2025/12/09 by Nair, Gowri S, Chakraborty, Amlan, Amendola, Luca +1 · 1 citation
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Phenomenology (hep-ph) #High Energy Physics - Theory (hep-th)
paper · doi:10.48550/arxiv.2512.08752
Cosmological constraints on the total neutrino mass, ∑ mν, are strongly shaped by assumptions about the dark-energy equation of state due to the well-known degeneracy between massive neutrinos and late-time cosmic acceleration. In this work, we move beyond the two-parameter Chevallier-Polarski-Linder (CPL) form adopted in recent DESI analyses and re-examine neutrino mass constraints using a flexible four-parameter dark energy equation of state (4pDE). We implement the 4pDE model in a modified version of CLASS and perform a full MCMC analysis using Planck, DESI DR2 BAO, and Pantheon+ data. Relative to our previous 4pDE study based on pre-DESI BAO datasets, the inclusion of DESI DR2 substantially tightens the constraints on the transition parameters while still yielding a relaxed neutrino-mass bound compared to ΛCDM, ∑ mν< 0.101 eV (95% C.L.). This upper limit is more stringent than the DESI DR2 constraint obtained within the w0waCDM framework. From the best-fit parameters, we reconstruct the evolution of the 4pDE equation of state along with both 68% and 95%C.L. We do not find a statistically significant phantom-crossing at z ∼ 0.5, consistent with the conclusion from the DESI collaboration; at higher redshifts, the reconstructed w(z) follows the CPL evolution and deviates only at low redshift. Additionally we also find reduction in Δχ2\rm min=-7.3 compared to ΛCDM model.