Do observations prove that cosmological neutrinos are thermally distributed?
- Dipartimento di Scienze Fisiche, Universita di Napoli Federico II, and INFN, Sezione di Napoli, Complesso Universitario di Monte Sant'Angelo, Via Cintia, I-80126 Naples (Italy)
It is usually assumed that relic neutrinos possess a Fermi-Dirac distribution, acquired during thermal equilibrium in the Early Universe. However, various mechanisms could introduce strong distortions in this distribution. We perform a Bayesian likelihood analysis including the first moments of the three active neutrino distributions as free parameters, and show that current cosmological observations of light element abundances, Cosmic Microwave Background anisotropies and Large Scale Structures are compatible with very large deviations from the standard picture. We also calculate the bounds on nonthermal distortions which can be expected from future observations, and stress that Cosmic Microwave Background and Large Scale Structures data alone will not be sensitive enough in order to distinguish between nonthermal distortions in the neutrino sector and extra relativistic degrees of freedom. This degeneracy could be removed by additional constraints from primordial nucleosynthesis or independent neutrino mass scale measurements.
- OSTI ID:
- 20709516
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 71, Issue 12; Other Information: DOI: 10.1103/PhysRevD.71.123501; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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