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Author  |
Bertolez-Martinez, T.; Esteban, I.; Hajjar, R.; Mena, O.; Salvado, J. |
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Title |
Origin of cosmological neutrino mass bounds: background versus perturbations |
Type |
Journal Article |
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Year |
2025 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
06 |
Issue |
6 |
Pages |
058 - 37pp |
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Keywords |
cosmological neutrinos; cosmological parameters from CMBR; neutrino masses from cosmology; neutrino properties |
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Abstract |
The cosmological upper bound on the total neutrino mass is the dominant limit on this fundamental parameter. Recent observations soon to be improved have strongly tightened it, approaching the lower limit set by oscillation data. Understanding its physical origin, robustness, and model-independence becomes pressing. Here, we explicitly separate for the first time the two distinct cosmological neutrino-mass effects: the impact on background evolution, related to the energy in neutrino masses; and the “kinematic” impact on perturbations, related to neutrino free-streaming. We scrutinize how they affect CMB anisotropies, introducing two effective masses enclosing background ( mBackg. nu ) and perturbations ( mPert. nu) effects. We analyze CMB data, finding that the neutrino-mass bound is mostly a background measurement, i.e., how the neutrino energy density evolves with time. The bound on the “kinematic” variable mPert. nu is largely relaxed, mPert. nu <0.8 eV. This work thus adds clarity to the physical origin of the cosmological neutrino-mass bound, which is mostly a measurement of the neutrino equation of state, providing also hints to evade such a bound. |
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Address |
[Bertolez-Martinez, Toni; Salvado, Jordi] Univ Barcelona, Dept Fis Quant & Astrofis, Diagonal 647, E-08028 Barcelona, Spain, Email: antoni.bertolez@fqa.ub.edu; |
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Publisher |
IOP Publishing Ltd |
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Language |
English |
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Original Title |
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Series Volume |
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Edition |
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ISSN |
1475-7516 |
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Notes |
WOS:001522131000002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
6737 |
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