Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constraining dark energy from the abundance of weak gravitational lenses   We examine the prospect of using the observed abundance of weak gravitational
lenses to constrain the equation-of-state parameter w of the dark energy. Here
we solve the spherical-collapse model with dark energy, clarifying some
ambiguities found in the literature, and provide fitting formulas for the
overdensity at virialization and the linear-theory overdensity at collapse. We
then compute the variation in the predicted weak-lens abundance with w. We find
that the predicted redshift distribution and number count of weak lenses are
highly degenerate in w and \Omega_0. If we fix \Omega_0 the number count for
w=-2/3 is a factor of 2 smaller than for the \LambdaCDM model. However, if we
allow \Omega_0 to vary with w such that the amplitude of the matter power
spectrum as measured by COBE matches that obtained from the X-ray cluster
abundance, the decrease in the predicted lens abundance is less than 25% for -1
< w < -0.4. We show that a more promising method for constraining the dark
energy---one that is largely unaffected by the \Omega_0 - w degeneracy as well
as uncertainties in observational noise---is to compare the relative abundance
of virialized X-ray lensing clusters with the abundance of non-virialized,
X-ray underluminous, lensing halos. For aperture sizes of 15 arcmin, the
predicted ratio of the non-virialized to virialized lenses is greater than 40%
and varies by 20% between w=-1 and w=-0.6. Overall, if all other weak lensing
parameters are fixed, a survey must cover > 40 degree^2 in order for the number
count to differentiate a \LambdaCDM cosmology from a w=-0.9 model to 3\sigma.
However, given uncertainties in the lensing parameters, the non-virialized lens
fraction provides the most robust constraint on w, requiring 50 degree^2 of sky
coverage in order to differentiate w=-1 from w=-0.6 to 3\sigma.

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The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
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The categories of this paper are: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
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The categories of this paper are: supr-con
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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph