2013/04/30 by Alireza Hojjati, Eric V. Linder, Johan Samsing
Physics and Astronomy · #Astronomy #Black Holes and Theoretical Physics #Cosmology #Cosmology and Gravitation Theories #Dark energy #Galaxies: Formation, Evolution, Phenomena #Metric expansion of space #Physics #Theoretical physics #astro-ph.CO
paper · pdf · doi:10.1103/physrevlett.111.041301
published as Phys. Rev. Lett. 111, 041301 (2013) · 5 pages, 3 figures; v2 matches PRL version
openalex publication_date 2013/07/24 · arxiv created 2013/08/02 · arxiv updated 2013/08/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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% C.L.). Within dark radiation, barotropic ether, and Doran-Robbers models, the early dark energy constraints are 3.3%, 1.9%, and 1.2%, respectively.