A grounded perspective on New Early Dark Energy using ACT, SPT, and BICEP/Keck

Abstract

We examine further the ability of the New Early Dark Energy model (NEDE) to resolve the current tension between the Cosmic Microwave Background (CMB) and local measurements of $H_0$ and the consequences for inflation. We perform new Bayesian analyses, including the current datasets from the ground-based CMB telescopes Atacama Cosmology Telescope (ACT), the South Pole Telescope (SPT), and the BICEP/Keck telescopes, employing an updated likelihood for the local measurements coming from the S$H_0$ES collaboration. Using the S$H_0$ES prior on $H_0$, the combined analysis with Baryonic Acoustic Oscillations (BAO), Pantheon, Planck and ACT improves the best-fit by $\hat{I}”\ddot{I}{‡}^2=-15.9$ with respect to $\hat{I}›$CDM, favors a non-zero fractional contribution of NEDE, $f_{\mathrm{NEDE}}>0$, by $4.8\ddot{I}ƒ$, and gives a best-fit value for the Hubble constant of $H_0=72.09$ km/s/Mpc (mean $71.48_{-0.81}^{+0.79}$ with $68\%$ C.L.). A similar analysis using SPT instead of ACT yields consistent results with a $\hat{I}”\ddot{I}{‡}^2=-23.1$ over $\hat{I}›$CDM, a preference for non-zero $f_{\mathrm{NEDE}}$ of $4.7\ddot{I}ƒ$ and a best-fit value of $H_0=71.77$ km/s/Mpc (mean $71.43_{-0.84}^{+0.84}$ with $68\%$ C.L.). We also provide the constraints on the inflation parameters $r$ and $n_s$ coming from NEDE, including the BICEP/Keck 2018 data, and show that the allowed upper value on the tensor-scalar ratio is consistent with the $\hat{I}›$CDM bound, but, as also originally found, with a more blue scalar spectrum implying that the simplest curvaton model is now favored over the Starobinsky inflation model.

32 pages, 10 figures, 14 tables, Journal version -- updated all figures and text with minor changes, conclusions unchanged