not associated with galaxies (i.e. ``failed''
clusters) are common. The rareness of wide lensing also sets limits on the
cosmological constant that are independent of limits derived from galaxy
lensing. The lensing statistics of larger quasar samples can probe the
structure, number, and evolution of clusters, as well as the geometry of space.

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The categories of this paper are: econ
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The categories of this paper are: chao-dyn
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The categories of this paper are: ao-sci
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The categories of this paper are: quant-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: plasm-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: math
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The categories of this paper are: chem-ph
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The categories of this paper are: cs
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The categories of this paper are: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: cmp-lg