Relaxing cosmological constraints on current neutrino masses

We show that a mass-varying neutrino model driven by scalar field dark energy relaxes the existing upper bound on the current neutrino mass to ${\sum m_\nu < 0.72}$ eV. We extend the standard $\Lambda$ cold dark matter model by introducing two parameters: the rate of change of the scalar field with the number of $e$-folds and the coupling between neutrinos and the field. We investigate how they affect the matter power spectrum, the cosmic microwave background anisotropies and its lensing potential. The model is tested against Planck observations of temperature, polarization, and lensing, combined with baryon acoustic oscillation measurements that constrain the background evolution. The results indicate that small couplings favor a cosmological constant, while larger couplings favor a dynamical dark energy, weakening the upper bound on current neutrino masses.