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Register a new userOn the most constraining cosmological neutrino mass bounds
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We present here up-to-date neutrino mass limits exploiting the most recent cosmological data sets. By making use of the Cosmic Microwave Background temperature fluctuation and polarization measurements, Supernovae Ia luminosity distances, Baryon Acoustic Oscillation observations and determinations of the growth rate parameter, we are able to set the most constraining bound to date, $sum m_ u<0.09$ eV at $95%$~CL. This very tight limit is obtained without the assumption of any prior on the value of the Hubble constant and highly compromises the viability of the inverted mass ordering as the underlying neutrino mass pattern in nature. The results obtained here further strengthen the case for very large multitracer spectroscopic surveys as unique laboratories for cosmological relics, such as neutrinos: that would be the case of the Dark Energy Spectroscopic Instrument (DESI) survey and of the Euclid mission.
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We consider the phenomenological implications of the violation of the Pauli exclusion principle for neutrinos, focusing on cosmological observables such as the spectrum of Cosmic Microwave Background anisotropies, Baryon Acoustic Oscillations and the primordial abundances of light elements. Neutrinos that behave (at least partly) as bosonic particles have a modified equilibrium distribution function that implies a different influence on the evolution of the Universe that, in the case of massive neutrinos, can not be simply parametrized by a change in the effective number of neutrinos. Our results show that, despite the precision of the available cosmological data, only very weak bounds can be obtained on neutrino statistics, disfavouring a more bosonic behaviour at less than $2sigma$.
We study models in which neutrino masses are generated dynamically at cosmologically late times. Our study is purely phenomenological and parameterized in terms of three effective parameters characterizing the redshift of mass generation, the width of the transition region, and the present day neutrino mass. We also study the possibility that neutrinos become strongly self-interacting at the time where the mass is generated. We find that in a number of cases, models with large present day neutrino masses are allowed by current CMB, BAO and supernova data. The increase in the allowed mass range makes it possible that a non-zero neutrino mass could be measured in direct detection experiments such as KATRIN. Intriguingly we also find that there are allowed models in which neutrinos become strongly self-interacting around the epoch of recombination.
We present strong bounds on the sum of three active neutrino masses ($sum m_{ u}$) in various cosmological models. We use the following baseline datasets: CMB temperature data from Planck 2015, BAO measurements from SDSS-III BOSS DR12, the newly released SNe Ia dataset from Pantheon Sample, and a prior on the optical depth to reionization from 2016 Planck Intermediate results. We constrain cosmological parameters in $Lambda CDM$ model with 3 massive active neutrinos. For this $Lambda CDM+sum m_{ u}$ model we find a upper bound of $sum m_{ u} <$ 0.152 eV at 95$%$ C.L. Adding the high-$l$ polarization data from Planck strengthens this bound to $sum m_{ u} <$ 0.118 eV, which is very close to the minimum required mass of $sum m_{ u} simeq$ 0.1 eV for inverted hierarchy. This bound is reduced to $sum m_{ u} <$ 0.110 eV when we also vary r, the tensor to scalar ratio ($Lambda CDM+r+sum m_{ u}$ model), and add an additional dataset, BK14, the latest data released from the Bicep-Keck collaboration. This bound is further reduced to $sum m_{ u} <$ 0.101 eV in a cosmology with non-phantom dynamical dark energy ($w_0 w_a CDM+sum m_{ u}$ model with $w(z)geq -1$ for all $z$). Considering the $w_0 w_a CDM+r+sum m_{ u}$ model and adding the BK14 data again, the bound can be even further reduced to $sum m_{ u} <$ 0.093 eV. For the $w_0 w_a CDM+sum m_{ u}$ model without any constraint on $w(z)$, the bounds however relax to $sum m_{ u} <$ 0.276 eV. Adding a prior on the Hubble constant ($H_0 = 73.24pm 1.74$ km/sec/Mpc) from Hubble Space Telescope (HST), the above mentioned bounds further improve to $sum m_{ u} <$ 0.117 eV, 0.091 eV, 0.085 eV, 0.082 eV, 0.078 eV and 0.247 eV respectively. This substantial improvement is mostly driven by a more than 3$sigma$ tension between Planck 2015 and HST measurements of $H_0$ and should be taken cautiously. (abstract abridged)
Axions, if realized in nature, can be copiously produced in the early universe via thermal processes, contributing to the mass-energy density of thermal hot relics. In light of the most recent cosmological observations, we analyze two different thermal processes within a realistic mixed hot-dark-matter scenario which includes also massive neutrinos. Considering the axion-gluon thermalization channel we derive our most constraining bounds on the hot relic masses $m_a < 7.46$ eV and $sum m_ u< 0.114$ eV both at 95 per cent CL; while studying the axion-pion scattering, without assuming any specific model for the axion-pion interactions and remaining in the range of validity of the chiral perturbation theory, our most constraining bounds are improved to $m_a<0.91$ eV and $sum m_ u< 0.105$ eV, both at 95 per cent CL. Interestingly, in both cases, the total neutrino mass lies very close to the inverted neutrino mass ordering prediction. If future terrestrial double beta decay and/or long baseline neutrino experiments find that the nature mass ordering is the inverted one, this could rule out a wide region in the currently allowed thermal axion window. Our results therefore strongly support multi-messenger searches of axions and neutrino properties, together with joint analyses of their expected sensitivities.
When combining cosmological and oscillations results to constrain the neutrino sector, the question of the propagation of systematic uncertainties is often raised. We address this issue in the context of the derivation of an upper bound on the sum of the neutrino masses ($Sigma m_ u$) with recent cosmological data. This work is performed within the ${{mathrm{Lambda{CDM}}}}$ model extended to $Sigma m_ u$, for which we advocate the use of three mass-degenerate neutrinos. We focus on the study of systematic uncertainties linked to the foregrounds modelling in CMB data analysis, and on the impact of the present knowledge of the reionisation optical depth. This is done through the use of different likelihoods built from Planck data. Limits on $Sigma m_ u$ are derived with various combinations of data, including the latest Baryon Acoustic Oscillations (BAO) and Type Ia Supernovae (SN) results. We also discuss the impact of the preference for current CMB data for amplitudes of the gravitational lensing distortions higher than expected within the ${{mathrm{Lambda{CDM}}}}$ model, and add the Planck CMB lensing. We then derive a robust upper limit: $Sigma m_ u< 0.17hbox{ eV at }95% hbox{CL}$, including 0.01 eV of foreground systematics. We also discuss the neutrino mass repartition and show that todays data do not allow one to disentangle normal from inverted hierarchy. The impact on the other cosmological parameters is also reported, for different assumptions on the neutrino mass repartition, and different high and low multipole CMB likelihoods.
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