Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measuring the Cosmic Equation of State with Counts of Galaxies   The classical dN/dz test allows the determination of fundamental cosmological
parameters from the evolution of the cosmic volume element. This test is
applied by measuring the redshift distribution of a tracer whose evolution in
number density is known. In the past, ordinary galaxies have been used as such
a tracer; however, in the absence of a complete theory of galaxy formation,
that method is fraught with difficulties. In this paper, we propose studying
instead the evolution of the apparent abundance of dark matter halos as a
function of their circular velocity, observable via the linewidths or rotation
speeds of visible galaxies. Upcoming redshift surveys will allow the linewidth
distribution of galaxies to be determined at both z~1 and the present day. In
the course of studying this test, we have devised a rapid, improved
semi-analytic method for calculating the circular velocity distribution of dark
halos based upon the analytic mass function of Sheth et al. (1999) and the
formation time distribution of Lacey & Cole (1993). We find that if selection
effects are well-controlled and minimal external constraints are applied, the
planned DEEP Redshift Survey should allow the measurement of the cosmic
equation-of-state parameter w to 10% (as little as 3% if Omega_m has been
well-determined from other observations). This type of test has the potential
also to provide a constraint on any evolution of w such as that predicted by
``tracker'' models.

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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
3
The categories of this paper are: physics
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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: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: funct-an