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 here if you are interested in other research of mine. 

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


The number is...


Max Tegmark, Matias Zaldarriaga Andrew Hamilton,


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!

Reference info:

astro-ph/0008167, Phys. Rev. D, 63, 043007-043020
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This page was last modified August 13, 2000.