Journal
PHYSICS LETTERS B
Volume 725, Issue 1-3, Pages 134-138Publisher
ELSEVIER
DOI: 10.1016/j.physletb.2013.07.001
Keywords
-
Funding
- JSPS [24740135]
- Inoue Foundation for Science
- World Premier International Center Initiative (WPI Program), MEXT, Japan
- [23540283]
- [24111702]
- [21111006]
- [23104008]
- [22244030]
- [21244033]
- Grants-in-Aid for Scientific Research [21111006, 24740135, 22244030, 24111702] Funding Source: KAKEN
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We consider a simple class of models where dark radiation has self-interactions and therefore does not free stream. Such dark radiation has no anisotropic stress (or viscosity), leaving a distinct signature on the CMB angular power spectrum. Specifically we study a possibility that hidden gauge bosons and/or chiral fermions account for the excess of the effective number of neutrino species. They have gauge interactions and remain light due to the unbroken hidden gauge symmetry, leading to Delta N-eff similar or equal to 0.29 in some case. (C) 2013 Elsevier B.V. All rights reserved.
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