Origin of cosmological neutrino mass bounds: background $\textit{versus}$ perturbations
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arXiv
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| Autores principales: | , , , , |
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| Formato: | Preprint |
| Publicado: |
2024
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| _version_ | 1866915309103874048 |
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| author | Bertólez-Martínez, Toni Esteban, Ivan Hajjar, Rasmi Mena, Olga Salvado, Jordi |
| author_facet | Bertólez-Martínez, Toni Esteban, Ivan Hajjar, Rasmi Mena, Olga Salvado, Jordi |
| contents | 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 $\textit{background}$ ($\sum m_ν^\mathrm{Backg.}$) and $\textit{perturbations}$ ($\sum m_ν^\mathrm{Pert.}$) 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 $\sum m_ν^\mathrm{Pert.}$ is largely relaxed, $\sum m_ν^\mathrm{Pert.} < 0.8\,\mathrm{eV}$. 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2411_14524 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Origin of cosmological neutrino mass bounds: background $\textit{versus}$ perturbations Bertólez-Martínez, Toni Esteban, Ivan Hajjar, Rasmi Mena, Olga Salvado, Jordi Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology 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 $\textit{background}$ ($\sum m_ν^\mathrm{Backg.}$) and $\textit{perturbations}$ ($\sum m_ν^\mathrm{Pert.}$) 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 $\sum m_ν^\mathrm{Pert.}$ is largely relaxed, $\sum m_ν^\mathrm{Pert.} < 0.8\,\mathrm{eV}$. 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. |
| title | Origin of cosmological neutrino mass bounds: background $\textit{versus}$ perturbations |
| topic | Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2411.14524 |