Restoring cosmological concordance with early dark energy and massive neutrinos?

The early dark energy (EDE) solution to the Hubble tension comes at the cost of an increased clustering amplitude that has been argued to worsen the fit to galaxy clustering data. We explore whether freeing the total neutrino mass Mν, which can suppress small-scale structure growth, improves EDE’s fit to galaxy clustering. Using Planck Cosmic Microwave Background and BOSS galaxy clustering data, a Bayesian analysis shows that freeing Mν does not appreciably increase the inferred EDE fraction fEDE: we find the 95 per cent C.L. upper limits fEDE < 0.092 and Mν<0.15eV⁠. Similarly, in a frequentist profile likelihood setting (where our results support previous findings that prior volume effects are important), we find that the baseline EDE model (with Mν=0.06eV⁠) provides the overall best fit. For instance, compared to baseline EDE, a model with Mν=0.24eV maintains the same H0(km/s/Mpc) = (70.08, 70.11, respectively) whilst decreasing S8 = (0.837, 0.826) to the ΛCDM level, but worsening the fit significantly by Δχ2 = 7.5. For the datasets used, these results are driven not by the clustering amplitude, but by background modifications to the late-time expansion rate due to massive neutrinos, which worsen the fit to measurements of the BAO scale.