Thawing dark energy and massive neutrinos in light of DESI

Abstract Recent analyses have shown that a dynamic dark energy modeled by the CPL parameterization of the dark energy equation of state (EoS) can ease constraints on the total neutrino mass compared to the standard ΛCDM model. This helps reconcile cosmological and particle physics measurements of ∑ m ν . In this study, we investigate the robustness of this effect by assessing the extent to which the CPL assumption influences the results. We examine how alternative EoS parameterizations — such as Barboza-Alcaniz (BA), Jassal-Bagla-Padmanabhan (JBP), and a physically motivated thawing parameterization that reproduces the behavior of various scalar field models — affect estimates of ∑ m ν . Although both the BA and JBP parameterizations relax the constraints similarly to the CPL model, the JBP parameterization still excludes the inverted neutrino mass hierarchy at ∼ 2.1 σ with ∑ m ν < 0.096 eV. The thawing parameterization excludes the inverted hierarchy at ∼ 3.3σ and yields tighter constraints, comparable to those of the ΛCDM model, with ∑ m ν < 0.071 eV. Finally, we show that the thawing model can be mapped into the BA and JBP w 0 – w a parameter space, with the apparent preference for the phantom regime actually supporting quintessence (non-phantom) models.