2003/02/28 by Patrick Crotty, Julien Lesgourgues, S. Pastor +1 · 2 citations
Physics and Astronomy · #Anisotropy #Astrophysics #CMB cold spot #Cosmic background radiation #Cosmic microwave background #Cosmology #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Degrees of freedom (physics and chemistry) #Neutrino #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum mechanics #Relativistic particle #Universe #astro-ph #hep-ph
paper · pdf · doi:10.1103/physrevd.67.123005
published as Phys.Rev.D67:123005,2003 · 5 pages, 2 figures (1 new figure). Version to be published
arxiv created 2003/05/12 · openalex publication_date 2003/06/24 · openalex created_date 2016/06/24 · arxiv updated 2016/08/30 · openalex updated_date 2026/08/05
We show that the first year results of the Wilkinson Microwave Anisotropy Probe (WMAP) constrain very efficiently the energy density in relativistic particles in the Universe. We derive new bounds on additional relativistic degrees of freedom expressed in terms of an excess in the effective number of light neutrinos \ensuremathΔNeff. Within the flat \ensuremathΛCDM scenario, the allowed range is \ensuremathΔNeff<6 (95% confidence level) using WMAP data only, or \ensuremath-2.6<\ensuremathΔNeff<4 with the prior H0=72\ifmmode±\else\textpm\fi8kms^\ensuremath-1Mpc^\ensuremath-1. When other cosmic microwave background and large scale structure experiments are taken into account, the window shrinks to \ensuremath-1.6<\ensuremathΔNeff<3.8. These results are in perfect agreement with the bounds from primordial nucleosynthesis. Nonminimal cosmological models with extra relativistic degrees of freedom are now severely restricted.