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Max Tegmark's library: concordance

**Movie 1***:
Why the dark matter density is so easy to measure.
*
Please click here to get a gzipped postscript file with
the paper, or here for a pdf version.
I've made a whole set of movies that accompany this paper, like the one above
but one for each cosmological parameter. To view them, click
here.
You're welcome to copy them and do whatever you want with them
- I put them here because some people asked
if they could use them for teaching.

Click if
you are interested in other research of mine.

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Towards a refined cosmic concordance model:
joint 11-parameter constraints from CMB and large-scale structure

or
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The number is...

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Authors:

Max Tegmark,
Matias Zaldarriaga
Andrew Hamilton,
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Abstract:

We present a method for calculating large numbers of power spectra C_l and P(k) that
accelerates CMBfast by a factor around 10^3 without appreciable loss of accuracy, then apply
it to constrain 11 cosmological parameters from current Cosmic Microwave Background (CMB) and
Large Scale Structure (LSS) data. While the CMB alone still suffers from several
degeneracies, allowing, e.g., closed models with strong tilt and tensor contributions, the
shape of the real space power spectrum of galaxies from the IRAS Point Source Catalogue
Redshift (PSCz) survey breaks these degeneracies and helps place strong constraints on most
parameters. At 95% confidence, the combined CMB and LSS data imply a baryon density 0.020 <
omega_b < 0.037, dark matter density 0.10 < omega_d < 0.32 with a neutrino fraction f_nu <
38%, vacuum density Omega_Lambda < 0.76, curvature -0.19 < Omega_k < 0.10, scalar tilt 0.86 <
n_s < 1.16 and reionization optical depth tau < 0.44. These joint constraints are quite
robust, changing little when we impose priors on the Hubble parameter, tilt, flatness, gravity
waves or reionization. Adding nucleosynthesis and neutrino priors on the other hand tightens
parameters considerably, requiring Omega_Lambda > 0.49 and a red-tilt.
The analysis allows a number of consistency tests to be made, all of which pass. At the 95%
level, the flat scalar ``concordance model'' with Omega_Lambda=0.62, omega_d=0.13,
omega_b=0.02, f_nu~0, n_s=0.9, tau=0.1, h=0.63 is consistent with external constraints.
The inferred PSCz bias b~1.2 agrees with the value estimated independently from
redshift space distortions. The inferred cosmological constant value agrees with the one
independently derived from SN 1a studies. Cosmology seems to be on the right track!
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Reference info:

astro-ph/0008167, *Phys. Rev. D*, **63**, 043007-043020

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This page was last modified August 13, 2000.
max@physics.upenn.edu