Primordial neutrinos fade to gray: constraints from cosmological observables
arXiv:2504.07178 · doi:10.1103/kg29-yq85
Abstract
We investigate the effect of potentially large distortions of the relic neutrino spectra on cosmological observables. To that end, we consider a phenomenological model of "gray" spectral distributions, described by a single parameter, which generalizes the traditional -distortions to possibly large negative values. Implementing these distortions in the primordial nucleosynthesis code PRIMAT, we can constrain the distortion parameter along with the presence of extra radiation, exploiting the complementarity of big bang nucleosynthesis and cosmic microwave background measurements to disentangle gravitational and non-thermal effects. These constraints rule out a distortion where more than of the neutrinos' energy density is replaced by dark radiation. Nonetheless, we find that large distortions, accompanied with extra radiation, are allowed-and even slightly preferred in some cases-by current cosmological observations. As this scenario would require substantial modifications to the physics of neutrino decoupling in the early Universe, these observational constraints call for a renewed attention on the possibility of large deviations from the standard cosmological model in the neutrino sector.
17 pages, 10 figures
References in corpus (30)
- Array Programming with NumPy
- DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations
- The Primordial Lithium Problem
- Planck intermediate results. LVII. Joint Planck LFI and HFI data processing
- Towards a precision calculation of in the Standard Model II: Neutrino decoupling in the presence of flavour oscillations and finite-temperature QED
- Neutrino decoupling including flavour oscillations and primordial nucleosynthesis
- A precision calculation of relic neutrino decoupling
- CMB power spectra and cosmological parameters from Planck PR4 with CamSpec
- A new tension in the cosmological model from primordial deuterium?
- EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-Poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension
- Improving Helium Abundance Determinations with Leo P as a Case Study
- Primordial Deuterium after LUNA: concordances and error budget
- Neutrino cosmology after DESI: tightest mass upper limits, preference for the normal ordering, and tension with terrestrial observations
- Constraining The Universal Lepton Asymmetry
- Cosmological lepton asymmetry with a nonzero mixing angle θ_{13}
- Improved constraints on lepton asymmetry from the cosmic microwave background
- Thermalization of large energy release in the early Universe
- Towards a precision calculation of in the Standard Model III: Improved estimate of NLO contributions to the collision integral
- Indications for a Nonzero Lepton Asymmetry from Extremely Metal-Poor Galaxies
- Resurrection of large lepton number asymmetries from neutrino flavor oscillations
- Primordial lepton asymmetries in the precision cosmology era: Current status and future sensitivities from BBN and the CMB
- Resolving conclusions about the early Universe requires accurate nuclear measurements
- What can CMB observations tell us about the neutrino distribution function?
- Constraints on primordial lepton asymmetries with full neutrino transport
- Incomplete neutrino decoupling effect on big bang nucleosynthesis
- When FIMPs Decay into Neutrinos: The Story
- A New Precise Determination of the Primordial Abundance of Deuterium: Measurement in the metal-poor sub-DLA system at z=3.42 towards quasar J1332+0052
- Primordial neutrinos and new physics: novel approach to solving neutrino Boltzmann equation
- Effects of an Intermediate Mass Sterile Neutrino Population on the Early Universe
- New physics decaying into metastable particles: impact on cosmic neutrinos