Towards early dark energy and $n_s$=1 with Planck, ACT and SPT

Abstract

We investigate the constraints on early dark energy (EDE) by combining the most recent CMB observations available, ACT DR4, SPT-3G, and Planck2018 (${\ell }_{\text{TT,max}}=1000$) data. This combined CMB dataset favors non-zero EDE fractions and large Hubble constants. The inclusion of BAO+Pantheon data has little effect on the results, leads to $H_0=71.6(72.9{)}_{-1.5}^{+2.0}$ and $73.17(72.74{)}_{-0.77}^{+0.55}$ km/s/Mpc for axion-like EDE and AdS-EDE, respectively. The axion-like EDE can fit the data significantly better ($\Delta {\chi }^2\lesssim -10$) than $\Lambda$CDM, which is mainly driven by the ACT data. It is found again that if the current $H_0$ measured locally is correct, complete resolution of the Hubble tension seems to be pointing towards a scale invariant Harrison-Zeldovich spectrum of primordial scalar perturbation, i.e. $n_s=1$ for $H_0\sim 73$ km/s/Mpc.

20 pages, 8 figures

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Cited by in corpus (1)

• Seven hints that early-time new physics alone is not sufficient to solve the Hubble tension