Cosmological bounds on neutrino statistics

Salas, Pablo F. de; Gariazzo, Stefano; Laveder, M.; Pastor, S.; Pisanti, O.; Truong, Nhut

doi:10.1088/1475-7516/2018/03/050

Cited by 8 publications

(29 citation statements)

References 74 publications

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“…However, it also means that cosmology is not a strong probe of neutrino properties beyond their contribution to the background and perturbed stress-energy tensor: it does not significantly constrain the neutrino phase-space distribution (see, e.g., Refs. [11][12][13]) and simply excludes the possibility of too strong non-standard neutrino interactions in cases where particle physics experiments do not already provide stronger bounds (see, e.g., Refs. [14][15][16][17][18][19][20]).…”

Section: Introductionmentioning

confidence: 99%

What will it take to measure individual neutrino mass states using cosmology?

Archidiacono¹,

Hannestad²,

Lesgourgues³

2020

Preprint

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We study the impact of assumptions made about the neutrino mass ordering on cosmological parameter estimation with the purpose of understanding whether in the future it will be possible to infer the specific neutrino mass distribution from cosmological data. We find that although the commonly used assumption of a degenerate neutrino hierarchy is manifestly wrong and leads to changes in cosmological observables such as the cosmic microwave background and large scale structure compared to the correct (normal or inverted) neutrino hierarchy, the induced changes are so small that even with extremely optimistic assumptions about future data they will remain undetectable. We are thus able to conclude that while cosmology can probe the neutrino contribution to the cosmic energy density extremely precisely (and hence provide a detection of a non-zero total neutrino mass at high significance), it will not be possible to directly measure the individual neutrino masses.

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Section: Introductionmentioning

confidence: 99%

What will it take to measure individual neutrino mass states using cosmology?

Archidiacono¹,

Hannestad²,

Lesgourgues³

2020

Preprint

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show abstract

“…A caveat to this is that sterile neutrinos have a Fermi-Dirac phase space distribution, while axions instead obey Bose-Einstein statistics. However, as demonstrated by [42], state-of-the-art CMB data cannot currently distinguish whether the energy density in even all three SM neutrinos is Fermi-Dirac or Bose-Einstein, so it certainly is insensitive to the statistics of just the small fraction of the energy density contained in ∆N eff . A similar result for matter clustering is shown by [43], the only exception being in the non-linear regime of halo cores, which are not considered here.…”

Section: Results For Qcd Axionsmentioning

confidence: 99%

New cosmological bounds on axions in the XENON1T window

Millea¹

2020

Preprint

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Motivated by a possible ∼ eV-mass solar axion explanation to excess events recently detected by the XENON1T experiment, I revisit and update cosmological constraints on axions in this mass range. I find that of the allowed XENON1T mass window (0.1 -4.1 eV for DFSZ axions and 46 -56 eV for KSVZ axions), only 0.1 -0.35 eV remains viable at 95% confidence given current cosmological probes. If a 0.35 eV DFSZ axion existed, it would be detectable at ∼ 7 σ via two independent physical effects with the next-generation CMB-S4 experiment. Conversely, even a combination of CMB-S4 with future DESI measurements falls just short of guaranteeing a 0.1 eV-mass axion can be detected or ruled out. A future limit of ∆N eff < 0.027 could rule out any generic axion-like particle across a wide range of masses as long as the reheating temperature is not too low, or alternatively, a future cosmological detection of such an axion-like particle could become the tightest existing observational lower bound on the reheating temperature.

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“…Before continuing, we note that several aspects of this possibility have been studied in the literature [24][25][26][27]. In particular, back in 2005, ref.…”

Section: Jcap02(2022)037mentioning

confidence: 90%

What can CMB observations tell us about the neutrino distribution function?

Alvey

Escudero

2022

J. Cosmol. Astropart. Phys.

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Cosmic Microwave Background (CMB) observations have been used extensively to constrain key properties of neutrinos, such as their mass. However, these inferences are typically dependent on assumptions about the cosmological model, and in particular upon the distribution function of neutrinos in the early Universe. In this paper, we aim to assess the full extent to which CMB experiments are sensitive to the shape of the neutrino distribution. We demonstrate that Planck and CMB-S4-like experiments have no prospects for detecting particular features in the distribution function. Consequently, we take a general approach and marginalise completely over the form of the neutrino distribution to derive constraints on the relativistic and non-relativistic neutrino energy densities, characterised by N eff = 3.0 ± 0.4 and ρν,0 NR < 14 eV cm-3 at 95% CL, respectively. The fact that these are the only neutrino properties that CMB data can constrain has important implications for neutrino mass limits from cosmology. Specifically, in contrast to the ΛCDM case where CMB and BAO data tightly constrain the sum of neutrinos masses to be ∑m ν < 0.12 eV, we explicitly show that neutrino masses as large as ∑ m ν∼ 3 eV are perfectly consistent with this data. Importantly, for this to be the case, the neutrino number density should be suitably small such that the bound on ρν,0 NR = ∑ m ν n ν,0 is still satisfied. We conclude by giving an outlook on the opportunities that may arise from other complementary experimental probes, such as galaxy surveys, neutrino mass experiments and facilities designed to directly detect the cosmic neutrino background. GitHub: Parameter files for MCMC analysis and code to reproduce all plots can be found here.

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Cosmological bounds on neutrino statistics

Cited by 8 publications

References 74 publications

What will it take to measure individual neutrino mass states using cosmology?

What will it take to measure individual neutrino mass states using cosmology?

New cosmological bounds on axions in the XENON1T window

What can CMB observations tell us about the neutrino distribution function?

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