Refitting Cosmological Data with Neutrino Mass and Degeneracy
Year: 2025
Type: article
Abstract: A simple and natural extension of the standard Lambda cold dark matter (ΛCDM) model is to allow relic neutrinos to have finite chemical potentials. We confront this ΛCDMξ model, a ΛCDM with neutrino mass M ν and degeneracy ξ 3 as additional parameters, with various cosmological data sets. We find that the H 0 and S 8 tensions become significant only in the presence of the cosmic microwave background (CMB) polarization data. Specifically, the global and local measurements agree to within 0.8σ and 1.6σ for the H 0 and S 8 tensions, respectively, when the CMB polarization data are not included. Therefore, the H 0 and S 8 tensions exist between CMB temperature and polarization data, both being global measurements. Fitting the ΛCDMξ model to the CMB temperature data, we find 3σ evidence for nonzero neutrino mass ( M ν = 0.5 7 − 0.13 + 0.17 eV ) and degeneracy ( ξ 3 = 1.1 3 − 0.19 + 0.41 ), and the O ( 1 ) neutrino degeneracy parameter is compatible with Big Bang nucleosynthesis data. The scalar index n s exceeds 1 slightly, which is compatible with some hybrid inflation models. Furthermore, the recent DESI baryon acoustic oscillation data prefer the ΛCDMξ model to the Planck ΛCDM model. Similar results are obtained when including additional supernova data, while the inclusion of the Atacama Cosmology Telescope τ prior shifts the preferred M ν and ξ 3 values closer to zero and brings n s back to the values favored when the polarization data are included.
Authors: Shek Yeung, Wangzheng Zhang, Ming-chung Chu
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,400
OpenAlex ID: W4413927419