New Constraints on the Early Expansion History

Abstract

Cosmic microwave background measurements have pushed to higher resolution, lower noise, and more sky coverage. These data enable a unique test of the early universe's expansion rate and constituents such as effective number of relativistic degrees of freedom and dark energy. Using the most recent data from Planck and WMAP9, we constrain the expansion history in a model independent manner from today back to redshift z=10^5. The Hubble parameter is mapped to a few percent precision, limiting early dark energy and extra relativistic degrees of freedom within a model independent approach to 2-16% and 0.71 equivalent neutrino species respectively (95% CL). Within dark radiation, barotropic aether, and Doran-Robbers models, the early dark energy constraints are 3.3%, 1.9%, 1.2% respectively.

5 pages, 3 figures; v2 matches PRL version

References in corpus (6)

• ACTPol: A polarization-sensitive receiver for the Atacama Cosmology Telescope
• SPTpol: an instrument for CMB polarization measurements with the South Pole Telescope
• Limits on Dark Radiation, Early Dark Energy, and Relativistic Degrees of Freedom
• The POLARBEAR Experiment
• Model Independent Early Expansion History and Dark Energy
• A Brief History of Curvature

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• New tracker models of dark energy
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• What is the Standard Cosmological Model?
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