Toward early dark energy and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>n</mml:mi></mml:mrow><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math> with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>P</mml:mi><mml:mi>l</mml:mi><mml:mi>a</mml:mi><mml:mi>n</mml:mi><mml:mi>c</mml:mi><mml:mi>k</mml:mi></mml:mrow></mml:math>, ACT, and SPT observations
Jun-Qian Jiang, Yun-Song Piao
Abstract
We investigate the constraints on early dark energy (EDE) by combining the most recent CMB observations available, ACT DR4, SPT-3G, and Planck2018 (${\ensuremath{\ell}}_{\mathrm{TT},\mathrm{max}}=1000$) data. This combined CMB dataset favors nonzero EDE fractions and large Hubble constants. The inclusion of $\mathrm{BAO}+\mathrm{Pantheon}$ data has little effect on the results, leads to ${H}_{0}=71.6(72.9{)}_{\ensuremath{-}1.5}^{+2.0}$ and $73.17(72.74{)}_{\ensuremath{-}0.77}^{+0.55}\text{ }\text{ }\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ for axionlike EDE and AdS-EDE, respectively. The axionlike EDE can fit the data significantly better ($\mathrm{\ensuremath{\Delta}}{\ensuremath{\chi}}^{2}\ensuremath{\lesssim}\ensuremath{-}10$) than $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$, 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 toward a scale invariant Harrison-Zeldovich spectrum of primordial scalar perturbation, i.e., ${n}_{s}=1$ for ${H}_{0}\ensuremath{\sim}73\text{ }\text{ }\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$.