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A precision calculation of the effective number of cosmological neutrinos
Open accessAbstract
The neutrino energy density of the Universe can be conveniently parametrized in terms of the so-called effective number of neutrinos, Nνeff. This parameter enters in several cosmological observables. In particular it is an important input in those numerical codes, like CMBFAST, which are used to study the Cosmic Microwave Background anisotropy spectrum. By studying the neutrino decoupling with Boltzmann equations, one can show that this quantity differs from the number of massless neutrino species for an additional contribution due to a partial heating of neutrinos during the e± annihilations, leading to non-thermal features in their final distributions. In this Letter we review the different results obtained in the literature and perform a new analysis which takes into account, in a fully consistent way, the QED corrections at finite temperature to the photon and e± plasma equation of state. The value found for three massless active neutrinos is Nνeff=3.0395, in perfect agreement with the recommended value used in CMBFAST, Nνeff=3.04. We also discuss the case of additional relativistic relics and massive active neutrinos.
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Planck 2015 results. XIII. Cosmological parameters
Planck Collaboration, Ade, P. A. R., Aghanim, N., Arnaud, M., Ashdown, M., Aumont, J., Baccigalupi, C., Banday, A. J., Barreiro, R. B., Bartlett, J. G., et al. (2015) · arXiv · doi:10.48550/arxiv.1502.01589 · Cited by 10,720
Planck 2015 results: XIII. Cosmological parameters
Planck Collaboration, Ade, P. A. R., Aghanim, N., Arnaud, M., Ashdown, M., Aumont, J., Baccigalupi, C., Banday, A. J., Barreiro, R. B., Bartlett, J. G., et al. (2016) · Astronomy & Astrophysics · doi:10.1051/0004-6361/201525830 · Cited by 10,583
Three‐Year Wilkinson Microwave Anisotropy Probe ( WMAP ) Observations: Implications for Cosmology
Spergel, D. N., Bean, R., Dore, O., Nolta, M. R., Bennett, C. L., Dunkley, J., Hinshaw, G., Jarosik, N., Komatsu, E., Page, L., et al. (2007) · The Astrophysical Journal Supplement Series · doi:10.1086/513700 · Cited by 6,778
FIVE-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE OBSERVATIONS: COSMOLOGICAL INTERPRETATION
Komatsu, E., Dunkley, J., Nolta, M. R., Bennett, C. L., Gold, B., Hinshaw, G., Jarosik, N., Larson, D., Limon, M., Page, L., et al. (2009) · The Astrophysical Journal Supplement Series · doi:10.1088/0067-0049/180/2/330 · Cited by 5,786
Dunkley, J., Komatsu, E., Nolta, M. R., Spergel, D. N., Larson, D., Hinshaw, G., Page, L., Bennett, C. L., Gold, B., Jarosik, N., et al. (2009) · The Astrophysical Journal Supplement Series · doi:10.1088/0067-0049/180/2/306 · Cited by 1,787
Metadata
- Authors
- Mangano, G., Miele, G., Pastor, S., & Peloso, M.
- Venue
- Physics Letters B
- Publisher
- Elsevier BV
- Published
- 2002-05
- Volume
- 534
- Issue
- 1-4
- Pages
- 8-16
- ISSN
- 0370-2693 (ISSN-L)
- OpenAlex
- W1981007048
- Cited by
- 287
- References
- 0
- FWCI
- 6.14
- Type
- journal article
- Language
- en
- Open access
- hybrid
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- Mangano, G., Miele, G., Pastor, S., & Peloso, M. (2002). A precision calculation of the effective number of cosmological neutrinos. Physics Letters B. https://doi.org/10.1016/s0370-2693(02)01622-2
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