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Advances in High Energy Physics
Volume 2013, Article ID 191047, 14 pages
http://dx.doi.org/10.1155/2013/191047
Research Article

Cosmic Dark Radiation and Neutrinos

1Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark
2IFIC, Universidad de Valencia-CSIC, 46071 Valencia, Spain

Received 28 June 2013; Accepted 18 October 2013

Academic Editor: Elisa Bernardini

Copyright © 2013 Maria Archidiacono et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

New measurements of the cosmic microwave background (CMB) by the Planck mission have greatly increased our knowledge about the universe. Dark radiation, a weakly interacting component of radiation, is one of the important ingredients in our cosmological model which is testable by Planck and other observational probes. At the moment, the possible existence of dark radiation is an unsolved question. For instance, the discrepancy between the value of the Hubble constant, , inferred from the Planck data and local measurements of can to some extent be alleviated by enlarging the minimal CDM model to include additional relativistic degrees of freedom. From a fundamental physics point of view, dark radiation is no less interesting. Indeed, it could well be one of the most accessible windows to physics beyond the standard model, for example, sterile neutrinos. Here, we review the most recent cosmological results including a complete investigation of the dark radiation sector in order to provide an overview of models that are still compatible with new cosmological observations. Furthermore, we update the cosmological constraints on neutrino physics and dark radiation properties focusing on tensions between data sets and degeneracies among parameters that can degrade our information or mimic the existence of extra species.